The first step in troubleshooting flash is to determine whether it is a filling problem or a packing problem.
I have a part with flash. It ran many times in the past without flash, but recently we have been using a new machine and it is often creating flash. We have tried many adjustments including packing pressure, clamp tonnage, transfer pressure, etc.
The first step in troubleshooting flash is to turn off packing and determine if you have flash during first stage injection. This will tell you immediately whether the problem is occurring during 1st stage injection or second stage packing. Ultimately, this will focus your attention very quickly.
In many cases, you see technicians adjust parameters such as packing pressure and clamp tonnage when the problem occurs during injection. The problem with this approach is that the technicians almost never return the clamp tonnage or packing pressure to their original settings when they ultimately fix the flash. As a result, the plant gets lots of other defects such as shorts, sinks, and burns afterwards.