6 | molding and casting


How it works (source - Karina Silvester):




Space on my mind this week.... model source:


Model Creation

1. Draw plane in the midde of the figure. Use plane to divide mesh in half, put each half on a different layer and then clean up any remaining mesh bits that are on the wrong side of the dividing plane. I found it was easer to duplicate the figure and fully delete each side as nessesary.

2. Add the registration points to the splitting plane, duplicated the whole thing, and then flipped the direction of the registration points on one half.

3. Add the top wax surface and extrude a curve down from that surface so that it is all joined as a continuous surface. At first I had a lot of trouble in the fab module because the registration points on the front side were not coming through to the png. Eventually i realized that the issue was the the surfaces were not joined correctly, and this was causing them to not be recognized from the stl to the png.




Problem png

No registration points showing up on the left. Depth on left and right is showing as the same, even though they are different. Went back and made sure all the surfaces were joined into one piece before exporting as bianary stl.


Final working png

Now everything looks good except the background turned off-white. I must have moved the whole thing down below the z-0. The resulted in the modela taking a bit of the top layer over the whole block.

Cutting on the Modela


Take a block of machinable wax and use hot glue to stick the wax down. Zero the bit.



Milling the rough cuts.



Origin was too far over in the x direction, lost a critical wall.... flip over and start again.



How to CANCEL a job



Final Positive Wax Mold

Rough and fine cuts completed. Athough there was space in the stl around the head, feet and hands this did not come through in the model. Next time more space is required and a separate casting pipe.




Casting the Flexible Mold



Oomoo was used. Equal parts of each substrate by volume. Mix really well. Tap the cup on the counter tand blow at bubble with a straw to remove bubbles.



Cast the Final Material



Drystone was used. Set up is 5 parts powder to 1 part water by weight.

Since the extremities of the astronaut reached the edge of the mold, i needed to patch these holes. Tape was not sticky enough but hot glue worked well, and came off right away afterwards.



Parents in town.... enlisted some stirring help.



Use a syringe to fill up the mold. Go slowly to help air escape.



Let it set over night.



Trim seams with sandpaper.



Final Astronaut

Lookin good




Oxygen tank in tact...!


All together: