Molding problems I need urgent help with

Hello,

I could really use someones help as soon as possible regarding my problem with silicone molds I am trying to make with pieces of an action figure model kit I got printed. I recently only make a few molds such as the crown, front & back torso, bottom part of mouth and a forearm piece.

The crown, when demolding it, I noticed that it molded the innerside of the crown as well and the only way I could remove it was by damaging the mold, there was no possible way, that I know of, to remove it. The front & back torso pieces were molded separatly and could not get them out of the mold due to silicone molding the inside of the pieces, which I want, but I dont know how to do it effectively. Also many of the smaller parts have peg holes and when I make molds for them, I already know its not going to be easy to remove. Ive wasted nearly $100 on silicone to have the molds turn out incorrect. If someone could please take the time who knows a lot about silicone molding, even if you skim though the video to each part and tell me what kind of molds I need to make, it would save me a lot of time, money, & hassle. Link to video is below. Thanks!

<a href="https://youtube.com/watch?v=NvEyib35PXw" target="_blank"></a>

WSF is a porous material, you'll need to seal/fill in the model to remove that aspect of the material. For a test project I used 3M Bondo Glazing and Spot Putty to fill it in. This took multiple coats and lots of sanding to achieve a smooth, solid finish. Once that was done I didn't have problems with the mold sticking to part.

any hollow areas should be filled with a clay suitable for the silicone used. Go pick up a book online from silicone molding companies. You Tube?

Cut the cured silicone into small blocks and use them to fill the next moulds after you have applied some new silicone.

Just to add, recycled silicone works best in volumes away from the surface of the master being molded. And don't be too greedy, I would say one third of recycled silicone to two thirds of gloopy silicone is about optimum. Using a thixotropic additive, that is, to add it to some silicone, and use that to coat the master will insulate the master from the conglomorate cured/uncured mix one adds. Finally, purely as an aside, using lego for mold walls is really useful.

I have yet to see the videos but it does sound as if you need to block off areas of your master object using some sort of wax or even silicone putty. It will cure hard and be pretty well permanent but it will do the job brilliantly. Just avoid undercuts where the silicone has no obvious path of release.

I'll check out the video and if I have anything extra to add I'll do so. Good luck!

OK...I have just had a look at your video, firstly, nice job! Secondly congratulations on your ambition. That's quite a peice to learn silicone mold making on.

In complex molding one has to make sure all holes are filled. Then identify trouble spots, and think of ways of assembling molds around them that can be dissembled easily without damaging the cast material.

The problem with the crown is a) in how to create a mold in multiple parts and b) avoiding massive airlocks once you use the resin in the mold.

So the first part of a mold for the crown will be one that sits inside it, forming a support for those mold parts on the outside of the crown; and also acting as a mold wall in it's own right, preventing uncured silicone from entering the space it occupies. So firstly, you'd need to make the inside part of the mold first. So using an appropriate wax or clay, surround the outside of the crown with it, and make sure there are no gaps at all. so you can pour silicone into the core without it leaking out. Also include pegs in the arrangement to allow the surrounding silicone pieces to lock into this central part of the mold. Then create the outer parts .... creating individual mold walls for each part, as you create them, one after the other, is going to be tricky. Thin lego can help with wax or clay filling in the gap. You will have to match the edge of the walls to the spikes from the crown as no filler is going to attach itself to silicone. Again, using pegs as you go so the whole lot interlocks. Lastly, you are never going to be able to pour anything into a mold like that outside of a vacuum without trapping a huge amount of air. The way around this is to use a thixotropic agent in whatever resin you are going to use, and brush it on the inside of the molds, then put the mold together and brace it together, not too tight as this will warp the object. Basically if you do it right you won't have to pour any resin into the mold. it will all be there, at least in the thin and narrow parts. Of course, use a mold release spray between each wall as you pour silicone onto cured silicone!

I think your biggest problem will be the mold walls. They will be really fiddly. Good luck!