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Sven. I’m no machinist or expert in working plastic , but The short answer is if your blades are carbide or HSS it shouldn’t be an issue for the small amount you are doing.
acetal isn’t particularly abrasive, so it won’t do any more damage to your planer knives than a stout hardwood, and will do less damage than those woods with a high silica content. It will do way less damage than something like plywood or MDF. Treat acetal like you were working African Blackwood or ebony. The same guidelines apply. Sharp tools, light cuts.
In production situations carbide tooling is often used to extend cutter life, but a sharp HSS blade will cut through Acetal like butter. All bets are off if the acetal you have is impregnated with glass fibers ( most isn’t) . Then expect some dulling.
The real issues with acetal are that the blades you use should be really sharp to begin with. Dull blades and heavy cuts will heat up the plastic and that causes it to swell and deflect, making accurate cutting impossible. But if you take light cuts and if your planer has a slow feed rate, select that. Acetal is a thermoplastic, so heating it up will get your cutters gummy. Also, dull blades will sound terrible as they whack at the plastic.
Don’t worry,to much about planer marks. Acetal sands and deburrs nicely, unlike most plastics.
If you are trying to get it thin, either hot glue it or use double faced tape to hold it down to a substrate. That deflection thing again.
Make sure you use a good extractor. The shavings will float around in the air and stick to everything with static electricity. Also, there will be some formaldehyde given off. Cut in a well ventilated area.
Commercial machining uses air or cutting fluid to keep the plastic cool, but go slow and you probably won’t have an issue.
And if you are going to tap threads in it, use a size slightly over the recommended steel sizes. I find wire sizes are often ‘tweener sizes to normal tap drills. Delrin doesn’t like being forced in tension. Taps often have negative or neutral cutting edges, and acetal likes a nice positive rake.
Hope that helps.