I'm having problems with small bubbles appearing in the wax part I'm working on. Seems you can't use vacuum to cast wax parts. I've tried tapping the side of the mold to try to release the bubbles. I'm spraying the mold with mold release. I'm heating the FF turquoise slowly and pouring it as soon as it's liquid. I'm not sure what temp it's at. Due to the shape of the part, I'm pouring some wax into the bottom of the mold, installing the top half of the mold and then filling the mold. (I had big gaps (air pockets) when I tried to do the entire pour from the top. ) Any suggestions? Thanks as usual
I finally got to see your first picture enlarged... If your silicone mold is brand new, try casting the part a few times. Often times, I find silicone needs to kinda season to get a clean wax finish on the part. Sometimes warming up the mold a bit with a hair dryer also helps. I never get a bubble free wax part the first time or two I try casting it in silicone.
I'll give that a try. I see a lot of benefits in having the mold warmed up. Maybe then I can just pour the wax from the top and it'll fill properly. Thanks
Can maybe try silicone mold release in the mold first before pouring. It may help break the surface tension and prevent air getting stuck under wax. Bubbles also seem to happen when the wax isn't at the right temperature. Pics aren't the greatest to see exactly the issue on the wax.
I spray mold release due to the complexity of the part. I'm heating the wax on my kitchen stove at the lowest possible setting, which I suspect is too high. I'm still in a proof of concept stage trying to find out if I can make parts before I spend a bunch of money on the equipment... The photo is the photo. It shows the holes in the wax. You could see it better if you copy it to the desktop on your pc. Thanks for the comments and suggestions.
Nahh it's not heat. I've tried, cold and hot and still had bubbles. When I slosh cast a silicone mold, I start with wax so hot its smoking! I shut the heat off, pour in, dump out. Wait 30seconds and repeat until I have the thickness I need. With that said, not all wax castings are perfect. If the visible parts are smooth, roll with it. If the back has an issue, get a hot knife and fix it. And no I dont run a double boiler. Heat is heat, I'd do it if I had a business and was afraid some 10dollar an hr employee would burn the joint down. My steel pot on the induction cooktop set to 190 works for most wax work. When I smoke it, I heat to 210 for my particular microcrystaline. I'd try real hot wax on your silicone a couple of times, I bet it calms down and you'll get a good pull.
I heated the molds in a toaster oven for 20 minutes at around 115 degrees. I did two pours. One with all the was through the top and one with the double pour. I'm not sure if it was coincidence or not but the single pour gave me a bad part. The second pour produced a better part. Since this is a trunk lock, there is only a small area that is seen...the area that needs a smooth finish. The edge needs a little trimming. Thanks for the advice.
Glad you got a good one. I don't know why, but silicone behaves after you have pulled a few wax copies out of it. Let's call it "seasoned" and roll with that. SO what about those threads???? Do you know what the pitch is? I haven't tried casting threads, but I think I'd be tempted to cast just a blonde one bigger than the required diameter and run a die down it after it's in metal. Seeing you are the creator here, you can set your own threads for what die you have on hand. Or what nut you can find... Too fine and they might turn out shit.
I think you are correct that the mold is getting seasoned now. I think heating it helps too. The threads are 5/8 x 18 but I'm not 100% certain. The master part is 50 years old and had some corrosion problems due to being made of pot metal and being on the car for 50 years. The nut was rusty. I rebuilt some threads using JB weld. The wax is not melting into the threads as nicely as I would like it to and I plan to run a thread chaser over the the thread area of the finished part. I might try cleaning up the threads on one of the wax parts to see if it improves a little. What I'm finding is, there is a little bit of degradation from master part to mold to finished product. Seems a little bit is lost at every step in the process. I want to keep the part as original as possible so I'm keeping the original thread. Thanks for your help and comments.
I pressure cast my wax which provides bubble free castings, the same process commonly used in resin casting. you can make a pressure chamber with a $100 paint sprayer.
You can find videos on youtube about pressure resin casting, it's the same concept but with wax instead of resin.
This is the only photo I have at the moment, next time I do it I will document it. This was pressure cast homemade machinable (parafin and HDPE.) 100% bubble free casting, behind it you can see my heated pressure chamber setup.
but in the OPs case it might not help since hes using a squash mold, when the pressure collapses the bubbles you need a reservoir of extra wax to pull from. I would add a sprew/riser to the part, if still to no avail, add pressure.
