I made the sock using LazaroFilm's mould but decided to try making my own. Having a few years of ceramic mould making experience myself, I thought that this would be a good experience. I decided to build the mould in 4 parts instead of three and added some tightening points in case they were needed.
The centre hole tightens fine with a 3Mx10mm machine screw. There are also two side tightening spots, as well as places for the hex nuts if necessary.
I left vent holes in the top to allow any excess silicone to exit the mould, hoping that this would allow me to slightly overfill and force out any air cavities. The parts are small so I printed with 100% infill and also used supports for the hex nut holes and the two points that extend out the side of the inside block.
Before applying silicone wipe the mould down with dish soap which acts as a separating compound. Don't leave excess soap inside. Wipe it lightly with a paper towel to remove any excess.
Squeezing the silicone through the tiny spout hole is really hard so I found that using a tube squeezer made it much easier.
I assembled the base and the casing and then filled the space slightly more than 1/2. I then placed the inner block and pressed it down slowly allowing the silicone to squeeze out around the block. I made sure it folded back in over the block and added a little more to ensure it covered the top of the core. I then carefully placed the top and pressed it down to a point where I could use the screw to tighten the top down. There should be enough silicone in the space to allow it to squeeze out the vent holes but not too much so that it comes out between the casing and the top. The lid should tighten down snugly but be careful not to over-tighten.
Allow the silicone about 24 hours to cure before disassembling. The parts should separate fairly easily. Trim off any excess silicone using a small set of scissors or clippers.
This sock fits my MPMD but you have to remove any existing insulation and kapton tape. It is a relatively snug fit.
Note: As with any mould, make sure that all parts fit together smoothly before using. None of the pieces should bind or you may have trouble releasing the mould later. The posts are slightly tapered but the corners of the posts are not, so you may need to sand them slightly. Also ensure that the inner block sits square on the post. If it doesn't file/sand the post so it does. I use a small set of diamond files for this but small nail files work fine.
Warning: If you forget to apply the release agent (soap) the silicone will stick to the PLA. If you are careful and the surface is smooth you might be able to separate it. If the silicone has not fully cured it will pull apart, as the inner silicone will be softer than the material at the surfaces. After 24 hours outer surfaces are quite well cured but the material is still soft inside. The silicone will bond pretty strongly if the surface is rough, which it is at 0.2 resolution.
EconoFil (filaments.ca) PLA
This is pretty obvious but just in case...
Make sure that when you are about to place the top on the mould, once it's filled with silicone, that the silicone is level to, or slightly lower than, the edges. The inside of the top will displace a small amount and if the mould is too full it will push out over the edges and make a bit of a mess. On the other hand if its too low your top surface won't end up nice and smooth.
Also, the silicone will spread a little easier if the soap has had a chance to dry before filling the mould with silicone. If it is wet the silicone and soap will mix together a little and may case some voids.