Cold Castings

[pixelplucker]

For those of you who have done 3d printing and/or have a 3d printer on hand and want to make something look like bronze, brass or nickel silver try cold casting.

 

I recently had a job that the finish product look like a brass casting. The client only needed one and detail was an issue so the only reasonable cost effective way was cold cast.

 

The process:

I made a 3d model

 

Had a 3d part printed in plastic (make sure the part is smooth since every little detail will show)

 

Mounted the part to the bottom of a metal pan with rubber cement

 

Poured in a liquid silicone rubber (slowly to avoid bubbles)

 

Carefully removed the cured mold

 

Mixed up the plastic resin and added the metal powder (mix ratio is 1:1:1+ small drop of colorant)

 

Poured the material into the mold and brushed out all bubbles and forced the material into all areas of the mold, keep brushing it until the material just starts to set

 

Once partially cured, slighlty tacky to touch add more resin and colorant (no metal powder) to back fill the part.

 

Once cured (1 hour) I removed the part and buffed it out with super fine steel wool.

 

Materials are from smooth-on.com and relatively inexpensive. No odor but I do recommend using it in a ventilated area.

Other molding material can be used such as the silicone 2 part putty which might be ideal for figurines. The resin could be painted on the inside of a figurine mold easily and once it tacks up and starts to set, simply assemble the mold back together.

 

I was going to do the model in AM but due to the large number of text models and time constraints I ended up tossing it through MOI which is a cad modeler, not quite that easy to do the free form shapes but got the job done. AM is definitely better for organic shapes. Anyways thought you guys might get a kick out of the process and spark some ideas. Be cool to see some of the characters done here in bronze

[itsjustme]

Looks fantastic, Ken!

[pixelplucker]

Thanks, the client was really happy. I was surprised how easy handling the material was.

[zandoriastudios]

Great job!

[Rodney]

Impressive!

 

I'm hoping to do some 3D printing starting next year and casting is definiitely on the schedule.

 

Do you have any pics of the molds?

 

Thanks for the detailed explanation of the process!

[robcat2075]

That's cool stuff!

 

Getting out the bubbles sounds tedious.

[pixelplucker]

Here is a pic of the mold used for this part since the part was just one sided it was an easy one. Most of the molds I make are for a centrifugal casting machine.

 

As far as getting the bubbles out with the resin it is much easier than you think. When brushing the material in it thickens and a soft natural fiber bristle brush like a disposable chip brush work fine, simply press down a little as you brush (not too hard or you will wear the release agent off).

 

Bubbles can be a problem especially with the liquid silicone (RTV) and many need a vacuum chamber to remove them. In this case the one I used didn't require it. I do plan on building a vacuum chamber, already have the pump just need the time to do it. Basically you can use a fairly large plastic container and put a nice rubber seal around the lid and attach a nipple for a vacuum pump. An inverted salad bowl on a nice piece of plexi sheet would work too. I believe you only need a few psi to draw the bubbles out.

[Rodney]

Very nice. Thanks!