MM1DM1 2012-13 With Solution

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The University of NottinghamMalaysia Campus

DEPARTMENT OF MECHANICAL, MATERIALS AND MANUFACTURING ENGINEERING

A LEVEL 1 MODULE, SPRING SEMESTER 2012-2013

DESIGN AND MANUFACTURE 1

Time allowed ONE Hour THIRTY Minutes

Candidates may complete the front cover of their answer book and sign their desk card butmust NOT write anything else until the start of the examination period is announced

Answer THREE question, ONE from each of Section A, B and C

Only silent, self contained calculators with a Single-Line Display or Dual-Line Displayare permitted in this examination.

Dictionaries are not allowed with one exception. Those whose first language is not Englishmay use a standard translation dictionary to translate between that language and English

provided that neither language is the subject of this examination. Subject specific translationdictionaries are not permitted.

No electronic devices capable of storing and retrieving text, including electronic dictionaries,may be used.

DO NOT turn examination paper over until instructed to do so

ADDITIONAL MATERIAL: SELECTION TABLE FOR WEDGE BELTS BS4500A

INFORMATION FOR INVIGILATORS: None

Turn Over


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3

SECTION B – MACHINING

3. (a) Explain the formation of built-up edge (BUE) chips. Identify an advantage ofthese chips during machining process.

[6 marks]

(b) Why does the temperature in cutting depend on the cutting speed, feed anddepth of cut? Explain in terms of the relevant process variables.

[9 marks]

(c) For a turning operation using a ceramic cutting tool, if the speed is increased by

50%, by what factor must the feed rate be modified to obtain a constant toollife? Use n = 0.5 and y = 0.6. Explain how this modification will maintain tool

life.V T n d x f y = C

[10 marks]

(Total: 25 marks)

4. (a) Explain the reason for the development of cutting inserts.

[5 marks]

(b) Thermal conductivity and coefficient of thermal expansion are properties thatcan be important to the life of a cutting tool. Explain the reasons.

[10 marks]

(c) A machining operation is being carried out with a cutting fluid that is an effective

lubricant. Explain the changes in the mechanics of the cutting operation if thefluid is shut off.

[10 marks]

(Total: 25 marks)

Turn over


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4

SECTION C – METROLOGY & TOLERANCING

5. (a) Explain the specifications that need to be considered when choosing a measuring

instrument.[10 marks]

(b) Explain the need for automated inspection and give an example of an industrialautomated inspection system.

[10 marks]

(c) Describe how flatness of a surface can be measured.

[5 marks]

(Total: 25 marks)

6. (a) Explain with the aid of neat diagrams what is meant by clearance fit, interferencefit and transition fit.

[9 marks]

(b) A shaft with nominal diameter of 50 mm has to be connected to a hole with the

same diameter. Calculate the maximum and minimum tolerances required toproduce:

i) H7p6 interference fit

[5 marks]

ii) H7k6 transition fit[5 marks]

(c) Explain the difference between dimensional tolerance and geometrical toleranceand their importance in manufacturing.

[6 marks]

(Total: 25 marks)

End


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2

SECTION A – MACHINE ELEMENTS

1. (a) List three advantages and three disadvantages of belt drives.Advantages:

Easy installation Low maintenance High reliability Good ‘twistability’, adaptability to non-parallel drive High transmission speed

Disadvantages Limited power transmission capacity Limited speed ratio capability Susceptible to changes in environment, i.e. contamination with

lubricants[2 marks]

(b) Describe two typical examples of chain drives and the advantages it has overbelt drives.

Chain drives are most commonly used in low speed high torque applications,especially where space is limited.Roller chain (most common type, i.e. use on bicycle)High load applications two or more rollers can be placed side by sideRoller chains are described in BS 228 and BS 2947Inverted tooth chainQuieter than the roller chain and may be run at higher speed

Advantages of Chain Drives:Having longer lives than belts but requires good lubrication

[4 marks]

(C) Design a wedge belt drive from a 55 kW electric motor which runs at 1440 rpmto a centrifugal pump running at 720 rpm. The centre distance is to beapproximately 900 mm and the duty is 24 hours per day. The motor shaft is 70mm diameter and the pump shaft is 80 mm diameter.


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[2 marks]

[2 marks]

[2 marks]

[2 marks]


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[6 marks]

[2 marks]

[3 marks]


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SECTION B – MACHINING

3.

[6 Marks]

[9 Marks]

[10 Marks]


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4.

[5 Marks]

[10 Marks]

[10 Marks]


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SECTION C – METROLOGY & TOLERANCING

5.

6.

[10 Marks]

[10 Marks]

[5 Marks]

[9 Marks]


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(b)

(C)

[5 Marks] [5 Marks]


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[6 Marks]

Documents

MM1DM1 2012-13 With Solution