To tal Quality - Assignment Brief This assignment is based on a case study in which a consultant (you) is asked to investigate a problem with an automotive assembly that is causing the company...

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Total Quality - Assignment Brief
This assignment is based on a case study in which a consultant (you) is asked to investigate a problem with an automotive assembly that is causing the company considerable embarrassment. You are therefore required to produce a report analysing the problem and making recommendations to:
(a) Deal with the immediate situation, and
(b) Prevent the problem from recurring.
Although the assignment does involve the use of statistical tools to perform the analysis there is considerable scope for discussion of a number of factors both with respect to the purchasing policy and the engineering implications. Submissions providing a mere statistical analysis will only attract minimum marks. Higher marks will depend on depth and extent of discussion including the practicality of any recommendations.
Points for consideration are:
1. What tolerances are necessary to ensure non-defective assemblies?
2. Is the critical dimension (protrusion of cotter thread) affected more by one part
than by the other?
3. Which suppliers are the likely cause of the problem?
4. What difference would it make if statistical tolerancing was to be used and what would be the implications/assumptions?
5. What could be done with supplies that are found to be defective?
6. What longer-term steps might the company take? Above are just some suggestions, the list is not exhaustive.

The Shackle
PIN AND SHACKLE ASSEMBLY
PROBLEM
A private auto parts supplier obtains samples of original parts and arranges for them to be made and supplied by alternative suppliers. Suppliers were not provided with drawings or specifications only samples. This assignment concerns a three-part assembly for leaf spring shackles. The shackle, pin and cotter when assembled should be such that the thread of the cotter protrudes between 9 and 19 mm to allow for a washer and nut.
Complaints have been received that the items, when bought separately, do not always comply with the above conditions. This results in either the protruding thread being insufficient to allow for the nut and washer or the cotter protruding so much that the nut can’t be tightened.
There are 10,000 shackles, pins and cotters in stock.

TASK
The task is to investigate the reasons for defective assemblies by carrying out a statistical analysis and to suggest recommendations for overcoming the problem.
FACTS
Three different suppliers supply the pins. Four different suppliers supply the shackles. One supplier supplies the cotters. Each of the items may be purchased separately and may be required to be assembled with parts supplied by original manufacturers.
PROCEDURE Pins:
A random selection of 24 pins was taken from each of the sources. They were inspected for width across the flat (dimension A).

A
Shackles:
A random selection of 24 shackles was taken from each of the suppliers. These were inspected for the distance between centres (dimension B).

B
Cotters:
24 cotters were assembled with various combinations of shackles and pins representing the two extreme conditions.
OBSERVATIONS
An analysis of the assembly in the light of observations revealed the following specification:
· Cotter: Taper is 1 in 15
· Pin: Width across flat is 19 mm nominal
· Shackle: Distance between centres is 13 mm nominalResults of inspection of samples
Pins (dimension A)
Supplier A
18.8718.9719.0318.9218.9719.0318.9519.00
19.0318.9519.0019.0518.9719.0019.0518.97
19.0319.0518.9719.0319.0518.9719.0319.10

Supplier B
19.0019.0519.1519.0019.0519.1819.0019.05
19.1819.0019.1019.1819.0019.1019.2319.00
19.1019.2319.0319.1019.2319.0519.1519.23

Supplier C
18.7019.8620.0918.7519.8920.1218.8519.91
20.1418.8719.9720.2218.9019.8720.2719.46
20.0220.3019.6920.0720.3219.8420.0720.37

Shackles (dimension B)
Supplier D
13.1013.2813.3613.1013.2813.3613.1013.28
13.3813.1313.1813.3013.4113.3013.4113.20
13.3013.4313.2513.3313.4313.2813.3313.46

Supplier E
12.9212.9713.0812.9212.9713.0812.9212.97
13.1012.9213.0013.1312.9513.0313.1312.95
13.0313.1312.9513.0513.1512.9713.0513.30

Supplier F
12.8712.9713.0312.9013.0013.0312.9213.00
13.0512.9213.0013.0512.9513.0013.0812.95
13.0313.1012.9713.0313.1012.9713.0313.15

Supplier G
12.7712.8512.9212.7712.8712.9212.8012.87
12.9212.8012.8712.9512.8212.9012.9512.82
12.9012.9512.8512.9012.9712.8512.9213.03

Cotters
The quality of the cotters was of the same quality as the originals. From the samples there was no reason to believe that these would be the source of trouble.
20.00
14.00±5

1 in 15
13.00
10.00
12.00
19.00
22.00
40.00
Answered Same DayDec 20, 2021

Solution

Robert answered on Dec 20 2021
3 Votes
pin and shackle assembly
5/28/2012
Review & Recommendations | students Name
ABC
INC.
PIN AND SHACKLE ASSEMBLY
TABLE OF CONTENTS
1 INTRODUCTION 2
2 PROBLEM DEFINITION 2
3 MEASURE THE PROBLEM 2
3.1 ESSENTIAL TOLERANCES 3
3.2 CRITICAL DIMENSION 3
3.3 SAMPLE DATA 4
4 ANALYSIS OF DATA 7
4.1 SUPPLIER A 7
4.2 SUPPLIER B 8
4.3 SUPPLIER C 9
4.4 COMPARISON OF SUPPLIER A, B, C 10
4.5 SUPPLIER D 10
4.6 SUPPLIER E 11
4.7 SUPPLIER F 12
4.8 SUPPLIER G 12
4.9 COMPARISON OF SUPPLIER D, E, F, G 13
5 SETTING UP TOLERANCE LEVELS 14
6 SETTING CONTROL LIMITS 14
6.1 CHECKING SAMPLES FOR CONTROL LIMITS 15
7 SUPPLIER RECOMMENDATION 18
7.1 DEFECTIVE MATERIALS: 18
8 STRATEGY 19
8.1 IMMEDIATE STRATEGY 19
8.2 LONG-TERM STRATEGY 19
9 CONCLUSION: 20
INTRODUCTION 1
The report is with reference to your work order to ABC INC. for analysis of the
Pin and Shackle assembly problem. We have analysed the product and
concluded on all probable causes of defects. Our observations and analysis of
the above problem along with recommendations is presented in this report. We
have analysed sample products from all of your suppliers and given a rating on
their quality standards. As quality is paramount for customer satisfaction we
have proposed to set stringent quality standards and control charts for Pin and
shackle assembly. Through the first phase of the report we have defined the
problem and listed the data collected for analysis of the problem. In next section
we have analysed the problem and presented our recommendations. In last
section we have presented the future strategy for your company and conclusion
of our study.
PROBLEM DEFINITION 2
It‟s important to understand the product to detect the problem. The pin and
shackle assembly is a high precision automotive assembly. The assembly has
three separate parts Pin, shackle and Cotter. Based on our study we find that
the three parts need to join together to form the complete assembly and the
precision level of all three components is vital for it to function as a unit. The
cotter is fitted with nut and washer. The problem occurs in two conditions:
 The cotter protruding head is so long that threaded part of cotter
ends and the nut cannot be tightened.
 The cotter protruding head is so short that threaded part is
insufficient for nut and washer.
The three components come from different vendors and they have not been
given any specification or design drawings. The product design at present is
ased on sample specification. The acceptance criterion/ tolerance level for
each component is not specified. However Cotter protrusion gives a tolerance
of 9 to 19 mm for the unit to be acceptable and function. Any protrusion
variation more than the above values will result in problems mentioned above.
MEASURE THE PROBLEM 3
Problem of misfit occurs when the components are purchased separately. The
causes of problem are shown with a cause effect diagram.
Fig 1: Cause effect diagram for the pin and shackle problem
The further detailing of the causes will require analysis of the supplier
processes and so has been excluded from the report.
3.1 ESSENTIAL TOLERANCES
From the above four causes we can conclude that he vital dimension for the
pin is dimension „A‟ and for shackle it is dimension „B‟. So we need to set
tolerances for the above two dimensions. The quality of cotters has shown no
deviation however the critical dimension for it will be the end diameter and the
converging slope.
3.2 CRITICAL DIMENSION
Fig 2: Product Diagram
If we observe the product diagram we can see that the pin is a circular
component and shackle has a circular opening for it. The centreline of the
opening will be critical for the pin to match the dimension „A‟. Even if the pin
shows a value within tolerance level still the acceptance of the unit will depend
on dimension „B‟. If in case pin has higher diameter then it will not fit in the
shackle slot and if smaller then it will slip out. So the critical dimension is „B „.
The dimension „B‟ is set by the shackle manufacturer while making the hole for
the pin. The centreline of this hole is critical for overall performance of the
assembly.
3.3 SAMPLE DATA
Below data are samples of dimension ‟A‟ and „B‟ from various suppliers and
some statistical measures for analysing them. The analysis would be done in
next section.
Scatter plot shows the deviation of the sample about its mean or objective
value. A scatter plot of closely spaced sample values shows less variation as
compared to large spread out points. Typically supplier A & F have all values
within a thinner band indicating less variation in sample .
Chart 1: Scatter plot for Supplier A (Dimension A)
18.85
18.9
18.95
19
19.05
19.1
19.15
0 5 10 15 20 25 30
Supplier A
Supplier A

Chart 2: Scatter plot for Supplier B (Dimension A)
Chart 3: Scatter plot for Supplier C (Dimension A)
18.95
19
19.05
19.1
19.15
19.2
19.25
0 5...
SOLUTION.PDF

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