Document4

Journal of Basrah Researches ((Sciences)) Vol. 35, No.6, 15 December ((2009))

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MM oohhaammmmeedd AA.. NNaassssaarr aanndd AAhhmmeedd NN.. NNiimmiirr Engineering College – Basrah University

Basrah - Iraq ISSN 2695ــ 1817ــ

((Received 12/7/2009, Accepted 3/11/2009))

Abstract

A CNC code generation intelligent and integrated package ara developed in the current work for machining parts with its interfaces to provide CAD/CAM integration which can be operated and used by average skilled operators. The developed package is composed of three main sections. The up most and starting unit includes a modeling CAD platform and a data extraction from Auto CAD software based on DXF files. The second section modules work and involve data base facilities. The last and down most section is Gcode interface that consists of the generation and the saving of CNC codes. The designed package and its modules are combined under a supervisory program and implemented on a virtual machine tool by simulation software CNCez Pro.

Keywords: CNC machine, Programming Package, CAD, Gcode, Visual Basic.

Introduction Computer Numerical Control (CNC)

machines are found almost everywhere, from small jobs in rural communities to fortune 500 companies in large urban areas. Numerical Control is most dynamic manufacturing process. Its impact on manufacturing is at least as great as that of any new process in the last 50 years [1]. After World War II, with the increasing demand for more complex parts, numerical control (NC) machine tools were invented. NC replaced the need of the coordinated control of skilled machine operators, a skill that takes years to master. Since the 1950s, more scientific and technological developments have occurred than throughout human history [2]. One of the most important developments is the invention of the digital computer. In discrete – product manufacturing, computers are essential to the development of NC, robotics, computer aided design (CAD), computer aided manufacturing (CAM), and flexible manufacturing systems (FMSs). These new computers – based technologies enable to produce small batch products at low cost. Many human decision making

functions are replaced or assisted by computers. Thus, they further increase human productivity [2].

The concept of Numerical Control is produced by John Parsons of Traverse city, Michigan. In 1947, Parsons developed a jig bore that was coupled with a computer. Scientists and engineers at M.I.T. built a control system for two – axis milling machine that used a perforated paper tape as input media. Since then, many improvements, in the machine and in the controller have been made [3]. Controlling a machine tool using variable input, such as a punched tape or stored program, is known as Numerical Control (NC). NC is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for tool movements. According to the Electronics Industry Association (EIA), a computer numerically controlled (CNC) system is one in which motions are controlled by direct insertion of numerical data at some points, and in which the system automatically interprets at least some portion of this data.

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Nassa Nassar & Nimir: A Programming Package to Convert the Engineering Projects …

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Recent researches and developments in manufacturing area have the objectives of increasing many activities in global CIM (Computer Integrated Manufacturing) system which is heading towards the Factory of the Future. For this purpose, an advanced production system called IMS intelligent, or sometimes ( Integrated Manufacturing System) is oriented towards the needs of the 21st century and designed to maintain and improve the vitality of manufacturing sector keeping it as the cornerstone of all economic activities and ensuring that manufacturing remains an attractive industrial area [4].

The acronym CIM for the expression Computer Integrated Manufacturing was first used by Harrington[5] to mean the integration of business, engineering, manufacturing and management information that spans company functions from marketing to product distribution. Therefore, the manufacturing and computers are the two key elements constituting the core of the CIM. CIM can be considered as the philosophy in

which the computer plays a central role for planning and controlling the manufacturing process. The operation of CIM system in factory may provide invaluable benefits compared with the conventional systems. Typical benefits are[6]:

1- Increase of productivity by 40 – 70 %. 2- Reduction of design costs by 15 – 30%. 3- Reduction of the in-shop time by 30 –

60%. 4- Better product quality. 5- Reduction of scrap by 20 – 50%. 6- Improved product design.

The most important elements of CIM are illustrated in Fig.(1).

In the current work, an attempt has been made to develop CAD/CAM system that helps the CNC programmers and skilled operators to convert their drawings (Auto CAD drawings or intrinsic entities in the package) into instructions as Gcode functions which are understood by CNC machines.

Historical review The roots of today’s CAD/CAM go back to

the beginning of the civilization when engineers of ancient Egypt, Greece and Rome acknowledged graphics communications. Some of the existing drawings in Egyptian tombs can be considered as technical drawings [7]. The inventions of computers and xerography have given graphics and consequently CAD/CAM their current dimensions and powers [7]. The first development in computer aided construction was done in the USA in the beginning of 1960’s, while CAM was first invented in 1954 [8]. At the end of the 1960’s the first commercialist CAD – system was lunched, but it was not until the 1980’s when personal computer became common and the prices of computer equipment decreased, the technology reached the small and middle – sized companies[7].

Since the birth of the first NC milling machine at MIT in (1947), a huge number of process plans for machine parts have been developed all over the world. Two of the most popular formats used for CNC machine tools are Initial Graphics Exchange Specification (IGES) and Data Exchange File (DXF). Extracting the necessary information from an exchange file to generate manufacturing parameters become an

important task [9]. In (1987), Turbo – CAPP was invented by Wang which is an intelligent process planning system which is able to generate a CNC part program for each planned work piece based on its geometric characteristics extracted from Auto CAD and the machining parameters stored in the knowledge base [10].

Wang and Lin (1987) generated linear and circular tool paths after offsetting the part profile by using the boundary representation of the part from a feature recognition system that is an interface between CAD and CAPP [11]. Shyu and Chen (1987) have developed a mini CIM for turning operations in which both cutting paths and CNC part programs are generated [12]. In 1988, Chin developed a feature based knowledge system for CAD/CAM integration in which a cutter location file is generated and stored firstly and then it is converted into an NC code file [13]. In (1990), a Technically Oriented System for Turned Parts, TECHTURN generated a CNC part program with little manual intervention by using outputs from EXCAP(Expert Computer Aided Process Planning) [14].



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In (1990) on the basis of the geometric data and process route generated by processing planning module, ICAPP can generate part programs in higher level language like ART (automatically Programmed Tools) and COMPACT II [15]. Boer (1991) developed a CAPP/CAM expert system in which the tool paths translating the information contained in the synchronized solution in an ART – like cutter location file [16]. Abdou and Cheng (1993) have developed an expert system to generate alternative process plans for mechanical parts with tolerance requirements by retrieving data from DXF [17].

Celik (1998) has used DXF for feature recognition, data extraction, data convection, and for allowing the surface profile to be viewed and manipulated within Auto CAD software or other applications that support DXF output [18]. In (2001), Emir Mutapcic et. al. developed algorithm and software system, which processes STL file format from CAD system (Solid Works) and produce NC part program to mill surface [19]. Adnan (2001) developed CAM system to generate Gcode for CNC lathe machine. The CAM software generates sub routines (as canned cycles) depending on radii difference value between finish part and the blank [20].

Nafis and Anwarul designed a program in C/C++ that extract information from DXF file [21]. Dmitry et. al. (2003) developed a CAM system for optimizing NC programs and work within Auto CAD environment [22]. Kasim and Moneer (2005) developed Auto CAM software using ActiveX

technique within Visual Basic [23]. The above works either work for milling or turning and not both. Also some of them only extract the data without NC code generation that required for NC machines and only for polyline.

The present work concentrates on the following points:

1- Developing a complete CAD/CAM package software as a means of integrating elements between design and manufacturing activities.

2- Studying and generating of Gcode functions.

3- Case study of CNC applications. 4- Studying the possibility of apply this

package on CNC machine.

The Quick CAD/CAM software in the current study is having more facilities:

1- Support NC functions more than the previous softwares.

2- Support canned cycle’s functions for some controller as FAUNC.

3- Have intrinsic geometric entities as point, line, arc, atc… .

4- Import line, polyline, arc, circle, and rectangle.

5- It works for any controller by little modification on its data base.

6- The extracted data form DXF can be used for DNC machine instead of converting them to Gcode by using the proposed procedure.

CNC Concepts and Code Functions The primary objects of blocks of flexible

manufacturing and computer integrated manufacturing system are numerically controlled (CNC) machine tools. CNC machine tools are complex assemblies, in general, any CNC machine tool consists of Computer unit, Control system unit, drive motor unit, tool changer unit as shown in Fig.(2). According to the construction of CNC machine tools, CNC machines work in the following (simplified) manner [3]:

1- the CNC machine control computer reads a prepared program and translates it into machine language, which is a programming language of binary notation used on computers, not on CNC machines.

2- When the operator starts the execution cycle, the computer translates binary codes into electronic pulses which are automatically sent to machine’s power units. The control units compare the number of pulses sent and received.

3- When motors receive each pulse, they automatically transform the pulses into rotations that drive the spindle and lead screw, causing the spindle rotation and slide or table movement. The part on the machine table or the tool in the lathe turret is driven to the position specified by the program.



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In many cases the stored program in CNC is the Part Program, and the process of writing such programs is known as Part Programming [24]. Part programs can be generated either on-line (at the machine control), or offline (away from the machine control). They can be written manually, in which the programmer performs all mathematical calculations and writes or types the program “longhand”. Other part programs can be written with the aid of a programming system as a CAM system [25].

The task of part programming is that of translating a representation of the geometry of a component – perhaps a drawing – first into a specification for the operations to be carried out by the machine tool, and then into a program of instructions for the controller. The programming of complex shapes has always been difficult, and form the early days on NC alternative approaches to part programming using computer assistance have been used. These approaches in particular assist with mathematical calculations for determining cutter path offsets for multiple cuts on a part, and have the additional merit of reducing the programming errors.

The main alternative routes for part programming are :

1- manual part programming which is recorded on a document by part programmer called Manuscript.

2- Computer assisted part programming which is faster and more reliable than manual programming techniques.

3- CAD part programming in which the NC program is created from CAD by allowing

part programmer to access the computer’s computational capabilities via an alternative graphics display console.

These alternative routes are shown in Fig.(3)

[24].

One of the core tasks in a CIM environment is to extract and identify the information in the CAD file model [9]. It is difficult for the end user to interpret or alter the database used by different CAD packages. CAD, CAM or CAPP system cannot completely understand a design file created by different software. To resolve this problem, some standard formats like Initial Graphics Exchange Specification (IGES), Data Exchange Format (DXF) are being used for transferring design information from one CAD system to another CAD, CAM or CAPP [26].

In the current study Data Exchange Format (DXF) is used for its rigidly defined structure. There are seven sections in a DXF file [27]. They are :

HEADER section. CALASSES section TABLES section BLOCKS section ENTITIES section OBJECTS section THUMBNAILIMAGE section

More information about construction and

main frames of DXF file can be found in Mohammed A. Nassar [28].

Quick CAD/CAM Package The system architecture of the software for

the proposed package is illustrated by a flowchart in Fig.(4). The input for the software tool is a two dimensional geometry which is created by auto CAD as DXF files or direct input using intrinsic graphics entities. Import DXF files from Auto CAD software includes many subroutines, and Fig.(5) shows the flowchart related with this branch of CAD model.

Functionally, the block generation process using the software tool can be summarized into the following steps:

1- Run the software 2- Specify the part origin as reference point 3- Set the proper syntax of Gcode and other

inputs that used on target machine tool. 4- Decide which type of applications and which

operations: Turning, Milling, or Drilling and



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what style of cutting e.g. finishing, roughing, or both.

5- Import a CAD model as DXF files or create it by entities.

6- Click generation button to get the required Gcode functions.

After the installation of the package, user can run it from Windows Start menu or type its

executable name at Run command dialog box. It is designed to be user friendly interface with multi windows which make users work in easy manner and no professional mastering is required to get their results. The Quick CAD/CAM consumes small memory which may be regarded as on of its advantages. Figures (7 and 8) show the welcome menu and option menu respectively.

Application of Quick CAD/CAM As mention previously, the proposed Quick

CAD/CAM which is designed in the current study can be applied in many CNC operations such as:

1- Grooving operation. 2- Threading operation. 3- Turning operation. 4- Drilling operation. 5- Milling operation.

In the following section, some of these applications will be introduced and the other

application with many work cases and details can be found in Mohammed [28]. The results of the applied cases were initiated by Quick CAD/CAM software. In order to prove software accuracy and confidentiality, the results were compared with geometrical calculations and CNCez Pro [29] to simulate the operations and according to NC tool machine.

Grooving operation Grooving is one of the most complicated

operation performed in the lathe machine [30] In the Quick CAD/CAM software, a location, width, depth, span between grooves, and numbers of grooves are given as canned cycle.

Figure (9) shows the required input data, part programming for this case, and a snap shot during simulation process using the interpreted data from proposed package.

Threading Operation The screw thread is an important mechanical

unit. It is most frequently performed. The operation of threading means cutting a helical groove of definite shape or angle, with a uniform advance for each revolution, on the surface of a round piece of

material or in a cylindrical hole [31]. Figure (10) shows the required input data, part programming for this case, and a snap shot during the simulation process of the results.

Turning Operation Turning is the machining operation that

produces cylindrical parts [32]. Part programmer who use this software draws the half path only and the revolution of spindle and moving of tool will remove stock material at the upper half of path to

get the finish part as shown in Fig.(11) in which the required input data, part programming for this case, and a snap shot during simulation process of the results can be seen.

Conclusions and Recomendations The proposed Quick CAD/CAM package is

developed from scratch and it depends on the concept of NC code functions with algorithms to resolve and analyze any drawing designed by Auto CAD software or initiated directly by

software’s entities and converts them into NC code functions according to targeted controllers.

The following functions of CAD/CAM integration are fulfilled by the current study:

1- CAD interface for creating primitive entities like line, arc, circle, …etc.



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2- Data extraction from CAD software as DXF drawings from Auto CAD software.

3- Wide interview about Gcode functions and how they work.

4- Post processor system, including the modules like read data module and coding module that convert data into acceptable syntax.

5- The entire system was implemented on a lath machine tool and machining center (virtually) with variety of applications.

1- Development of the CAD interface. 2- Support other graphical entities in

extraction data module from Auto CAD software.

3- CAD/CAM should include what is known as "reverse engineering".

COMPUTER INTEGRATED MANUFACTURING (CIM)

CAD/CAM PRODUCTION PLANNING & CONTROL

CAD

Computer Aided Design

CAM

Computer Aided

Manufacturing

CAPP

Computer Aided Process

Planning

CAQQ

Computer Aided Quality

Control

Manufacturing Resources Planning

Materials Requirement Planning

Order Release

Lost Sizing & Time Phasing

Manufacturing Control

Figure (1) The Most Important Elements of CIM.(3)

The results obtained from this study can provide an additional degree of flexibility for the planning and manufacturing resources in machining industry. With the developed package, it would be possible to reduce the times spent in part programming and to contribute to the success of the manufacturing industry. This will lead to an increased utilization of CNC machine tools and maximization of CNC productivity which are commonly considered as ultimate goals of CIM. The work in the current study can be extended to the following fields:



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Figure (2) General Assemblies in A CNC Machine(6).

Post Processor

Part Geometry Part Geometry MDI

Compile

Write Program

Remote Presentation

Manual Code

Manual Code

Tool path

Part Geometry

Machine Controller

Machine

Manual Code

Computer Assisted CAD/CAM

Future?

MCD

MCD

MCD

MCD

MCD

CLDATA

CLDATA

MDI = Manual Data Input

Figure (3) The Main Alternatives for Part Programming.(24)



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START

Welcome Window

Main Window

Drawing Window

Gcode Window

Coordinates Window

Options Window

Entities Creation Window

Part Origin

Gcode Function Database

User Input

Graphics Entities

DXF Importing

Clean All

User Input

User Input

Figure (4) System Architecture of Software For Proposed Package Quick CAD/CAM.



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While Not EOF

STSRT

Open DXF Database

Read Codes

DXF Database

Close DXF Database While Not EOF

Path End Sub

Read Codes

Is Section Reached?

Is Entities Reached? Read Codes

Read Codes

Is Line Reached?

While Entities = "LINE"

Close DXF Database Read Codes

A

B

C

False

True

True

True

True

False

False

False

True

False True

Figure (5) The Main Routine and Subroutines in proposed Package.



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False

False

B Is Circle reached?

Is Ellipse reached?

While Entity Ellipse

While Entity Circle

Get Coordinates of center point and semi major end point

Get Coordinates of center point

Read Gcode

Read Gcode

C

False

False

Is Arc reached?

While Entity Arc

Get Coordinates of center point and start

end angle values

Read Gcode

A

Is I.WPolyline

reached?

While WPolyline Entity Arc

Get Coordinates of vertices

Read Gcode

C False

False True

False C

Figure (6) Continued to Fig.(5)



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Figure (7) Welcome Window of Quick CAD/CAM Package

Figure (8) Options Menu of Quick CAD/CAM Package



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Part Programming Grooving

N1 G20 N3 G50 X10Z10 N4 G99 N5 G90 N6 S1000 N7 M03 N8 M08 N9 G00X6.1Z-0.8 N10 G75 X5 Z-2.8 I0.05 K1.0 F0.005 N11 G00X10Z10 N12 M30

Required Input Data

Snap shot of Simulation

Figure (9) Applied Case - Grooving Operation.



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Part Programming Threading N1 G20 N3 G50X10Z10 N4 G99 N5 G90 N6 S1000 N7 M03 N8 M08 N9 G00X3.2Z0.3 N10 G76 X2.69 Z-2.00 K0.1533 D150 F0.25 N11 G00X10Z10 N12 M30

Figure (10) Applied Case – Threading Operation.

Required Input Data

Snap Shot of Simulation



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Part Programming Turning

N1 G20 N2 G50X10Z10 N3 G99 N4 G90 N5 S1200 N6 M03 N7 M08 N8 G71 P9Q14U0.06W0.05D1200F0.012 1 N9 G00X1.0Z0.0 2 N10G01X1.5Z-0.25F0.008 3 N11G01X1.75Z-1.0 4 N12G01X1.75Z-1.0 5 N13G02X2.5Z-1.75R0.375 6 N14 G01X2.5Z-2.0 N15 G70P9Q14 N16 G00X10Z10

Required Input Data

Snap Shot of Simulation

Figure (11) Applied Case – Turning operation.

References 1- “The basic of computer numerical control”,

Interactive Article, website: http://www.cncci.com/articles/cnc%20base%20intro.htm

2- Tien – Chen Chang, Richard A. Wysk, and Hsu-Pin Wang “Computer Aided Manufacturing”,

second edition, Prentice Hall,Inc., Englewood Gliffs, U.S.A., 1998.

3- Petter J.Amic, “Computer Numerical Control Programming”, first edition, Prentice Hall, Inc., Simon & Schuster, U.S.A., 1997.



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4- Bell R. “Planetary Speech of 1st National symposium on Intelligent Manufacturing Systems”, Sapanca, Sakarya, Turkey, 1996.

5- Harrrington, J. “Computer Integrated Manufacturing”, R.E. Kreiger, Huntington, NY, U.S.A., 1973.

6- Rembold , N., ”Computer Integrated Manufacturing”, R.E. Kreiger, Huntington, NY, U.S.A., 1973.

7- Emma Bodemyr, “How Improve CAD/CAM/CNC process”, Master’s thesis, 2005.

8- Tim Mercer, “CAD/CAM Selection for Small Manufacturing Companies”, Research Paper, 2000.

9- Ersan Aslan, “Data Extraction from CAD Model for Rotational Parts to be Machined at Turning Centers”, Tr. J. Engineering and Environmental Science, Paper No. 23, pp. 339 – 347, Seker Univ., 1999.

10- Wang, H.P. and Wysk, R.A., “Intelegent Reasoning for Process planning”, Computers in Industry, No. 8, pp. 293 – 309., 1987.

11- Wang, H.P. and Lin, C. A., “Automated Generation of NC Part Programs for Turned Parts Based on 2-D Drawing Files”, International Journal of Advanced Manufacturing Technology, Vol. 2, No. 3, pp. 23 – 36., 1987.

12- Shyu, J. and Chen, Y. W., “ A Mini CIM System for Turning “, Annals of the CIRP, Vol. 36, No. 1, pp. 277 -280, 1987.

13- Chin, S.C., “Developing a Feature Based Knowledge System for CAD/CAM Integration”, Computer and Industrial Engineering, Vol. 15, No. 1-4, pp. 34 – 40, 1988.

14- Joseph, A.T., “ Automatic Generation of NC Programs for Turned Components from CAD Product Models”, Proceedings of the 28th International MATADOR Conference, pp. 289 – 294, 1990.

15- Ssemakula, M.E., “ Process Planning System in The CIM Environment”, Computers and Industrial Engineering, Vol. 19, No. 1-4, pp. 452 – 456, 1990.

16- Boer, C.R., “CAPP/CAM Expert System for a High Productivity, High Flexibility CNC Turning Center”, Annals of the CIRP, Vol. 39, No. 1, pp. 481 – 483.

17- Abdou, G. and Cheng, R., “TVCAPP, Tolerance Verification in Computer Aided Process Planning”, Int. Journal of Prod. Res., Vol. 31, No. 2, pp. 393 – 411, 1993.

18- Celik, I. “Process Planning and Graphics simulation of The Parts to be Machined at Turning Centers”, Univ. of Sel-cuk, institute of Science and Technology, M.Sc. Thesis, Konya, 1998.

19- Emir Mutapcic, Dr. Pio Iovenitti, Dr. Jason Hayes, “Automatic NC Part Programming Interface for a UV Laser Ablation Tool”, paper, 2001.

20- Adnan, A. J., “Off Line CNC Code Generation System for Turning Machines”, M.Sc. thesis, Univ. of Technology, Iraq, 2001.

21- Nafis Ahmed, Anwarul Haque, “Manufacturing Feature Recognition of Parts Using DXF Files”, 4th International Conference on Mechanical Engineering, Dec., 26 – 28, Dhaka, Bangladesh, VI, pp. 111- 115, 2001.

22- Dmitry I. Troitsky, Maria V. Novikova, Mark W. Bannatyne, “NC Modeling”, paper, 2003.

23- Kasim M. Daws, Moneer M. Yousif, "CAD/NC Integration with the OOP Support", College of Engineering, Baghdad University, 2005.

24- Chris McMahon, Jimmie Browne, “CAD/CAM Principles, Practice and Manufacturing Management”, second edition, Addison Wesley Longman ltd., England, 1998.

25- “Are G-code Losing Money For Your Shop!”, Technical Article, Website http://www.gibbscan.com/news_events/tech_articles/ta_gcode.shtml.

26- Hill, A.E. and Pilkington, R.D., “ A Completed Auto CAD Databook”, Prentice Hall, Inc. UK, pp. 246 – 250, 1990.

27- Auto CAD 2004 Developer Help, DXF reference, Autodesk Inc.

28- Mohammed A. Nassar, "A Programming Package to Convert the Engineering Projects Designed by CAD Programs into Manufacturing Instructions on CNC Machines", M.Sc. thesis, Engineering College, Basrah University.

29- CNCez Pro Software, website: http://www.cncezpro.com.

30- “Grooving on The Lathe”, Website: http://www.jjjtrain.com/vms/lath_grooving.html.

31- Lascoe, Nelson, Porter, “Machine shop, Operation and Setups”, Fourth Edition, American Technical Society, Chicago, 1973.

32- Turning Information Center, Michigan Technological Univ., website: http://www.mfg.mtu.edu/marc/primers/turning/turn.html.



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الخالصة

في الدراسة الحالية تم تصميم حقيبة برمجية ذكية ومتكاملة لتوليد الشفرة الخاصة لتشغيل المنتج على مكائن القطع الرقمية ولتكون

تتكون الحقيبة المطورة . مشغل ذي الخبرة المتوسطة حلقة وصل بين التصميم والتصنيع الرقميين والتي يمكن ان تشغل و تدارحتى من ال

و استخراج (CAD)القسم األول وهو وحدة البداية التي تضم واجهة الرسم الهندسي منصة الـ. في الدراسة الحالية من ثالثة اقسام رئيسة

مع الوحدة األولى وتتضمن قاعـدة تعمل الوحدة الثانية. Auto CAD) ( من برامج(DXF)البيانات على شكل تنسيق لنقل البيانات

الحقيبة المصممة في هذه الدراسة والبرامج المكونة لها قد . و ايضا الخزنGcodeيشمل القسم األخير واجهة توليد الشفرة بشكل . البيانات

.(CNCez Pro)طبقت على ماكنة قطع افتراضية ضمن برنامج محاكاة



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