Presentation on theme: "By: Alex Brett, R.T.P.O.(c). Cast (with minimum 2” of plaster above trim line) 400ML Silicone Cartridge (durometer of your choice) 400ML Injection."— Presentation transcript:
We will then drill two shallow “key” holes on either side of the cast. These will give our injection mold something to lock into.
Pull two nylon stockinette over the mold and set up in your forming station
Cut two pieces of PETG approximately 6-8” longer and 6-8” wider than the cast (based on side profile). Trim the parting film back 1.5” around the perimeter of the plastic. This will provide a good vacuum seal during molding, yet allow the two halves of the mold come apart once trimmed.
Parting film is what makes this technique possible. It doesn’t matter if the film is clear or blue, but your prepared sheets should have a border of film removed and look something like this:
We will be fabricating a clam shell type mold This is the only step that will require the assistance of a helper. Heat both sheets of PETG in the oven at the same time. Assure that the parting film with trimmed edge is facing up.
Carefully sandwich the mold with the PETG. Assure that the cast is centered well before applying vacuum. This step can be a little bit tricky so pay close attention when lining everything up.
Once the holes are drilled around the perimeter, trim the PETG approximately 1” away from the holes The halves will now separate and the pelite dummy can be popped out easily thanks to the parting film.
With a ½” bit, drill a hole at the lowest point of the mold to inject the silicone.
A short ½” pipe nipple will thread into the PETG by hand. No tap is required.
When using ¼” PETG, the pipe nipple will stay recessed. If for some reason it protrudes you may need to bond the nipple to the PETG with some epoxy (this is rarely required).