Machining information

Non-reinforced thermoplastic polymers can be machined using high speed tools. For reinforced materials, carbide tipped tools are necessary. In all cases, only correctly sharpened tools should be used. Due to the poor thermal conductivity of plastics, good heat flow must be ensured. The best form of cooling is heat dissipation via the chips.

Dimensionally accurate parts presuppose the use of stress relieved semi-finished products. Heat from machining will otherwise unavoidably result in the release of machining stresses and distortion of the part. If large material volumes are to be machined, intermediate annealing may be necessary after rough machining to relieve the resulting thermal stresses. Specific temperatures and times to be used according  to material can be obtained from us upon request.
Materials with high moisture absorption (e.g. polyamides) may have to be conditioned before processing.
Plastics require higher production tolerances than metals. Furthermore, the much higher thermal expansion needs to be taken into consideration.

Guide values for tool geometry are given in the table. For surfaces with particularly high quality requirements, the cutting edge must be designed as a broad smoothing tool.
For parting off, the lathe tool should be ground to prevent the formation of burrs.
On the other hand, for thin-walled and particularly flexible workpieces, it is better to work with tools that are ground to a knife-like cutting geometry.

For plane surfaces, end-milling is more economical than peripheral milling. For circumferential and profile milling the tools should not have more than two cutting edges so that vibrations caused by the cutters can be kept low and the gaps between the chips is sufficiently large.
Optimum cutting performance and surface finish are obtained with single-cutter tools.

Twist drills can generally be used; these should have an angle of twist of 12 ° to 16° and very smooth spiral grooves for good swarf removal.
Larger diameters should have a pilot hole drilled or should be produced using hollow drills or by trepanning. Particular attention should be paid to using properly sharpened drills when drilling into solid material, as otherwise the resulting compression stresses can increase to the extent that the material splits.
Reinforced plastics have higher residual processing stresses and a lower impact resistance than non-reinforced plastics and are therefore particularly susceptible to cracking. Where possible, they should be heated to around 120 °C before drilling (heating time approx. 1 hour per 10 mm cross-section). This method is also recommended for polyamide 66 and polyester.

Unnecessary heat generation caused by friction must be avoided, as generally thick-walled parts are cut with relatively thin tools during sawing. Well-sharpened and strongly offset saw blades are therefore recommended.

Threads are best cut using thread chasers; burring can be avoided by using twin-toothed chasers. Die cutters are not recommended as re-cutting can be expected during removal of the cutter. A machining allowance (dependent on material and diameter; guide value: 0.004 Inch) must frequently be taken into account when using tap drills.

Failure to observe the machining guidelines can result in localized overheating which can lead to material degradation. Decomposition products which may be released, e.g. from PTFE fillers, should be removed using extraction facilities. In this respect, tobacco products should be kept out of the production area due to the risk of contamination.

Through the following link you can download further Ensinger machining guidelines for our materials.

> Machining guidelines

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