CNC milling of plastic: Speeds, feed rates and common pitfalls
Here at PlastShop.se, we work with plastic on a daily basis and know how important it is to have the right tools and knowledge to ensure successful milling. A key factor in CNC milling of plastic is the speed and feed rate. Too high a speed can melt the plastic, whilst too low a speed can result in a poor surface finish.
What speed and feed rate should you actually use for a specific plastic? It’s a relevant question, as different plastics require different settings to be milled correctly.
Speeds and feed rates for different materials
We offer a wide range of plastics, each with its own unique properties. For example, PE-HD (also known as PEHD or PE-300) requires a higher speed than PA6G to prevent melting. Generally speaking, PE-HD can be milled at 10,000 to 20,000 revolutions per minute, whilst PA6G requires 5,000 to 10,000 revolutions per minute.
When it comes to feed rate, it is important to strike a good balance. Too high a feed rate results in a poor surface finish, whilst too low a feed rate makes the process unnecessarily slow. A good rule of thumb is to use a feed rate of 0.1 to 0.5 mm per revolution for PE-HD, whilst PA6G requires 0.05 to 0.2 mm per revolution.
Tool selection: single-cutter or multi-cutter?
The choice of tool is also crucial when CNC milling plastics. Should you choose a single-flute or multi-flute tool? It depends on the plastic and the application. Single-flute cutters are often better for PE-HD and PE-1000, whilst multi-flute cutters are better suited to PA6G and POM C (also known as Acetal).
Why is a single-flute cutter better for certain plastics? Well, it often produces a smoother surface and reduces the risk of melting. However, for other plastics, such as PA6G and POM C, a multi-flute cutter can offer higher cutting speeds and greater efficiency.
Chip evacuation and cooling
Chip removal and cooling are important aspects of CNC milling of plastics. If the chips are not removed properly, this can adversely affect the surface finish 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 PE-HD and PE-1000, whilst mist cooling may be better for PA6G and POM C. The difference? Air cooling uses a stream of air to cool, whilst mist cooling uses a water-based solution.
Common mistakes and solutions
There are a number of common mistakes that can be made when CNC milling plastics. One of the most common is using too high a speed or feed rate, which can lead to melting or a poor surface finish. Not using the right tools or cooling is another common problem, which can slow down the process or produce poor results.
How can you avoid melting and a poor surface finish? Use the correct speed and feed rate, the right tools and coolant, and ensure that chips are removed efficiently.
Do you have any questions about material selection or machining? Please feel free to contact us for advice!
CNC Milling of Plastic: Speeds, Feeds, and Common Pitfalls