Introduction
Making strong and accurate PEEK (Polyether Ether Ketone) parts isn’t just about using the right machine or material. You also need a smart mold design and the right steps after molding.
In this guide, you’ll learn how design and post-processing help avoid common problems like warping, cracking, or poor surface quality—especially with tough materials like PEEK.
Why Mold Design Matters So Much
If the mold isn’t built just right, the part won’t turn out well. Poor mold design can cause:
- Unbalanced flow
- Uneven cooling
- High stress during ejection
All of these can lead to part defects. Common causes include:
- Bad gate placement: The gate is where melted plastic enters the mold. If it’s in the wrong place, the material won’t flow evenly.
- Uneven wall thickness: This leads to uneven cooling, which causes warping.
- Weak cooling systems: PEEK needs a stable, controlled cooling rate. Without it, parts may crack or deform.
One solution is conformal cooling. This type of cooling follows the shape of the mold and gives better temperature control.
(Source: Injection Molding Handbook, Rosato & Rosato)
The Role of Draft Angles
Draft angles are small slopes on the mold walls. They help the part come out of the mold more easily.
Without enough draft (usually 2–4° for PEEK), you might get:
- Warping
- Cracking
- Surface scratches
You also risk damaging the mold itself. Draft angles reduce the force needed to push the part out, which lowers wear on the tooling and helps the part keep its shape.
Managing Internal Stress with Annealing
Even with perfect molding, stress can build up inside the part. This internal stress comes from uneven cooling or material flow.
If it’s not fixed, it can cause:
- Warping later on
- Weaker parts
- Lower fatigue life (how long a part lasts under repeated stress)
That’s where annealing comes in. Annealing is a heat treatment process that relaxes the molecules in the plastic. It reduces stress and makes the part more stable.
You should anneal the part before machining. This helps make sure the final part stays in the correct shape after being cut or drilled.
Finishing Touches: Machining and Surface Treatment
After molding and heat treatment, precision machining is often needed. PEEK is hard, so use:
- Sharp, wear-resistant tools
- Slow cutting speeds
- Proper cooling to avoid heat buildup
This helps you hit tight size limits and fine details.
You can also add surface treatments, depending on your application. For example:
- Sandblasting: improves texture or grip
- Polishing: gives a smoother surface
- Plasma treatment: boosts surface energy for better bonding or coating
Key Design and Processing Tips for PEEK
To make strong, accurate PEEK parts, focus on:
- Smart gate and runner layout
- Even wall thickness
- Enough draft angles (2–4°)
- Conformal cooling if possible
- Post-molding annealing
- Precision machining after heat treatment
- Surface finishing to match your end-use needs
Conclusion
For PEEK parts to work in tough jobs, they need more than good material and machines. You also need careful mold design and proper post-processing.
By planning ahead and taking the right steps after molding, you can make sure your PEEK parts are strong, stable, and ready for critical use.
