Hello, I have this 3 piece figurine, I made 2 silicone moulds, but both of them are coming with defects, when casting, so I screapped them both. Could someone please give me an advice on where to make the air wents and how to place the parts so the mould is gonna make a good casts?
Most issues comes with the ears, teeth and either top or bottom of the head. Also the tail is bended, that's issue also.
Last Edit: Jul 29, 2020 6:28:48 GMT -5 by saphirka
What I would do is be sure to make small molds or if you want, you can go with two piece molds for each but I think you can do this with one piece molds.
On the head, I wouldn't put any vent holes but use the piece where it attaches to the body as the pour hole. Pour in small amounts and on the first pour, rotate the resin around a bit to cover the inside of the mold and to give the air a way to escape before you pour more. You can add a slit or two on either side of the pour hold when you demold the original to make it easier to demold the copies but the silicone will go back to its original shape and shouldn't give you too noticeable (if any) lines that you have to trim off. Plus by having the slits you can open up the cavity more when you pour to allow any bubble to rise out of it.
On the body, since it has a flat bottom, you can just leave most or almost all of the bottom open and just pour from the bottom. Any bubbles should be able to come right up but you can also help them up by swirling a toothpick in the mold.
On the tail, if you add a thin line on the bottom so that the silicone doesn't completely meet on both side of the bottom then you can get almost all of the roundness and use that as the pour area. You'll have to either take off that little bit of resin that fills the pour area or make sure to not pour the resin to the top of the pour area. By adding the little line, you will be able to open the mold up to pour in the resin which will enable any bubbles to rise right out of it.
By doing large pour areas you might need to do a little sanding on the bottom of each part but it would probably give you the best molds. I hope this helps.