Box mold for casting plaster

thingiverse

A demonstration of a technique for printing two part molds for box-like objects. Instructions This is mainly a demonstration of a technique for making molds of things with flat bottoms (like boxes), and not too useful otherwise (unless you want the exact box I made). Some helpful notes: Model the object you want to create, then subtract it from a solid to get a mold negative. No overhangs or undercuts. Leave the top open; that will be your flat bottom. Add flanges to the bottoms, both to give yourself somewhere to put some indexing features (I used mortise and tenons with a 0.2mm clearance), and to give you some leverage to pry the molds apart without having to push on the plaster. Don't forget to add some draft to your mold, or you will have a hard time getting it unmolded. I used ten degrees on all sides. Hollow out the bottom to save on printing time; the bridging won't be on the plaster side so its quality doesn't matter. Try to avoid having interior curves on overhanging walls (like I have), or be confident you can print them without dropping threads to the inside. Johnson's Paste Wax is a good mold release agent when using PLA and plaster. The cast in the photos is my first attempt, so don't laugh too much at my poor casting technique.