Machining HDPE 4

[PUMPDESIGNER]

We asked a machine shop to make some parts for a pump intake out of HDPE pipe and 1/2" thick sheet.

The machinist if having severe problems, breaking bits, bending tool shafts, etc.

I know nothing have seen nothing, but that seems strange, very strange.

The machinist has never machined anything as soft as HDPE, has no idea what he is doing, but I know he has machined some harder plastics for us no problem.

I know this is vague, but I know nothing at all about the subject.
Any big hints would be appreciated.

PUMPDESIGNER

 

[btrueblood]

Tell him to slow down. Heat build-up in the PE parts will cause it to expand and/or melt and "grip" the tool. Slow speed, heavy feed works best, as does peck drilling, and intermittent cutting with mill/lathe (i.e. stop frequently and let things cool off). Use some coolant too.

 

[dwightdixon]

Use wood working bits. Have very sharp tools with plenty of relief. Lots of lubricant to cool the piece. Tools intended for steel have too low a cutting angle and just rub as the piece deflects out of the way and build up heat due to friction. Sharp tools with deeper cuts are the answer.

 

[ornerynorsk]

The stuff machines beautifully! Use lower speeds and higher feeds than what you would use for aluminum. I use conventional high speed steel tooling all the time, and it works great. Never had a problem.

 

[patprimmer]

The secret it not to generate enough heat to soften it, otherwise you start a death cycle. you generate heat, it softens, that generates more heat it softens even more etc.

Woodwork tools work best. High speed steel tools will work.

If you sharpen your own tools, compared to woodworking specs, use very low rake angles to avoid digging in, use high back clearance angles to reduce friction, use extra set or side clearance to reduce friction and allow for clearance of schwarf.

Regards

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