(a) Distinguish between allowance and tolerance. What are unilateral and bilateral systems of specifying tolerance? What is the condition for a force fit or an interference fit between mating parts? Why is hole basis system preferred over a shaft basis system?
(b) A person operates a machine that makes capacitors. He has been advised to keep track of the percent defectives at his work centre. He knows that with this type of process, they expect about 4% defectives plus or minus some chance variation. He wishes to initially construct a control chart for defectives. He has prepared ten daily samples of hundred capacitors each.
|
Sample Number
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
|
% defectives
|
4
|
3
|
3
|
6
|
1
|
9
|
5
|
12
|
4
|
3
|
Construct the relevant control chart. What are the upper and lower control limits?
Plot the data points on the proposed control chart. Is the process under control? What follow up steps should be undertake, if any?