Definition: Defining 1.to make clear, 2.to determine
Probably the most critical aspect of troubleshooting anything is to define exactly what the issue is, so as to solve the issue and or problem. Within the plastics processing industry this is critical and complicated due to variables and what tools are allowed to be used to correct the results of the issue.
Some basic problems or issues we come across for example would be non-fill or short shots, black specs, flash, contamination, dimensional variation, etc. With any of these numerous books and trouble shooting guides well explain the possible causes and possible solutions. Fairly simple or so it would seem. A point to be made here is that flash, short shots, black specs are really results of something but are typically called the problem.
But the fact is that it is complex at times due to our rush to come up with a solution in that we do not take the time to solve the issue. This is what some may refer to a Band-Aid approach.
An example might be flash on one part in a multicavity tool. One fix would be to block off the cavity, (creating numerous other issues), changing the pressure so as to minimize the amount or rate of material going into the cavity, lowering melt temperature so material does not flow as easy, etc. But the question than comes up as to why is the cavity flashing? Did we really solve the issue of why? No and in many cases we have now done more harm with our finished product than the issue of flash.
To solve the issue to define the problem is to get to root cause. Some would say to ask WHY 5 times. For example:
Why do we have flash?
Answer: It flashed because too much material was injected into the mold cavity.
Why are we putting too much material into that cavity?
Answer: Too much material goes in because we have tool damage and it vents easier.
Why do we have tool damage?
Answer: Because we caught a part and it coined the tool.
Why did we catch a part?
Answer: We caught a part because that cavity fills first and over packs.
Why does it fill first?
Answer: Because it is closer to the sprue, has a larger gate...etc.
This can go on but the point is to look further so as to get to the root cause of the issue and not just the results of the issue.
It has been found on numerous occasions by the author that we may be limited to solving the issue due to the time factor, and that time is money and we need parts now. This is understandable, fixing the issue with a Band-Aid, but if the root cause is never found or the issue is not investigated completely the problem well continue to come back and in most cases the process window for allowable parts well shrink so as to cause profit loss.
The definition of an issue should start with the problem. We find the problem; we clarify the problem and then find the cause.
So the mindset now to defining the cause for the issue is:
1- What is the issue...? (Problems such as black specs, short shots, flash ...etc.)
2- Define the cause of the issue....( flash our result is caused due to tool damage due to parts sticking because we over packed the cavity, due to gate size being larger)
3- Solve the current/immediate issue, flash
4- Solve the root cause when allowed. (hopefully now but in all honesty later if you are lucky)
If we are lucky than #3 of above is forgotten and we go immediately to number 4 which now becomes our number 3...
SLSilvey
