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Unformatted text preview: ent it recurring. There are two types of abnormalities: those that can be
identified through inspections, and those that cannot be identified through inspections. Abnormalities that can be identified through inspections
2. Typical abnormalities that are found in inspections are:
a. A greater number of defects than usual.
b. A new type of defect.
These may be found by inspectors during periodic inspections, by employees conducting
their own inspection, or they may be seen in control charts (see Text 9.8).
3. In periodic inspections the current values of the product or process are compared with
the standard or target values (the values you want to have). The term ‘dispersion’ (see
Text 9.7) is used to describe how the current values differ from the standard or target
values. Some dispersion is expected and accepted, but if dispersion goes beyond that,
then you have an abnormality. Wherever possible, convert the values observed in
inspection into numerical figures, and present them visually in graphs or charts so that
abnormalities can be easily spotted. A control chart is a typical graph for identifying
abnormalities. It shows how the values are dispersed and will immediately show the
presence or absence of abnormalities.
4. However, dispersion during the production processes is not always caused by
abnormalities. It may also be caused by chance, even when standard processes are
strictly observed. We need to know which type of dispersion is occurring. This is where
the control chart will help. With its control lines and control limits, it will show the
dispersion type. When it shows that dispersion results from abnormalities, investigate the
causes and take appropriate action. Abnormalities that cannot be identified through inspections
5. There are some abnormalities that are not spotted in inspections. When machines, for
example, produce a greater amount of noise than usual, or material surfaces have a
different feel, the situation can be described as abnormal. Such slightly unusual events
should be reported as abnormalities by anyone who happens to notice them. This is a
responsibility that everyone shares. Unit 9 - Problem solving 6 A Roadmap to Quality 05-87581_unit 9.qxd 09/09/2005 11:49 Page 7 6. Example: This example involves plastic auto parts that were injection moulded. Injection
moulding is followed by the process of gate(runner)-cutting. One day, a woman in
charge of gate cutting thought that the moulded parts felt somewhat “fragile”. She did
not know what exactly was wrong, but she felt there was something unusual about the
moulded parts, and immediately called her team leader.
7. The team leader, wondering if “the material had changed or if the temperature of the
metal melds was lower than usual”, suspended production and investigated the reported
abnormality. After establishing that all the other factors in the process except the
material were normal, production was resumed using a substitute material. The original
material was put on hold. No abnormality appeared after production was resumed.
8. Meanwhile, the suspended material was examined carefully by the manufacturer. The
examination confirmed that the material was different from usual. It was found to
possess different particle diameters because of a minor abnormality in its manufacturing
process. Early detection of the abnormality prevented major losses. Damages were
minimized by the woman who “felt something was wrong” and reported it immediately.
This employee had never been instructed to take any actions when moulded parts
seemed “fragile”. All she had been asked to do was perform gate cutting. However, she
sensed the difference and reported the abnormality on her own initiative. Her good
sense and appropriate response prevented an increase in the number of defective
Figure 9.8d Control chart for the consumption of steam in drying synthetic rubber Discussion
The following questions ask you to think about how the ideas in the text could be applied in
your company. Some of the ideas may not be relevant to you. Concentrate on what is
relevant. Keep notes of your conclusions – you will need them to prepare your action plan
afterwards. Where appropriate ask yourself the RADAR questions.
Note: Always include in your discussion any figures referred to in the text, if you feel these
are relevant to your company.
a. Parag. 1: Do you think that abnormalities may often not be noticed in your
company? Why do you think this? Do you think they are often ignored? Why do you
think so? Give examples of some kinds of abnormalities that may not be noticed or
may simply be ignored. What could be done about this?
b. Parag. 1: Which of these two types of abnormality do you think are most common in
your company? Give one or two examples.
c. Parag. 2: What typical abnormalities are recognized during inspections in your
d. Parag. 3: To what extent can abnormalities found in your work processes be
converted into numerical figures? How could they be presented visually?
e. Parag. 4: Have you often found that dispersion has be...
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This note was uploaded on 10/07/2013 for the course MKT marketing taught by Professor Anamika during the Spring '12 term at Punjab Engineering College.
- Spring '12