Need Help!- One-use casting mold

[Svetlana]

Hello to everybody!

Honestly I can say that I'm lammer in CNC. But in the call of duty I'll have to learn smth about that.

Now I want you to help me with creation the technology of doing one-use casting mold for soft flexible polyurethane foams (in Russian the name of the kind of these polyurethane foams is L-45, I don't know how to translate to English, sorry). The pressure of the foam is 3 kg per sm2, so the mold must be enough tensile (strong for stretching). The mold must be made by computer 3-D model, its maximum dimensions are 70x70x130 cm.

There are two main problems: the price - it must be enough low, because these molds are all one-use; and procedure time - it should be minimum. So expensive epoxy molds with their gigantic procedure time don't feet...

I will be very glad to consider and discuss all varients!

Sorry for my English

Thanks everybody, who will able to help or just turn the attention to my problem!

Kind regards,
Sveta

[awerby]

I've cast flexible polyurethane foam into silicone rubber molds; it released fine and I could use the mold repeatedly. It had a shell I could close off to retain pressure. What's different about your project?

If you really need a one-use mold, try machinable wax for that. It machines quickly, releases well from most things, and can be recycled by melting and recasting.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

Originally Posted by Svetlana Hello to everybody! Honestly I can say that I'm lammer in CNC. But in the call of duty I'll have to learn smth about that. Now I want you to help me with creation the technology of doing one-use casting mold for soft flexible polyurethane foams (in Russian the name of the kind of these polyurethane foams is L-45, I don't know how to translate to English, sorry). The pressure of the foam is 3 kg per sm2, so the mold must be enough tensile (strong for stretching). The mold must be made by computer 3-D model, its maximum dimensions are 70x70x130 cm. There are two main problems: the price - it must be enough low, because these molds are all one-use; and procedure time - it should be minimum. So expensive epoxy molds with their gigantic procedure time don't feet... I will be very glad to consider and discuss all varients! Sorry for my English Thanks everybody, who will able to help or just turn the attention to my problem! Kind regards, Sveta

[Svetlana]

Dear Andrew,
thak you for your reply.

1. I was talking with some manufacturer of car seats and headrests. They do their products out of polyurethane foam that I precisely will use. And they told me, that silicone is a defoaming agent.. Can it be only for this type of polyurethane that I need?

2. As for machinable wax - thats good idea, i've thought about it earlier, in particular about solid paraffine wax. But how to close it tight?

3. There were some other ideas among wich is using of some kind of damage-proof elastic film with powder inside it, that then must be vacuumized. In my estimation this mold should stand the pression of foam. What do you think?


Kindest regards,
Svetlana

Originally Posted by awerby I've cast flexible polyurethane foam into silicone rubber molds; it released fine and I could use the mold repeatedly. It had a shell I could close off to retain pressure. What's different about your project? If you really need a one-use mold, try machinable wax for that. It machines quickly, releases well from most things, and can be recycled by melting and recasting. Andrew Werby ComputerSculpture.com — Home Page for Discount Hardware & Software

[awerby]

[QUOTE=Svetlana;904539]Dear Andrew,
thak you for your reply.

1. I was talking with some manufacturer of car seats and headrests. They do their products out of polyurethane foam that I precisely will use. And they told me, that silicone is a defoaming agent.. Can it be only for this type of polyurethane that I need?

[There are de-foaming agents made with silicone; it's also used to inflate women's breasts. But the type I'm talking about is a 2-part compound that when mixed together, sets to form a flexible rubber. It's commonly used in the sculpture industry to make molds. It's one of the few things that polyurethane rubber won't stick to. The silicone rubber mold is usually supported by a rigid shell made of plaster or fiberglass/resin that would have to be sealed at the top with a clamped or screwed-on cover after the foam is introduced. ]

2. As for machinable wax - thats good idea, i've thought about it earlier, in particular about solid paraffine wax. But how to close it tight?

[Machinable wax is different from paraffin. It's mixed with some plastic (LDPE) to make it easier to machine without flaking. It can be welded, but making the top of the mold flat and clamping a wax plate over that would probably be best for closing the mold and holding pressure.]

3. There were some other ideas among wich is using of some kind of damage-proof elastic film with powder inside it, that then must be vacuumized. In my estimation this mold should stand the pression of foam. What do you think?

[Vacuum-formed plastic might make a good mold surface to cast the foam against (you'd have to test it to see if it released cleanly), but it's thin and flimsy by itself. You'd have to encase it in some kind of rigid shell to make it work in your application.]


Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software