CNC Milling of Plastic: Speeds, Feeds, and Common Pitfalls

CNC Milling of Plastic: Speeds, Feeds, and Common Pitfalls

At PlastShop.se, we work with plastic daily, and we know how important the right tools and knowledge are for successful milling. A key factor in CNC milling of plastic is speed and feed. Too high a speed can melt the plastic, while too low a speed can result in a poor surface finish.

What speed and feed should you actually use for a specific plastic? That's a relevant question, as different plastics require different settings to be milled correctly.

Speeds and Feeds for Different Materials

We offer a wide selection of plastics, each with its own unique properties. For example, HDPE (also called PEHD or PE-300) needs a higher speed than PA6G to avoid melting. Generally, HDPE can be milled at 10,000 to 20,000 RPM, while PA6G requires 5,000 to 10,000 RPM.

When it comes to feed, a good balance is important. Too high a feed results in a poor surface, while too low a feed makes the process unnecessarily slow. A good rule of thumb is to use a feed of 0.1 to 0.5 mm per revolution for HDPE, while PA6G requires 0.05 to 0.2 mm per revolution.

Tool Selection: Single-Flute or Multi-Flute?

The choice of tool is also crucial in CNC milling of plastic. Should you choose single-flute or multi-flute? It depends on the plastic and the application. Single-flute is often better for HDPE and UHMWPE, while multi-flute is better suited for PA6G and POM-C (also called POM-C or Acetal).

Why is single-flute better for some plastics? Well, it often gives a finer surface and reduces the risk of melting. But for other plastics, such as PA6G and POM-C, multi-flute can provide higher speed and better efficiency.

Chip Evacuation and Cooling

Chip evacuation and cooling are important aspects of CNC milling of plastic. If the chips aren't removed properly, it can negatively affect the surface and increase the risk of melting. We recommend using air cooling or mist cooling to cool the plastic and remove the chips.

Air cooling often works well for HDPE and UHMWPE, while mist cooling may be better for PA6G and POM-C. What's the difference? Air cooling uses an airflow to cool, while mist cooling uses a water-based solution.

Common Mistakes and Solutions

There are some common mistakes you can make when CNC milling plastic. One of the most common is using too high a speed or feed, which can lead to melting or a poor surface finish. Not using the right tool or cooling is another common problem, which can make the process slow or give poor results.

How do you avoid melting and a poor surface? Use the right speed and feed, the right tool and cooling, and make sure the chips are removed effectively.

Do you have questions about material selection or machining? Feel free to contact us for advice!