"lost foam" CAD/CAM mould making

pensterh · Post by **pensterh** » Mon Jun 09, 2003 3:03 pm

Hi, I am new to this board, so perhaps this has been discussed before, but....

I have recently been working with CAD/CAM technologies and glass casting, and am wondering if any one else out there has experience with this process?? I made laser ("LYDAR") scans of my body, which I manipulate in digital 3D modeling programs, then CNC mill master forms in foam, and finally do "lost foam" castings into silica/plaster or Zircar moulds.

I would like to begin working on a large scale (closer to life-size, rather than the doll-size I've been doing) and could use any advice or stories from your experiences...

Sorry for all the acronyms!!

Thanks, Penny

watershed · Post by **watershed** » Mon Jun 09, 2003 10:03 pm

You go girl!! Someone over on craftweb, had Access to a cad/cam.

Greg

pensterh · Post by **pensterh** » Tue Jun 10, 2003 4:16 pm

Thanks Greg, just signed up for craftweb & found the thread! Have you done or seen any of this stuff yourself? (Just curious what's out there, I haven't been able to find much except for one company making digital models for suncatchers + other tchotchkes.)

watershed · Post by **watershed** » Tue Jun 10, 2003 6:53 pm

Not yet, but maybe at Gas. I'll let you know

Greg

Joe Ruelle · Post by **Joe Ruelle** » Fri Jun 13, 2003 5:14 pm

How do you remove the foam from the mold?

Joe from Wisconsin

Nikki ONeill · Post by **Nikki ONeill** » Fri Jun 13, 2003 10:13 pm

'finally do "lost foam" castings into silica/plaster or Zircar moulds"

Very curious: what is the foam material and how do you "lose" it. Sounds like an interesting alternative to wax. Isn't Zircar a really expensive but strong material? Would you mind sharing a little of your experience? Thanks.
Curious Nikki

John Kurman · Post by **John Kurman** » Fri Jun 13, 2003 11:09 pm

I could be wrong, but...

Since this all sounds like "rapid prototyping" that has been done in the metals industry for several decades now, I suspect the foam is the same type - which is your standard polystyrene foam used in insulation and packaging and what have you. Acetone works quite well in removing this type of foam.

If it is something else, then I have no idea.

Ron Coleman · Post by **Ron Coleman** » Fri Jun 13, 2003 11:35 pm

Nikki O'Neill wrote:'finally do "lost foam" castings into silica/plaster or Zircar moulds"

Very curious: what is the foam material and how do you "lose" it. Sounds like an interesting alternative to wax. Isn't Zircar a really expensive but strong material? Would you mind sharing a little of your experience? Thanks.
Curious Nikki

The lost foam technique is used in metal casting. The basic process is make your piece in foam, imbed the foam in casting sand, pour in hot metal and the foam goes up in smoke.

I suppose in glass casting you could make a plaster mold over the foam and then burn it out and them cast the glass. Its got to be really smelly.

One method I've been messing around with is to make a pattern in Styrofoam (blue board) and then coat it with wax to build up an even layer. After the wax cools, use acetone to dissolve out the Styrofoam and leave the wax shell. Acetone doesn't attack the wax at all, but the foam shrinks up into a blob of goo that needs to be cleaned out. The resulting wax shell is then invested in a plaster/silica mix.

This process works well for closed shapes like vases where the opening is smaller than the body of the piece.

Ron

pensterh · Post by **pensterh** » Sun Jun 15, 2003 9:29 pm

Hi all.

I've figured most of this out on my own, so I can't say if any of these methods are conventional, but, in no particular order...

the foam i use is just blue or pink insulation foam (easy to scavange for free)

yes, it is the same basic process as rapid prototyping. i have been working at the yale school of architecture, so i don't really know about accessing this equipment in a commercial setting. but i was just curious if anyone has applied this process to art glass, b/c all i have found online is some kinda cheesy suncatchers.

yes, zircar is super expensive, but interesting to work with, very strong and picks up a lot of detail -- AND i had a small grant to cover it

ron - that process sounds really cool, i'll have to try it!! do you find that the acetone produces terrible fumes? do you have any images of your pieces/process? you're right, i just torch the foam outside while wearing a respirator & saftety equipment, but it none the less smells awful. sometimes though, with a relief mould, i can just pop out the foam...

can anyone let me know if there is a way to post pictures on this board and i will put up images of the whole process and some of the results!

take care,
penny

Ron Coleman · Post by **Ron Coleman** » Sun Jun 15, 2003 11:26 pm

pensterh wrote:
ron - that process sounds really cool, i'll have to try it!! do you find that the acetone produces terrible fumes? do you have any images of your pieces/process? you're right, i just torch the foam outside while wearing a respirator & saftety equipment, but it none the less smells awful. sometimes though, with a relief mould, i can just pop out the foam...

can anyone let me know if there is a way to post pictures on this board and i will put up images of the whole process and some of the results!

take care,
penny

The acetone smell isn't that bad, but you do need good ventilation. I dump in about a half cup and cover the opening with a rag. I check it in a few min and dump out the used acetone.

Here's the first piece I did using this process. I have some others but need to get pictures.

If you have a picture stored anywhere on the web you can add a link to it in your message.

Ron