Introduction
Making high-quality injection molded parts takes more than just a good machine. You need to plan carefully before molding starts. And you also need to take the right steps after the part is made.
This is especially true when working with tough materials like PEEK. These parts are often used in demanding jobs, where small flaws can cause big problems. That’s why design and post-processing matter so much.
Why Draft Angles Matter
A draft angle is a small taper added to the walls of a molded part. It helps the part come out of the mold smoothly.
Without draft, parts can stick. This increases the force needed to push them out, which can damage both the mold and the part. You might also see:
- Cracks
- Warping
- Scratches or scuff marks
A good rule of thumb is to design with at least 1° of draft per side, but the exact angle depends on the part’s shape and material.
Smart Mold Design Prevents Problems
The gate is where plastic enters the mold. Runners are the channels that carry the plastic to different parts of the cavity. These must be designed to create smooth, even flow.
If the flow isn’t balanced, you may see:
- Voids (empty pockets inside the part)
- Weak areas
- Uneven shrinkage
For materials like PEEK, which flow slowly, this is even more important.
Cooling channels inside the mold also need to be designed right. If some areas cool faster than others, stress builds up. This leads to defects like sink marks or warping.
Managing Internal Stress with Heat Treatment
As plastic cools, it can lock in internal stress. This stress isn’t always visible right away. But over time, it can cause:
- Deformation
- Reduced strength
- Changes in size
One way to relieve this stress is annealing. This is a type of heat treatment. The part is reheated slowly and held at a specific temperature to let the molecules relax and settle into place. This makes the part more stable and helps it hold its shape.
Precision Machining After Molding
Sometimes, a molded part still needs more work. You may need to machine it to get tight tolerances or detailed features.
Machining PEEK can be tricky. It’s hard and tough, so it wears down tools quickly. You need sharp cutting tools, slow speeds, and good cooling to avoid damaging the part.
Also, machining should come after annealing. That’s when the part is most stable and ready for fine detail work.
Key Elements for High-Quality Molded Parts
To get parts that meet high standards, focus on:
- Using draft angles to aid clean ejection
- Designing flow paths and cooling systems for balance and control
- Applying annealing to reduce stress and improve strength
- Performing precise machining only after heat treatment
Conclusion
Great injection molded parts don’t happen by chance. They require smart design choices and careful finishing steps. When you manage every part of the process—from mold design to post-processing—you improve part quality and long-term performance.
