Creating molds from 3D Printing?

[Davo]

We've printed gaskets with RTV Silicone. We don't have a video, but I'll request one.

We are working on various fast-curing Silicones to speed the printing process - otherwise it's a slow print (waiting for each layer to set), or a sloppy print.

Our machines can print in just about any emulsifiable extrudable that is thick enough that it doesn't just run out of the tube and across the build platform. Essentially from the consistency of mayonnaise through precious metal clays. We have videos of our machines printing in clay, plasticine, plah-doh and sugru (rubber). The sugru is probably the closest consistency to RTV of anything we've filmed.

Anyway, the idea is to just print the mold, rather than printing a sample piece and then building a mold around it.

[awerby]

Great tutorial, I done this but was not happy with the results, too many air pockets. What is the advanrtage adding the glycerine?

If you really can't get proper 2-component mold rubber, silicone caulk can work as an inferior substitute. But as Navkram points out, the substance is too thick to avoid entraining air next to the surface of the model. It's better to at least use real silicone mold rubber as a first coat, painted on and allowed to cure, to get the detail, before applying caulk as a second coat (although you can also use a thickened mixture of the 2-component rubber). It not only picks up the details without bubbles, but releases much better than the caulk, which was formulated for adhesion, not removal.

Andrew Werby
Juxtamorph.com

[cipher0]

I don't understand how you can use printed plastic molds and pour molten metal, etc. in them. Won't the temperature of the molten metal cause the plastic mold to melt itself?

[3dkarma]

There's an scad program you can download from thingiverse that will generate a two-part mold from your model. I've successfully used this to create something with sugru. The original designer has cast pieces with wax, Knox gelatin, Oogoo and chocolate and has made casting tips and notes on metal casting via lost PLA available.

Parametric two-part mold generator for OpenSCAD

[jzatopa]

IF you need to do a lot of molding you may want to check out this roto-mold that looks like it will be on kickstarter soon. RotoMAAK

[awerby]

Cipher, there are many things that can be poured into plastic and rubber molds that aren't too hot. Yes, most molten metals would be destructive to a plastic mold, but an indirect method can be used if one wants to produce metal parts. One of these is lost wax (assuming wax was cast in the mold). The casting is encased in an outer mold made from plaster and silica powder which is heated in a kiln until the wax is burned away, then metal is introduced into the cavity. Then the plaster is washed away, so the metal object remains. The "lost PLA" method mentioned above is a variant on this technique, with a positive PLA model used instead of a wax one.

Andrew Werby
www.computersculpture.com

[python]

excuse my english, i dont understand. Is there maybe a video of that process?

[3dkarma]

excuse my english, i dont understand. Is there maybe a video of that process?

Do you mean the mold creation process, or one of the others in the link? I'm not aware of any videos of the mold creation process, but the instructions on the thingiverse page are fairly detailed. If these aren't clear or you need further help, feel free to post your questions here or on the thingiverse page. I'm not the creator of the script, but I'll help where I can.

[python]

sorry. i didnt understand how the indirect method with wax or pla works.

[3dkarma]

sorry. i didnt understand how the indirect method with wax or pla works.

Ah, OK. There's a good writeup (with lots of pictures and video) of lost PLA casting here: http://3dtopo.com/lostPLA/

Edit: Comprehensive writeup of lost ABS casting here: http://jason-webb.info/2012/11/lost-...minum-casting/