Week 12

This week’s assignment was to design a 3D mold, machine it, and cast parts from it in as many different materials as possible. I decided to use the 3d model i made in week 2, a lightsaber in Fusion, for the cast. So my next step was to design the mold and i decided to use Tinkercad to do that.

To start with i saved the lightsaber from fusion as a STL file, and then i imported it to Tinkercad. After that i duplicated the lightsaber and rotated the copy by 180°, next i drew two boxes, about 2-3cm bigger, around the lightsabers. Next i aligned the lightsabers in the middle of the boxes and made two joints on each bow, one male and one female, to stick the rubber molds together. Then i made a paraboloid at the end of both the boxes, to make a hole to pour the material in, and walls around the box to have some depth in the rubber mold and in the end i grouped everything together.

My next step was then to save the tinkercad file as a STL file and import it to Vcarve Pro to get it ready for the shopbot machine. In Vcarve i made two toolpaths, first a 3D roughing toolpath and then a 3D finishing toolpath, and then i saved the toolpaths as shopbot files. In the finishing toolpath i changed the stepover percentage, in the tool menu, from 40% to 11% to get a smoother surface on the mold.

I was going to mill the mold out in foam, so before the milling i fastened the foam to the shopbot plate with screws and one wooden plate. Then after some time when the milling was over i cut the molds out and the next step was getting it ready for the rubber mold.

The first thing i did after the milling was to make the foam more dense, because the it had quite a lot of small holes in it, i did that by blowing on the foam with a hot air gun. But be careful not getting too close to the foam with the gun or it will melt which happened to me so i had to make another top part for the mold. I also painted the foam with a thin layer of Gesso to make it denser and allowed it to stand for maybe 3 hours to dry. Next i had to mix the liquid rubber mold, i used the one from smooth-on. I combined equal amounts of liquid parts A and B, then i mixed the liquid rubber thoroughly and before pouring it in the foam i sprayed the foam with a universal mold release from Smooth-on and then poured the liquid rubber carefully in the foam mold and allowed it to dry for about 16 hours.

The next day the rubber mold was ready and i was pretty pleased with the outcome except for the joints they were unsuccessful.

Before making the hydrostone cast i had to enlarge the hole for pouring the hydrostone in, i simply did that with a knife and because the joints on the mold were unsuccessful i had to stick the two rubber molds together with clamps.

So now i mixed the hydrostone powder with water and poured it into the rubber mold and after about 30-45 minutes the hydrostone lightsaber was ready. I must have stretched the saber a little bit in tinkercad because it came pretty flat out of the mold, i’ll have to watch out for that next time i’ll make a mold.

I also made a plastic cast of the saber, the mix i used for that was also from Smooth-on and is mix like the liquid rubber. I’m fairly pleased with the outcome but the saber is of course way to flat, but everything else was successful.

Files