Help with making Vents in my molds

[bdbrooker]

Hello again!

Some of the 3D printed models I'm trying to make molds out of have so problem areas where air is getting caught. I plan to make vents in the specific areas. What is the best way to go about this. I've seen wax strips be used when pouring the silicon but I'm not sure where to find these bendable wax strips. Whats a good alternative to the wax strips? any other techniques or strategies for making vents?

Thanks
Brandon.

[mangozac]

You can make them out of anything: wire and styrene rod being the most obvious. I generally use round styrene rod 1-2mm diameter. Also if necessary later on you can always cut vents into the silicone mould using a knife.

[Fleafa]

Like Zac says, vents can be made of anything. As they are not feeding resin, they can be super thin. I have used electrical wire and thin plasticard in the past.

[RageofAchilles]

For small problem areas , I use a quill (aka dropper) needle once the mould is cured. I push the needle through the rubber and it creates what is essentially a rubber core sample it leaves a 0.5 mm vent in the mould which is just right for air to escape.

[Fleafa]

That is pretty fantastic!

[RageofAchilles]

It works great if the needle is long enough.
Of course you can do the same with some brass tubing, if you don't mind coring out a larger aperture vent.

[mangozac]

I did this to create a "blind vent" in the Helian Cruiser hull mould. There was an annoying spot that always ended up with a tiny air pocket that obscured detail. I used some brass rod about 1.5mm diameter and turned a sharp edge on the lathe.

I then used that tool to punch a series of blind vents in the up direction from a flat part of the detailed spot. It removes a cylindrical piece of silicone about 5mm long. During casting, the air is forced up into these vent areas (along with a little bit or resin). So the model is left with a couple of small, spiky protrusions that are simple to remove with a knife.

This is apparently common practice with spincast metal moulds...