Hi
I would like to cast components using 3D printed molds.
The 3D printing process uses laser sintered nylon which has a rough porous surface,
the first attempt using blue PVA release agent and polyurathane casting failed, and using Easy-Lease did not work well either
with the casting material sticking to the mold.
Do you have any recommendations on types of surface preparation, release and casting compounds ?
Alternatively I could cast a silicon mold from a 3D printed positive, however dimensional stability is important - I am looking for 0.3mm in 100mm.
Many thanks.
Regards
Paul

put simply ... You WILL have to do something more than release treatment of the rough/porous Nylon surface...   Can it be sanded/polished?

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I will probably go back to making a silicone mold from a positive master.

Also, would wax make a good mold material - e.g. lost wax casting wax ? It should be hard and dimensionally stable.

I will be using shellac to seal the sintered prototype.

Durability will be the biggest issue with any wax based moulds.  If you can seal the mould surface then you will be fine with the 3D printed mould.  Try several coats of PVAMould Release Agent which should seal the surface if the pores aren't too big.  Also the layer should'nt be too thick and hence dimensional changes won't be much.  Alternatively sray paint the surface to seal it.   Many of the resin based pattern systems build up a reasonable thickness which may not be compatible with your design intent dimensionally.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I have an FDM delta 3d printer. I make plugs out of PLA. I primer the parts and even clear coat them to make them smooth. I then am able to pva them for molding. I think the trick is getting rid of the roughness. After that is done normal moulding process can be done.  

when ive done 3d printed tools, especially the nylon ones, it takes a lot of surface cleaning and sanding to get smooth. they then need to be painted ideally and then polished but it depends on your application.
Plus the nylon starts deforming at 80degrees so if you are doing prepreg or post cure in the tool you need to be aware of that too