jawwadaklodhi.files.wordpress.com€¦ · Web viewAnjuman College Of Engineering & Technology, Sadar, Nagpur. L. A. BORA. T. OR. Y. MA. N. UA. L. D. E. PAR. T. ME. N. T. OF ME

Roll No:____

Name:__________________

Sem:_______Section______

Anjuman College Of Engineering & Technology, Sadar, Nagpur LABORATORYMANUALDEPARTMENT OF MECHANICAL ENGINEERING

Practical Experiment Instruction Sheet YEAR : 2017-18

FinalYear SEM-VIII SUBJECT: Automation in production

CERTIFICATECertified that this file is submitted by

Shri/

Automation In Production




Ku.___________________________________________________________

Roll No.________a student of ________ year of the course __________________

______________________________________as a part of PRACTICAL/ORAL as

prescribed by the Rashtrasant Tukadoji Maharaj Nagpur University for the

subject_Automation in Production in the laboratory of Dept. of Mech Engg.

during the academic year 2018-19 and that I have instructed him/her for the said

work, from time to time and I found him/her to be satisfactory progressive.

And that I have accessed the said work and I am satisfied that the same is up to that

standard envisaged for the course.

Prof. K.I. Ahmad Dr. Akash Langde

Date:- Signature & Name Signature & Name of Subject Teacher of HOD

Anjuman College of Engineering and TechnologyVision

To be a centre of excellence for developing quality technocrats with moral and

social ethics, to face the global challenges for the sustainable development of

society.

Mission




To create conducive academic culture for learning and identifying career goals.

To provide quality technical education, research opportunities and imbibe

entrepreneurship skills contributing to the socio-economic growth of the Nation.

To inculcate values and skills, that will empower our students towards development

through technology.

Vision and Mission of the Department

Vision:

To impart technical education for facing challenges with humane approach for

sustainable development in Mechanical Engineering.

Mission:

To provide an environment for technical knowledge gain for overall development of

students.

To create awareness and provide environment for research.

To instill spirit, commitment and develop skills in students for socio economic

development.

To guide students for adopting engineering approach to conserve natural resources.

Program Educational Objectives (PEOs)




To have strong aptitude and fundamental knowledge in mechanical engineering for

successful career.

To take up research based improvement to provide solutions for technical problems

of society.

To resolve societal, technical /business challenges to hone personal development.

Enhance professional progress and technical understanding through continuing

education for sustainable development.

Program Specific Outcomes (PSOs)

Able to apply, analyze mechanical engineering knowledge for sustainable

development of society and self.

Able to effectively communicate in small and large teams and work as a team

member

Able to use creativity in design, thermal, industrial engineering to improve

mechanical systems and processes.




PROGRAM: ME DEGREE: B.E

COURSE: Automation In Production SEMESTER: VIII CREDITS: 1

COURSE CODE: BEME804P COURSE TYPE: Regular

COURSE AREA/DOMAIN: Production CONTACT HOURS: 2 hours/Week.

CORRESPONDING LAB COURSE CODE :

BEME804P

LAB COURSE NAME : Automation In Production

COURSE PRE-REQUISITES:

C.CODE COURSE NAME DESCRIPTION SEM

BEME802T5 Automation In Production Production VIII

LAB COURSE OBJECTIVES:

This course is designed to acquaint the students with automation basics.

Students will be able to understand how automation is used to increase the production.

This will also introduce them to various types of automation systems, CNC machines, DNC

and robot applications.

To cultivate understanding of group technology, FMS and automated system of transport and

storing.

At the end of the course, students will be conversant with industrial applications of automation.




COURSE OUTCOMES: Design Patterns

After completion of this course the students will be able -

SNO DESCRIPTION BLOOM’S TAXONOMY

LEVEL

CO.1 apply programming knowledge to write manual part programming for

a component in CNC Lathe.

[1,2,3,5]

CO.2 apply programming knowledge to write manual part programming for

a component in CNC Milling machine.

[1,2,3,5]

CO.3 create a part programming for a component using APT language. [1,2,3,4,5]

CO.4 identify and define various links and joints and movements of Robot. [1,2,4]

CO.5 justify codification of parts using Group Technology [1,2,3,4]

CO.6 analyze and defend case study on Automated system of Industry. [1,2,4,5]




Lab Instructions:

۞ Students are informed to present 5 min before the commencement of lab.۞ Students must enter their name in daily book before entering into lab.۞ Students must leave Foot wares before entering lab.۞ Students must not carry any valuable things inside the lab.۞ Students must inform lab assistant before He / She uses any computer.۞ Do not touch anything with which you are not completely familiar. Carelessness may not only break the valuable equipment in the lab but may also cause serious injury to you and others in the lab. ۞ For any software/hardware/ Electrical failure of computer during working, report it immediately to your supervisor. Never try to fix the problem yourself because you could further damage the equipment and harm yourself and others in the lab. ۞ Students must submit Record book for evaluation before the commencement of lab.۞ Students must keep observation book (if necessary).۞ Students must keep silent near lab premises.۞ Students are informed to follow safety rules.۞ Students must obey lab rules and regulations.۞ Students must maintain discipline in lab.۞ Do not crowd around the computers and run inside the laboratory.۞ Please follow instructions precisely as instructed by your supervisor. Do not start

the experiment unless your setup is verified & approved by your supervisor




Continuous Assessment PracticalExp

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Programme: Mechanical EngineeringCourse: Automation In ProductionCourse Code: CO804PCourse Outcomes:The Student would be able to:

CO804P.1 apply programming knowledge to write manual part programming for a component in CNC Lathe

CO804P.2 apply programming knowledge manual part programming for a component in CNC Milling machine.

CO804P.3 create a part programming for a component using APT language.

CO804P.4 identify and define various links and joints and movements of Robot.CO804P.5 justify codification of parts using Group Technology.CO804P.6 analyze and defend case study on Automated system of Industry.

Course Objectives :

This course is designed to acquaint the students with automation basics.

Students will be able to understand how automation is used to increase the production.

This will also introduce them to various types of automation systems, CNC machines, DNC

and robot applications.

To cultivate understanding of group technology, FMS and automated system of transport and

storing.

At the end of the course, students will be conversant with industrial applications of automation.




LIST OF EXPERIMENTS:

1. Performance, Simulation on CNC lathe (at least two Complex Geometries) 2. Performance, Simulation on CNC milling (at least two Complex Geometries) 3. Practice Programming on Manual Part Program4. Practice Programming on APT5. Case Study on Automated System of any Industry.6. Robot Performance/Study7. GT coding

.




Experiment No. 01

Ai m : Case study on automated system of any Industry.

O b j e c tiv e : To provide proper interfacing of theory aspects and real practical situation.

Th eory:

Par t- A

1) Definition of automation: -

The word ‘Automation’ is derived from greek words “Auto”(self) and “Matos” (moving). Automation therefore is the mechanism for systems that “move by itself”. However, apart from this original sense of the word, automated systems also achieve significantly superior performance than what is possible with manual systems, in terms of power, precision and speed of operation. Definition: Automation is a set of technologies that results in operation of machines and systems without significant human intervention and achieves performance superior to manual operation A Definition from Encyclopaedia Britannica The application of machines to tasks once performed by human beings or, increasingly, to tasks that would otherwise be impossible. Although the term mechanization is often used to refer to the simple replacement of human labour by machines, automation generally implies the integration of machines into a self governing system.

Automation is the technology by which a process or procedure is accomplished without human assistance. It is implemented using a program of instructions combined with a control system that executes the instructions, to automate a process. Power is required, both to drive the process itself and to operate the program and control system.

Control is perhaps correct to expect that the learner for this course has already been exposed to a course on Control Systems, which is typically introduced in the final or pre-final year of an undergraduate course in Engineering in India. The word control is therefore expected to be familiar and defined as under. Definition: Control is a set of technologies that achieves desired patterns of variations of operational parameters and sequences for machines and systems by providing the input signals necessary.




2) Type of production:-Types of production systems Major industrial processes can be categorized as follows based on their scale and scope of production.

Continuous flow process: Manufactured product is in continuous quantities i.e., the product is not a discrete object. Moreover, for such processes, the volume of production is generally very high, while the product variation is relatively low. Typical examples of such processes include Oil Refineries, Iron and Steel Plants, Cement and Chemical Plants.

Mass Manufacturing of Discrete Products: Products are discrete objects and manufactured in large volumes. Product variation is very limited. Typical examples are Appliances, Automobiles etc. ¾ Batch Production: In a batch production process the product is either discrete or continuous. However, the variation in product types is larger than in continuous-flow processes. The same set of equipment is used to manufacture all the product types. However for each batch of a given product type a distinct set of operating parameters must be established. This set is often referred to as the “recipe” for the batch. Typical examples here would be Pharmaceuticals, Casting Foundries, Plastic moulding, Printing etc.

Job shop Production: Typically designed for manufacturing small quantities of discrete products, which are custom built, generally according to drawings supplied by customers. Any variation in the product can be made. Examples include Machine Shops, Prototyping facilities etc.

The above types of production systems are shown in Figure 1.1 categorized according to volumes of production and variability in product types. In general, if the quantity of product is more there is little variation in the product and more varieties of product is manufactured if the quantity of product is lesser.

Fig. 1.1 Types of Production Systems




Fig: 1.2 Types of facilities and layouts used for different level of production quantity and product variety

3) Types of automation:-

Types of Automation Systems: Automation systems can be categorized based on the flexibility and level of integration in manufacturing process operations. Various automation systems can be classified as follows.

Fixed Automation: It is used in high volume production with dedicated equipment, which has a fixed set of operation and designed to be efficient for this set. Continuous flow and Discrete Mass Production systems use this automation. e.g. Distillation Process, Conveyors, Paint Shops, Transfer lines etc. A process using mechanized machinery to perform fixed and repetitive operations in order to produce a high volume of similar parts. Fixed automation is a system in which the sequence of processing (or assembly) operations is fixed by the equipment configuration. Each of the operations in the sequence is usually simple, involving perhaps a plain linear or rotational motion or an uncomplicated combination of the two; for example, the feeding of a rotating spindle. It is the integration and coordination of many such operations into one piece of equipment that makes the system complex. Typical features of fixed automation are:

• High initial investment for custom-engineered equipment• High production rates• Relatively inflexible in accommodating product variety




Programmable Automation: It is used for a changeable sequence of operation and configuration of the machines using electronic controls. However, non-trivial programming effort may be needed to reprogram the machine or sequence of operations. Investment on programmable equipment is less, as production process is not changed frequently. It is typically used in Batch process where job variety is low and product volume is medium to high, and sometimes in mass production also. e.g. in Steel Rolling Mills, Paper Mills etc. In programmable automation, the production equipment is designed with the capability to change the sequence of operations to accommodate different product configurations .The operation sequence is controlled by a program, which is a set of instructions coded so that they can be read and interpreted by the system. New programs can be prepared and entered into the equipment to produce new products. Some of the features that characterize programmable automation include:

• High investment in general purpose equipment• Lower production rates than fixed automation• Flexibility to deal with variations and changes in product configuration• Most suitable for batch production

Flexible Automation: It is used in Flexible Manufacturing Systems (FMS) which is invariably computer controlled. Human operators give high-level commands in the form of codes entered into computer identifying product and its location in the sequence and the lower level changes are done automatically. Each production machine receives settings/instructions from computer. These automatically loads/unloads required tools and carries out their processing instructions. After processing, products are automatically transferred to next machine. It is typically used in job shops and batch processes where Version 2 EE IIT, Kharagpur 11 product varieties are high and job volumes are medium to low. Such systems typically use Multi purpose CNC machines, Automated Guided Vehicles (AGV) etc.

Flexible automation is an extension of programmable automation.A flexible automated system is capable of producing a variety of parts (or products) with virtually no time lost for changeovers from one part style to the next. There is no lost production time while reprogramming the system and altering the physical setup (tooling, fixtures, machine settings). Consequently, the system can produce various combinations and schedules of parts or products instead of requiring that they be made in batches. What makes flexible automation possible is that the differences between parts processed by the system are not significant. It is a case of soft variety, so that the amount of changeover required between styles is minimal. The features of flexible automation can be summarized as follows:• High investment for a custom-engineered system• Continuous production of variable mixtures of products• Medium production rates• Flexibility to deal with product design variations




Integrated Automation: It denotes complete automation of a manufacturing plant, with all processes functioning under computer control and under coordination through digital information processing. It includes technologies such as computer-aided design and manufacturing, ۞ computer-aided process planning,

۞ computer numerical control machine tools, ۞ Flexible machining systems, ۞ Automated storage and retrieval systems, ۞ Automated material handling systems such as robots and automated cranes and conveyors, ۞ Computerized scheduling and production control.

It may also integrate a business system through a common database. In other words, it symbolizes full integration of process and management operations using information and communication technologies. Typical examples of such technologies are seen in Advanced Process Automation Systems and Computer Integrated Manufacturing (CIM) As can be seen from above, from Fixed Automation to CIM the scope and complexity of automation systems are increasing. Degree of automation necessary for an individual manufacturing facility depends on manufacturing and assembly specifications, labor conditions and competitive pressure, labor cost and work requirements. One must remember that the investment on automation must be justified by the consequent increase in profitability. To exemplify, the appropriate contexts for Fixed and Flexible Automation are compared and contrasted.

Fixed automation is appropriate in the following circumstances. A. Low variability in product type as also in size, shape, part count and material B. Predictable and stable demand for 2- to 5-year time period, so that manufacturing capacity requirement is also stable C. High production volume desired per unit time D. Significant cost pressures due to competitive market conditions. So automation systems should be tuned to perform optimally for the particular product.

Flexible automation, on the other hand is used in the following situations. A. Significant variability in product type. Product mix requires a combination of different parts and products to be manufactured from the same production system B. Product life cycles are short. Frequent upgradation and design modifications alter production requirements C. Production volumes are moderate, and demand is not as predictable




Fig: 1.3 Three types of Automation relative to production quantity and product variety

3) Reasons for Automating:-Companies undertake projects in manufacturing automation and computer-integrated manufacturing for a variety of good reasons. Some of the reasons used to justify automation are the following:

1. To increase labor productivity 2. To reduce labor cost. 3. To mitigate the effects of labor shortages. 4. To reduce or eliminate routine manual and clerical tasks.

5. To improve worker safety. 6. To improve product quality. 7. To reduce manufacturing lead time..8. To accomplish processes that cannot be done manually. .9. To avoid the high cost of not automating.

4) Automation strategies1. Specialization of operations. 2. Combined operations. 3. Simultaneous operations 4. Integration of operations. 5. Improved material handling and storage..6. On-line inspection. 7. Process control and optimization. 8. Plant operations control. 9. Computer-integrated manufacturing (CIM). .




5) Methods of work part transport:

a) Continuous transfer:-Continuous transfer with the continuous method of transfer, the work parts are moved

continuously at constant speed. This requires the work heads to move during processing in order to maintain continuous registration with the work part.

b) Intermittent transfer:-As the name suggests, in this method the work pieces are transported with an intermittent

or discontinuous motion. The workstations are fixed in position and the parts are moved between stations and then registered at the proper locations for processing. All work parts are transported at the same time and, for this reason, the term ―synchronous transfer system‖ is also used to describe this method of work part transport. Examples of applications of the intermittent transfer of work parts can be found in machining operations, press working operations or progressivedies, and mechanized assembly. Most of the transfer mechanisms reviewed. Provide the intermittent or synchronous type of work part transport.

c) Asynchronous transfer:-This system of transfer, also referred to as a ―power-and-free system, allows each work

part to move to the next station when processing at the current station has been completed. Each part moves independently of other parts. Hence, some parts are being processed on the line at the same time that others are being transported between stations. Asynchronous transfer systems offer the opportunity for greater flexibility than do the other two systems, and this flexibility can be a great advantage in certain circumstances.

6) Transfer mechanismI) Linear transfer mechanisms:Walking beam systems:

Fig: 1.4 Walking Beam transfer system. Showing various stages during transfer cycle




Chain-drive conveyor systemFigure illustrates this type of transfer system. Either a chain or a flexible steel belt is used

to transport the work carriers. The chain is driven by pulleys in either an ―over-and-under‖ configuration, in which the pulleys turn about a horizontal axis, or an ―around-the-corner‖ configuration, in which the pulleys rotate about a vertical axis. This general type of transfer system can be used for continuous, intermittent, or non synchronous movement of work parts.

Fig:1.5 Chain - Driven Conveyor, “Over and under" type.

II) Rotary transfer mechanisms:-There are several methods used to index a circular table or dial at various equal angular

positions corresponding to workstation locations. Those described below are meant to be a representative rather than a complete listing.

Fig: 1.6 rack and pinion mechanism for rotary indexing table

Rack and Pinion: This mechanism is simple but is not considered especially suited to the high-speed operation often associated with indexing machines. The device is pictured in Figure and uses a piston to drive the rack, which causes the pinion gear and attached indexing table to rotate. A clutch or other device is used to provide rotation in the desired direction.




Ratchet and Pawl: This drive mechanism is shown in Figure. Its operation is simple but somewhat unreliable, owing to wear and sticking of several of the components.

Fig: 1.7 Ratchet - and -Pawl mechanism.

Geneva Mechanism: The two previous mechanisms convert a linear motion into a rotational motion. The Geneva mechanism uses a continuously rotating driver to index the table, as pictured in Figure. If the driven member has six slots for a six-station dial indexing machine, each turn of the driver will cause the table to advance one-sixth of a turn. The driver only causes movement of the table through a portion of its rotation. For a six-slotted driven member, 120° of a complete rotation of the driver is used to index the table. The other 240° is dwell. For a four- slotted driven member, the ratio would be 90° for index and 270° for dwell. The usual number of indexing per revolution of the table is four, five, six, and eight.

Fig: 1.8 Geneva mechanism.6) Buffer storage:-

A storage system can be used as a buffer storage zone between two processes whose production rates are significantly different. A simple example is a two-process sequence in which the first processing operation feeds a second process, which operates at a slower production rate. The first operation requires only one shift to meet production requirements, while the second step requires two shifts to produce the same number of units. An in-process buffer is needed between these operations to temporarily store the output of the first process.




7) Automated flow lines with storage buffers:-An automated flow line consists of several machines or workstations which are linked togetherby work handling devices that transfer parts between the stations. The objectives of the use of flow line automation are, therefore:

• To reduce labor costs• To increase production rates• To reduce work-in-process• To minimize distances moved between operations• To achieve specialization of operations• To achieve integration of operations

Fig: 1.9 Symbolic Representation




PA RT -B

Case study of any one local based industry having a fair amount of automationObjective- Company profile- Plant layout-Product specifications-Type of operation in industry- Advancement in industry- Find Out the Production Time, Ideal Cycle time along with Rate of production.Reasons for downtime etc.All the above parameter without automation and with automation.

Suggestion if any-Conclusion-




VIVA VOCE QUESTIONS

1. What is automation?2. Classify automation?3. List various transfer mechanisms?4. Explain various methods of work part transfer?5. Discuss different reasons for automation?6. What are different automation strategies?7. Define buffer storage?8. Compare upper bound and lower bound approach?9. Interpret line pacing?10. Summarize your understanding with relation to automated / manual flow lines?11. Identify various components of cycle time?12. What is hourly production rate?13. Discuss Uptime (E) and down time (D) of flow lines?14. How cost per piece is calculated?15. Outline various reasons for breakdown.16.




Experiment No. 02

Aim: Practice programming on manual part program.

Objective: To formulate part for lathe and milling using manual part program.

Theory-1. Introduction to Numerical control technique

Modern precision manufacturing demands extreme dimensional accuracy and surface finish. Such Performance is very difficult to achieve manually, if not impossible, even with expert operators. In cases where it is possible, it takes much higher time due to the need for frequent dimensional measurement to prevent overcutting. It is thus obvious that automated motion control would replace manual “handwheel” control in modern manufacturing. Development of computer numerically controlled (CNC) machines has also made possible the automation of the machining processes with flexibility to handle production of small to medium batch of parts. In the 1940s when the U.S. Air Force perceived the need to manufacture complex parts for highspeed aircraft. This led to the development of computer-based automatic machine tool controls also known as the Numerical Control (NC) systems. Commercial production of NC machine tools started around the fifties and sixties around the world. Note that at this time the microprocessor has not yet been invented.Initially, the CNC technology was applied on lathes, milling machines, etc. which could perform a single type of metal cutting operation. Later, attempt was made to handle a variety of workpieces that may require several different types machining operations and to finish them in a single set-up. Thus CNC machining Centres capable of performing multiple operation were developed. To start with, CNC machining centres were developed for machining prismatic components combining operations like milling, drilling, boring and tapping. Gradually machines for manufacturing cylindrical components, called turning centers were developed. Numerical Control Automatically controlling a machine tool based on a set pre-programmed machining and movement instructions is known as numerical control, or NC. In a typical NC system the motion and machining instructions and the related numerical data, together called a part program, used to be written on a punched tape. The part program is arranged in the form of blocks of information, each related to a particular operation in a sequence of operations needed for producing a mechanical component. The punched tape used to be read one block at a time. Each block contained, in a particular syntax, information needed for processing a particular machining instruction such as, the segment length, its cutting speed, feed, etc. These pieces of information were related to the final dimensions of the workpiece (length, width, and radii of circles) and the contour forms (linear, circular, or other) as per the drawing. Based on these dimensions, motion commands were given separately for each axis of motion. Other instructions and related machining parameters, such as cutting speed, feed rate, as well as auxiliary functions related to coolant flow, spindle speed, part clamping, are also provided in part programs depending on manufacturing specifications such as tolerance and surface finish. Punched tapes are mostly obsolete now, being replaced by magnetic disks and optical disks. NC




equipment has been defined by the Electronic Industries Association (E1A) as “A system in which actions are controlled by the direct insertion of numerical data at some point. The system must automatically interpret at least a portion of this data.” This is an old definition as is apparent from the terminology used in the definition Computer Numerically Controlled (CNC) machine tools, the modern versions of NC machines have an embedded system involving several microprocessors and related electronics as the Machine Control Unit (MCU). Initially, these were developed in the seventies in the US and Japan. However, they became much more popular in Japan than in the US. In CNC systems multiple microprocessors and programmable logic controllers work in parallel for simultaneous servo position and velocity control of several axes of a machine for contour cutting as well as monitoring of the cutting process and the machine tool. Thus, milling and boring machines can be fused into versatile machining centers. Similarly, turning centers can realize a fusion of various types of lathes. Over a period of time, several additional features were introduced, leading to increased machine utilisation and reduced operator intervention. Some of these are: (a) Tool/work monitoring: For enhanced quality, avoidance of breakdowns. (b) Automated tool magazine and palette management: For increased versatility and reduced operator intervention over long hours of operation (c) Direct numerical control (DNC): Uses a computer interface to upload and download part programs in to the machine automatically.

2. Advantages of a CNC Machine CNC machines offer the following advantages in manufacturing. • Higher flexibility: This is essentially because of programmability, programmed control and facilities for multiple operations in one machining centre, • Increased productivity: Due to low cycle time achieved through higher material removal rates and low set up times achieved by faster tool positioning, changing, automated material handling etc. • Improved quality: Due to accurate part dimensions and excellent surface finish that can be achieved due to precision motion control and improved thermal control by automatic control of coolant flow. • Reduced scrap rate: Use of Part programs that are developed using optimization procedures • Reliable and Safe operation: Advanced engineering practices for design and manufacturing, automated monitoring, improved maintenance and low human interaction • Smaller footprint: Due to the fact that several machines are fused into one. On the other hand, the main disadvantages of NC systems are • Relatively higher cost compared to manual versions • More complicated maintenance due to the complex nature of the technologies • Need for skilled part programmers. The above disadvantages indicate that CNC machines can be gainfully deployed only when the required product quality and average volume of production demand it.

3. Numerical control is a form of programmable automation in which the mechanical actions of a machine tool or other equipment are controlled by a program containing code and alphanumeric data. The alphanumerical data represent relative positions between a work head and




II work part as well as other instructions needed to operate the machine, The work head ie, a cutting tool or other processing apparatus, and the work part is the object being processed, When the current job is implanted. The program of instructions can be changed to process a new job.Numerical control can be applied to a wide variety of processes.

The applications divide into two categories; (1) machine tool applications, such as drilling, milling, turning, and other metal working; and (2) non machine tool applications such as assembly, drafting, and inspection. The common operating feature of NC in all of these applications is control of the work head movement relative to the work part.

3) Components of NC- a) Program of Instructions The program of instructions of the NC machine is the step-by-step set of instructions that tells the machines what it has to do. These instructions can tell the machine to turn the piece of metal to certain diameter, drill the hole of certain diameter up to certain length, form certain shape etc. The set of instructions are coded in numerical or symbolic form and written on certain medium that can be interpreted by the controller unit of the NC machine.

b) Controller Unit or Machine Controller Unit (MCU) The controller unit is most vital parts part of the NC and CNC machines. The control unit is made of the electronics components. It reads and interprets the program of instructions and converts them in the mechanical actions of the machine tool. Thus the controller unit forms an important link between the program and the machine tool. The control unit operates the machines as per the set of instructions given to it.

c) Machine Tool It is the machine tool that performs the actual machining operations. The machine too can be any machine like lathe, drilling machine, milling machine etc. The machine tool is the controlled part of the NC system. In case of the CNC machines, the microcomputer operates the machine as per the set of instructions or the program. The NC machine also have the control panel or control console that contains the dials and switches using which the operator runs the NC machine. There are also displays to display information to the user. Most of the modern NC machines are now called as the CNC machines.




Fig: 2.1 Basic component basic of an NC system.4 Classification of NC Systems: (Motion Control Systems) Some NC processes are performed at discrete locations on the work part (e.g., drilling and spot welding). Others are carried out while the work head is moving (e.g., turning and continuous arc welding). If the work head is moving, it may be required to follow a straight line path or a circular or other curvilinear path. These different types of movement are accomplished by the motion control system, whose features are explained below.

Motion control systems for NC can be divided into two types: (1) point-to-point

a. Point-to-point or contouring : depending on whether the machine cuts metal while the workpiece moves relative to the tool 2. Incremental or absolute : depending on the type of coordinate system adopted to parameterise the motion commands 3. Open-loop or closed-loop: depending on the control system adopted for axis motion control Point-to-point systems Point-to-point (PTP) systems are the ones where, either the work piece or the cutting tool is moved with respect to the other as stationary until it arrives at the desired position and then the cutting tool performs the required task with the motion axes stationary. Such systems are used, typically, to perform hole operations such as drilling, boring, reaming, tapping and punching. In a PTP system, the path of the cutting tool and its feed rate while traveling from one point to the next are not significant, since, the tool is not cutting while there is motion. Therefore, such systems require only control of only the final position of the tool. The path from the starting point to the final position need not be controlled. b. Contouring systems In contouring systems, the tool is cutting while the axes of motion are moving, such as in a milling machine. All axes of motion might move simultaneously, each at a different velocity. When a nonlinear path is required, the axial velocity changes, even within the segment. For example, cutting a circular contour requires sinusoidal rates of change in both axes. The motion controller is therefore required to synchronize the axes of motion to generate a predetermined path, generally a line or a circular arc. A contouring system needs capability of controlling its drive motors independently at various speeds as the tool moves towards the specified position. This involves simultaneous motion control of two or more axes, which requires separate position and velocity loops. It also requires an interpolator program that generates the position and velocity set points for the two drive axes, continuously along the contour.




In modern machines there is capability for programming machine axes, either as point-to-point or as continuous (that is contouring)

5) Coordinate system and machine motion The coordinate system is defined by the definition of the translational and rotational motion coordinates. Each translational axis of motion defines a direction in which the cutting tool moves relative to the work piece. The main three axes of motion are referred to as the X, Y. and Z axes. The Z axis is perpendicular to both X and Y in order to create a right-hand coordinate system, such as shown in Fig. 23.5. A positive motion in the Z direction moves the cutting tool away from the workpiece. The location of the origin is generally adjustible. Figure 23.4 shows the coordinate system for turning as in a lathe while Fig. 23.5 shows the system for drilling and milling. For a lathe, the infeed/radial axis is the x-axis, the carriage/length axis is the z-axis. There is no need for a y-axis because the tool moves in a plane through the rotational center of the work. Coordinates on the work piece shown below are relative to the work

.Fig: 2.2 coordinate systems used in NC: (a) for flat and Prismatic work and (b) Rotationalwork. (On most turning machines, the 2-axis is horizontal rather than vertical as we have shown it.)

Fig. 2.3 Co-ordinate system for turningIn drilling and milling machines the X and Y axes are horizontal. For example, a positive motion command in the drill moves the X axis from left to right, the Y axis from front to back, and the Z axis toward the top. In the lathe only two axes are required to command the motions of the tool. Since the spindle is horizontal, the Z axis is horizontal as well. The cross axis is denoted by X. A positive position command moves the Z axis from left to right and the X axis from back to front in




order to create the right-hand coordinate system.

Fig.2 .4 Co-ordinate system for drilling and milling

For a tool with a horizontal spindle the x-axis is across the table, the y-axis is down, and the zaxis is out. In addition to the translational motion, rotary motions around the axes parallel to X, Y, and Z can also be defined. Similarly, in addition to the primary motion coordinates, secondary coordinates can also exist. Incremental Systems In an incremental system the movements in each Part program block are expressed as the displacements along each coordinate axes with reference to the final position achieved at the end of executing the previous program block.

Fig. 2.5 A trajectory for drilling

Consider, for example, the trajectory of rectilinear motions shown in Fig. 2.5 for a PTP system. In an incremental system, the motion parameters, along the X-axis, for the segments, A-B, B-C, C-D, D-E, E-F and F-A, would be given as, 50, 20, 60, -30, -70 and –30, respectively. Absolute System: An absolute NC system is one in which all position coordinates are referred to one fixed origin called the zero point. The zero point may be defined at any suitable point within the limits of the machine tool table and can be redefined from time to time. Any particular definition of the zero point remains valid till another definition is made. In the Fig. 2.5 considering the X-coordinate for point A as zero, the X-coordinate for points B and C would be 50 and 70, respectively, in an absolute coordinate system. Most modem CNC systems permit application of both incremental and absolute programming methods. Even within a specific part program the method can be changed These CNC systems provide the user with the combined advantages of both methods




The control system software, which controls the axis motion, is called the axis manager. The axis manager controls the movement of the axes on the machine tool. This control may be divided into two distinct activities, namely, - Axes interpolation Axes servo control These two activities are executed by two specific routines, namely the interpolation and servo control routines, which communicate by means of a buffer for the exchange of data. The axis manager is processed by one or more dedicated CPUs. In a multi-processor architecture, the interpolation and the servo control can be split between the various CPUs according to different combinations, such as, - interpolation of all the axes on one CPU and servo control of all the axes on another CPU –

interpolation of all the axes on one CPU and servo control of part of the axes on the same CPU and servo control of the remaining axes on another CPU. Interpolation: Interpolation consists in the calculation of the coordinated movement of several axes using the programmed parameters, in order to obtain a resulting trajectory, which can be of various types, such as: - Straight line – Circular – Helicoidal The interpolation module computes instant by instant position commands for the servo module, which in turn, drives the motors. There are two types of interpolators, namely: - Process interpolator (for continuous axes) - Point-to-point interpolator (for point-to-point axes)

Servo Control Servo control consists of all the activities which allow several axes to effectively maintain the trajectory calculated by the interpolator. Continuous axes are continuously controlled by the system both for “speed” and for “position” so as to guarantee that the calculated trajectory is maintained. In contrast, for point-to-point axes there is no guarantee that the trajectory will be maintained. The only guarantee is that the final point will be reached.

Types of servo control for motion axes The axes controlled by the axis manager may be divided into various types according to the specific function they perform on the machine tool. Some of these types are described below.

Coordinated Axis: This is a working axis, which may be interpolated along with other axes of the same type. This is necessary for generating specific 2D or 3D contours. The movement of one of the axes can be taken as the master and the other axes slaved to it. The mechanical and electrical features of the slave axis must be identical to those of the master. A coordinated axis can also be rotary and programmed in degrees. Note that for rotary axes, it may or may not be needed to map angular displacements to a (0-2π) interval.

Point-to-point Axis: This axis is not required to be interpolated with others, since it is used for only for positioning from one point to another. Such an axis may be viewed as an independent mechanical component fitted with a positioning transducer.




Spindle Axis: There are two types of spindle axes. For some, only the speed of the axis need to be controlled and not the position by the spindle servo control system. Such an axis essentially realizes a “motorized” tool. For the second type, the speed of this spindle axis, as well as its angular position can be controlled. This has application in controlling threading processes. It is also possible to drive the spindle in coordinated motion, interpolated with the other axes. This uses the spindle transducer value as the set point for the other axes. A typical example is the C axis in lathes. One can command a controlled acceleration ramp for the spindle rotation command. However, for improved angular positioning, this must be eliminated. It is also possible to have spindle drives without servo control, generally for spindles driven with ac motors. The only control needed in such a case is for reversal of spindle rotation.

For control of tool and workpiece motion in the various ways described above, one of two kinds of control systems is employed.

Open Loop Systems: The term open-loop means that there is no feedback, and in open loop systems the motion controller produces outputs depending only on its set points, without feedback information about the effect that the output produces on the motion axes. We have already seen that the effects of controller outputs on the plant may not be the same always, since it depends on factors such as loads, parameter variations in the plant etc. In open loop systems, the set points are computed from the instructions in the Part program and fed to the controller, which may reside in a different microprocessor, through an interface. These motion commands may be in the form of electrical pulses (typical for step motor drives) or analog or digital signals, and converted to speed or current set points by the controller. These set points, in turn, are sent to the power electronic drive system that applies the necessary voltage/current to the motors. The primary drawback of open-loop system is that there is no feedback system to check whether the commanded position and velocity has been achieved. If the system performance is affected by load, temperature or friction then the actual output could deviate from the desired output. For these reasons, the open-loop system is generally used in point-to-point systems where the accuracy requirements are not critical. Contouring systems do not use open-loop control.

Closed Loop systems: Closed-loop control, as described in the module on controllers, continuously senses the actual position and velocity of the axis, using digital sensors such as encoders or analog sensors such resolvers and tacho generators and compares them with the setpoints. The difference between the actual value of the variable and its set point is the error. The control law takes the error as the input and drives the actuator, in this case the servo motor and its drive system, to achieve motion variables that are close to the set points. As we know, closed loop systems can achieve much closer tracking of set points even with disturbances and parameter variations in the system with, say, with temperature. Closed-looped systems, on the other hand, require more complex control as well as feedback devices and circuitry in order for them to implement both position and velocity control. Most modern closed-loop CNC systems are able to provide very close resolution of 0.0001 of an inch.



Final Year SEM-VIII SUBJECT: Automation in production

Part Programming: A part program is a set of instructions often referred to as blocks, each of which refers to a segment of the machining operation performed by the machine tool. Each block may contain several code words in sequence. These provide:

1. Coordinate values (X, Y, Z, etc.) to specify the desired motion of a tool relative to a work piece. The coordinate values are specified within motion codeword and related interpolation parameters to indicate the type of motion required (e.g. point-to-point, or continuous straight or continuous circular) between the start and end coordinates. The CNC system computes the instantaneous motion command signals from these code words and applies them to drive units of the machine.

2. Machining parameters such as, feed rate, spindle speed, tool number, tool offset compensation parameters etc.

3. Codes for initiating machine tool functions like starting and stopping of the spindle, on/off control of coolant flow and optional stop. In addition to these coded functions, spindle speeds, feeds and the required tool numbers to perform machining in a desired sequence are also given. 4. Program execution control codes, such as block skip or end of block codes, block number etc. 5. Statements for configuring the subsystems on the machine tool such as programming the axes, configuring the data acquisition system etc. A typical block of a Part program is shown below in Fig. 2.6. Note that the block contains a variety of code words such G codes, M codes etc. Each of these code words configure a particular aspect of the machine, to be used during the machining of the particular segment that the block programmes.

Fig. 2.6 Structure of a block in a part program

Appendix-1 provides some details of these codes. A typical sequence of operations in a




part program would be, A. Introductory functions such as units, coordinate definitions, coordinate conventions, such as, absolute or relative etc. B. Feeds, speeds, etc. C. Coolants, doors, etc. D. Cutting tool movements and tool changes E. Shutdown




Appendix-1In this appendix we provide a list of G and M-codes for the reader to have an idea of the kind of functionality that can be realized using these codes. These codes were originally designed to be read from paper tapes and are designed to direct tool motion with simple commands. A basic list of ‘G’ operation codes is given below. These direct motion of the tool. G00 - Rapid move (not cutting) G01 - Linear move G02 - Clockwise circular motion G03 - Counterclockwise circular motion G04 - Dwell G05 - Pause (for operator intervention) G08 - Acceleration G09 - Deceleration G17 - x-y plane for circular interpolation G18 - z-x plane for circular interpolation G19 - y-z plane for circular interpolation G20 - turning cycle or inch data specification G21 - thread cutting cycle or metric data specification G24 - face turning cycle G25 - wait for input to go low G26 - wait for input to go high G28 - return to reference point G29 - return from reference point G31 - Stop on input G33-35 - thread cutting functions G35 - wait for input to go low G36 - wait for input to go high G40 - cutter compensation cancel G41 - cutter compensation to the left G42 - cutter compensation to the right G43 - tool length compensation, positive G44 - tool length compensation, negative G50 - Preset position G70 - set inch based units or finishing cycle G71 - set metric units or stock removal G72 - indicate finishing cycle G72 - 3D circular interpolation clockwise




G73 - turning cycle contour G73 - 3D circular interpolation counter clockwise G74 - facing cycle contour G74.1 - disable 360 deg arcs G75 - pattern repeating G75.1 - enable 360 degree arcs G76 - deep hole drilling, cut cycle in z-axis G77 - cut-in cycle in x-axisG78 - multiple threading cycle G80 - fixed cycle cancel G81-89 - fixed cycles specified by machine tool manufacturers G81 - drilling cycle G82 - straight drilling cycle with dwell G83 - drilling cycle G83 - peck drilling cycle G84 - taping cycle G85 - reaming cycle G85 - boring cycle G86 - boring with spindle off and dwell cycle G89 - boring cycle with dwell G90 - absolute dimension program G91 - incremental dimensions G92 - Spindle speed limit G93 - Coordinate system setting G94 - Feed rate in ipm G95 - Feed rate in ipr G96 - Surface cutting speed G97 - Rotational speed rpm G98 - withdraw the tool to the starting point or feed per minute G99 - withdraw the tool to a safe plane or feed per revolution G101 - Spline interpolation




M-Codes control machine functions. M00 - program stop M01 - optional stop using stop button M02 - end of program M03 - spindle on CW M04 - spindle on CCW M05 - spindle off M06 - tool change M07 - flood with coolant M08 - mist with coolant M08 - turn on accessory (e.g. AC power outlet) M09 - coolant off M09 - turn off accessory M10 - turn on accessory M11 - turn off accessory or tool change M17 - subroutine end M20 - tailstock back M20 - Chain to next program M21 - tailstock forward M22 - Write current position to data file M25 - open chuck M25 - set output #1 off M26 - close chuck M26 - set output #1 onM30 - end of tape (rewind) M35 - set output #2 off M36 - set output #2 on M38 - put stepper motors on low power standby M47 - restart a program continuously, or a fixed number of times M71 - puff blowing on M72 - puff blowing off M96 - compensate for rounded external curves M97 - compensate for sharp external curves M98 - subprogram call M99 - return from subprogram, jump instruction M101 - move x-axis home M102 - move y-axis home M103 - move z-axis home




Appendix-2Typical Specifications of a CNC System

1. Number of controlled axes : Two/Four/Eight, etc. 2. Interpolation : Linear/circular/parabolic or cubic/cylindrical 3. Resolution : Input resolution (feedback)

Programming resolution 4. Feed rate : Feed/min : Feed/revolution 5. Rapid traverse rate : Feed rate override : Feed/min 6. Operating modes : Manual/Automatic/MDI(editing)/Input/Output/

Machine data set-up/Incremental, etc. 7. Type of feedback : Digital (rotary encoders with train of pulses).

Analog (transducers, etc.). Both

8. Part program handling : Number of characters which can be stored. Part program input devices. Output devices.Editing of part program

9. Part programming : Through MDI.Graphic simulation.Blue print programming.Background editing.Menu driven programming. Conversational programming.

10. Compensations : Backlash Lead screw pitch error Temperature Cutter radius compensation Tool length compensation

11. Programmable logic controller : Built-in (integrated)/External : Type of communication with NC Number of inputs, outputs, timers, counters and flags User memory Program organization Programming Languages

12. Thread cutting/Tapping : Types of threads that can be cut 13. Spindle control : Analog/Digital control

Spindle orientationSpindle speed overrides RPM/min; constant surface speed




14. Other features : Inch/metric switchover Polar coordinate inputs Mirror imaging Scaling Coordinate rotation system Custom macros Built-in fixed cycles Background communicationSafe zone programming Built-in diagnostics, safety function, etc. Number of universal interfacesNumber of active serial interfacesDirect numerical control interface Network interface capability




Experiment No. 03

Ai m : Performance on CNC lathe.

O b j e c tiv e : To design part program and perform actual working on

CNC Lathe.

Example 1.

Simple CNC Programming Example

N01 G91 G71 G94 M03 S800 T01 F200;N05 G00 X65 Z2;N10 G01 X0 Z0;N15 G01X20; N20 G01 Z-10;N25 G01 X40;N30 G01 Z-20;N35 G01 X60; N40 G01 Z-30;N45 G00 X65; N55 G00 Z2;N60 M02;







Example 2

N5 G00 X0 Z2;N10 R3 1 N10 G01 Z0.F0.25N15 X24;N20 X30 Z-3; N25 Z-22;N30 G02 X36 Z-25 R3 ; N35 G01 X50;N40 G03 X61 592 Z-29.447 R6; N45 G01 X70 Z-45;N50 Z-55;N60 G02 X80 Z-60 R5; N65 G01 X94;N70 G03 X100 Z-63 R3; N75 G00 X105;N80 G00 Z2; N85 M02;




Example 3 At the bottom of grooves a dwell of one second is to be programmed.

N05 G91 G71 G94 M03 S800 T01 F200; N10 G00 X65 Z2;N15 G01 X0 Z0; N20 G00 X45N25 G01 Z-15 ;N30 G01 X30 F0.2 ;N35 G04 X1 ; (Dwell of 1 second) N40 G00 X45;N45 G01 Z-25 ; N50 G01 X30 ;N55 G04 X1 ; (Dwell of 1 second) N60 G00 X45;N65 G01 Z-35; N70 G01 X60; N75 G01 Z-50; N80 G00 X65; N85 G00 Z2; N90 M02;




Example 4 Stock Removal Cycle

N10 G28 U0 W0; G50 S2000; T0101;G96 S180 M03G00 X100 Z5 M08Z0.5 X0 F0.2G01 Z0G71 P11 Q12 U0.25 W0.2 D1000 F0.2;

N11 G00 X0;G42 G01 Z0.5 F0.2; G01 X25;G01 X30 Z-10; G01 X60;G01 X100 Z-15; G00 X110G00 Z2

N12 G70 P11 Q12; G00 U5 Z5 M09; G40 M05;

N20 G28 U0 W0; M30;







Example 6

Fig: Simple CNC Programming Example

N10 T0101;N20 G91 S500 M03; N30 G00 X65 Z2; N40 G01 X0 Y0; N50 G01 X25 F0.2; N60 G01 Z-7.5;N70 G01 X40 Z-15; N80 G01 Z-25;N90 G01 X60 Z-35; N100 G00 X65;N110 G00 Z2; N120 M30;




Example 7 Lathe CNC Programming Example

Fig: Lathe CNC Programming Example

N10 G91 S500 M03; N20 G00 X25 Z5; N30 G01 G95 Z0 F1; N40 G01 Z-7.5 F0.2; N50 G01 X60 Z-35; N60 G01 Z-50;N70 G00 X62; N80 G00 Z2; N90 M30;




Example 8 - Chamfer and Radius Program Example

Fig: Chamfer and Radius Program Example

N10 G91 G71 G94 M03 S800 T01 F200; N20 G00 X90 Z2;N30 G01 X0 Z0; N40 G01 X26 Z-20; N50 G02 X32 Z-26 R6; N60 G01 X86;N70 G01 X86 Z-26 C3; N70 G01 Z-53;N80 G00 X90; N90 G00 Z2; N100 M30;

Resu lt – Performed the job on CNC Lathe.







Experiment No. 04

Ai m : Programming for CNC Mill.

O b j e c tiv e : To design part program and perform actual working on CNC Mill.

Example 01Write the part program to drill the holes in the part shown in Figure 1 The part is 12.0 mm thick. Cutting speed = 100 m/min and feed = 0.06 mm/rev. Use the lower left corner of the part as the origin in the x-y axis system. Write the part program in the word address format using absolute positioning

40100

125160

200225

2540

60

100

125

10 dia., 6 holes

P0

P1

P2 P3 P4

P5P6

Solution: At the beginning of the job, the drill point will be positioned at a target point located at x = 0, y = 0, and z = + 10. The program begins with the tool positioned at this target point. Feed is given as 0.06 mm/rev. Rotational speed of drill is calculated as follows:

N = = 3183 rev/min




NC part program code N001 G21 G90 G92 X0 Y0 Z010.0;N002 G00 X040.0 Y025.0;N003 G01 G95 Z-20.0 F0.06 S3183 M03;N004 G01 Z010.0;N005 G00 Y100.0;N006 G01 G95 Z-20.0 F0.06;N007 G01 Z010.0;N008 G00 X100.0;N009 G01 G95 Z-20.0 F0.06;N010 G01 Z010.0;N011 G00 X160.0;N012 G01 G95 Z-20.0 F0.06;N013 G01 Z010.0;N014 G00 X125.0 Y060.0;N015 G01 G95 Z-20.0 F0.06;N016 G01 Z010.0;N017 G00 X200.0 Y040.0;N018 G01 G95 Z-20.0 F0.06;N019 G01 Z010.0;N020 G00 X0 Y0 M05;N021 M30;

Comments Define origin of axes.Rapid move to first hole location.Drill first hole.Retract drill from hole.Rapid move to second hole location.Drill second hole.Retract drill from hole.Rapid move to third hole location.Drill third hole.Retract drill from hole.Rapid move to fourth hole location.Drill fourth hole.Retract drill from hole.Rapid move to fifth hole location.Drill fifth hole.Retract drill from hole.Rapid move to sixth hole location.Drill sixth hole.Retract drill from hole.Rapid move to target point, stop spindle rotation.End of program, stop machine.




Example 02The part in Figure 2 is to be drilled on a turret-type drill press. The part is 15.0 mm thick. There are three drill sizes to be used: 8 mm, 10 mm, and 12 mm. These drills are to be specified in the part program by tool turret positions T01, T02, and T03. All tooling is high speed steel. Cutting speed = 75 mm/min and feed = 0.08 mm/rev. Use the lower left corner of the part as the origin in the x-y axis system. Write the part program in the word address format using absolute positioning.

25

5075

100

25

7550

100150

175200

25125

25 rad.

12 dia., 1 hole

10 dia., 2 holes

8 dia., 3 holes

P0

P1 P2 P3

P4P5

P6

Solution: At the beginning of the job, the drill point will be positioned at a target point located at x = 0, y = 0, and z = + 10. The program begins with the tool positioned at this target point. Feed is given as 0.08 mm/rev. Rotational speeds for the three drill diameters are calculated as follows:For the 8 mm drill, N = 75/(8 x 10-3) = 2984 rev/minFor the 10 mm drill, N = 75/(10 x 10-3) = 2387 rev/minFor the12 mm drill, N = 75/(12 x 10-3) = 1989 rev/min




NC part program code N001 G21 G90 G92 X0 Y0 Z010.0;N002 G00 X025.0 Y025.0 T01;N003 G01 G95 Z-20.0 F0.08 S2984 M03;N004 G01 Z010.0;N005 G00 X150.0;N006 G01 G95 Z-20.0 F0.08;N007 G01 Z010.0;N008 G00 X175.0;N009 G01 G95 Z-20.0 F0.08;N010 G01 Z010.0;N011 G00 X100.0 Y075.0 T02;N012 G01 G95 Z-20.0 F0.08;N013 G01 Z010.0;N014 G00 X050.0;N015 G01 G95 Z-20.0 F0.08;N016 G01 Z010.0;N017 G00 X050.0 Y075.0 T03;N018 G01 G95 Z-22.0 F0.08;N019 G01 Z010.0;N020 G00 X0 Y0 M05;N021 M30;

Comments Define origin of axes.Rapid move to first hole location, select 8 mm drill.Drill first hole.Retract drill from hole.Rapid move to second hole location.Drill second hole.Retract drill from hole.Rapid move to third hole location.Drill third hole.Retract drill from hole.Rapid move to fourth hole location, select 10 mm drill.Drill fourth hole.Retract drill from hole.Rapid move to fifth hole location.Drill fifth hole.Retract drill from hole.Rapid move to sixth hole location, select 12 mm drill.Drill sixth hole.Retract drill from hole.Rapid move to target point, stop spindle rotation.End of program, stop machine.




Example 03The outline of the part in Figure 3 is to be profile milled, using a 20 mm diameter end mill with two teeth. The part is 10 mm thick. Cutting speed = 125 mm/min and feed = 0.10 mm/tooth. Use the lower left corner of the part as the origin in the x-y axis system. The two holes in the part have already been drilled and will be used for clamping the part during milling. Write the part program in the word address format with TAB separation and variable word order. Use absolute positioning.

10 dia., 2 holes

2575

150

30 rad.

50

25

75

125

35 deg.P0

L7

L1P1

L3P2L4C1

L5P3

L6P4

Solution: As stated, the two holes will be used to clamp the workpart during milling. The part will be fixtured so that its top surface is 40 mm above the surface of the machine tool table, and the x-y plane of the axis system will be defined 40 mm above the table surface. As given, a 20 mm diameter end mill with two teeth will be used. The cutter is assumed to have a side tooth engagement length of 30 mm. Throughout the machining sequence the bottom tip of the cutter will be positioned 20 mm below the part top surface, which corresponds to z = -20 mm. Since the part is 10 mm thick, this z position will allow the side cutting edges of the milling cutter to cut the full thickness of the part during profile milling. Cutting speed is specified as 125 m/min. Rotational speed of the cutter is calculated as N = 125/(20 x 10-3) = 1989 rev/min. Given a feed = 0.10 mm/tooth, feed rate is calculated as 1989(2)(0.10) = 398 mm/min. Cutter diameter data has been manually entered into offset register 05. At the beginning of the job, the cutter will be positioned so that its center tip is at a target point located at x = -50, y = -50, and z = + 10. The program begins with the tool positioned at this location.




NC part program code N001 G21 G90 G92 X-050.0 Y-050.0 Z010.0;N002 G00 Z-020.0 S1989 M03;N003 G01 G94 G42 Y0 D05 F398;N004 G01 X075.0;N005 G01 X150.0 Y043.02;N006 G01 Y070.0;N007 G01 X080.0;N008 G17 G02 X050.0 Y100.0 R030.0;N009 G01 Y125.0;N010 G01 X0;N011 G01 Y0N012 G40 G00 X-050.0 Y-050.0 Z010.0 M05;N013 M30;

Comments Define origin of axes.Rapid to cutter depth, turn spindle on.Bring tool to starting y-value, start cutter offset.Mill lower horizontal edge of part.Mill angled edge at 35 degrees.Mill vertical edge at right of part.Mill horizontal edge leading to arc.Circular interpolation around arc.Mill vertical step above arc.Mill top part edge.Mill vertical edge at left of part.Rapid move to target point, cancel offset, spindle stop.End of program, stop machine.




Experiment No. 5

Aim: Practice programming on APT.

O b j e c tiv e : Programming with automatically programmed tools

Th eory:

APT language statement:-

APT stands for Automatically Programmed Tool. It is a language that defines the tool path with respect to the part geometry, and often forms the basis for post-processor generated NC files. The APT language consists of four types of statements. Geometry statements will be used to specify the elemental features defining the part shape. Motion statements are used to specify the path taken by the tool. Post-processor statements control the machinery, controlling coolants as well as the feeds and speeds. Auxiliary statements complete the picture, specifying the part, required tools, etc. The following sections describe each of the APT statements.

Geometry Statements All geometric elements must be defined before tool motion may be programmed. Geometry statements associate a symbol with a description of the geometric element and its parameters. The general form for a geometry statement is:

symbol = geometric type/parametric descriptionThe symbol consists of up to six alpha-numeric characters, containing at least one alpha character, and avoiding APT reserved words. The symbols provide a means to name the geometric features. The equals sign separates the symbol from the geometric type. The geometric type describes these features. POINT, LINE, PLANE, and CIRCLE are valid APT geometric types. The forward slash character separates the geometric type from the parametric description of the feature. The parametric description specifies the location and size of the feature. It may include dimensional data, positional data, and other APT words relating the feature to previously defined APT symbols. The APT language provides a rich means to specify the geometry, as is evidenced by the following examples. To specify a point:

P0 = POINT/1.0, 1.2, 1.3 specifies a point at XYZ coordinates 1.0, 1.2, and 1.3, respectively.

P1 = POINT/INTOF L1, L2 specifies a point at the intersection of lines L1 and L2, which must have been defined prior to the statement.

P2 = POINT/YLARGE, INTOF, L3, C1 specifies a point at the intersection of line L3 and circle C1 at a Y position above the center point of the circle.




To specify a line:

L1 = LINE/P0, P1 specifies a line by two points, previously defined. L1 = LINE/1.0, 1.2, 1.3, 2.0, 2.1, 2.3 specifies a line by two points, given as explicit

coordinates. L2 = LINE/P2, PARLEL, L1 specifies a line through point P2 and parallel to line

L1. L3 = LINE/P1, RIGHT, TANTO, C1 specifies a line through point P1 and tangent to circle

C1 on the right side of the center point. L4 = LINE/P1, ATANGL, 45, L1 specifies a line through point P1 at an angle of 45o to

line L1.

To specify a plane: PL0 = PLANE/P0, P1, P2 specifies a plane through three, non-colinear,

previously defined points. PL1 = PLANE/P3, PARLEL, PL0 specifies a plane through a point P3 parallel to a plane

PL0.

To specify a circle: C0 = CIRCLE/CENTER, P0, RADIUS, 1.0 specifies a circle of radius 1 from a center point of

P0. Lines and planes extend infinitely. Circles are always complete. The same geometry may be defined

only once, and may not have more than one symbol.

Motion Statements The format for motion commands follows the pattern:

motion/descriptionThe initial motion starts from a home position, and takes the form:

FROM/P0 or FROM/ 0.0, 1.0, 2.0The FROM motion statement occurs only once for each set of a motion type, at the start of the set of motions. Contouring motion – is the most common motion used in APT programming, and these statements specify the tool path continuously throughout the motion. They make use of three surfaces: (a) drive; (b) check; and (c) part surfaces. Drive surfaces represent the surface along which the vertical edges of the tool will follow. Part surfaces specify the surfaces the tip of the tool will follow. And check surfaces describe where the tool will come to rest after it has completed the motion of the current step. There are four locations for the tool to stop with respect to a check surface. These four possibilities each have their own modifier words.




The TO modifier stops the tool when the first surface of the tool would come into contact with the check surface. The ON modifier stops the tool where the center point of the tool would come into contact with the check surface. The PAST modifier stops the tool where the last surface of the tool would contact the check surface. And the TANTO modifier stops the tool at the point of circular tangency with the edge of the tool.

The initial contouring motion statement is the GO/TO, which defines the initial drive, part and check surfaces. It takes the form:

GO/TO, drive surface, TO, part surface, TO, check surface An example would be: GO/TO, L1, TO, PL1, TO, L2 specifying that the tool should use line L1 as the drive surface, plane P1 as the part surface, and line L2 as the check surface.

Note: the GOTO and the GO/TO statements are not the same. The former specifies point to point motion (see below), and the latter initiates contouring motion. Continuing contouring motion statements are given from the vantage point of a person sitting on the top of the tool. The motion words are: (a) GOLFT; (b) GORGT; (c) GOFWD; (d) GOBACK; (e) GOUP; and (f) GODOWN. The sense of these words depends on the direction the tool has

been coming from, and is depicted in Figure 5.1

Fig. 5.1Point to point motion – may be specified as absolute, or as incremental (relative to the last point visited). An example of absolute, point to point motion is:

GOTO/P0An example of incremental, point to point motion is:

GODLTA/1.0, 2.0, 3.0Point to point motion is useful in peck drilling or similar operations, since the motion path in-between the points is unimportant.




The instruction for the tool to move forward, with the drive surface, S1, on the left hand side, and past the check surface, S2, is given by the statement:

GOLFT/S1, PAST, S2.

Post-Processor Statements These statements provide processing parameters to the post-processor program. Typical programs will require parameters for feeds, speed, and other tool/spindle/machine controls. Examples: SPINDL/600 specifies the spindle to be 600 rpm. FEDRAT/6.0 specifies a feed rate of 6 inches per minute. TURRET/T2 specifies loading tool # 2 in the turret. A final post-processor statement must specify to the post-processor program what type of machine is intended for the final NC code and the specific controller to generate the code for. An example is: MACHIN/MILL, 2 specifies a mill machine type, and controller type 2 COOLNT/ON speicifies the coolant on statement:

Auxiliary Statements These statements complete the APT programming language, and include the FINI statement to mark the end of the program as well as statements to define the width of the tool. An example of the latter is: CUTTER/0.25 specifies a quarter-inch cutter diameter. The computer would then know to calculate a 0.125 inch offset to accommodate the cutter diameter in computing the center of the tool.APT words used in auxiliary statements:

CLPRNT INTOL/ CUTTER OUTTOL/ FINI PARTNO




APT PROGRAMS Example 1:

AP T Pro g ra m Li st ing

PARTNO EXAMPLE labels the program ―EXAMPLE‖ MACHIN/MILL, 1 selects the target machine and controller type CUTTER/0.5000 specifies the cutter diameterP0 = POINT/0, -1.0, 0P1 = POINT/0, 0, 0P2 = POINT/6.0, 0, 0P3 = POINT/6.0, 1.0, 0P4 = POINT/2.0, 4.0, 0 geometry statements to specify theL1 = LINE/P1, P2 pertinent surfaces of the partC1 = CIRCLE/CENTER, P3, RADIUS, 1.0L2 = LINE/P4, LEFT, TANTO, C1L3 = LINE/P1, P4PL1 = PLANE/P1, P2, P3SPINDL/573 sets the spindle speed to 573 rpm FEDRAT/5.39 sets the feed rate to 5.39 ipm COOLNT/ON turns the coolant onFROM/P0 gives the starting position for the toolGO/PAST, L3, TO, PL1, TO, L1 initializes contouring motion; drive, part, and check surfacesGOUP/L3, PAST, L2GORGT/L2, TANTO, C1 motion statements to contour the partGOFWD/C1, ON, P2 in a clockwise directionGOFWD/L1, PAST, L3RAPID move rapidly once cutting is done GOTO/P0 return to the tool home position COOLNT/OFF turn the coolant offFINI end program




Example 02

Write the complete APT part program to perform the drilling operations for the part drawing in Figure 4.2. Cutting speed = 0.4 m/s, feed = 0.10 mm/rev., and table travel speed between holes = 500 mm/min. Postprocessor call statement is MACHIN/DRILL, 04.

Solution: Points are defined 10 mm above part surface for convenience in subsequent drilling.

Spindle speed N = 0.4(60)/(10 x 10-3) = 764 rev/min. See drawing in previous solution.

40100

125160

200225

2540

60

100

125

10 dia., 6 holes

P0

P1

P2 P3 P4

P5P6

PARTNO PART P6.6 DRILLINGMACHIN/ MACHIN/DRILL, 04CLPRNTUNITS/MMREMARK Part geometry. Points are defined 10 mm above part surface.P0 = POINT/0, 0, 10.0P1 = POINT/40.0, 25.0, 10.0P2 = POINT/40.0, 100.0, 10.0P3 = POINT/100.0, 100.0, 10.0P4 = POINT/160.0, 100.0, 10.0P5 = POINT/200.0, 40.0, 10.0P6 = POINT/125.0, 60.0, 10.0REMARK Drill bit motion statements. Rapid traverse speed (RAPID) set at 500 mm/minFROM/P0RAPIDGOTO/P1SPINDL/764, CLWFEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P2SPINDL/764, CLWFEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P3SPINDL/764, CLW




FEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P4SPINDL/764, CLWFEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P5SPINDL/764, CLWFEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P6SPINDL/764, CLWFEDRAT/0.10, IPRGODLTA/0, 0, -30GODLTA/0, 0, 30RAPIDGOTO/P0SPINDL/OFFFINI




Example 03

Write the complete APT part program to profile mill the outside edges of the part in Figure 4.3. The part is 15 mm thick. Tooling = 30 mm diameter end mill with four teeth, cutting speed = 150 mm/min, and feed = 0.085 mm/tooth. Use the lower left corner of the part as the origin in the x-y axis system. Two of the holes in the part have already been drilled and will be used for clamping the part during profile milling. Postprocessor call statement is MACHIN/MILL, 06.

25

5075

100

25

7550

100150

175200

25125

25 rad.

12 dia., 1 hole

10 dia., 2 holes

8 dia., 3 holes

P0P1

L2L1

P2L3C1

L4P3L5

P4L6

P5

L7 P6 P7P8

P9P10

P11

Fig 4.3

Solution: Spindle speed N = 150/(30 x 10-3) = 1592 rev/min. Feed rate fr = 1592(4)(0.085) = 541 mm/min.




PARTNO PART P6.7 PROFILE MILLINGMACHIN/ MACHIN/MILL, 06CLPRNTUNITS/MMINTOL/0.01CUTTER/30.0REMARK Points are defined 25 mm below part upper surface to provide full engagement of cutter.PTARG = POINT/-20.0, -30.0, -25.0P0 = POINT/0, 0, -25.0P1 = POINT/200.0, 0, -25.0P2 = POINT/200.0, 50.0, -25.0P3 = POINT/125.0, 100.0, -25.0P4 = POINT/25.0, 100.0, -25.0P5 = POINT/0, 50.0, -25.0L1 = LINE/P0, P1L2 = LINE/P1, P2L3 = LINE/P2, PARLEL, L1L4 = LINE/P3, PERPTO, L3L5 = LINE/P3, P4L6 = LINE/P4, P5L7 = LINE/P0, P5C1 = CIRCLE/XLARGE, L4, YLARGE, L3, RADIUS, 25.0PL1 = PLANE/P0, P1, P3FROM/PTARGSPINDL/1592, CLWFEDRAT/541, IPMGO/TO, L1, TO, PL1, TO, L7GORGT/L1, PAST, L2GOLFT/L2, PAST, L3GOLFT/L3, TANTO, C1GOFWD/C1, TO, L4GOFWD/L4, PAST, L5GOLFT/L5, PAST, L6GOLFT/L6, PAST, L7GOFWD, L7, PAST, L1GOTO/PTARGSPINDL/OFFFINI




Example 04Mill the shown shape

Fig:4.5 Apt Sample Part 2

Feed = 50 mm/min., Speed = 1000 rev/min., Cutter diam. = 20 mm.

PARTNO SAMPLE PART MILLING OPERATION MACHIN/MILLING, 02CLPRNT UNITS/MM CUTTER/20.0REMARK Part geometry, Points and Lines are defined 25 mm Bblow part top surface.PTARG = POINT/0, -50.0, 10.0P1 = POINT/0, 0, -25.0P2 = POINT/160.0, 0, -25.0P3 = POINT/160.0, 60.0, -25.0P4 = POINT/35.0, 90.0, -25.0P8 = POINT/130.0, 60.0, -25.0L1 = LINE/P1, P2L2 = LINE/P2, P3C1 = CIRCLE/CENTER, P8, RADIUS, 30.0L3 = LINE/P4, LEFT, TANTO, C1L4 = LINE/P4, P1PL1 = PLANE/P1, P2, P4REMARK milling cutter motion statements.FROM/PTARGSPINDL/1000, CLW FEEDRAT/50, IPMGO/TO, L1, TO, PL1, ON, L4GORGT/L1, PAST, L2GOLFT/L2, TANTO, C1GOFWD/C1, PAST, L3




GOFWD/L3, PAST, L4GOLFT/L4, PAST, L1RAPIDGOTO/PTARG SPINDL/OFF FINI




Example 06

Fig: 4.6

PARTNO N/C 360 APT SAMPLE PART PROGRAM SP = POINT/ 0, 0, 0L1 = LINE/ 4, 0, 0, 4, 8, 0PT = POINT/ 4.0, 8.0, 0L2 = LINE/ PT, ATANGL, 45L3 = LINE/ 8, 12, 0, 12, 12, 0L4 = LINE/ 14, 5, 0, 14, 10, 0L5 = LINE/ 0, 2, 0, 10, 2, 0C1 = CIRCLE/ 12, 10, 0, 2.0C2 = CIRCLE/ 14, 2, 0, 3.0INTOL/ 0OUTTOL/ .005CUTTER/ .25SPINDL/ 2000, CLW COOLNT/ ON FEDRAT/ 20.0FROM/ SP GO/ TO, L1TLLFT, GOLFT/ L1, PAST, L2GORGT/ L2, PAST, L3GORGT/ L3, TANTO, C1GOFWD/ C1, TANTO, L4GOFWD/ L4, PAST, C2GORGT/ C2, PAST, L5GORGT/ L5, PAST, L1GOTO/ SP COOLNT/ OFF SPINDL/ OFF FINIRE S UL T :- Practice programming on APT has been studied.




Experiment No. 06

Aim: Introduction to Robotics.

O b j e c tiv e : To learn about basics of robotics

Th eory:

An important part of the automation scene is the area of “Robotics” a multidisciplinary field that involves mechanical, electronics and several other engineering disciplines. An industrial robot is a general-purpose, programmable machine possessing certain anthropomorphic characteristics. The most obvious anthropomorphic characteristic of an industrialrobot is its mechanical arm, that is used to perform various industrial tasks. Other human- like characteristics arc the robot's capability to respond to sensory inputs, communicate with other machines, and make decisions. These capabilities permit robots to perform a variety of useful tasks.Reasons for the commercial and technological importance of industrial robots include the following:• Robots can be substituted for humans in hazardous or uncomfortable work environments.• A robot performs its work cycle with a consistency and repeatability that cannot be attained by humans.• Robots can be reprogrammed. When the production run of the current task is completed, a robot can be reprogrammed and equipped with the necessary tooling to perform an altogether different task.• Robots are controlled by computers and can therefore be connected to other computer systems to achieve computer integrated manufacturing.

History of robots: 1954- Devol & Engleburger – establish Unimation Incorporation. 1961- Robots are used in die casting application. 1968- AGVs (automated guided vehicles) implemented. 1970- Stanford arm developed. 1979- SCARA robot for assembly developed in Japan .

Robot Anatomy:The manipulator of an industrial robot is constructed of a series of joints and links. Robot anatomy is concerned with the types and sizes of these joints and links and other aspects of the manipulator's physical construction.

Joints and Links

A joint of an industrial robot is similar to a joint in the human body: It provides relative motion between two parts of the body. Each joint, or axis as it is sometimes called, provides the robot with a so-called degree-of-freedom (dof) of motion. In nearly all cases, only one degree-of-freedom is associated with a joint. Robots are often classified according to the total number of degrees-of-freedom they possess. Connected to each joint are two links, an input link and an output link. Links are the rigid components of the rabat manipulator. The purpose of the joint is to provide controlled relative movement between the




input link and the output link.

Nearly all industrial robots have mechanical joints that can be classified into one of five types: two types that provide translational motion and three types that provide rotary motion. These joint types are illustrated in Figure 6.1.

The five joint types are:

(a) Linear joint(type L joint).The relative movement between the input link and the output link is a translational sliding motion, with the axes of the two links being parallel.(b) Orthogonal Joint (type O joint). This is also a translational sliding motion, but the input and output links are perpendicular to each other during the move.

Fig. 6.1(c) Rotational Joint (type R joint). This type provides rotational relative motion, with the axis of rotation perpendicular to the axes of the input and output links.

(d) Twisting joint (type T joint). This joint also involves rotary motion, but the axis or rotationis parallel to the axes of the two links.

(e) Revolving joint (type V joint)). In this joint type, the axis of the input link is parallel to the axis of rotation of the joint and the axis of the Output link is perpendicular to the axis of rotation.




Figure 6.2 Five types of joints commonly used in industrial robot construction: (a) linear joint (type L joint), (b) orthogonal joint (type o joint), (c) rotational joint (type R joint),(d) twisting joint (type T joint), and (e) revolving joint (type V joint).

Common Robot ConfigurationsA robot manipulator can he divided into two sections: a body-and-arm assembly and a wrist assembly. There are usually three degrees-of-freedom associated with the body-and- arm, and either two or three degrees-of-freedom associated with the wrist. At the end of the manipulator's wrist is a device related to the task that must be accomplished by the robot.The device, called an end effector is usually either (1) a gripper for holding a workpart or (2) a Tool for performing some process. The body-and-arm of the robot is used to position the end effector and the robot's wrist is used to orient the end effector.There are only five basic configurations commonly available in commercial industrial robots. These five configurations are:

1. Polar configuration. This configuration (Figure a) consists of a sliding arm (L joint) actuated relative to the body, that can rotate about both a vertical axis (T' joint) and a horizontal axis (R joint).

2. Cylindrical configuration. This robot configuration (Figure b) consists of a vertical column, relative to which an arm assembly is moved up or down. The arm can be moved in and out relative to the axis of the column. Our figure shows one possible way in which this configuration can be constructed, using a T joint to rotate the column about its axis An 1. joint is used to move the arm assembly vertically along the column, while an 0 joint is used to achieve radial movement of the arm,

3. Cartesian coordinate robot. Other names for this configuration include rectilinear robot and x-y-z robot. As shown in Figure c, it is composed of three sliding joints, two of which are orthogonal.

4. Jointed-arm robot. This robot manipulator (Figure d) has the general configuration of a human arm. The jointed arm consists of a vertical column that swivels about the base using a T joint. At the top of the column is a shoulder joint (shown as an R joint in our figure), whose output link connects to an elbow joint (another R joint)




5. SCARA. SCARA is an acronym for Selective Compliance Assembly Robot Arm. This configuration (Figure e) is similar to the jointed arm robot except that the shoulder and elbow rotational axes are vertical, which means that the arm is very rigid in the vertical direction. but compliant in the horizontal direction. This permits The robot to perform insertion tasks (for assembly) in a vertical direction, where some side-to-side alignment may be needed to mate the two parts properly.

Wrist Configurations. The robot's wrist is used to establish the orientation of the end effector. Robot wrists usually consist of two or three degrees-of-freedom. Figure 6.3 illustrates one possible configuration for a three-degree-of-freedom wrist assembly. The three joints are defined as: (1) roll, using a T joint to accomplish rotation about the robot's arm axis: (2) pitch, which involves up-and-down rotation, typically using a R joint; and (3) yaw, which involves right-and-left rotation, also accomplished by means of an R joint,A two-dof wrist typically includes only roll and pitch joints (T and R joints).To avoid confusion in the pitch and yaw definitions, the wrist roll should be assumed in its center position, as shown in our figure. To demonstrate the possible confusion, consider a two-jointed wrist assembly. With the roll joint in its center position, the second joint (R joint) provides up-and-down rotation (pitch). However, if the roll position were 90 degrees from center (either clockwise or counterclockwise), the second joint would provide a right-left rotation (yaw).




Fig 6.3

The SCARA robot configuration (Figure 6.4) is unique in that it typically does not have a separate wrist assembly. As indicated in our description, it is used for insertion type assembly operations in that the insertion is made from above. Accordingly. the orientation requirements are minimal,and the wrist is therefore not needed. Orientation of the object to be inserted is sometimes required, and an additional rotary joint can be provided for this purpose. The other four body-and-arm configurations possess wrist assemblies that almost always consist of combinations of rotary joints of types Rand T.

Fig 6.4End Effector• Attached to the wrist a hand “end effector”.• The end effector is not considered as part of the robot’s manipulator.• An end-effector is a tool or gripping mechanism attached to the end of a robot arm used to make intentional contact with an object or to produce the robot’s final effect on its surroundings to accomplish some task.

Tools• Tools are used in applications where the robot must perform some processing operation on the work-part .Tools are used in applications where the robot must perform some processing operation on the workpart. The robot therefore manipulates the tool relative to a stationary or slowly moving object (e.g., work part or subassembly). Examples of the tools used as end effectors by robots to perform processing




applications include:• spot welding gun• arc welding tool• spray painting gun• rotating spindle for drilling, routing. grinding, and so forth• assembly tool (e.g., automatic screwdriver)• heating torch• water jet cutting tool.

GrippersGrippers are end effectors used to grasp and manipulate objects during the work cycle. The objects are usually work-parts that are moved from one location to another in the cell.

Examples of Grippers• Mechanical grippers, in which the part is held between mechanical fingers and the fingers are mechanically actuated• Vacuum grippers, in which suction cups are used to hold flat objects• Magnetized devices, for holding ferrous parts• Adhesive devices, where an adhesive substance is used to hold a flexible material such as fabrics.

Grasping ForceThe factors that determine the grasping force are:– The weight of the object;– Consideration of whether the part can be grasped about its center of mass;– The speed and acceleration with which the robot arm moves, and the orientational relationship between the direction of movement and the position of fingers on the object;– Whether physical constriction or friction is used to hold the part;– Coefficient of friction between the object and the gripper fingers.

Mechanical Gripper Vacuum Gripper

Sensors In RoboticsA sensor is an electronic device that transfers a physical phenomenon (temperature, pressure, humidity, etc.) into an electrical signal.Sensors in Robotics are used for both internal feedback control and external interaction with the outside environment.Sensors used in industrial robotics can be classified into two categories: (1) internal and (2) external.




Internal sensors arc those used for controlling position and velocity of the various joints of the robot. These sensors form a feedback control loop with the robot controller. Typical sensors used to control the position of the robot arm include potentiometers and optical encoders.To control the speed of the robot arm, tachometers of various types are used.External sensors are used to coordinate the operation of the robot with other equipment in the cell. In many cases, these external sensors are relatively simple device such as limit switches that determine whether a part has been positioned properly in a fixture or that indicate that a part is ready to be picked up at a conveyor. Other situations require more-advanced sensor technologies, including the following:• Tactile sensors. Used to determine whether contact is made between the sensor and another object. Tactile sensors can be divided into two types in robot applications:(1) touch sensors and (2) force sensors, Touch sensors are those that indicate simply that contact has been made with the object. Force sensors are used to indicate the magnitude of the force with the object. This might be useful in a gripper to measure and control the force being applied to grasp an object.• Proximity sensors. Indicate when an object is close to the sensor, When this type of sensor is used to indicate the actual distance of the object, it is called a range sensor.• Optical sensors: Photocells and other photometric devices can be utilized to detect the presence or absence of objects and are often used for proximity detection.• Machine vision: Used in robotics for inspection, parts identification, guidance, and other uses. • Other sensors. This miscellaneous category includes other types of sensors that might be used in robotics, including devices for measuring temperature, fluid pressure, fluid flow, electrical voltage, current, and various other physical properties.

Desirable Features of Sensors• Accuracy.• Precision.• Operating range.• Speed of response.• Calibration.• Reliability.• Cost.• Ease of operation.

PotentiometersThe general idea is that the device consists of a movable tap along twofixed ends. As the tap is moved, the resistance changes. The resistancebetween the two ends is fixed, but the resistance between the movable part and either end varies as the part is moved.In robotics, pots are commonly used to sense and tune position for sliding and rotating mechanisms.Switch SensorsSwitches are the simplest sensors of all. They work without processing, at the electronics level. Switches measure physical contact. Their general underlying principle is that of an open vs. closed circuit. If a switch is open, no current can flow; if it is closed, current can flow and be detected.




Principle of Switch SensorsContact sensors: detect when the sensor has contacted another object. Limit sensors: detect when a mechanism has moved to the end of its range. Shaft encoder sensors: detects how many times a shaft turns by having a switch click (open/close) every time the shaft turns.

ROBOT CONTROL SYSTEMSRobot Control System TaskThe task of a robot control system is to execute the planned sequence of motions and forces in the presence of unforseen errors.Errors can arise from:– inaccuracies in the model of the robot,– tolerances in the workpiece,– static friction in joints,– mechanical compliance in linkages,– electrical noise on transducer signals, and– limitations in the precision of computation.The actuations of the individual joints must be controlled in a coordinated fashion for the manipulator to perform a desired motion cycle. Microprocessor-based controllers are commonly used today in robotics as the control system hardware. The controller is organized in a hierarchical structure as indicated in Figure 6.5 so that each joint has its own feedback control system, and a supervisory controller coordinates the combined actuations of the joints according to the sequence of the robot program. Different types of control are required for different applications. Robot controllers can be classified into four :(1) limited sequence control, (2) playback with point-to-point control, (3) playback with continuouspath control, and (4) intelligent control.

Fig 6.5 Hierarchical control structure of a robot micro computer controller.

Limited Sequence Control. This is the most elementary control type. It can be utilized only for simple motion cycles, such as pick-and-place operations [i.e., picking an object up at one location and placing it at another location). It is usually implemented by setting limits or mechanical stops for each joint and sequencing the actuation of the joints to accomplish the cycle. Feed back loops are sometimes used to to indicate that the particular joint actuation has been accomplished so that the next step in the sequence can




be initiated. However there is no servo-control to accomplish precise positioning of the joint. Many pneumatically driven robots are limited sequence robots.Playback with point to point control: Playback robots represent a more sophisticated form of control than limited sequence robots. Playback control means that the controller has a memory to record the sequence of motions in a given work cycle as well as the locations and other parameters (such as speed) associated with each motion and then to subsequently play back the work cycle during execution of the program. It is this playback feature that gives the control type its name. In point-to-point (PTP) control, individual positions of the robot arm are recorded into memory. These positions are not limited to mechanical stops for each joint as in limited sequence robots. Instead. each position in the robot program consists of a set of values representing locations in the range of each joint of the manipulator. For each position defined in the program, the joints arc thus directed to actuate to their respective specified locations. Feedback control is used during the motion cycle to confirm that the individual joints achieve the specified locations in the program.Playback with Continuous Path Control. Continuous path robots have the same playback capability as the previous type. The difference between continuous path and point-to-point is the same in robotics as it is in NC A playback robot with continuous path control is capable of one or both of the following:Greater storage capacity.Interpolation calculation.Intelligent Control. Industrial robots are becoming increasingly intelligent. In this context an intelligent robot is one that exhibits behavior that makes it seem intelligent.Some of the characteristics that make a robot appear intelligent include the capacity to:• interact with its environment• make decisions when things go wrong during the work cycle• communicate with humans• make computations during the motion cycle•respond to advanced sensor inputs such as machine visionIn addition, robots with intelligent control possess playback capability for both PTP or continuous path control. These features require (1) a relatively high level of computer control and (2) an advanced programming language to input the decision-making logic and other "intelligence" into memory.

Work Volume. The work volume (the term work envelope is also used) of the manipulator is defined as the envelope or space within which the robot can manipulate the end of its wrist. Work volume is determined by the number and types of joints in the manipulator (body-and-arm and wrist), the ranges of the various joints, and the physical sizes of the links. The shape of the work volume depends largely on the robot's configuration. A polar configuration robot tends to have a partial sphere as its work volume, a cylindrical robot has a cylindrical work envelope and a cartesian coordinate robot as a rectangular work volume.

Drive systemsBasically three types of drive systems are commonly used to actuate robotic joints. These are electric, hydraulic, and pneumatic drives. Electric motors are the prime movers in robots. Servo-motors or steeper motors are widely used in robotics. Hydraulic and pneumatic systems such as piston-cylinder systems,




rotary vane actuators are used to accomplish linear motions, and rotary motions of joints respectively.Pneumatic drive is regularly used for smaller, simpler robotic applications; whereas electric and hydraulic drives may be found applications on more sophisticated industrial robots. Due to the advancement in electric motor technology made in recent years, electric drives are generally favored in commercial applications. They also have compatibility to computing systems. Hydraulic systems, although not as flexible as electrical drives, are generally used where larger speeds are required. They are generally employed to carry out heavy duty operations using robots.The combination of drive system, sensors, and feedback control system determines the dynamic response characteristics of the manipulator. Speed in robotic terms refers to the absolute velocity of the manipulator at its end-of-arm. It can be programmed into the work cycle so that different portions of the cycle are carried out at different velocities. Acceleration and deceleration control are also important factors, especially in a confined work envelope. The robot's ability to control the switching between velocities is a key determinant of the manipulator's capabilities. Other key determinants are the weight (mass) of the object being manipulated, and the precision that is required to locate and position the object correctly. All of these determinants are gathered under the term ‘speed of response', which is defined as the time required for the manipulator to move from one point in space to the next. Speed of response influences the robot's cycle time, which in turn affects the production rate that can be achieved.Stability refers to the amount of overshoot and oscillation that occurs in the robot motion at the end-of-arm as it attempts to move to the next programmed location. More oscillations in the robotic motion lead to less stability in the robotic manipulator. However, greater stability may produce a robotic system with slower response times.Load carrying capacity is also an important factor. It is determined by weight of the gripper used to grasp the objects. A heavy gripper puts a higher load upon the robotic manipulator in addition to the object mass. Commercial robots can carry loads of up to 900 kg, while medium-sized industrial robots may have capacities of up to 45kgThe actions of the individual joints must be controlled in order for the manipulator to perform a desired motion. The robot’s capacity to move its body, arm, and wrist is provided by the drive system used to power the robot.The joints are moved by actuators powered by a particular form of drive system. Common drive systems used in robotics are electric drive, hydraulic drive, and pneumatic drive.Types of Actuators*Electric Motors, like: Servomotors, Stepper motors or Direct-drive electric motors*Hydraulic actuators*Pneumatic actuatorsCharacteristics of Actuating Systems*Weight, Power-to-weight Ratio.*Operating Pressure.*Stiffness vs. Compliance.*Use of reduction gears.ApplicationsElectric motors are the most commonly used actuators. Hydraulic systems were very popular for large




robots. Pneumatic cylinders are used in on/off type joints, as well as for insertion purposes.

Hazardous work environment for humans. Repetitive work cycle. Difficult handling for humansMultishift operation. infrequent changeovers, Part position and orientation are established in the work cell. The applications can usually be classified into one of the following categories: (1) materia! handling, (2) processing operations,(3) assembly and inspection.

Result: Robot’s study was completed.




Experiment No. 07

Aim - Study on Part Coding and Group Technology. Objective - To study the coding and group technology. Theory -1. Introduction.

Group technology is a manufacturing philosophy in which similar parts are identified andgrouped together to take advantage of their similarities in design and production. Similar parts are arranged into part families, where each part family possesses similar design and/or manufacturing characteristics. for example, a plant producing 10,000 different part numbers may be able 10 group the vast majority of these parts into 30-40 distinct families. It is reasonable to believe that the processing of each member of a given family is similar and this should result in manufacturing efficiencies.

2. Part familiesApart family is a collection of parts that are similar either because of geometric shape and size orbecause similar processing steps are required in their manufacture. The parts within a family are different, but their similarities are close enough to merit their inclusion as members of the part family. Figures show two different part families. The two parts in Figure 1 are very similar in terms of geometric design, but quite different in terms of manufacturing because of differences in tolerances, production quantities, and material. The ten parts shown in Figure 2 constitute part family in manufacturing, but their different geometries make them appear quite different from a design viewpoint.

Fig:- Part Families

Fig:- Process Type Layout




Fig:- Group Technology Layout

3. Coding-technology - This is the most time consuming of the three methods. In parts classification and coding,

similarities among parts are identified, and these similarities are related in a coding system. Twocategories of part similarities can be distinguished:(1) Design attributes, which are concerned with part characteristics such as geometry, size, and material; and(2) Manufacturing attributes, which consider the sequence of processing steps required to make a part.

The parts coding scheme consists of a sequence of numerical digits to identify the parts design and manufacturing attributes. Coding scheme for part classification can be of two basic structures.

1. Hierarchical structure – In this code structure, the interpretation of each succeeding symbol depends on the value of the preceding symbols.2. Chain – type structures – In this type of code, the interpretation of each symbol in the sequence is fixed. It does not depend on the value of the preceding symbol3. mixed-mode structure. which is a hybrid of the two previous codes

4. Obstacles to GT.1) Identifying the part families (the biggest problem) If the plant makes 10,000 different parts,reviewing all of the part drawings and grouping the parts into families is a substantial task2) Rearranging production machines in the plant into the appropriate machine cells It takes time to plan and accomplish this rearrangement, and the machines are not Producing during the changeover

5. Methods of classification. i) Visual inspection.ii) Classification and coding system. iii) Production flow analysisi) Visual inspection involves arranging a set of parts into groups by visually inspecting the physical characteristics of the parts.ii) Parts classification and coding - identifying similarities and differences among parts and relating them by means of a coding schemeiii) Production flow analysis - using information contained on route sheets to classify parts




6. Types of classification and coding systemSome of the coding system of Process Planning are:a) OPITZ Systemb) The CODE System c) The KK-3 Systemd) The MICLASS System e) The DCLASS Systemf) COFORM (Coding For Matching)

a) THE OPITZ CLASSIFICATION SYSTEM:The opitz system is of historical interest because it was one of the first published classification

& coding schemes for mechanical parts. This parts classification & coding system was developed by it opitz of the university of Aachess in West Germany. It represents one of the pioneering efforts in the group technology areas and is probably the best known of the classification & coding schemes. The Opitz coding system uses the following digit, sequence:

12345 6789 ABCDThe basic code consists of nine digits, which can be extended by adding four more digits. The first nine digits are intended to convey both. Design & manufacturing data. The first five digits 1 2 3 45, are called the ―form code and describe the primary design attributes of the part of the part. The next four digits 6 7 8 9, constitute the ―supplementary code which indicates some of the attributes that would be of use to manufacturing. The extra four digits, A B C D are referred to as the ―secondary code and are intended to identify the production operation type & sequence. The secondary code can be designed by the firm to serve its own particular needs.

Fig-Basic structure of the Opitz system of parts classification and coding




7. Benefits of well designed classification and coding system. I. EngineeringReduction of number of similar partsElimination of duplication parts Identification of expensive parts Reduction of drafting effortsEasy retrieval of similar functional partsIdentification of substitute parts

II. Equipment Specification and Facility PlanningFlow line layout of production equipmentLocation of bottlenecksLocation underutilized machine tools Reduction of part transportation times Improvement of facility planningIII. Process PlanningReduction of number of machining operationsShortening of production cycles Improvement of machine loading operation Easier prediction of tool wears and tool changes

8. Benefits of Group Technologya) Standardization of tooling, fixtures, and setups is encouragedb) Material handling is reducedc) Parts are moved within a machine cell rather than entire factorye) Process planning and production scheduling are simplified e) Work-in-process and manufacturing lead time are reduced f) Improved worker satisfaction in a GT cellg) Higher quality work

Result – Study of the coding and group technology is done successfully.




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