ZERO REWORK Tooling Project
We are manufacturing parts for the automotive industry mainly made of PA GF XX%. Parts are usually injection moulded and welded. One of our main problems are burrs. They require rework and rework causes product contamination. It is a big waste and seems to be an evil circle.
Now I have been requested to launch a company wide Zero Rework project. It shall include all stages of product and process development + manufacturing.
Does anyone have experienced similar projects? Can someone support me with some example or with a similar project plan?
Thank you in advance.
To properly approach such a challenge the effort needs to start in the product design phase. One complete through product DFM then you need to work with your tool shop or supplier partner to properly design the tool. The robustness of the tool design and tolerancing of various shutoff surfaces become paramount. For our efforts we had prescribed the amount of "pinch" to be applied for the primary, secondary and tertiary shutoff surfaces
I wish you well and will continue to follow this discussion to see what others have to offer.
Often times I see parts where there are no radii on ribs and the end of the part cross section is squared off. Many times these are from customers using designers not familiar with polymers. Those 90 degree walls will kill you.
Good luck to you! But I don't think you can completely reduce the problem.
1.For my understanding, if you say part need rework the burrs, that mean the part has big burrs, then this is caused by tool and molding process. You need fix the mold and improve the producing parameters. If you want a zero rework project, you need start from part design anaylsis, mold design, mold production, molding parameter testing, molding production process control, mold maintenance control etc. it's a system process chain. Hope my experience can help you.
2.if the "burrs" is not the flash( we usually call it), please explain it with more details.
Flash in GF resins would always be problematic when our high production tools (10k parts per day) began to wear even the slightest amount. The problems were anticipated by examining the proposed parting lines early in the tool design, and assuming that there would be flash at some level during the tool life. By creating alternate parting line geometries ( stepped or with bypassing cores) we were able to tolerate levels of flash that did not affect function. In those areas where there was no apparent solution, the tools were intentionally inserted for easy maintenance.
As Matt mentioned, depending on the part/tool design, you might need to have some " press " on the shutoffs to keep the flash down.
Have you done the pressure loss study?
A balanced fill will provide for a much greater processing window and keep you from fighting non-fill in some cavities and burr in others.
Please however note that a properly designed and built tool should withstand the pressure imbalance that results in some cavities flashing. Additionally an often overlooked tool design consideration is the height of any inserted runner plate. The runner plates need to be line to line or even slightly less than line to line (perhaps 5 microns under).