On the feed chamber side: the clay mixture spreads quite differently than the commercial plaster powder. Whereas the plaster seemed to flow nicely on the front side of the roller, the clay doesn’t. It seems to want to agglomerate under the spinning roller. Every so often (perhaps 10 passes) the pressure builds up and eventually it goes all at once, resulting in slight tearing on the surface.
Manual spreading of CDF P-MF #1 powder. Note the tearing on the build side.
The powder spreads on a massive scale, rather than as individual free flowing particles.
Early stages while spreading the CDF P-MF #1 powder. These images show how the powder behaves on a macro scale moving as one, rather than as individual, free, flowing particles (this doesn’t happen with the commercial powder). While this condition improves with subsequent spreads, it never fully disappears.
The powder on the build side never really gets perfectly smooth like it would with a commercial powder. There are always areas that remain “pitted”. These pitted areas never get filled as the powder isn’t really loose and able to do its own thing (as mentioned above).
A small crater on the build side while manually spreading CDF P-MF #1 powder. This never fully heals, even with subsequent spreads.
I’ve tried both really compressing the powder in the build chamber, and hardly compressing it at all prior to starting. The latter seems to work better but still not as well as it think it should. I posted this on http://open3dp.me.washington.edu/2009/09/redart-terracotta-slip/
Mark suggests a couple of remedies:
1-Could be particle size related. I should try much finer materials. The largest they have successfully printed was 200 mesh glass powder, and that was fairly coarse. I should be aiming for at least the 400-600 mesh range. 400 mesh is 38 microns (0.038 mm or 0.0015 inches). Not sure that will be possible as some of the materials are 200 mesh from the bag (i.e. 75 microns or 0.075mm or 0.0029”). This should still be ok for the lowest machine layer thickness setting of 0.0035”). The Icing sugar won’t be a problem through the 200 mesh. Not sure about the maltodextrin though. I’ll try plate-milling it.
2-Could be moisture related.
3-Also suggested adjusting the layer thickness through the control software. Try a 0.007-0.008 in layer (using a non-plaster setting).
Perhaps before doing anything else, I should try to just spread some non-hygroscopic material (like flint or feldspar). This will get rid of the clay-clumping factor and show me what a 200 mesh particle does.
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