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Cork Institute of Technology
Bachelor of Engineering (Honours) in Mechanical Engineering – Stage 3
(NFQ – Level 8)
Autumn 2006
Manufacturing Engineering
Time: 3 Hours
Instructions: Answer FIVE questions Answer TWO from each of Sections A and B and ONE from section C Use a separate answer book for each section
Examiners: Mr. M. P. O’Mahony Dr. M. Woods Mr. D. Fallon Mr. J. E. Hegarty Prof. M. Gilchrist
Section A
Q
(a) List THREE advantages and/or disadvantages of thread rolling. (3 (^) Marks ) (b) Briefly describe ONE method of Thread grinding. ( 5 Marks ) (c) What factors contribute to the accuracy of the finished workpiece in a Gear Forming operation? (5 Marks) (d) The plug method is to be used to check the pitch diameter of a 36T tooth, 5mm module, 20 o^ Pressure angle spur gear, calculate: (i) The plug size (2 Marks) (ii) Distance over plugs placed in opposite spaces (2 Marks) (iii) Distance over plugs spaced 10 teeth apart (3 Marks)
Q
(a) List FIVE Casting Parameters. (5 Marks) (b) State Chvorinov’s Rule and explain the terms used in the equation. (4 Marks) (c) Explain (^) Directional Solidification and how it is achieved in the casting process. (5 Marks) (d) Describe THREE casting defects and their possible causes. (6 Marks)
Q
(a) List Three ways of countering the effects of Springback in a bending operation. (3 Marks) (b) Fig Q3 shows the dimensions of a bracket required to be bent from a flat strip of mild steel of 450N/mm^2 yield stress. If the work is drawn to a depth of 18mm below the top surface of the die, find the punch load required for: (i) Bending (1 Marks) (ii) Overcoming friction, assuming the sides of the component are very slightly ironed, take μ=0.15 (2 Marks) (iii) Planishing at the end of the stroke. (2 Marks)
(c) In the context of Deep Drawing: (i) List the material properties which principally determine how well a metal may be drawn. (2 Marks) (ii) State the rules which should be observed to obtain the maximum drawing ratios. (2 Marks)
(d) List FIVE guidelines for the design of Blanking/Piercing Tools. (5Marks)
(e) What is SHEAR in the context of a Press Tool and what is its purpose? (3 Marks)
Fig Q 3
Q
(a) (i) Explain the microscopic origins of friction between metal surfaces. (ii) Give ONE example of an undesirable effect of friction. ( 6 marks )
(b) State THREE criteria which must be satisfied by a lubricant oil acting as a boundary lubricant. Describe how an oil operates as a boundary lubricant. ( 7 marks ) (c) Explain how old style waxed wood skis maintained a low coefficient of friction. What happens at temperatures below approximately -10 o^ C? How has the design of modern skis improved on the performance of waxed wood skis? ( 7 marks )
Section C: Quality Engineering
Q
(a) (i) A process which is in statistical control has a mean of 50 and a standard deviation of 5. What is the probability that a random sample of 16 items will yield a mean greater than 53? ( 4 Marks ) (ii) A process is in control at X = 100, R = 7.3 with n = 4. If the process level shifts to 101.5, with the same R , what is the probability that the next X point will fall outside the old control limits? ( 6 Marks ) (iii) A process is in control with a mean of 50 and a standard deviation of 2. The upper specification for the product being produced is 60, and the lower specification is 42. Assuming symmetrical tolerancing, what is the value of Cpk? ( 4 Marks )
(b) Explain clearly the difference between capability and control. ( 6 Marks )
Q
(a) One of Deming’s 14 points urges that organisations “cease dependence on inspection to achieve quality. Eliminate the need for mass inspection…” Discuss this assertion in detail in the context of quality in manufacturing. ( 10 Marks ) (b) A theoretical model for optimum quality costs shows that total quality costs are minimised at a point, which is other than 100% good. Present and discuss this traditional model of quality costs. What are the limitations of the model? How can the model be interpreted in the context of continuous improvement? ( 10 Marks )
