Glass-filled engineering plastics are abrasive in a way that surprises people coming from unfilled material. Thirty percent glass by weight is a lot of hard mineral in contact with the cutting edge, and it will dull carbide noticeably faster than machining aluminium.
Tool material helps: polycrystalline diamond coated or solid PCD inserts last several times longer than uncoated carbide, and for long production runs they pay for themselves quickly. But the bigger lever is the tool path. Climb milling, a positive rake and a smaller radial engagement with a higher feed per tooth all reduce the distance the edge spends in cut per part, which extends tool life more than any coating.
Two things to avoid. Never dwell — a stationary tool rubbing in the cut generates localised heat that degrades the polymer and destroys the edge together. And keep the material supported; glass-filled grades are brittle relative to unfilled ones, so the same part that machines cleanly in natural PPS can chip at the exit side in the 40 percent glass version. Reduce feed at exit or add a backer.
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