Turning Plastic: Tools, Speeds, and Surface Finish

Turning Plastic: Tools, Speeds, and Surface Finish

When we turn plastic on a lathe, several factors affect the result. We need to choose the right tools, speed, and cutting conditions to achieve a good surface finish and avoid problems such as heat buildup and poor cutting results.

An important factor is the tool geometry. A tool with a positive rake angle and sharp edges is often better suited for turning plastic than a tool with a negative rake angle and dull edges. This is because a positive rake angle provides better cutting force and reduces the risk of heat buildup.

Tool Selection

When we select tools for turning plastic, we must consider the material's properties. For example, HDPE and UHMWPE are both soft and ductile materials that require a tool with sharp edges and a positive rake angle to prevent the material from \"sticking\" to the tool. On the other hand, POM-C is a harder and more brittle material that can be handled with a tool with a smaller rake angle and more dull edges. So how do we choose the right tool for our plastic material? A good starting point is to read the material's datasheet and look for information on recommended cutting conditions and tool geometry. We can also try different tools and see which works best for our specific material and application.

Cutting Speeds per Material

Cutting speed is another important factor when we turn plastic. If we turn too slowly, the material can get too hot and begin to melt or deform, while too high speeds can result in a poor cutting result or even tool damage. So how can we choose the right cutting speed for our material?

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• For HDPE and UHMWPE, we recommend a cutting speed of 50 to 150 m/min.
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• For POM-C, we recommend a cutting speed of 100 to 250 m/min.
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• For PC and ABS, we recommend a cutting speed of 150 to 300 m/min.
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But what if we don't have access to the material's datasheet or if we're unsure which cutting speed is appropriate? In such cases, we can always start with a lower speed and increase it gradually until we achieve a good cutting result.

Surface Finish and Heat Buildup

A good surface finish is important for most applications, and we can achieve this by choosing the right tools, cutting speed, and cutting conditions. How can we avoid heat buildup, which can result in a poor cutting result or even tool damage? A good strategy is to use a tool with a positive rake angle and sharp edges, as well as to maintain an appropriate cutting speed. We can also use a coolant, such as water or air, to reduce heat buildup. But what if we don't have access to a coolant? In such cases, we can always try to increase the airflow around the turning area or use a tool with built-in cooling.

Long Chips and Short Chips

When we turn plastic, we can sometimes encounter problems with long or short chips. Long chips occur when the material is too soft and ductile, and can result in a poor cutting result or even tool damage. Short chips, on the other hand, occur when the material is too hard and brittle, and can result in a good cutting result but also in tool damage. How can we handle these problems? A good strategy is to adjust the tool geometry and cutting speed to suit the material's properties. For example, we can use a tool with a more positive rake angle and sharp edges to handle long chips, while a tool with a smaller rake angle and dull edges may be more suitable for short chips.

We hope this article has given you some good tips and advice for turning plastic on a lathe. If you have more questions or need help with your plastic project, don't hesitate to contact us for more information and guidance.