Lab Manual MECH2118 2011

Sohar University

Faculty of Engineering

Mechanical & Mechatronic Engineering Program

Laboratory/Workshop Manual

MANUFACTURING PROCESSES

MECH2118

Level 2

Course Coordinator: Dr. Ghassan Al-Kindi

E-mail: [email protected]

Tel: 26720101 Ext. 125

Teaching Assistant: Mrs. Sarraa Naser

E-mail: [email protected]

Tel: 26720101 EXT 186

Year: 2011-2012

Laboratory

Manual

MECH2118

FACULTY OF ENGINEERING - SOHAR UNIVERSITY

Manufacturing Processes – MECH2118 Page 2

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No Contents

Page

Number

1 General instructions 3

2 Safety precautions 4

3 Instructions for lab experiments 6

4 Guidelines for writing lab report 7

5 Experiment# 1 Workshop activities 12

6 Experiment# 2 Heat Treatment of Steel 15

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GENERAL INSTRUCTIONS

The exercises in this manual are designed to give the students an introduction to

laboratory and workshop procedures for performing experiments in manufacturing

processes. The purpose is to provide students with a deeper understanding of theoretical

principles by observing phenomena, by measuring physical characteristics and by

comparing measured versus calculated results. This “hands-on” experience is essential to

an engineering technology student.

In addition to following the procedures given for a lab, each group of students will be

required to submit a lab report documenting the experiment and the results. Documenting

laboratory and workshop results in a clear and concise manner is just as important as

conducting an experiment properly. The laboratory discipline and the reporting principles

presented herein will extend directly to any engineering test lab in industry.

A goal of the Faculty of Engineering is training students to work well in teams in the

pursuit of a common objective such as a lab experiment. Thus students have to learn to

organize themselves into team groups, and to allocate responsibilities among themselves.

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SAFETY PRECAUTIONS

It is important that each student should read the safety precautions and procedure

followed before coming to the lab.

I. All equipment and instrumentation shall be handled carefully to avoid damage

during experimental operations. At no time shall any equipment be relocated from

its position in the Lab. Any anomalies encountered with equipment during an

experiment shall be brought to the instructor‟s attention immediately.

II. No repairs or attempted repairs shall be performed on any lab equipment;

including instrumentation, fixtures, and especially pressurized systems or

components Only the equipment specified in the Equipment List for each

procedure shall be used. When given in test procedures, the sequence of steps

specified in each procedure is mandatory. No steps shall be performed out of

sequence.

III. Operational areas shall be maintained clean and orderly, free of trash or

combustible materials.

IV. Food and beverage are not permitted in the Lab.

V. Smoking is prohibited.

VI. Equipment taken from storage racks or cabinets shall be returned to designated

storage locations. The area where the lab was conducted shall be cleaned, and

returned to the condition found when entering the lab to begin the procedure.

VII. Should an unsafe condition develop during the experiment, report to the

instructor to prevent injury to team members or damage to lab equipment.

VIII. Upon observing a hazardous or potentially hazardous condition that could occur if

uninterrupted operation is allowed, ANYONE participating in or observing the

experiment can issue a “STOP” command.

IX. Keep fingers and loose items of clothing away from all moving parts

X. Liquids like tea, coffee etc are need to be kept well clear of the equipment

XI. No joking, playing or horsing around in the laboratory

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XII. For any queries contact the concerned staff member.

XIII. If any emergency arises call on the following numbers

EMERGENCY TELEPHONE NUMBERS:

Emergency

Help:

Fire

Department:

Campus

Security:

STUDENT NAME: ____________________________

STUDENT ID NUMBER: _______________________

SEMESTER AND YEAR: ____________________

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INSTRUCTION FOR LAB AND WORKSHOP EXPERIMENTS

1- A team consisting of 4 to 6 students will perform each experiment.

2- Lab reports are due at stated and advertised dates, normally within two weeks from

the activity date.

3- All students are expected to read the experiment thoroughly before starting the

lab/workshop work. Questions about procedures or precautions should be resolved

by asking your laboratory instructor before the experiment. Each group must

prepare their own report.

4- Lab groups will consist of groups. Grades will be based on participation, accuracy

of data recording and reduction, completion of tasks for lab procedures and the

report itself.

5- The marks allotted for Lab work is out of 10 and Laboratory reports are graded on

a scale of 0 to 10. Please refer to your course profile to know the final mark weight

allocated to the Lab/workshop activities.

6- When students have finished the experiment, they must clean their

apparatus/equipment and leave their bench clean and tidy.

7- Your reports are due for submission by the stated date. If not submitted by

the required date they will be rejected.

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GUIDELINES FOR WRITING LABORATORY REPORT

A lab/workshop report is the perfect place to start practicing technical writing. Each

student will be responsible for preparing a report after completing each laboratory

exercise. The required content and format of the report are given in the following

sections.

Cover page

Introduction

Objectives

Theory

Equipments used

Procedure

Observation and calculations

Sample calculation

Results ,analyses and discussion

Conclusions

References

Cover Page

The report shall have a cover page with the following information provided:

Experiment Number.

Title of experiment.

Laboratory Manual

Course title

Date of submission

Student‟s name

Student ID

A standard cover page is shown in the following page:

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Sohar University

Faculty of Engineering

Mechanical & Mechatronic Engineering Program

Laboratory/Workshop Report

MANUFACTURING PROCESSES

MECH2118

Lab/Workshop Experiment # 1,2,3 etc

Title of the experiment

Student’s Name 1:…………………………………………..…….. SID…………………..






Group:…………………………………………..……..

Date:…………………………………………..………..

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Objectives

Objective is the aim of the experiment to be done in the laboratory/workshop. The

objective or objectives of the experiment should be stated at the beginning of the report.

One or two sentences are usually sufficient to summarize the purpose of the experiment.

Theory

For an engineering lab class this will probably involve one or two explanations, and a

statement of key mathematical expressions. Unless you have been asked to do so, there is

no point in writing out standard derivation from textbooks.

Equipments Used

This section should include a brief description of the test/work apparatus and

instrumentation that was used. Where appropriate, a schematic diagram should be

included that identifies the major components of the test system.

Procedure

A description of the procedure that was used to obtain the test results shall be provided.

Summarize the detailed steps that were used; do not repeat the detailed steps in this

section. There is a well established tradition of using the passive voice when describing

experimental procedure

Results and analysis

Experimental results should be presented in a clear and concise manner. The way you

describe the outcome of your experimental results and theoretical relationship is

important. Test results obtained from the experiment shall be

• Tabular

• Graphs/Engineering drawing

• Digital photographs

• A combination of the above.

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Conclusions

This section summarizes your conclusion regarding the results. If the results differ from

those expected, provide an explanation based on an analysis of the data. Examine any

assumptions that were used that could be adversely affecting the results. Consider

experimental error as a cause of the differences. The conclusions should be based on (1)

the experimental results, and (2) supporting technical rationale and analysis.

References

Give references used like books, web site and other documents etc.

a. Books

Author, A. A., Author, B. B., and Author, C. C. (year). Title of book: Subtitle. (Edition [if not

first]). Place of publication: Publisher.

Example

Holtz, R. D. and Kovacs, W. D. (1981). An Introduction to Geotechnical Engineering, 1st

Edition, Prentice Hall.

b. Thesis

Author, I.N. (YEAR). Title of Thesis. Unpublished PhD Thesis. University.

Example

Jones, H. C., Cross, W & Smith, K. M. (1999). Get your dissertation done. Baltimore: University

of Baltimore Press.

c. Journal or Conference Papers

Author(s) Year, „Article Title‟, Journal Name, vol. Volume, no. Issue, pp. Pages.

Example:

Seaman, C.B., Mendonca, M.G. & Kim, Y.M. 2003, „User evaluation and evolution of a

prototype management tool‟, IEEE Transactions on Software Engineering, vol. 29, no. 9, pp.

838-51.

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d. Websites

Author. (Date published if available; n.d.-no date- if not). Title of article. Title of web site .

Retrieved date. from <URL>.

Example

United Nations Environment Programme (2001). Environmental Aspects of Phosphate and

Potash Mining. Retrieved January 2008. From

www.mineralresourcesforum.org/docs/pdfs/phosphate_potash_mining.pdf

http://www.mineralresourcesforum.org/docs/pdfs/phosphate_potash_mining.pdf

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Experiment # 1

Workshop Activity – Manufacturing of Door Sliding Lock Assembly

INTRODUCTION:-

Mechanical workshops are currently considered as the heart of all industries. The most

important tasks of mechanical workshop are the development and construction of

equipment and machinery, tools, jigs and fixtures, and all mechanical assemblies.

Different manufacturing operations can be conducted in each mechanical workshop;

however, the types and size of available machinery, tools, raw materials, handling

equipment, and the experience of the technical operators all dictate the capability of that

workshop to manufacture/assemble a certain part or equipment.

Mechanical workshops usually contain general-purpose conventional machines to allow

manufacturing flexibility in producing variety of parts and assemblies. However the

successful operation of such conventional machines heavily depends on the skill and

experience of these machine operators.

In this activity students will learn how to use workshop machinery and practice several

manufacturing tasks to improve their understanding on how things are made as well as to

broaden their knowledge on workshop technology.

OBJECTIVES:-

To practically apply metal cutting including turning and drilling, metal forming,

welding, and fitter works towards the manufacturing of a door sliding-lock

assembly.

To experience the practical workshop atmosphere, understand the safety

procedure in workshops, be familiar with workshop safety gears, and use the

different workshop tools properly.

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APPARATUS:-

Different machines and tools will be used during this session. The main of these are:

1. Reciprocating sawing machine.

2. Conventional turning machine (Lathe machine).

3. Vertical drilling machine.

4. Arc welding equipment.

5. Hydraulic press equipped with metal forming die.

6. Different hand-held files.

7. Calipers, Scales, and Vernier.

Set of proper tools suitable for each operation will also be provided.

PROCEDURE:-

A number of steps are required to be followed. The student will be given a certain

manufactured assembly of the door lock, hence their task is to do a reverse engineering

by attempting to manufacture similar assembly.

After a quick tour inside the workshop, the student will be briefed on how to handle their

task. The achievement of the student tasks will include a number of practical steps. These

steps may include the following stages:

Stage 1 Dimensional measurement of the model and identifying the types and shapes

of the required raw materials.

Stage 2 Sawing of the base plate (6mm thickness)

Stage 3 Fitter works (sharp edge chamfering)

Stage 4 Cutting of the cylindrical shaft by sawing

Stage 5 Turning operation of the shaft on a conventional lathe machine (Metal

Cutting)

Stage 6 Metal-forming on a hydraulic press

Stage 7 Drilling operations on a vertical drill

Stage 8 Assembly of the parts

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Stage 9 Welding (Arc welding)

Stage 10 Finishing operations (Chamfering, Cleaning, and Inspection)

OBSERVATION AND CALCULATIONS:-

It is expected that students observe and identify the types of tools used in each operation

as well as recognize the different parameters (e.g cutting speed, depth of cut, federate,

etc.) used in each manufacturing operation. Students are expected to apply engineering

calculations that they learned during this course and present these calculations in their

report. Calculations may include but not limited to force, pressure, and power utilized in

metal forming, machining time, cutting forces, and power requirement during machining.

RESULTS AND ANALYSIS:-

Students are required to comprehensively measure all manufactured parts and assembly

dimensions. They will use these to produce proper engineering drawing of each part as

well as the final assembly. The students are also required to discuss all process stages that

they followed to manufacture the required assembly and provide detail information about

each process stage.

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Experiment # 2

Heat Treatment of Steel

INTRODUCTION: -

Heat treatment operations are performed on metal work parts at various times during their

manufacturing sequence in order to achieve one of the following aims:

To soften a metal for forming prior to shaping.

To relieve strain hardening that occurs during forming.

To strengthen and harden the metal near the end of the manufacturing

sequence.

The principle heat treatment types of steel include the following:

Annealing.

Hardening (Martensite formation).

Tempering of Martensite.

Surface hardening.

OBJECTIVES: -

The purposes of this experiment are to:

Investigate the processes of heat treating of steel

Study hardness testing and its limits

Examine microstructures of steel in relation to hardness

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APPARATUS:-

Electric furnace (up to 1300oC).

Rockwell/Brinell Hardness measurement machine.

THEORY:-

To understand heat treatment of steels requires an ability to understand the Fe-C phase

diagram shown in the provided Figure. Steel with a 0.77 wt% C is said to be a eutectoid

steel. Steel with carbon content less than 0.77 wt% C is hypo-eutectoid and greater than

0.77 wt% C is hyper-eutectoid. The region marked γ (austenite) is face-centered-cubic

(FCC) and α (ferrite) is body-centered-cubic (BCC).

There are also regions that have two phases. If one cools a hypo-eutectoid steel from a

point in the austenite region, reaching the upper transformation line, ferrite will form

from the austenite. This ferrite is called pro-eutectoid ferrite. When the lower

transformation line is reached, a mixture of ferrite and iron carbide (cementite) forms

from the remaining austenite. The microstructure of hypo-eutectoid steel upon cooling

would contain pro-eutectoid ferrite plus pearlite (α+ Fe3C).

The size, type and distribution of phases present can be altered by not waiting for

thermodynamic equilibrium. Steels are often cooled so rapidly that meta-stable phases

appear. One such phase is martensite, which is a body-centered tetragonal (BCT) phase

and forms only by very rapid cooling.

Much of the information on non-equilibrium distribution, size and type of phases has

come from experiments. The results are presented in a time-temperature-transformation

(TTT) diagram shown in the provided Figure. As a sample is cooled, the temperature will

decrease as shown in the Figure. At point Ps, pearlite (a mixture of ferrite and cementite)

will start to form from austenite. At the time and temperature associated with point Pf, the

austenite will have completely transformed to pearlite. There are many possible paths

through the pearlite regions. Slower cooling will cause coarse pearlite to form, while fast

cooling will cause fine pearlite (Bainite) to form.

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Cooling can produce other phases. If a specimen were cooled at a high rate of cooling,

martensite, instead of pearlite, would begin to form at Ms temperature, and the austanite

would be completely transformed to martensite at temperature Ms by avoiding the

enterance in the nose of the pearlite zone boundary. Martensite causes increased hardness

in steels. Unfortunately, hardness in steels also produces brittleness. The brittleness is

usually associated with low impact energy and low toughness. To restore some of the

toughness and impact properties it is frequently necessary to "temper" the steels. This is

accomplished by heating the steel to a temperature between 500ºF (260ºC) and 1000ºF

(540ºC).

Tempering removes some of the internal stresses and introduces recovery processes in the

steel without a large decrease in hardness or strength.

To obtain the desired mechanical properties it is necessary to cool steel from the proper

temperature at the proper rates and temper them at the proper temperature and time.

Heat Treatment of Steels

Common steels, which are really solid solutions of carbon in iron, are body-centered-

cubic. However, the carbon has a low solubility in bcc iron and precipitates as iron

carbide when steel is cooled from 1600oF (870

oC). The processes of precipitation can be

altered by adjusting the cooling rate. This changes the distribution and size of the carbide

which forms a laminar structure called pearlite during slow cooling processes.

If steel is quenched into water or oil from 1600oF (870

oC) a metastable phase called

martensite forms, which is body-centered-tetragonal. This phase sets up large internal

stresses and prevents carbide from forming. The internal stresses produce a high hardness

and unfortunately, low toughness. After cooling, to restore toughness, steels are tempered

by reheating them to a lower temperature around 800oF (426

oC) and cooling. The

tempering relieves the internal stresses and also allows some iron carbide to form. It also

restores ductility.

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PROCEDURE:-

You will be provided with 6 specimens of SAE1045 steel (Medium carbon plain steel)

for your study. Measure the hardness of all specimens using the HRA scale.

1. Heat the six specimens in one furnace at 1600oF (870

oC) for 1/2 hour.

2. Remove one specimen from the furnace and cool it in air on a brick.

3. Remove two specimens and quickly drop them into water; the transfer should take

less than one second. A little rehearsal could help. Be careful not to touch the

specimens before they are cooled in water.

4. Remove another two specimens and quickly drop them into oil; the transfer

should take less than one second. A little rehearsal could help. Be careful not to

touch the specimens before they are cooled in oil.

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5. Turn off the furnace with the one left specimen inside. Allow the sample to

remain in the furnace for one hour. The air-cooled and furnace-cooled specimens

can be cooled in water after one hour. (Why? Answer this in your report).

6. Measure Rockwell hardness of the quenched specimens before the next step.

7. Temper 1 each of the quenched specimens (one specimen quenched in water and

one specimen quenched in oil) 30 minutes at 800oF (430

oC). After tempering, the

specimens can be cooled in water.

8. Measure hardness of all 6 samples using the Brinell and Rockwell A or C scales.

OBSERVATIONS AND CALCULATIONS:-

1. While hardness measurement, if more than one impression is made per sample,

average the Brinell diameters for each specimen.

2. Compute the Brinell hardness numbers and compare with the numbers read from

a conversion chart for Rockwell A or C to Brinell.

3. Graph BHN (x-axis) versus Rockwell Hardness numbers (y-axis).

4. Graph Rockwell A or C hardness vs. tempering temperature (oC).

5. Compute the ultimate tensile strength (psi) of all specimens from the average

BHN for each specimen using:

σult= 500 x B.H.N.

RESULTS AND ANALYSIS:-

Within your report you should discuss the data referenced in the "OBSERVATIONS

AND CALCULATIONS” as well as the following:

What is the purpose of quenching and tempering steel?

Discuss the sources of error for the various hardness testers, the relative ease with

which they may be used, and the comparative consistency of test results.

What factors probably contributed to the scatter in the hardness data?

Which hardness test appears to be most accurate?

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Using the inverse lever law, estimate the amount of carbide (Fe3C) present at

1338oF (just below the eutectoid temperature) for SAE 1045.

What are (or should be) the differences in the microstructure for each heat

treatment process and how do these differences correlate with hardness?

Discuss errors in this experiment and their sources.

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Lab Manual MECH2118 2011