Wooddave-It looks like you had a productive lunch break, thanks for the demo.
Hans-Thanks for the videos, I like the first one. I also think a little design in the mold would be good.
Storm-Inspired yet? When’s that first batch coming? I hope it’s a fun project.
-J
here’s a wholesaler
http://www.wholesalesuppliesplus.com/soap-making-supplies/soap-molds/bar-silicone-molds.aspx
soap bar or wax bar about the same size
My daughter bought a set of Hello Kitty molds similar to the soap molds. She used them to bake cakes, so they can handle a fair amount of heat. I’m sure you can find something similar made from silicone that will work. She has about 4 sheets and they make about a dozen or so each. Very soft and flexible.
There are tons of videos on youtube about mixing corn starch and silicone together to make molds. They come out pretty flexible so you can remove the wax easier. This is gonna be the cheapest and easiest way to make a flexible mold that will work with the wooden plug you built. If you want to step it up to the next level and spend a bit more money, look up a company named "Smooth-on’', they have all things mold related. good luck and let us know
I have made similar moulds with nothing more than cheap multi perpose silicone from the hardware store and a wood mild like you have. Just wax the mould with furniture wax and then just paste on the silicon, I let it dry well between coats and built it up till I was happy. I have been usinging them for casting concrete and they work great. You can also get casting silicon which is more expensif but probably a lot easier to use ether way it’s a very simple process and the flexability means you can do almost any shape without worrying about draft angles
Make your wooden plug out of MDF, not out of plywood. With good tools and a little fairing you can make a completed plug that will be very smooth and ready for you to make a quality mould.
Silicone is the most practical material, It’s durable and flexible…
You mentioned that your first attempt at a silicone mold didn’t go to well so I was offering an alternative…
I’ve only made molds using casting silicone (which is expensive but VERY cool stuff) so I can’t share any experience with using tube silicone,
If you were using actual wax to form your mold from silicone it’s likely that some chemical in the wax inhibited the cure,leaving a slippery uncured mess at the interface…
Forming it around an MDF mold that has been sealed… and allowing plenty of time to cure will likely give you better results than you got the first time…
Does anybody know why corn starch would be added to the silicone when casting??
My guess is that it’s to aid in curing, putting air into the mixture but that’s just a W.A.G.
Enclosed are some pics of some messing around I started about a week ago and finished today. The top row is the hardware store silicone mold version, the bottom row the thermoformed HDPE mold version. The second pic is the thermoforming rig and materials.
The plug was designed in FreeCAD, 75mm x 75mm x 14mm with a round dimple on the smaller square face. That’s just about 3 x 3 x 5/8 inches.
The silicone mold plug was left in the plywood stock to help contain the silicone. I made the wall cavities for the silicone 3/8", next time I would only make it 1/4" or so. I added the top ring to make the mold bottom thickness closer to the sides. The wooden mold was sealed with epoxy. I sanded it a little, but was too curious to try it to finish it more. Then the mold was coated with mold release wax.
The silicone mix was about 3 fl oz of 100% silicone caulk, super-old and mined from a half-cured tube, 1.5 fl oz cornstarch, and some xylene in an attempt to thin it. I slopped the mix into the mold and went to the movies. I came back a few hours later and it had set. I waited a day and did the first wax pour. It still smells like xylene, perhaps that was not the best solvent to cut half-cured silicone…I read that the cornstarch is a carrier for moisture which the thicker sections of silicone need to cure but cannot draw from the surrounding air.
I had never done thermoforming before, at least not intentionally, so I searched online and read what I could find on Instructables, Youtube, and Hackaday. I made a little vacuum table, think miniature air hockey game table without the sides, about 10 x 15", with 1/16" holes on a 1/2" grid. The extra holes got covered with masking tape so only the holes under the plug and frame were in use. I made another plug out plain wood, no bottom or sides, no epoxy, and added holes to allow air to escape from the top and dimple of the plug.
I dug through the recycle bin and got a couple of HDPE jugs, the kind used for milk and windshield washer fluid in the US. I cut out the middles of the jug and made a plywood frame to staple the plastic to for its trip into the oven. The frame had drywall scew legs to allow heated air to both side of the plastic and so that it would not sag onto the cookie sheet and make a mess. Oven was set at 325 degrees F, I put the frame and the plug in and watched for the plastic to turn from cloudy to clear, only a couple of minutes. Then I turned on the vacuum attached to the vacuum table, put the plug in the middle, and pushed the heated HDPE over the plug and down to the table. Once the edge of the frame seals to the table it’s only a few seconds until the plastic is formed and turns cloudy again.
The first time I tried I did not heat the plastic enough and it did not draw around the plug, coaxing with a heat gun only caused the plastic to tear. Once heated evenly from cloudy to clear it formed easily. The level of detail is amazing-grain in the wood, sandpaper scratches, etc.-all in the plug and then reproduced in the mold. Once again, curiosity trumped tooling of the plug. I poured one of the HDPE molds with purple wax. Both bars are raspberry with coconut if anyone cares.
The results are crude in comparison to commercial products, but I enjoyed the process. If I were to take it to the next level it would be using nicer tooled plugs (no grain or scratches) and commercial materials: either ready-made thermoform sheets or a real 2-part, room-temp, mold-making silicone like Wooddave mentioned. I also tried a 2-part, heat-cure silicone from work, but the wooden mold acted as an insulator and kept the business surface of the mold from curing properly.
Now that is an impressive bit of tinkering. Kudos !
Maybe they can custom make them for you!
http://www.tapplastics.com/product/plastics/cut_to_size_plastic
-Thanks Bill. I was hoping folks would get a kick out of it, especially Storm since he’s the one looking for molds. Some of my kids saw me do it and now they want to make some stuff too. Molded chocolates sound kinda good right now…
One more thing I would do is make the plugs a little deeper 1/16" or 1/8" since there is a radius formed between the plug and the vacuum table that would be a liability for molding anything brittle.
-Thanks Tom. Here are some other links for plastic sheets I found. Styrene is said to be forgiving for beginners:
http://www.usplastic.com/catalog/item.aspx?itemid=28983&catid=715
http://www.amazon.com/Styrene-Sheet-Thick-White-Shear/dp/B00DCKP3IO
-J
One way is you make a mold. I havent really looked into it but you could probably make a silicon mold. What I am thinking, is that you make a wood box that fits the wax with some space on each side. Then stick something in the wax so that it suspends in the middle of the box without touchung the botom. Then you mix up the silicon and por it in . Once its dry, the wax should peel out with the silicon in the shape of the wax. I am not sure if this will work but ill put in some links to help you out. Here is the easy way http://www.instructables.com/id/Worlds-easiest-silicone-mold/?ALLSTEPS. I wa thinking about using some sort of liquid silicon or latex but you might have to do some more research.
