# Tools to carve plaster? (CNC)



## Scottart (Jan 8, 2015)

Gents, I have a project that involves carving 36' x72' plaster blocks for another artist.

The plaster is specifically molding plaster, the type that is used to create molds for ceramic slip casting.

I'm looking at qty of 6, 12 hour carving runs with .25' ball nose bits. It is essentially carving stone dust....so expecting it to eat bits

Anyone have any suggestions on bit selection?

Thanks. 

Scott


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## Bushwhacker (Jun 16, 2009)

Did you mean 36" by 72".??


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## rkaligian (Jan 22, 2011)

Plaster is really gypsum (calcium sulfate dihydrate) and on the Mohs Hardness scale is pretty soft - slightly greater than talc. Dihydrate means there are two molecules of chemically bound water contained within the mineral. This means that the plaster does a pretty good job of minimizing heat since the chemically bound water tends to act like a heat sink. 

United States Gypsum (USG) used to have a product called Rayite Machinable Media. Not sure if they still make the product but it was specifically made to be machined. 

At a minimum use carbide cutters. It's the dust that can be annoying so hopefully you have a dust collection system.


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## johnnie_dr (Jan 8, 2016)

ScottArt,

Besides doing woodworking, I also carve stone. I carve alabaster, soapstone and marble...the first two are semi-soft stone, whereas Marble and granite are very hard.

Plaster, as rayk2 points out, is very soft. I have specially hardened steel chisels and gouges for my stone work. 

For plaster, you can easily use a standard woodworking chisel and/or gouge, since the plaster is soft. You can also buy rotary burrs that will work well to grind away at the plaster. I have a tool from Foredom Tools 
( Foredom Electric Co. ), that has a motor , flex shaft and bits. But you can buy a flex shaft that will attach to a standard drill, where you can attach burrs to it. Just Google it... 

Sounds like a pretty big piece to be working on, even if it is 3 ft x 6 ft...that's allot of carving and dust !!

Good luck

John


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## Scottart (Jan 8, 2015)

Bushwhacker said:


> Did you mean 36" by 72".??


Oops. Yes inches not feet


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## Scottart (Jan 8, 2015)

johnnie_dr said:


> ScottArt,
> 
> Besides doing woodworking, I also carve stone. I carve alabaster, soapstone and marble...the first two are semi-soft stone, whereas Marble and granite are very hard.
> 
> ...


Thanks John, I have also carved soap stone with a foredom and dremels with burrs. This will be done at 12000 rpm in a CNC spindle.. the carving runs for each slab will approach 12 hours... so never carved soapstone 12 hours non stop..


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## Scottart (Jan 8, 2015)

rayk2 said:


> Plaster is really gypsum (calcium sulfate dihydrate) and on the Mohs Hardness scale is pretty soft - slightly greater than talc. Dihydrate means there are two molecules of chemically bound water contained within the mineral. This means that the plaster does a pretty good job of minimizing heat since the chemically bound water tends to act like a heat sink.
> 
> United States Gypsum (USG) used to have a product called Rayite Machinable Media. Not sure if they still make the product but it was specifically made to be machined.
> 
> At a minimum use carbide cutters. It's the dust that can be annoying so hopefully you have a dust collection system.


Thanks Ray, Yes the dust collector and masks will be on full time. Do you think carbide will stay sharp for a 12 hour run?


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## Stick486 (Jan 4, 2013)

I'd worry about DC big time...
regular DC rules do not apply...


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## DaninVan (Jan 1, 2012)

Neat!




That baseplate mounted dust collector looks pretty efficient.


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## rkaligian (Jan 22, 2011)

I really don't know if the cutter will last 12 hours - it depends on all the typical machining factors - depth of cut, speed, heat generation etc. Stick486 is also correct in the a typical shop vac being used as a DC will probably not like bring on for 12 hours.

If it were me I would break the machining into segments that allow for the cooling of the machine components.


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## honesttjohn (Feb 17, 2015)

I run my Ridgid vac sometimes for up to 20 hours a day, and it keeps on running. But I do have it hooked to a Dust Deputy.


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## Scottart (Jan 8, 2015)

rayk2 said:


> I really don't know if the cutter will last 12 hours - it depends on all the typical machining factors - depth of cut, speed, heat generation etc. Stick486 is also correct in the a typical shop vac being used as a DC will probably not like bring on for 12 hours.
> 
> If it were me I would break the machining into segments that allow for the cooling of the machine components.



I do have a large dust system attached to the CNC machine, and yes, breaking this into shorter runs so i can check the bits is a great idea.

thanks.


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## rkaligian (Jan 22, 2011)

Would love to see your completed project!


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## Pro4824 (Oct 17, 2015)

honesttjohn said:


> I run my Ridgid vac sometimes for up to 20 hours a day, and it keeps on running. But I do have it hooked to a Dust Deputy.


20 hours a day????? Dang HJ you need to take a break.


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## honesttjohn (Feb 17, 2015)

With a long finish cut --- set it all up and go to bed.

Or if the cut will run late a nap on the sofa til it's done. And then set it right back up first thing in the morning.


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## Pro4824 (Oct 17, 2015)

HJ, I'll be glad when I get enough confidence to walk away from mine. And I'm a long way from being able to go to sleep while it's cutting but hopefully I'll get there soon. Or not.


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## 4DThinker (Feb 16, 2014)

I left a long 3D cut running once while I went to bed and the only thing wrong when I got back in the morning is that somehow part of the cut was a visible fraction thicker than it should have been. As if during the cut the MDF bed had sagged just a bit. Probably just gradually but when the bit got to one side and then went back to finish an area it had missed, that area was visibly higher than the rest of the cut. Consistent with my decades of experience using MDF, just unexpected. Makes a good argument for additional support cross bracing under the bed on the probotix CNCs. 

4D


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## MT Stringer (Aug 15, 2012)

honesttjohn said:


> With a long finish cut --- set it all up and go to bed.
> 
> Or if the cut will run late a nap on the sofa til it's done. And then set it right back up first thing in the morning.


ha ha, just got to thinking...

Some day when I get more confidence in my CNC and my ability to design, I will be able to set up a long cut, then go outside and fire up the pellet cooker, put on a couple of pork butts, and let them smoke all night! :grin::grin::grin:


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## honesttjohn (Feb 17, 2015)

Fresh pulled pork for breakfast is good!!


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## Scottart (Jan 8, 2015)

Just wrapped up the Plaster Carve.

5 Slabs 3" thick X 36" wide x 72" long

Plus three smaller slabs that were 15" x 12"x 3" thick.

The other artist provided my with 3 D models of some local Glaciers, the models came from Government satellite shots, so very detailed and interesting.

They ran from 1,170,000 vectors to over 2,254,000 vectors. Each of the big slabs took 12 to 15 hours of carving time using a .25 round nose carbide bit. So cumulatively over 50 hours of carving at 14000 RPMS, 250IPM on a single carbide bit... that seems no worse for the ware.

Pictures to follow..


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## Scottart (Jan 8, 2015)

attached are some images of the Carved PLaster Glaciers.


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## 4DThinker (Feb 16, 2014)

They look great! All the plaster dust would have killed at least 2 shop vacs and an air cleaner if I'd tried that. Impressive how well it carved.


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## honesttjohn (Feb 17, 2015)

Cool -- you gonna get a pic of the finished display when it's all put together??


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## Scottart (Jan 8, 2015)

4DThinker said:


> They look great! All the plaster dust would have killed at least 2 shop vacs and an air cleaner if I'd tried that. Impressive how well it carved.


Yes, killed a shop vac, and I hauled out about 250 pounds of collected dust. 

Interesting note, the 4" dust collecting hoses from my cnc run about 12 feet in a couple of loops across the roof to the master vac separator, filter and bagging system. But the 4" corrugated hose acted like a Gold separator in that the dust dropped out along the path and quickly filled up the bottom of the tube at the low spots. I had to shake out those long hoses every couple hours to keep the system working..


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## Scottart (Jan 8, 2015)

*Museum display*

these are the Images of the 5 large plaster carvings, and the smaller ones as they were laid out at the Museum.

It was a creation call Ephemeral State 2017... Which is long word for "short lived, Temporary, not long for this world". which I guess ice and glaciers somehow qualify.. 

The carvings are permanent capture of a temporary thing......


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## Dalton cnc (Sep 27, 2017)

This is freakin awesome lol I never thought about milling plaster I might have to try it 

I would have loved that job!! 

so what tools did you ultimately use? just a standard carbide ballnose? 

what sorta feeds and speeds do you run I imagine that in the plaster you could almost treat it like foam run 400-600 ipm on your CNCRP machine 

looks like you are on the v-con system from cncrp I imagine that is alot better with the dust than linear bearings like my machine


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