Some advice on making silicone or rubber parts


#1

I’d like to make some small silicone like parts. Is this something I can do with formlabs casting resin? I see a lot onf info on silicone mold making but nothing for making silicone parts.


#2

You could print a mold directly?
Take your object, boolean subtract it from an appropriate base shape, hollow out where necessary and split in two.

Add some vents and a pouring hole, print and voila.

(That is, if you’re using silicone that cures at low(ish) temps.)


#3

Exactly right. I’m doing this on a daily basis. Grey resin works great as the mold for silicone parts, and no release is even needed.

Here’s the mold injector press I’ built and use:


You can see a small mold in position. I clamp it down with a ‘Y’ bar clamp (you can see half of it in the pic with the red rubber tip).

Here’s the reservoir showing the injector tip:

Here’s a shot of the mold used in the picture above just after injecting. This mold was actually printed on a 3DSystems printer - the cost of this mold is what made me buy the Form1+ :smile:

-C


#4

Wow, that is quite a set up. Can you just pour the silicone into rhe mold or does it need to be under pressure?


#5

@Joshua_Herskovic
my molds have removable cores, and the parts that come out typically have a 0.75mm wall thickness. a fair amount of pressure is required to get the somewhat high viscosity silicone into all the nooks and crannies.

I’ll vacuum de-gas the silicone first (in a custom hacked degasser for another post), then pour (and scoop) that into the reservoir cylinder. The piston has an O-ring on it to make a very tight seal into the cylinder. I pull down the lever slowly until I get a good flow coming out if the vents, then I stop up the vents with m2 screws, and hang a heavy weight on the lever to keep it under pressure until it sets. sometimes I’ll use a hairdryer on the mold to acellerate the cure. this pressurized approach produces the best quality part I’ve been able to make thus far.

-C


#6

really cool, Christopher


#7

I make silicone mold for resin casting. I too vacuum de-gas the silicone before pouring the molds in forms. I then also vacuum de-gas the those poured molds to get the silicone into the fine details on the master resin pieces in the molds. I do flat top and two part molds this way.

It would be interesting to see the mold parted after injection and also the part molded in some photos. I’m assuming you have the screws holding the two halves of the mold together while the silicone sets up before de-molding it.

-Walt


#8

That is a great setup. What is your silicone viscosity that you inject into the mold?


#9

So far, 23,000 and 30,000 cps platinum cure silicone, and also 1,100 cps urethane.


#10

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