Tool Steel For Medical Molding

[joeprocess]

We have a mold here that the customer has changed to quality expectations on. They now want "Zero" ejector pin grease. We already have grease-less ejector pins and sent out the core for ultra-sonic cleaning and coating (Ni-bor), but still have dirty show up on the ejector pins within 2 hours of running. We then have to pull the mold and clean it. The only thing I can come up with is to why the tool keeps bleeding is maybe the tool steel is leeching out something. Like aluminum will do. The tool core is S-7.

We have opportunity to re-build mold and wonder what mold steel would work best?

[JayDub]

What’s the resin? Medical grade Urethane, for example, is exceptionally gassy. The ejectors need to be ring-vented and highly polished and they still need to be cleaned every couple of thousand shots.

As far as steel, for body-contact parts (i.e. they may get stuck in someone but they don’t stay there) we just use regular H13 with a light smear of grease on the leader pins, none in the ejection system. For implantables the tools I’ve worked with were 420 SS, no grease at all, moving parts (slides or cams) hard-chromed to minimize galling.