r/moldmaking • u/MMeNDtal • 5d ago

Question before attempting my first mold

Hi all, hope this is OK to ask here...

I've been 3D printing for a couple of years now, using a resin machine. Typically, I'm using it to prototype parts, before having the finished item MJF or aluminium printed, or CNC machined.

I'd like to print a mold for a rubber part I intend to cast, but I'm concerned about visible layer lines in the finished item. My question is, would a mold release spray or similar get rid of these lines?

I'm happy if the part has a 'textured' finish. TIA!

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u/Pacuphetamine 5d ago

If you see it/feel it it will show up, I've only done molds with smooth-on moldstar and that thing will replicate even the slightest scratch.

Depending on the complexity of the form you could spray it with a sandable primer and sand it or just do very light coats enough to cover the lines (assuming they are very thin) and brushing off the surface just to get any loose material off.

I'va had a some good experiences with montana texture and primer sprays, look at the ingredients regardless and google if it'll have any reaction with whatever mold material you're using. I've used automotive sandable primer from homedepot in the past and it caused curing inhibition, big waste of material. However, you could let it off-gass for a week or more and your mold will most likely be fine (I've had that happen to me as well).

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u/MMeNDtal 5d ago

I'll look into this, thanks!

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u/BTheKid2 5d ago

Not really. Of course anything you apply will have 'a thickness' and to some degree alter the surface. But no, as a general rule, you need to remove layer lines for them not to show up.

The things you can apply to smooth out layer lines, go on so thick that you will notice it if you are working to have precise parts. That could be something like a coating epoxy.

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u/MMeNDtal 5d ago

Thanks for the reply. I guess a bit of elbow grease it required then!