Introduction
PEEK (Polyether Ether Ketone) is used in tough environments like aerospace, medical, and electronics.
But molding PEEK is tricky. If something goes wrong, your part can warp, crack, or shrink in ways you didn’t expect. These problems often come from stress trapped inside the part, uneven cooling, or poor mold design.
Based on our extensive production experience, let’s analyze the root causes of these issues and how to prevent them before they arise.
What Causes PEEK to Deform?
When you mold PEEK, it cools and shrinks. If that cooling isn’t even, stress builds up inside the part. This stress can lead to cracks or warping.
Other causes include:
- Using too much pressure during injection
- Not keeping the right melt and mold temperatures
- Poor material flow in the mold
- Bad mold design (wrong gate placement or uneven wall thickness)
- Improper draft angles that make it hard to remove the part from the mold
PEEK also has a high crystallinity, meaning its molecules line up tightly when it cools. That’s good for strength, but it also makes the material more likely to warp if cooling isn’t controlled.
Key Mold and Process Design Fixes
You can avoid most problems by planning carefully. Here’s what helps:
- Keep barrel temperatures between 380–400°C for proper melting
- Maintain mold temperatures between 200–300°C to control cooling
- Pre-dry PEEK pellets at about 150°C for 3–4 hours to remove moisture
- Use short injection times and the right pressure to avoid internal stress
- Design gates and runners for even flow and filling
- Add draft angles of at least 2°–4° for smooth part ejection
- Use mold temperature controllers or water-based systems for even cooling
Adding conformal cooling channels—cooling paths that follow the shape of the mold—can also improve cooling balance.
Why Annealing Matters
Even with the best setup, some internal stress may remain. This is where annealing helps.
Annealing means heating the part to a set temperature (usually 180–220°C), holding it there, and then cooling it slowly. This allows the molecules to relax and reset, reducing stress and helping the part stay in shape.
If you need to machine the part later, annealing first is especially important. It keeps your final dimensions stable and prevents distortion during cutting.
Don’t Skip Material Prep or Inspections
Moisture in the material can cause big problems—bubbles, voids, and warping. Dry your PEEK well before use.
Also, check your parts after molding:
- Use visual checks to catch surface flaws
- Run CMM (coordinate measuring machine) scans to confirm key dimensions
- Do real-time monitoring during molding to catch pressure or temperature shifts
- For sensitive parts, track each batch and process setting for full traceability
Summary Checklist
Here’s how to prevent PEEK from deforming:
- Control barrel and mold temps (380–400°C and 200–300°C)
- Pre-dry PEEK pellets at 150°C
- Use short injection times and proper pressure
- Design with proper gate placement, wall thickness, and draft angles
- Cool evenly using good mold design and temperature control
- Anneal molded parts to relieve stress
- Inspect parts and monitor quality at every stage
Conclusion
PEEK deformation is a complex issue, but it’s manageable.
By getting your mold design right, dialing in your process settings, adding post-mold heat treatment, and inspecting carefully, you can avoid costly part failures and get the reliable performance PEEK is known for.
If there are any other aspects we haven’t discussed yet, or if you encounter any issues or have concerns during the project, feel free to reach out to us. We’re here to provide full transparency and answer any questions you have.
