Anybody ever milled hard plaster?

[KevinWilkins]

I have a potential client asking if I can mill hard plaster for some type of relief plaque. The pieces are about 12 inches in diameter. I have a TM-1 and even with the dust collection system I have, I'm afraid the plater dust would get into everything. I also have no idea what type of tooling would be best.

Anybody ever tried to cut plaster?

I am asking the client if I could substitute alu or some type of plastic instead of plaster. Otherwise I'm tending to decline the project.

I'd appreciate any tips anyone might have to offer!

[Geof]

Decline would be my approach.

You are talking gypsum plaster, plaster of Paris, the stuff used in wallboard?

Very dusty, very abrasive. I have done it on manual machines but I would be very reluctant to put in on a CNC, especially one with exposed guides like a TM.

[High Seas]

Offer to make him a master from another material and then encourage him to use that as a buck for a silicone mold --IF he really wants plaster!

Jim

[martinw]

Dear kevin,

With a diamond-tipped cutter, you should be able to do the work. With excellent dust extraction, your machine may survive. It is , however, not a job I would take on unless you are confident that the dust will not destroy your machine. Angle grinders are built to resist this type of dust, but spindles/routers are not.
My 2c
Best wishes,
Martin

[KevinWilkins]

Thanks guys, that's what I was thinking too. I guess I could say, "For €25,000 I'll do it." :-) I doubt my dust extraction would get all that dust and it would make the job a major money looser.

I'll pitch the idea of using another material such as alu, if not, I'll suggest looking for a mason!

[dertsap]

i couldn t imagine what that kind of stuff would do to a coolant system ,

[littlerob]

I machined some material designed as an arc shield for high output limit switches that was similar to dry wall----Murder on the machine, literally, we scraped it when the job was done, (VF-2) and those ways are covered. Robert

[KevinWilkins]

You scrapped a VF-2 after one job! I hope that was a well paying job...

[littlerobb]

The job ran for about 2 and a half years.

[Geof]

I machined some material designed as an arc shield for high output limit switches that was similar to dry wall----

Just as a matter of interest how long ago did you do this? My first guess, years ago, about the composition of something used as an arc shield is that it would contain asbestos. Now I don't know what is used.

[littlerob]

It was not long ago maybe 5 years, the material was called transite, nothing good about the stuff, I dont know enough about it to say whether the tecnology was modern or not, just that the warning labels persuaded me to wear a respirator all day. I don't think it contained asbestos though.

[awerby]

that's made by USG specifically for machining. I've used it with okay results. After casting it into your rough shape, you need to let it dry thoroughly before cutting it, or its sticky chips will make a big mess (don't ask...)

But if it's not absolutely necessary to make this directly in plaster, I'd certainly advise cutting it in something more user-friendly, like machinable wax, and casting the plaster in a mold made off that. The wax gets a great surface, and makes an excellent master for molding.

Modern transite doesn't contain asbestos, but the free silica in it makes it something you want to protect yourself from breathing anyway. It's abrasive too, so you wouldn't want it around your mill, unless you've got a job that will buy you another one...

Andrew Werby
www.computersculpture.com