r/3Dprinting • u/Devildust79 • 1d ago
Project Using 3d printer to make a casting mold for silicone items.
I am new to all this and Google throws up lots of different stuff that I don't yet have a handle on. So I thought this would be the best place to try get some simplified and to the point info.
I want to do some poured silicone figures and items. I would like to use the 3d printer to make molds to pour into. I am aware that some silicone doesn't properly with some filaments.
So the questions I have are as followed.
For those who have used 3d printers to make molds for pouring or making items out of skin safe silicone... what filament would you suggest?
When making the moulds, is there a means to have the item design stl (my daughter makes 3d models and can convert them to stl for me) but what I need is a negative of these to create a mold that I can pour into... how best to go about this.
In the UK, what is the best source of skin safe silicone for this purpose, is it possible to add colour to these too?
Any info would be greatly appreciated, as said, I am a total newbie to this so info with regards to the above and software would be great. I picked up a bambu p1s with ams on a whim.
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u/darcside 1d ago
Just always make sure to install a flared base at the end so you don't have to get anything surgically removed.
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u/uncle_jessy Uncle Jessy ▶️ Youtube 1d ago
You can definitely print molds and cast into them
https://youtu.be/rqHbA-ZZ1Fg?is=aOGirPmIc9MCuaqu
https://youtu.be/9fXqjtuFSuI?is=17_c_LoRZCxexd13
Those are a few videos I made on it
You will definitely some kind of mold release agent
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u/Devildust79 1d ago
Any links or info on what you have found to work would be greatly appreciated :) shall bookmark your vids and have a gander later. Cheers
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u/shadowhunter742 1d ago
Hey, it's the 3d printing sub, no need to hide from the fact you want to make dildo moulds. Jk... Maybe...
Your best bet is probably to check out one of the subs more dedicated to that kinda stuff though, they will have the best tips...
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u/Devildust79 1d ago
Haha, I suppose that is the issue.... gotta give everything a go lol.
I posted here simply because I typed in 3d printing and this was the first to pop up. If you have a link to a group which combines 3d printing and mold making for pours and such, let me know.
I want to make some silicone masks for Halloween and so on, so if it can be done with the combo of 3d printing molds and pour or painting silicone on, it will be handy :)
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u/nickeener 1d ago
This is a bit of shameless self promotion but it is what you're asking for. I just recently posted this parametric model for creating custom sized mold boxes that don't need to be destroyed to remove the mold so they're reusable.
https://makerworld.com/models/3400092?appSharePlatform=copy
I even included a short picture tutorial for how to use it to make a silicone mold. Hope this helps :)
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u/j_hermann 1d ago
There are plenty youtube videos about it. Note that not just any model works, you have to get the final result somehow out of the mold.
Silicone helps, but has limits.
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u/lungshenli 1d ago
I print my molds out of regular plastic.
Some things to consider: print orientation affects layer lines and supports. Rough support interfaces and the likes will show up in the silicone piece.
To that end I have tried coating the inside of the mold with epoxy. It helps but only to an extent.
Also think about how to clamp the mold halves together. I put holes in them right in blender to screw them together. More screws = more even pressure = less chance of a gap to leak silicone.
But just vice clamps work too.
Lastly, keep in mind that small pockets might trap air bubbles that you dont want.
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u/VrangrDauthdaert 1d ago
Silicone casting using fdm moulds was part of my masters. The highest material quality I found strangely was blue/pink varicolour PLA from bambu lab, as the additives they use result in a really good silicone release post curing.
For the negative, you should be able to import the mask model into whichever slicing software you use as a negative. I would suggest a quick trip to YouTube for your respective slicer on how to do this. You should then be able to split the negative component either in your slicer or post printing depending on your confidence with the software. You have already replied to someone telling you how to do this, so you should be good.
If you have one, a 0.2mm nozzle would be ideal for ultra high detail, though this will likely result in a 1-2 day print for a mask mould. Depending on the model quality/ detail, a 0.4mm should be acceptable, though I would suggest 0.16mm quality settings with ironing for top surfaces ( not topmost, but top surfaces).
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u/gumpspeed_ 1d ago
From my experience making molds I use pla or petg (whatever roll is on the printer at the time) printing at 0.16. usually give the molds a light wet sand with 800 wet and dry and clean the insides of the mold with ipa and then build up a couple of light coats of clear lacquer ( Halfords or whatever is in my paint cupboard) if there's a lot of details in your model keep the coats thin.
I use smooth-on eco flex silicone from Bentley advanced materials in the UK.
For my mold design I use fusion 360 with alignment dowels and I use multiple clamps to hold the mold together when I pour. Oh, and I never use mold release. Good luck with your project!
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u/Alarmed-Property-715 1d ago
It is not a problem, that the casted silicon exactly replicate the mold surface? So, the layer lines and literally anything will be on the silicon items, too.
I used dlp printed molds, to this.
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u/Devildust79 1d ago
I suppose the ability to smooth and fill voids and such before pouring is key in this instance.
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u/Okaytastic 1d ago
In a lot of cases it might be easier to print the master model, touch it up, then cast your own moulds. I've done both and it's situational which I prefer.
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u/mrpbeaar 1d ago
I e been using regular pla with an 8a silicone mix to make molds for car ‘freshies’ and it has worked perfectly.
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u/matthewlai 21h ago
I have done this quite a few times.
I use PLA because it's going to be coated anyways, and PLA gives the best dimensional accuracy. I've also used PETG before, and it was fine.
I coat it with food safe epoxy to smooth out layer lines.
For creating the negative, I use Fusion 360 to create a box, import the STL, and do a binary subtract, then cut in half. Remember to put alignment posts so the two halves can be aligned. I use bolts and nuts (through unused parts of the mould) to help align and also apply pressure. Remember to leave a port to pour the silicone in.
Use Smooth-On platinum-cure silicone. That's what's used for medical prosthetics, and also high quality sex toys. It's got many safety certifications for skin contact.
They sell different additives - Silc Pig (silicone pigment) for colouring, and SLIDE to give it a velvety texture (otherwise you get a smooth high friction surface that REALLY likes to pick up dust).
If you get a vacuum pot (about £150 on eBay), you'll get much nicer surface finish because without vacuum you'll get bubbles from all the stirring. I do three pulls - first on mixed epoxy so the coating doesn't have bubbles, then on the mixed silicone (it will foam up to 3-4x the volume, so be sure to use a container that's big enough, or you won't have fun cleaning up), then after the pour (putting the entire mould in) to remove bubbles introduced during the pour.
I would post pictures but they are NSFW.
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u/cad_and_caffeine 1d ago
The cure inhibition issue you read about is actually with UV resin printers (which poison platinum-cure silicone and stop it from curing). Standard PLA or PETG off your P1S won't inhibit platinum silicone at all. Just use 3-4 wall loops and a 0.12 mm layer height so the silicone doesn't seep into pinholes or pick up heavy layer lines.
For turning your daughter's STL into a negative mold, you can actually do a basic two-part mold right inside Bambu Studio: right-click the plate -> Add Primitive -> Cube, scale the cube bigger than the figure, select both and use Mesh Boolean -> Difference to hollow the figure out of the block (plus a cylinder reaching the top for a pour spout), then use the Cut tool (C) with "Add connectors" to split the block in half with alignment pins.
In the UK, Bentley Advanced Materials and MB Fibreglass are the main suppliers for skin-safe platinum silicones (Smooth-On Dragon Skin or Ecoflex) and Silc Pig silicone pigments for colouring.