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Best Wire - Manufacturing Engineering - Exam, Exams of Manufacturing Systems Design

National Institute of Industrial EngineeringManufacturing Systems Design

Main points of this past exam are: Best Wire, Advantages, Disadvantages, Thread Rolling, Thread Grinding, Nominal Outside Diameter, Whitworth Form, Nominal Size, Minus, Acceptable

Typology: Exams

2012/2013

Uploaded on 03/28/2013

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Cork Institute of Technology
Bachelor of Engineering (Honours) in Mechanical Engineering - Stage 3
(NFQ - Level 8)
Autumn 2007
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. P. Clarke
Prof. M. Gilchrist
Mr D. Fallon
Mr. M. P.O Mahony
Dr. M.E. Woods
Section A
Q1 (a) List FIVE advantages and/or disadvantages of thread rolling. (5 Marks)
(b) Briefly describe ONE method of Thread grinding. (5 Marks)
(c) A special fine thread has a nominal outside diameter of 4 inches. The pitch is 0.25in
and the threads are of Whitworth Form. The thread is acceptable if the effective
diameter is between nominal size and minus 0.008 in. When checked with wires of
diameter 0.15in the dimensions over wires was 4.070 in. If the flank angle and pitch
are correct, calculate the effective diameter and hence state whether the thread is
acceptable.
(Note Height of fundamental triangle for Whitworth H= 0.9605P) (8 Marks)
(d) When measuring the effective diameter of a thread, explain what is meant by the term
“Best Wire”? (2 Marks)
Q2. (a) State and define the terms in the Hollomon Equation. (5 Marks)
(b) Explain Strain Hardening. (4 Marks)
(c) Illustrate the THREE rules that should be followed when designing parts that are to be
upset-forged. (6 Marks)
(d) Determine the maximum reduction on a piece of steel 250mm thick, during cold
rolling when µ=0.1 and during hot rolling when µ=0.6 for a roll radius of 500mm.
Comment on how to achieve maximum draft when rolling. (5 Marks)
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Cork Institute of Technology

Bachelor of Engineering (Honours) in Mechanical Engineering - Stage 3

(NFQ - Level 8)

Autumn 2007

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. P. Clarke Prof. M. Gilchrist Mr D. Fallon Mr. M. P.O Mahony Dr. M.E. Woods

Section A

Q1 (a) List FIVE advantages and/or disadvantages of thread rolling. ( 5 Marks ) (b) Briefly describe ONE method of Thread grinding. ( 5 Marks ) (c) A special fine thread has a nominal outside diameter of 4 inches. The pitch is 0.25in and the threads are of Whitworth Form. The thread is acceptable if the effective diameter is between nominal size and minus 0.008 in. When checked with wires of diameter 0.15in the dimensions over wires was 4.070 in. If the flank angle and pitch are correct, calculate the effective diameter and hence state whether the thread is acceptable. (Note Height of fundamental triangle for Whitworth H= 0.9605P) (8 Marks) (d) When measuring the effective diameter of a thread, explain what is meant by the term “Best Wire”? (2 Marks)

Q2. (a) State and define the terms in the Hollomon Equation. (5 Marks) (b) Explain Strain Hardening. (4 Marks) (c) Illustrate the THREE rules that should be followed when designing parts that are to be upset-forged. (6 Marks) (d) Determine the maximum reduction on a piece of steel 250mm thick, during cold rolling when μ=0.1 and during hot rolling when μ=0.6 for a roll radius of 500mm. Comment on how to achieve maximum draft when rolling. ( 5 Marks )

Q3. (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. ( 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

Q6 (a) What is fatigue failure in a material? [2 marks] (b) There are two categories of fatigue in materials which are initially un-cracked. (i) Name the two categories. (ii) State the relevant stress condition and ONE operational condition for each of the categories of fatigue in initially un-cracked materials. (iii) Give ONE example for each category listed in (i) of a mechanical situation where that category of fatigue failure may occur. (iv) For ONE of the named categories, describe with the aid of a diagram the process of fatigue failure in a sample. [13 marks] (c) Define friction and wear. Give ONE example where friction and wear both occur with one as a desirable effect and the other as an undesirable effect. [5 marks]

Section C: Quality Engineering

Q7 Resistors for electronic circuits are being manufactured on a high-speed automated machine. The machine is being set up to produce a large run of resistors of 1,000 ohms each with a tolerance of ± 30 ohms. To set up the machine and to create a control chart to be used throughout the run, 15 samples were taken with four resistors in each sample. The complete list of samples and their measured values are as follows:

Sample Number (^) Sample Average X Sample Range R 1 993 25 2 998.5 15 3 1004 25 4 1010.5 22 5 1007.5 26 6 998.5 11 7 995.75 38 8 994.75 15 9 1001.75 18 10 996 28 11 997 17 12 1004.25 28 13 991 22 14 991 15 15 1003 21 Fig. 7.1 Process samples for resistor values in ohms

(i) Using the tables and control chart provided, develop an X chart and an R chart and plot the values. (10 Marks) (ii) Using appropriate calculations make a comment on both the control and capability of the process. (10 Marks)