Designing 3D Molds, Milling it Using a 3-axis Finish Cut CNC machine, and Casting the Parts
Objective:
To design multiple 3D molds (1- a scoop/spoon; 2- a cartoon face) and cast their parts.
Materials:
(a) CAD software (Autodesk Fusion 360) to design the 3D model;(b) Part Works 3D software (by ShopBot) for creating the toolpath (roughing and finishing) and milling it by Desktop ShopBot CNC for milling;
(c) Smooth-On Oomoo 25 Silicone Rubber (1:1 ratio in volume for Kits A & B); (d) Hydrostone (22ml:100ml for water and hydrostone powder; for example, 88 ml water and 400 ml hydrostone);
(e) Alloy of a mixture of tin and bismuth; (f) Wax; (g) Talcum powder; (h) Machinable wax bar/block (for milling)
Fabrication:
(a) CAD design: At first, I designed the 3D models using the Fusion 360. Next, I used a machinable wax block to mill my mold in it.
(b) Molding using the CNC milling: Then I created the toolpaths for roughing and finishing using the Part Works 3D software, and loaded them in the CNC Desktop Shopbot to be milled.
(c) Positive template: After milling the block, I got my positive template.
(d) Negative tamplate (or Reverse impression): Later on, I poured the Oomoo solution to make my negative template in form of a silicone block. It took around 75 minutes to cure the negative block.
(e) Casting my final molds: Finally, I made my original mold (the 2nd positive) by pouring the casting materials (e.g., hydrostone/alloy) on the negative mold and curing it. It took around 30 minutes to cure the blocks.
Most importantly, I had to use a wax block (as suggested by Neil) to cover the scoop head (hollow space) of the negative template while pouring the hydrostone solution in it. It ensured, I had the holloness inside my scoop.
Otherwise it would have been filled up scoop head like the first positive template.
(f) Finishing: I used a mechanical polisher to polish of the surface of my alloy mold of the cartoon face to give a better and a smooth finishing.
Fabrication Mishaps:
(a) While making the negative template for the cartoon face model, the silicone solution didn't get into small holes (eyes and mouth) mold properly. So it didn't create a proper negative template after being cured.
So, I had to redo it and this time, I used a stick to properly poke/guide the solution in these small holes first, and then pouring the silicone solution into the rest of the mold.
