Printing a silicone split mould
If only you could print with silicone directly.... 😥
But it's special properties make it impossible to be used like PLA and ABS and other plastics.
It does not stick well, it is very heat resistant, it is flexible and durable and not much else sticks to it once it has cured. It is the perfect material for many mould making applications, because a variety of resins can be cast into silicone without need for release agents, and it can take the heat when the resin heats up while curing.
Nylon is about the closest printable material to silicone, as far as it's properties go, but it's nowhere near as good for mould making as silicone, and nylon is difficult to print.
So I figured I'd test if silicone (Silastomer P40 is my favourite so far) would bond to PLA, and it turns out that it does not. I checked a few different PLAs, all release easily from Silastomer P40.
When I tried to print PLA moulds, they always warped a little bit, no matter what I tried. Even 0.5mm warping is way to much for what I want.
Eventually the penny dropped: I do not need to take the print off the print bed before casting the silicone into the 'mould-mould'. And the heated plate can even be used to control the curing speed of the Silastomer P40. 😀
Re: Printing a silicone split mould
Pouring Silastomer P40 into the mould-mould:
Gravity is your friend here, the printer must stand level so that the top surface of the silicone stays in it's box.
Once this one has set, I'll take the silicone out of the mould, remove the PLA mould from the printer, and then print the other half of the 'mould-mould' .
The eventual aim of all this is to laminate fibreglass (or carbon fibre cloth) with epoxy resin between the silicone split mould halves. This will hopefully produce a very tough but dimensionally accurate base for a surfboard fin.
It might be possible to print fins (of various shapes and materials) that fit perfectly on the fibre/epoxy laminate fin base.
Re: Printing a silicone split mould
Nice. I've been looking at making mould-mould for a couple different projects as well (3 off the top of my head).
It doesn't look like you de-gassed your silicone. Do you know about the "long drop" trick?
Re: Printing a silicone split mould
Thanks, gz1!
I have not had need for a de-gasser (although it would be nice to have one).
I don't think the slow thin pour method, or along a sloping object would help much with Silastomer P40, because it takes several hours before it starts to set. The vast majority of the bubbles rises spontaneously and bursts at the surface, only the very small ones remain. The surface in contact with the mould has always been practically perfect, it's just not quite as transparent as it could be after de-gassing.
The second half of the mould worked out well, too.
And best of all, they fit together perfectly.
The keys were printed separately, some using the 'Spiral vase' function, very nice. They should have printed as straight cylinders, but they are thicker at the bottom, which is perfect because they snap into the mould and stay in the side they were inserted to. You can lift the other side off without the keys coming out with it.
It remains to be seen if the dimensions are exact enough when I de-mould epoxy resin from this silicone split-mould.
Re: Printing a silicone split mould
I work with molds all the time- you can make a quick pressure chamber from a glass canister (Walmart, kitchen or dried flower dept), and a plastic cutting board or a 1/4" thick piece of plexiglass. that fits the top. Make a ring gasket from air dry silicone.
A couple parts from harbor freight and you're good to go. Heres a video that pretty much sums it up. You'll get much better results from the molds.
Yeah, its that guy... 3D Nexus
Re: Printing a silicone split mould
Crap, Just noticed you are in AU. Forgive my geographic sillyness. You can still muster the parts, just not the same way.
Yeah, its that guy... 3D Nexus
Re: Printing a silicone split mould
Thanks, Ancientwolf, you convinced me that I can start to use vaccum as a tool much cheaper than I thought!
I think I'll go even more basic and convert a hand pump to a vacuum pump. Maybe not enough suction for complete de-gassing, but easy and cheap.
I imagine I can just add a nozzle to the lid of empty jars and use them for single-use degassing containers, rather than just tossing them.
Maybe I can prepare a lid with attachment for the hose for those commonly recurring jars, and re-use the lid and just change jars after de-gassing.
See this video for what I have in mind for the pump:
And this for the single-use de-gassing jar:
Re: Printing a silicone split mould
Ive done exactly that with mason jars before, but you have to be careful with the amount of vac you impose on them, the lids mainly. You know, you can easily 3D print a thicker cap with holes for the fittings, and line the groove with silicone. Thinking about this just pushed me over the edge to do just that. Hand pumping the vacuum can be pretty rough, and the parts (of the pump) can be also subject to the same forces and may not hold up so well (internal seal fail) Theres alot of available pumps out there and if you do these molds enough, the better pump while pricey, would be well worth the investment.
I'm gonna grab a couple mason jars and measure, and whip up a cap like I mentioned in Tinkercad. I think we could be on to something. Hehe
Yeah, its that guy... 3D Nexus
Re: Printing a silicone split mould
Something like this is more my style, Im sure anybody can source these...
https://www.walmart.com/ip/Mainstays-1-2-Gal-Heritage-Hill-Jar-with-Cover/17043674#about-item
The benefit is a very thick glass and alot of different sizes. I use a 2 gallon one in my current setup but its usually bigger than I need.
Yeah, its that guy... 3D Nexus
Re: Printing a silicone split mould
Too early in the morning for me to get out to the studio, but heres a quick example. Its public so you can edit it for your own sizes, its basically a demonstrative version. If you need to alter the sizes, just select everything and ungroup it all.
https://www.tinkercad.com/things/bFHCPsh5JgT-vacuum-chamber-lid-prototype-example
Yeah, its that guy... 3D Nexus
Re: Printing a silicone split mould
I found that some silicone casting material bonds quite well to glass, although it sticks to nothing else.
I don't know if the transparent Silastomer P40 will do that, too, but can find out.
If Silastomer P40 binds to glass, then one can make a universal lid for various vacuum chamber sizes, by 'hand-printing' a hot melt glue ring onto a glass plate (10mm glass or thicker I guess), then pouring a thin film of silicone onto the glass surface, so that any size jar (or pressure cooker pot etc) will fit under it. A thin layer of Silastomer P40 will be transparent enough to see how the de-gassing is going under the glass.
Need to drill at least one hole into the glass without breaking it, that's the trickiest part.
Re: Printing a silicone split mould
Thats why I initially went with a plastic cutting board for the lid, and regular clear window silicone from the dept store for the gasket. Being able to drill holes for the various fittings (gauge, vac line, etc) was easy through the board and the silicone gasket used to seal those as well worked. Being able to print one as I described for me works because it was way cheap and it will now save me having to drill holes for the fixtures.
I work with alot of precision stuff, but in this case having a selection of vacuum options just made life alot easier.
Yeah, its that guy... 3D Nexus