Page 32 - Injection Molding Advanced Troubleshooting Guide

1.4 Troubleshooting Methodology 13

Continue to work through the STOP methodology cycle until the root cause is
determined, corrected, and verified. Remember that it may take weeks of run time
to fully determine the true impact of the change.

1.4.6„ Hard Fix versus Processing around Problem

Whenever possible a permanent hard fix should be implemented to resolve the
true root cause of the issue. If a physical change can be implemented in the mold
or part design, the process window tends to be much larger. Implementing a hard
fix to a mold may involve some up-front cost but will lead to long-term savings. Do
not be short-sighted when troubleshooting, but rather think of the multiple years
that the mold may run in production.
The importance of implementing a hard fix becomes more magnified when consid-
ered against the human ability to detect part defects. If the plant quality system is
relying on detection from a person to catch defects the resulting customer returns
will become very costly. However, if a hard fix is implemented the defects are pre-
vented and human error and judgment do not play into shipping bad parts to the
customer. Do not rely on human detection; prevention is the key to eliminating
shipping bad product.

1.4.7„ Troubleshooting Tools

In addition to the 4M methodology discussed above there are many additional tools
and techniques that can help with troubleshooting including the following:
ƒ 5 Why
ƒ Fishbone diagram
ƒ Scrap recording sheets
ƒ Brainstorming
ƒ Design of experiments (DOE)
ƒ Is/Is Not
ƒ Change log

1.4.7.1„ 5 Why

5 Why is a process that was developed by Sakichi Toyoda and used initially at
Toyota for problem solving. The intent of the 5 Why process is to continue to ask
questions until the true root cause is determined. An example would be:
ƒ Problem with splay on parts.
ƒ Why? Material is wet.