Plaster of paris, gypsum powder

unfortunately the gypsum mixture in drywall is not dense enough to 3d carve, it will cut fine though. I’m going to start at about 1in deep and make it nice and dense.

First test is getting underway, this is a 1" thick 8x8 block being cast of plaster of paris. I used a vibration table to bring as many bubbles as possible to the surface. When it drys i will I will surface off the imperfections and see how it mills. I’ll keep the thread updated if you guys are interested in this little project. I hope to be able to do 24x24 panels if all goes well.

B.

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I saw someone on YouTube use it to make a form… https://www.youtube.com/watch?v=YqDD6nKZ1n8

While it wouldn’t be my first choice for molding aluminum (kinda dangerous with the water content of the plaster) It looks like it machines awesome! I’m looking forward to trying it out

Well the finished block looks great, it’s about 7.5 x 7.5 x 1.25, no major air holes, looks nice, dense and solid. But at this thickness it looks like it’s going to take some time to truly cure, I probably should’ve went thinner to start, but you have to start somewhere. So as I pick out a cool design for my test on this, I’ll wait for it to dry, not that I would have much time to do anything as we are expecting a blizzard in New York City tomorrow. Looks like I’ll be spending my time fiddling with the snowblower instead of the X-carve

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Ok, decision made for the plaster block design. Here’s the video of the simulation.

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Sped up the drying process in the microwave for a few minutes

Well the plaster block is in the machine running at the moment. A lot less dusty than I thought it would b,e seems to be running well except it only did one layer of the roughing path like I had shown above in the simulation and then went straight into a finishing path which is fine since it’s a soft material, but I can’t figure out why it didn’t finish the roughing path. the tool paths were done in aspire and combined and I’ve never had the problem before. I’m running the program through easel as I always do. anyway here is the video of it going and I’ll post the finished product hopefully looking well when it’s done

Well plaster mills great on the X-carve! The detail is beautiful, very minimal mess when using a dust shoe (Less than wood actually) I darkened the finished product with some water so the detail would come out in the photo. I love using new materials, I can see many uses for plaster in the future. Next I want to try Micarta (anyone try it yet?). What other materials would be cool? @Zach_Kaplan ready to do some architectural design improvements to the Inventables headquarters? :slight_smile:

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Back in ye old days, I did a lot of molding/casting with hydrocal and ultracal. We used an additive called Acryl 60 to harden and increase the detail. I would think it would work with plaster as well.

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@BrianSaban mind blown.

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How solid is plaster of Paris? I’ve never worked with it, will this thing just crumble or does it have some backbone?

While it is solid, it is fragel on thinner areas and easily breakable like a piece of pottery. It can be strengthened by using strands of fiber mixed in when making it. It really depends what you will be using the end product for. The nice thing about the product is it shows great detail, is ridiculously cheap (a 25lb bag of powder is less than $20) and mills very nicely and needs no roughing stage (which drastically speeds up milling jobs).

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I’ve done a lot of concrete molding, you do need to be very careful with curing as not to get cracks in the concrete. If you do plan to use molds, My suggestion would be to mill your item in plaster as above then make your mold in silicone, because if you were to make a negative mold in plaster it would only last once and may not even hold up to the moisture content of the concrete.

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Looking good!

My only concern with milling plaster products would be rapid dulling of the bits. (I don’t know how abrasive it would be but I am assuming it is grater than wood?) But this is easily addressed by having a separate set of bits for plaster work. :slight_smile:

Back when I first got into CNC I played around with making plaster molds for metal casting.
I would carve the master in blue jeweler’s wax, make a silicone mold, cast it in plaster, pour molten metal in that. (I used low a low melt casting metal I got from micromark (expensive) and silver plumber’s solder, heated with a propane torch.)

It worked, ok. Most of my attempts were flawed in some way. I had a lot to learn about mold design, optimizing the shape for metal casting, adding sprues and pour holes, etc. But because of the multi-step process and the expense of making a new silicone mode for each revision I never pursued it.

But I never considered milling the plaster directly. That would seem to be a better approach for the prototyping process. Then, if you wanted to make a lot of them, you could make a silicon mold of the perfected design and cast a bunch of them in plaster for metal casting.

Thanks for sharing this. I will have to give this a try sometime!

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I wouldn’t worry about dulling your bits, plaster of paris is a very soft material unlike concrete or harder mixes that would dull your bits. Do be sure to clean your bits well as moisture in the air can set the dust left on your bits.

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Thanks Arron, hope to see people experiment with more materials and really see what our machines are capable of creating. Next I want to try making and milling my own Micarta (a paper or fabric and epoxy mixture) and try milling items like these colorful knife handles in the picture below.

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Just a heads up: plaster, hydrocal, ultracal is very corrosive. You have to thoroughly clean your machine, tools, etc. or you will have a mess.

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Time to go big, need to find a design for this 20" x 20" x 2.5" block of plaster! It’s about 3 1/2 times the size of the last one :stuck_out_tongue_winking_eye:

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