Building and using a centrifugal caster

[Pico]

I've been thinking about this for a long time and finally decided on building a cheap and easy caster for white metal. I've cast in two piece molds but a centrifugal caster will force the molten metal into the mold so you get much finer detail. I decide to use a small fan ( $10 from Walmart) and make the mold from 3" plumbing waste pipe. Plywood bottom with a turned center to fit into the center of the fan. It will be held on by rubber bands.

[Pico]

Next step, make the mold. Using another 3" pipe, fill halfway with clay. Then press the item to be cast into the clay. Build up underneath if the item is angled, like the windshield. In the center, place a conical shaped plug, that, when removed, will make the volume into which you will pour. Notice that the plug is wider at the bottom than at the top. This is because the molten metal will gather in the bottom and be thrown out through the sprues. If it is wider at the top, the molten metal will be thrown up and out the sides of the opening. If this happens, it will spoil your day. I have some 3d printed door handles to pour, also I've made sprue paths with electrical wire and impressed the handles into the clay. I use Smooth-on's Mold Max 60 as the molding material. It is a silicon rubber that will withstand heat up to 560 F. (284 C.). It's main drawback is the mix is 100 parts rubber to 3 parts hardener by weight. I got a small kitchen scale from Walmart for $20 that will weight down to 1 gram. It's necessary if you are casting small parts. It recommends a 24 hour cure but usually is faster than that. Carefully remove the clay, spray with mold release and cast the second half. Remove from the pipe and remove the items from the mold. Make certain the sprues are open to the items openings. Next I made a box to hold the fan and a cover with a center hole for it.

[Pico]

First photo: this is why you need a cover. I use lead free britannia metal, from ebay,  I heat it in a ladle with a mapp gas torch to about 400 F, then carefully pour it in. Watch out with the standard safety precautions! The mold is a 3/16" under the cover so if you miss the hole some molten metal will be pitched out. Be careful and stand back! It cools fairly quickly but not fast enough if it's on you skin. This is the result of my first pour, which I think is a success.

[Pico]

If you are casting smaller objects and don't want to use a large amount of Mold Max 60; make a plug of plaster of paris to fill the mold, then the two part rubber mold. Be certain the plaster of paris has set for several days and is dry before pouring in molten metal. The windshield is a success, I'll also use metal door handles on the outside of this model.

[vintagercr]

That is pretty cool.

[Gramps46]

You are a clever man Pico!

Gary

[oldcarfan]

That is too cool! Could you use it to cast resin too?

[Pico]

You could but it's not necessary. Resin flows easily so you don't have to force it into the mold. The problem with molten metal in a non-spin cast mold is it cools quickly and may not fill the mold. In a spin caster the centrifugal force throws it into all parts of the mold.