Our products employ the use of an O-Ring to provide for a low pressure seal (60 psi). With all of the constraints we have, there is no standard size/material O-Ring available that meets our specifications.
I purchased the new elastic resin and an LT Tray, and printed several tests. The durometer is good, but the support removal is virtually impossible on a 5"+ O-Ring.
We have the specs defined and have received quotes from a local vendor for sample quantities for testing. Not inexpensive! I was explaining our dilemma to my son who used to run a plastic sales and fabrication shop and he asked me “Why not cast your own?” He pointed out that materials are available in silicone and urethane. He used a piece of acrylic with a groove machined into it, of the appropriate cross-section and diameter with an acrylic lid, (square profile O-Ring). BUT he was building a vacuum chamber, not a for-sale product!
I first considered using that process, but I then decided to print the mold. Why not?
This is what I came up with:
Two piece mold and one removal device. It works in my mind!
The holes are for resin conservation. After seeing the Preform results I’m thinking that 1/8" will work, so I’ll shave an 1/8" off of the removal device and the mold.
Removal device: Hex for orientation, pins to press the O-ring and the filler ring out of the mold.
I’m printing this in rigid, hopefully the pins will be strong enough.
If not, I’ll print one with holes and we’ll epoxy in steel pins.
The hex registers before the pins engage
The mold: you can see two of the 18 removal holes, matching the pins above
The ring: fills the mold except .139” for the cast of the actual O-ring.
Clean the supports and smooth the bottom of the filler ring.
Apply mold release to mold & ring
Place the filler ring into the mold
Apply mold release
Mix the silicone or urethane and degas it
Carefully pour or inject the mixed material into the mold
Let it cure
Trim the top with a razor blade
Place the mold onto the removal platform
Ensure that all 18 pins are aligned with the holes
Gently press the mold down forcing the O-ring out of the mold
Trim any flash from the O-ring
Clean the mold parts
Repeat as desired/required