HELP! Material suggestions: clear/smooth molding plastic...

I’m having a lens injection molded. (Almost 1/2" thick in the middle).

We’re finding that with polycarbonate, the plastic tends to “sink”, causing lens distortion. The engineers suggest using GPPS which I haven’t seen yet, but I’m told is not glass-clear as polycarbonate is. I need both clarity and smoothness. What should I do?!?!? Someone please help me. Is there a material that has both properties I need?

David Harlan


Have you spoken with your tooling supplier to investigate other possible remedies to the sink? It may be a modification of tooling parameters or the tool design itself that needs to be looked at. PC should be a good material for lenses.

I’ve heard of Radel R being used for lenses, and I’ve seen it molded thick.

Haven’t seen it used for thick lenses though, and it’s pricey.

Also, whatever is causing the sink in the PC would likely affect the Radel as well.

With molding you will always have some shrinkage though generally less with higher grade polymers such as PPSU/Radel.
I advise to CNC them instead, acrylic will be a good alternative.

If you’re going for mid level (on the higher end of mid) or high levels of production though CNC will more than likely be cost prohibitive. I would start discussions immediately with your plastic supplier and molder simultaneously, I would be very surprised if they haven’t ran into a similar issue in the past that they can lean on for understanding.