Over-molding Aluminium with PEEK

[moldingppm]

Hi everyone,

I have a customer that is requiring us to over-mold aluminium with PEEK. Are there any suggestions for processing that anyone has? We've never molded anything this exotic, so any insight would be helpful. Can standard machines run this material? or will I have to do some modifications to our machine to process this material?

Thanks

[JayDub]

PEEK runs hot but it will run on standard equipment, & you can get processing conditions from the manufacturer. The only difference may be that you need to have the mold at least around 375 or 400 F, so you need hot oil or electric heat (cal rods).
Cooling times are long – don’t try to save time on this: PEEK has a Tg well over 300 F, and you need to let it fully crystallize to develop its optimum properties.
Given the temperatures, use high quality PPE (personal protective equipment) – heavy gloves, Kevlar sleeves, safety glasses, etc. Remember that parts come out of the mold hotter than some materials process, so handle accordingly – for instance, if you try to eject them into a PP parts bin they will melt right through the bottom.
Make sure the aluminum insert has features to make a mechanical bond with the plastic.
Run with sprue break to avoid nozzle freeze.
Lastly, watch your residence time: the manufacturer will deny it, but experience shows that PEEK will crosslink over time at processing temperatures and get immovable. So, if you need to go to lunch half way through a run, bank the heats well down.
Other than that, it’s a piece of cake – have fun and good luck!

[Huw Durban]

It may be worth preheating the aluminium insert before putting it in the tool, sometimes over molded parts will crack around an insert when it shrinks on cooling. Some modern machines will not reach the processing temperatures required for PEEK, this is always to do with software and can usually be reset in the engineer pages of the controller. I had this issue with an Arburg machine, they wanted to charge for an upgraded board but their service engineer on his next visit made the software change in a couple of minutes.

[JayDub]

One more thought - make sure the mold has half-inch thick insulator boards. If you don't insulate the mold, you'll spend the profit margin of the job on heating the machine platens.