How to Become a Tooling Troubleshooter, not a Tooling Replacer
When a mold has to be repaired due to excess flashing on a part, technicians usually try to get the job done as quickly as possible so the mold can go back into production. Many times, that solution works and the repaired mold runs at 100% efficiency. But in repairing the mold, did the technician simply replace tooling which might not yet have been at the end of its useful life? If so, was the old tooling thrown out, or was it tossed onto a shelf or into a cabinet?
FineKing Plastic Mould Ltd
That's where troubleshooting comes in, which is a lot different that just replacing a mold. Technicians who are skilled at troubleshooting understand how their molds function.
How technicians usually repair molds
* Examining defect samples to determine exact flash locations;
* Determining which piece of tooling (core, sleeve or cavity) caused the flash;
* Removing and examining tooling areas forming the flashed area of the part;
* If nothing obvious is found, looking in the tool crib for the tooling that may have caused the damage;
* Measure the tooling, compare their measurements to print tolerances and then replace tooling if measurements are under print specifications (NOTE: For many shops, this step is mandatory)
* Installing the replaced tooling in the mold and completing the repair.
How tooling troubleshooters repair molds
Now let's look at the steps that a tooling troubleshooter would take to determine the root causes of flashing to ensure that proper corrective actions can be taken:
Examine defect samples to determine the exact location AND direction of the flash – Knowing the direction of the flash will help you identify its root cause and correct the problem. For example, a vertical flash is usually caused by too much plastic between a core and sleeve or other tooling (where clearance is determined by a running fit). If the flash is horizontal, it's usually due to excess plastic between two shutoffs (the "A" and "B" plate cavity faces, for example). It can also be caused by excess plastic between tooling where preload (total tooling stack) or clamp pressure and other shut-off factors affect clearance.
Remove and examine tooling that forms the flashed area of the part – This is a great example that differentiates tooling troubleshooters from tooling replacers.
First, if two or more parts (positions) have the exact same defect, it's best to examine all tooling at the same time rather than analyzing and correcting defects while going around the mold in a clockwise fashion.
Second, use your micrometer to measure the tooling but don't assume it's bad if it's under print dimensions. Many tooling components that are 0.001 - 0.003 under print tolerances make perfectly acceptable parts. Print tolerances should be a factor in replacement decisions, not the deciding vote.
Third, develop a standard method to examine tooling; for example:
Remove suspect tooling from the mold after making sure that each piece is numbered with its mold position number;
Get a matching piece of new or replacement tooling from the tool crib;
Bring part defects with the old and new tooling to your high quality stereo microscope;
Orient tooling in the way it should fit in the mold;
Set the scope's power to 10 (or more if micro-molding); anything over that amount can make a good running fit look like it should cause flashing;
Compare the mated tooling to the flash area on the part, being aware of flash direction, length and thickness. After you identify which piece is flashing, make a mental note of the clearance between tooling. Replace that piece with new tooling and recheck the clearance to see if it's the same or less. If it's a dynamic fit (core or sleeve), does the clearance feel the same, tighter or looser?