Concrete ashtray mold

You'll need a printer, filament, and sandpaper.
Use these to make the mold.

Now you'll need some hard technical grease, a brush, and 700 grams of concrete.
Grease the inside of the tub like you would a cake tin with butter.
Press the molded parts into the grease and remove the excess grease with a brush.
I've included a 0.3 mm gap in the mold in case your printer is inaccurate.
If your printer is properly calibrated, a small gap will appear which you can fill with grease using the brush.
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I will only release the OpenSCAD script if 10 users have left a comment.