Making Significant Changes…

As a follow-up to a previous post, I was asked to expand in the second rule of processing…

The 5 Basic Rules of Processing (from before):
Rule 1 – Make one process change at a time
Rule 2 – Make significant changes
Rule 3 – If a change does not help, change it back
Rule 4 – Document the process
Rule 5 – Document all changes to the process
Rule #2
The idea behind this is that you always want to know you are making a change which is important. Too often people will tweak different parameters without any direct knowledge as to the effectiveness of the change.
When you make a change, you want to ensure it is large enough to make a difference. Remember any change to the process can be reversed either completely or partially.
Additional Thoughts
I have seen many molders who make small adjustments with the belief it will improve the situation. A symptom of this behavior is a control panel with a large amount of numbers which do not end in either 5 or 0. For instance, if the injection profile looks like the following… V1=11.1 mm/s, V2=30.3 mm/s, V3=23.4 mm/s, V4=28.4 mm/s, and V5=12.7 mm/s. It is very unlikely that each of those velocities have been optimized and each speed in the profile can be properly justified. This type of profile is almost always the result of someone tinkering with the process until a good part came out of the machine.

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