If you’re searching for ways to machine PEEK, you likely value tough, high-performance plastics for critical projects. PEEK’s remarkable durability makes it a popular choice—but it can also be tricky to work with, especially for those not familiar with its unique properties.
Understanding how to machine PEEK correctly is essential for achieving precise, reliable results without damaging materials or tools.
In this article, you’ll find clear step-by-step instructions, practical tips, and expert insights to help you machine PEEK with confidence.
Related Video
How to Machine PEEK: The Complete Guide to PEEK Machining
What Is PEEK Machining?
PEEK, or Polyether Ether Ketone, is a high-performance plastic known for its remarkable strength, chemical resistance, and thermal stability. When you machine PEEK, you’re shaping, cutting, or drilling this resilient material into precise parts used in industries like aerospace, medical, and electronics.
Machining PEEK involves specialized processes. Because PEEK combines the toughness of metals with the lightweight benefits of plastics, it requires specific techniques, tools, and best practices for optimum results.
Why Choose PEEK for Machined Parts?
Before diving into machining tips, it’s important to understand why PEEK stands out among engineering plastics:
- High temperature resistance: Can withstand continuous use up to 250°C.
- Excellent chemical resistance: Strong against acids, bases, and organic solvents.
- Mechanical strength: Holds its shape under stress, even at high temperatures.
- Dimensional stability: Maintains precise dimensions over time.
- Biocompatibility: Approved for medical implants and devices.
- Low outgassing: Suitable for aerospace and vacuum applications.
These qualities make PEEK ideal for parts that need to survive harsh environments while retaining precision.
Key Aspects of Machining PEEK
Machining PEEK requires a different approach from standard plastics and even some metals. Here’s what you need to know:
1. Preparation: Understanding PEEK’s Behavior
PEEK’s properties mean it acts differently than metals or soft plastics. It doesn’t expand or contract unpredictably under machining heat, but you should still:
- Use annealed material: Annealing relieves internal stresses, reducing the risk of warping and cracking during machining.
- Dry the material if needed: PEEK absorbs a small amount of moisture, which can affect precision. For ultra-high-precision parts, dry the rods or sheets at 150°C for several hours before starting.
2. Tool Selection and Setup
Sharp, high-quality tools are crucial for clean finishes and tight tolerances.
- Material: Use carbide or polycrystalline diamond tools for best results.
- Geometry: Tools should have positive rake angles and a polished cutting edge to reduce heat generation and material build-up.
- Speed and feed: High cutting speeds with moderate feeds work well. Typical surface speeds are 250–500 m/min (800–1600 ft/min).
- Coolant: Air blast is preferred, but minimal water-based coolants are acceptable. Avoid heavy coolant flows to prevent absorption.
3. Machining Techniques by Process
Turning
- Use carbide tooling with sharp edges.
- Moderate speeds (1000–4000 rpm are common), depending on part size.
- Fine or finish passes minimize material stress.
Milling
- Carbide end mills are recommended.
- Use multiple shallow passes for deep cavities.
- Maintain stable clamping to prevent chatter.
Drilling
- Use point angles of 90–118° for best chip evacuation.
- Peck drilling helps to remove chips and prevent heat build-up.
- Keep the drill sharp and withdraw frequently.
Sawing and Cutting
- Use fine-toothed blades with positive rake.
- Reduce feed rates to avoid melting or burning the PEEK.
Tapping and Threading
- Remove chips regularly; PEEK does not self-lubricate like metals.
- Lower speeds (15–30 rpm for small threads) to keep threads clean.
- Consider thread milling for deep or critical threads.
Grinding and Polishing
- Use wet silicon carbide paper up to 600 grit for a fine finish.
- PEEK polishes well for medical or optical applications.
4. Managing Heat and Chip Removal
Although PEEK can take heat, excessive temperatures during machining can lead to unwanted softening or deformation.
- Use air or vacuum systems to remove chips promptly.
- Employ quick, light cuts to limit heat buildup.
- Keep tools cool with air blasts rather than heavy liquid coolants.
5. Fixturing and Support
PEEK needs secure fixturing as you would use for metals:
- Use padded or soft jaws to avoid surface marking.
- Allow for easy chip evacuation around fixtures.
- Support thin parts adequately to avoid flex during machining.
Practical Tips and Best Practices
Here are proven tips for getting the best results when machining PEEK:
- Start with annealed rods or sheets for the best stability.
- Clean tools before use. PEEK parts are often used in clean environments.
- Avoid excessive clamping pressure—PEEK, while strong, can dent if pressed too hard.
- Pre-drill holes before threading to reduce stress and improve precision.
- If you must use coolant, dry the part in an oven before use to remove absorbed moisture.
- Use finish passes to achieve high-tolerance surfaces.
Common Challenges and How to Overcome Them
Tool Wear
PEEK’s abrasion resistance can wear down tools quickly. Use carbide or diamond-coated tools and inspect them often.
Dimensional Changes
Heat from machining can soften PEEK. Keep cuts light and use air or mist cooling. Allow parts to cool between steps for best accuracy.
Surface Finish
Gummy or rough surfaces result from dull tools or too-slow speeds. Keep tools sharp and maintain recommended speeds.
Chip Removal
Clogged tools cause overheating and chatter. Use compressed air and peck cycles, especially with deep drilling or narrow slots.
Cost-Saving Tips for PEEK Machining and Shipping
PEEK is more expensive than many plastics, so efficient machining and smart shipping choices save money:
- Plan part geometry to minimize waste. Optimize part layouts and use near-net shape blanks if possible.
- Reuse scrap and offcuts for development work.
- Group orders with other parts or customers to lower per-piece shipping costs.
- Select lightweight packaging for parts, as PEEK is sturdy and doesn’t require heavy padding.
- Consider shipping from local suppliers to reduce both transport time and costs, especially if you’re ordering internationally.
Concluding Summary
Machining PEEK is both an art and a science. Its unique combination of strength, chemical resistance, and temperature performance make it a top choice for demanding parts—but they also require special attention.
With the right preparation, tool choices, and machining strategies, you can produce PEEK parts with excellent precision and finish. Pay attention to cooling, chip removal, and part support, and you’ll tap into the full potential of this advanced material for your most critical applications.
Frequently Asked Questions (FAQs)
What is the best tool material for machining PEEK?
Carbide tooling is most common for PEEK, but for high-production runs or ultra-fine finishes, polycrystalline diamond (PCD) tools are excellent. They reduce heat, produce very clean finishes, and last longer.
Can I use coolant when machining PEEK?
Yes, but sparingly. Air blast or minimal water-based coolant is okay. If liquid coolant is used, always dry the parts after machining to prevent moisture absorption, which can affect precision and performance.
Do I need to anneal PEEK before machining?
For critical or high-precision parts, yes. Annealing relieves internal stresses and reduces the risk of part movement, cracking, or warping during and after machining.
How do I avoid surface melting or roughness?
Use sharp tools, maintain high cutting speeds, and avoid excessive feed rates. Remove chips with air blasts, and pause to cool the part if it starts to heat up. Always make a light finishing pass for best results.
Is PEEK suitable for CNC machining?
Absolutely. CNC machines are ideal for PEEK due to their precision and repeatability. Just be sure your tool paths, feeds, and speeds are dialed in for plastics—not metals—for best outcomes.