Problems with casting small resin parts

[spejic]

I'm trying to make resin copies of parts for a 1/144 model. The mold is good, but I keep getting big bubbles in the parts. It isn't bubbles in the resin, but voids in the mold where the resin can't get into. Are there some techniques for solving this problem?

I'm using the Smooth-On kit if that means anything.

[Netz]

Your trapping air in the mold.

Take a pin or knife and poke/cut a slice at the spot where the void is, this will let the trapped air have a place to go, you might have a bit of flash there but at least you will have a complete part.

When you pour the resin in the mold, only put in a drop or two, use a tool/wire to open up that slice to get some resin in there, then continue to fill the mold.

Then drop it in your pressure pot......:} What no pot!!!!!

Curt

Edited January 18, 2012 by Netz

[Pierre Sacha]

Hi,

I've been casting for a while now. One answer. Pressure pot! you don't even need venting holes with a pressure pot. The only thing is to try and use a slower curing resin as this will give it time to fill all the crevices of even the most intricately detailed molds. I use THIS with perfect results most of the time. I inflate my pot to about 4 bar using the same compressor I use for airbrushing.

Good luck,

Pierre

[sting]

I had the same problems when I started making parts. One thing you can do is dip an old paint brush into the resin and use the brush to get the resin into the small areas of the mold it has problems flowing into. Of course you have to work fast, but after using the paint brush and you're satisfied you worked the resin into the small areas, pour the rest of the resin into the mold. The resin applied with the brush and the resin poured in aferward will combine for a solid mold. Even if the resin cures, after brushing it into the small areas, before you can pour the rest into the mold, you can mix up another batch of resin and pour it in. It will adhere to the cured resin making a solid piece when finished. You may see a color differences, but it will be a solid piece.

[salvine]

Here is a pic of a small mold. I used it just like you are talking about to replicate helicopter miniguns in 1/144. The fill port is on the far right and you can see two vent tubes over where the guns are located. I left the original parts on the sprue to help with filling. I considered a pressure pot but make so few parts right now that it seamed like a waist. I fill the mold with a small hobby syringe and fill until the mold until is flows out the vents. make the vent at the highest point to help aid in removing the air. I also use a crock pot to place the mold in to add heat to aid in curing.