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Post by notoes on Oct 31, 2017 16:10:16 GMT -5
I have been *attempting* to make two piece molds of posed action figures to cast in resin. The mold are coming out okay but I keep getting bubbles in the resin no matter what I do. The figure(s) is 5 1/2 inches tall, about 1 1/2 inch wide and I've got at least an inch of silicon around each side (some have a little more) and vents on every undercut I can put one on. The fill hole is in the feet and I am mixing up only an half an ounce of resin at a time (they take about two ounces of resin) and tapping the sides or rotating the mold as much as I can to get the bubbles to move to the top. I do three or four small pours, one a few seconds after another to try to tap out/rotate the bubbles in between pours while still getting enough resin in at one time to generate the correct amount of heat to cure correctly.
The figure I'm attempting to copy in resin has spiky hair that turns up at the ends, cat ears, and tail. He's "leaning" against a wall, one leg up with the foot against the wall, one arm straight down with the other across his waist. I've done two different types of molds of this pose - one where I pour from the feet and one where he's "face down" and I pour from his back. Both get bubbles on the hair ends, under the chin, or the cat ears. Or the pour doesn't fill the entire body (bubbles make the body hollow). Both have as many vents as I can put in so the bubbles shouldn't get trapped.
Bad thing is my smaller molds and one sided molds are mostly bubble free. I've also got a girl figure mold where she's simply standing straight with her hands folded at her waist that is also is getting bubbles under the chin and is pour from the feet.
So anyone have an idea of what I am doing wrong or any advice on what to try next? I've wasted almost two pounds of High Strength 3 rubber and 32 ounces of a different liquid mold rubber and am scared to keep wasting my materials (and money) on molds that are not working right. |
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Post by Brian on Oct 31, 2017 18:02:28 GMT -5
Try these 2 things....not at the same time unless you got a spare set of hands  1) As you pour the resin, squeeze the mold halves together forcing the pockets of air to escape thru the vents and gates...I do this often with success. OR 2) Using something like a long, wooden shish kabob skewer or thin piece of wire to work the air pockets up thru the vents and gates by moving the whatever you decide to use up and down in the pour gates and vents.......think along the same lines as when concrete is poured and the construction workers work the air pockets out of the concrete with a vibrator or even a 2X4 ..what ever works........I have used toothpicks before on some of my smaller pours.
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Post by notoes on Nov 1, 2017 7:18:29 GMT -5
I've done the squeeze thing with a small mold for hands that would get bubbles at the tips so I've tried doing that a bit though with such a large mold it does work to some extent, it doesn't get all of them or the ones right at the tips of the hair. I've done the work out air with something when I helped pour concrete but never thought to try it. The biggest problem is the vents were made with wooden skewers and the limbs are very thin while the head is large so I don't have wire thin enough to get in them. I'll have to try holding a hair clipper against the mold while I pour and see if that helps. If it doesn't, I might have flip it and try a pour from the head and see what that does.
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Post by notoes on Nov 1, 2017 15:09:38 GMT -5
Okay tried the squeezing the molds and the vibration ideas and they worked on the standing girl but still got only half the mold poured before the resin solidified on the boy. I also widened the vents on the girl mold which also helped but it looks like I might need to start over on the boy and make a new mold with bigger vents and a pour hole in a different place and see if that works better. Thanks for the help though.
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Post by carol - Alumilite Corp on Nov 9, 2017 8:43:31 GMT -5
Brian is right in everything he said I have done those tips myself. I have been told by some they put their mold (with a board under it in case of a spill) on the spin cycle of a washing machine to act as a vibration table with incredible results, whatever works right? ;-)
The other thing Notoes, is it may have to be cast under pressure. Pressure pots are not real expensive, sometimes it is better than wasting time trying to manipulate a mold multiple times and having sporadic results and having to scrap some pieces.
If you would like to send me picture of the piece you are having trouble with, please do. carol@alumilite.com
Warmest Regards,
Carol
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Post by notoes on Nov 29, 2017 13:31:38 GMT -5
Okay I have an update to this mold. I did find that I had to make the mold into a 3 piece mold and it worked a LOT better. And I think I also need a slower curing resin. But I made a new 3 piece mold for this character and had a much better casting. With just the first 2 pieces of the mold (top of head to waist) put together, I was able to get almost all the bubbles out and filled up the cavity better. The resin I used is getting a bit old so I didn't get all the bubbles out but I feel that if I use a fresher resin I won't have any problems. Plus I used RC-3 which has a 3 minute open time and something with a longer open time would have gotten all the bubbles out better.
So what I learned was this:
for thin, long parts with spikey areas - use a 3 or even 4 part mold and a resin with a longer cure time.
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Post by ronnyj on Dec 1, 2017 1:22:43 GMT -5
I'm glad I read this - I was going to try a 2-part mold, but think it will be a 3 part mold instead. Also, a thin resin may work better at getting the bubbles to release, and have a longer work time.
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Post by notoes on Dec 1, 2017 17:46:29 GMT -5
You also have to know that part of my problem was the original item I was trying to make a mold of - it is a 6 inch action figure with almost pencil thin limbs and it had spiky hair where the hair ends turned up. I have made great 2 and 1 piece molds of items that were a little shorter and thicker around with no problem. But I'm glad my problem helped someone else, this is a great place to get good advice and how others solved their problems  |
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