Here’s a reprint of a model that I scaled up to see how large I could print. The final was 5.5 inches tall and had to be positioned diagonally across the build volume. I printed at 0.05. Print time was 10+ hours according to Preform (but I believe the actual time may have been a bit shorter).
I hollowed out just the head by using booleans to subtract a modified cylinder which had an extruded poly face extending beyond the chin region - so that I would end up with an air hole.
I had to fix the model first in https://modelrepair.azurewebsites.net/ so the booleans would work cleanly, but once done, it loaded into preform with no troubles.
I looked at automatic generation of supports, but the result was so incredibly dense, it would have taken me quite some time to strip it down. Multi-select in support-editing mode would help that immensely.
Even so, it seemed like a good test again to see if I could manage things myself, esp on a larger model. Note that I chose this orientation specifically so the supports would stay off the base - and so the fingers needed minimal supports as they grew downwards. (they were a bear to clean up on the first version of the print).
As you may guess, my first test failed. I had placed the head well opposite the hinge and it did not have nearly enough supports. The result was apparently that the forehead region separated quickly from the build platform and I had to stop the print.
Here’s the second try - I just added about 20% more supports - but very carefully placed to ensure that no “island” in a slice started printing without a support directly beneath it. It took about 45 minutes to set up, in total.
Here’s how the good print looked after removing a few supports. I had to do that to give it a proper IPA bath, as it would not fit in the IPA bin:
Uncured - IPA rinse done.
You can see above that there were problems printing the head. The head IS hollow, and the way I printed, there should not have been a blow out here, unless the wall thickness was just to much for the printer, but I have printed thicker and so I am not sure what was going on. This section was opposite the hinge again, so maybe this is a peeling problem? Or perhaps just something bad at that corner of the print? Not sure. But I see this a lot and am getting a sense for when it is going to happen (never on mid-thickness arms, legs, midsection, etc. Generally on thicker areas.)
I should say also that this same model (without the hollowed head) printed just fine at about 1/3 the scale.
(still learning how to paint… not my forte )
Here’s a view of the top of the head:
But here’s a look at the slice where the problem occurred:
Does not seem too thick, but not sure. Also there was a hole under the chin, so even though this section remained open for quite a few more layers, it should not have had any blow outs when it closed. (FWIW this does not really look like a blow out to me, based on what I’m starting to recognize as a blow out).
Another shot before cleaning:
And some beauty shots:
(still needs a bit more clean up)