If you have been a processor in a molding shop, big or small, you have had this issue once or twice before: slowing cycle times down to accommodate stress whitening or sink marks on the surface of your parts. Sometimes it can be a result of under-packing the cavity but a lot of the time it is a result of poor tooling. So often in trial shops prior to receiving the tools in house, processes will be established with longer cycle times to compensate for the tooling problem.
Just a few things to look for are:
- Tooling EDM marks in the ribs or towers
- Insufficient draft on the ribs or towers
- Timing of the lifters
- Insufficient water flow if any to those areas
- Gating location to prevent over-packing in those rib/locator areas
- There are processing issues that can also create or intensify the defect
- Overpacking the area of the defect
- Material residence time / Degraded material
- Heat deflection temperature
- There are a few settings in the clamp opening and part ejection of the molding cycle that can be adjusted to compensate for the above issues.
- Clamp open break away speed
- Ejector start speed if 2 stage
If you would like more information about setting up a sound purge process, or would like for me to take a look at your color change or material change procedure and cost, please contact me at firstname.lastname@example.org.
I would like the opportunity to help you capture a cost saving.Learn more about how purging compounds impact your production efficiency.