We have a project where we need to machine slots into an already molded part.  The material is a teflon filled polypropylene.  We have tried many options as far as cutter style, feeds, speeds, etc..  We are trying to minimize the burrs left after machining.  Does anyone have some good recommendations on cutters and speeds?

Milling cutters for plastic should be sharp enough to draw blood on even minor contact, and should _never_ be used to cut anything else.  Carbide probably can't hold an edge radius that's small enough.

Other options:

A slot-shaped hollow punch in a really big soldering iron.  It will require manual deburring.

Cut the slot with a waterjet.

Mike Halloran
Pembroke Pines, FL, USA

I work in a shop that machines poly all day everyday. We cut teflon, and glass filled as well. Carbide endmills only is the way to go. High helix aluminum cutting work really well.We cut between 2000- 1500SFM, flood coolant or air blast. Also cut plastics and silicone on waterjet but i would not recommend it. We do all deburr on machine. Consistent edge breaks may be a problem with molded parts though. We also deburr with a glass bead blast this works well for quick deburring. Just dont hold nozzle in one spot for long time. Also cryogenic Deburr adds operation but parts are free off any burrs or "fur". In my opinion you will always have to deburr slots in one way or another.

My .02

You might be able to de bur PP with a flame if the burrs are very fine.

Regards

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We cut slots in teflon using a wood router (20000 rpm or better).  We tried helical-flute endmills at first and had lots of stringy burrs.  A straight-sided router bit, the type used for wood, works the best for us.

onsrud specializes in cutters for plastics. Call them for help.