Milling a Circuit

Project by Jeremy Fryer-Biggs


casting metal with your microfactory!

The microfactory is a great tool for metal casting! To show off this capability we purchased a block of microcrystalline casting wax, designed our own minimalist chess set and then set about using the microfactory to mill out the shapes. Because we don't have an oven in-house to perform a burn out, we opted to sand cast the parts rather than lost-wax cast them (but you can do either). We wound up with simple, clean looking pieces which feel substantial and will last a LONG time!

project parts list

  • microcrystalline casting wax
  • scrap aluminum
  • green sand
  • casting box (we constructed our own)
  • baby powder
  • cut-off wheel (for removing the sprues)
  • crucible
  • heat source (we used an oxy/acetylene torch)
  • piece of wood to tamp sand down
  • sand paper (for finishing)
required bits

you will need a 1/8th downcutting bit for milling the microcrystalline casting wax.

Eagle Speaker Circuit Layout Image By Jeremy Fryer-Biggs

milling the wax

first we designed our chess pieces. When I was growing up there were two chess shops on Thompson street in New York City. There were a few minimalist and art deco sets in the windows which never ceased to fascinate me every time I walked by. For this project, I wanted to create something with our microfactory, in the spirit of those designs, that had its own distinctive look. Every piece is derivative of the simple oval shape of the king - every other piece we modeled started as a king and then had some portion of the top sliced off (and in the case of the rook and the knight minor embellishments added for clarity when playing).

CAD rendering of dock by Jeremy Fryer-Biggs

we then CAMed up all of the parts using CamBam. For the smaller pieces (pawns) we put a planing step into the beginning of the program. For the larger ones (everything else) we planed the entire piece of wax then just executed the program.

Photo by Rachel Tine

next we cut the large block of wax we purchased into more manageable sizes. The default thickness was 1.5in so we stacked 2 blocks together height wise for the taller pieces (using a heat gun to bond them) and used the 1.5in height for the pawns. I must stress that your choice of wax is important (for your own safety) we recommend the de-oiled products sold in art stores specifically for casting. Also we recommend buying one that is fairly hard (or you are going to have a lot of fun cleaning up afterwards :) )

Photo by Rachel Tine

then we milled out all 16 pieces (a single set). You can mill one of each (6) but that will then require additional casting runs to complete.

Photo by Rachel Tine

(see a short video of the microfactory milling microcrystalline casting wax)

casting the pieces

once all the pieces were milled, we constructed a casting box out of scrap plywood. The casting box is two rectangles (each rectangle holds half the sand mold) and an unattached bottom. We used additional pieces of ply to create an extension from one side of the mold to the other in 6 places ensuring that the two halves aligned perfectly.

Photo by Jeremy Fryer-Biggs

next we poured sand into one half of the mold, scraping the top flat. "Greensand" is a reusable casting medium that is a combination of fine grain silicate and bentonite clay and 6 percent water. You can make your own with products purchased at a hardware store OR buy it pre-mixed.

Photo By Rachel Tine

we added baby powder to the pieces to act as a mold release. Next we dug shallow holes into the mold and inserted the pieces. When inserting the pieces, orientation matters - we suggest not pushing the pieces down too deeply. Also be sure to place them so that both sides are symmetrical (the finished product looks better and it makes the mold easier to work with). Once all of the pieces are in the mold sprinkle a little more baby powder on top.

Photo By Rachel Tine

then we placed the second wooden mold frame on top of the first and poured sand in over the top until it was full

Photo By Rachel Tine

afterwards we used a flat ended piece of wood to compact everything down and used that same piece of wood to smooth the top. then we flipped the mold over and removed the sand from the first half (because it was loosely packed). We added more baby powder and refilled it with sand, packing it firm this time. Then we gently seperated the molds and extracted the wax pieces (unlike lost-wax casting, in sand casting the orignals are not consumed).

Photo By Rachel Tine

next we used a wooden dowel to bore two sprue holes in each piece (one is a pour hole and the other an air hole).

Photo By Rachel Tine

one final check to make sure everything looks good and the mold is put back together

Photo By Rachel Tine

pieces of aluminum are pre-cut and placed in the crucible

Photo By Rachel Tine

these are then heated until molten

Photo By Rachel Tine

and poured into the appropriate cavity

Photo By Rachel Tine


Photo By Rachel Tine

(watch a short video of the process here)

after sitting for 10 min the mold is opened

Photo By Rachel Tine

and allowed to cool

Photo By Rachel Tine

the sand is then broken up

Photo By Rachel Tine

and the pieces are then extracted

Photo By Rachel Tine

the sprues are removed and the pieces sanded...

Photo By Rachel Tine

finally the pieces were anodized in red and black
and voila a beautiful cast aluminum chess set!!

Photo By Rachel Tine

special thanks to