Svarva plast: verktyg, hastigheter och ytfinish

Turning plastic: tools, speeds and surface finish

När vi svarvar plast på en svarvmaskin finns det flera faktorer som påverkar resultatet. Vi behöver välja rätt verktyg, hastighet och skärförhållanden för att uppnå en bra ytfinish och undvika problem såsom värmeuppbyggnad och dåliga skärresultat.

En viktig faktor är verktygsgeometrin. Ett verktyg med positiv skärvinkel och vassa kanter är ofta bättre anpassat för svarvning av plast än ett verktyg med negativ skärvinkel och slöa kanter. Detta beror på att positiv skärvinkel ger en bättre skärkraft och minskar risken för värmeuppbyggnad.

Choice of tool

When selecting tools for turning plastic, we must consider the properties of the material. For example, PE-HD and PE-1000 are both soft and ductile materials that require a tool with sharp edges and a positive rake angle to prevent the material from ‘clinging’ to the tool. On the other hand, POM C is a harder and more brittle material that can be machined using a tool with a smaller rake angle and blunter edges. So how do we choose the right tool for our plastic material? A good starting point is to read the material’s data sheet and look for information on recommended cutting conditions and tool geometry. We can also try out different tools and see which one works best for our specific material and application.

Cutting speeds by material

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

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• För PE-HD och PE-1000 rekommenderar vi en skärhastighet på 50 till 150 m/min.
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• För POM C och PA6G rekommenderar vi en skärhastighet på 100 till 250 m/min.
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• För PC och ABS rekommenderar vi en skärhastighet på 150 till 300 m/min.
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But what if we do not have access to the material’s technical data sheet, or if we are 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 build-up

A good surface finish is important for most applications, and we can achieve this by selecting the right tool, cutting speed and cutting conditions. How can we avoid heat build-up, 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, and to maintain a suitable cutting speed. We can also use a coolant, such as water or air, to reduce heat build-up. But what if we do not have access to a coolant? In such cases, we can always try to increase the air flow around the machining area or use a tool with built-in cooling.

Long chips and short chips

When turning plastic, we may 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 cut but also in tool damage. How can we deal with 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 deal with long chips, whilst a tool with a smaller rake angle and blunt edges may be more suitable for short chips.

We hope this article has provided you with some useful tips and advice on turning plastic on a lathe. If you have any further questions or need help with your plastic project, please do not hesitate to contact us for more information and guidance.