Precision Injection Molding PEEK Part

Avoid weak spots: The walls around the U-shaped openings are usually thin –it’s definitely that we can’t place ejector pins there, or we'll face the punching through or deforming problem.

Use ribs and boss bases: it’s better to put ejector pins at the bottom around the square mounting holes, or at the intersections of internal ribs. These spots exhibit the greatest structural rigidity and can withstand higher ejection forces without deforming.

Use ejector plates or blocks for extra support: Since PEEK has a high shrinkage rate (about 0.4–0.7%), we need more power to eject. For that large odd-shaped hole in the middle, use a block-type ejector instead of standard round pins – it gives us more contact area, spreads out the ejection pressure, and prevents obvious pin marks around the hole edges.

Balanced layout: A symmetrical pin arrangement can keep the part from tilting and getting stuck in the mold.

Internal surfaces (core side): PEEK is hard but not super tough, so the inside walls of holes and U-shaped slots need enough draft to eject easily. We recommend at least 1°30' as a minimum – if the depth goes over 20mm, bump it up to 2° or more.

External surfaces (cavity side): Outside surfaces have less resistance, but we still need at least 1° of draft to keep a nice surface finish and avoid scratches from ejection.

Texture factor: If the part surface has a grain or texture, we recommend that for every 0.025mm of texture depth, you'll need to add an extra 1° to 1.5° of draft.

Mirror finish: PEEK melt has high viscosity and doesn't flow easily, so the core surface really needs an SPI-A1 mirror polish to reduce friction.

Clearance for venting: The gap between ejector pins and the mold plate isn't just for ejection – it's also a key venting path. For PEEK, we recommend cutting some venting slots (about 0.01–0.02mm deep) on non-mating surfaces to prevent trapped gas that causes short fills or burning. Good venting also helps to avoid the vacuum seal, making ejection smoother.