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Hollowing out for 3D Printing for Investment Casting

Question asked by Dennis Dohogne on Jul 17, 2018
Latest reply on Jul 17, 2018 by Frederick Law

I am doing some work with some pretty complicated geometry that will be investment cast.  I want to 3D print the parts using some of the new castable SLA resins.  Formlabs just introduced one with 20% wax that is supposed to yield much better results for surface finish and burnout.  Since the printed part only needs to be strong enough to survive the ceramic coating process the part can be printed pretty well hollowed out.  This would shorten the print time and save on resin, but would also make the burnout much easier.

 

Supposedly, some of the 3D printer software handles this, but the folks I have been dealing with do not give me a lot of confidence.  They seem to only be interested in using the castable resin for jewelry and dental castings, which are very small and do not need to be hollowed out.  My parts are on the order of 50 X 50 X 125mm with wall thicknesses at least 3mm.  So there would be a lot of benefit if I can hollow out these parts.  No, shelling will not work.  Since I don't have a printer and am relying on someone else I would like to send them a file that is already hollowed out.

 

Some of you have 3D printers.  Does the software do a good job of hollowing out the parts like I want?  I know they can do some things to create a less-than-solid-fill, but since I don't have any direct experience with this I don't know if that itself is suitable.  I think there is still a lot of internal lattice with that and more than what my prints will need.  Really, what I'd like to have is akin to the exterior surfaces being offset by a minimal shell thickness of 1mm (or less if the resulting print is strong enough), and only where there appears to be a big internal void would I consider adding in some support.  But I don't know if that is the best approach, or even how to achieve it so I am turning to the helpful forum for advice.

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