Compared to metal materials, plastics have a lower thermal conductivity and a lower modulus of elasticity. Especially when machining POM-plates we recommend to be careful, because improper milling can lead to too high temperatures and the material expands due to heat. The heat released during CNC milling can also contribute to stresses within the semi-finished products. With regard to the general tension, we pay particular attention to the fact that we never work with a blunt milling machine, since such carelessness can result in deformations of the workpiece. These can then be seen in the form of dimensional deviations that lie outside the tolerance range.
For these reasons, the K&B plastics turning shop recommends that you take material-related guidelines into account when machining or CNC milling plastics in order to achieve perfect work results.
First of all, it is advisable to use tempered semi-finished products for milling technical plastics such as polyoxymethylene and to aim for the highest possible cutting speeds. In order to prevent the chips from being drawn in by the milling cutters used, a properly functioning removal of the chips should be ensured. In addition to the advantages of sharply ground cutting edges of the milling cutters, the importance of which has already been mentioned, we recommend that the chips be removed evenly on all sides when milling in order to avoid distortion within the blanks. In addition, clamping impressions should always be kept as low as possible, as otherwise impressions of the clamping tools in the plastic can be the consequence. In order to be able to carry out “clean” machining with the milling machine, the plastic plate should be sufficiently supported due to the tendency towards low material stiffness and should rest on the machine table with the full surface if possible. When milling technical plastics, it is important to ensure that the CNC milling machines run with as little vibration as possible so that high-quality blanks can be produced.
The production of dimensionally accurate parts, which require high cutting volumes or uneven chip removal, is a somewhat more complicated task. Cut-to-size parts should be pre-machined to a residual dimension in order to temper them afterwards. In addition, we recommend one-day intermediate storage in order to reduce the heat and residual stresses generated by the milling cutter. The plastic blank can then be finally machined.
Are you interested in tailor-made blanks that meet your individual application requirements? Do not hesitate to contact us! We would be pleased to deal with your request and make you a non-binding offer!