I’ve been attempting to print a LARGE piece. Basically a box (with lots of fiddly details) that is 12" x 12" x 4".
It stands on one of the 4" x 12" ends.
this photo is taken after a failed print. 87% done at failure.
The head (once again) hit the piece and pushed the whole thing off the print bed and table. Fell 4’ to the floor.
This time I had setup a 1mm Z-Hop, so it got further before it failed.
Note that I am using a 1mm nozzle to cut the print time down from 4 days to 1 1/2 days.
(Using Cura to generate the stl)
With this kind of failure, I don’t think using a 0.4mm nozzle will make a difference.
As far as I can tell, the problem is that the PLA is going to warp a little. In this case, I’ve held the bottom up to a straight edge after the failure, and it does appear to have warped about 1mm over the 12" length.
Hi John,
Do you think a 2mm Z-hop would do the trick?
My only other suggestion would be to build a custom bed with a thicker metal layer that won’t bend and secure it with more than just the magnets. It will take longer to heat up.
Are you turning the bed temperature down after the first layer?
BTW, what is your cougars name? I think that is way cool.
Tone
Holding the magnetic pad down isn’t likely to help. As the PLA warps, it’ll just pull from the bed - which is what happens with my SnapMaker 1.
Bed starts out at 65, then cools to 60 during print.
I’ve never seen a larger PLA print NOT warp some.
I MIGHT be able to use a 2mm Z-hop, though it would be better if I could come up with a way to keep the PLA from warping.
What’s the density of your infill? Less dense Infill can help shrinkage. I know you said you wanted strength but maybe the every other layer of infill would be a little less strong but help out in the shrinkage department.
I did a print today with every third layer of infill with a .5 nozzle. With layers .25 thick that means is was trying to print .75 high infill! It worked ok. It wasn’t a large part. This was on a Lutzbot at my work.
Have you tried an enclosure? Normally needed for ABS but could help shrinkage with PLA.
How does an enclosure prevent shrinkage?
A point that was brought up on the FB forum.
Warping doesn’t happen suddenly, so as the piece warps, the printhead will just be smushing each new layer down a little. The Warp shouldn’t ever cause the printhead to hit the piece.
This makes me wonder if as the piece warped, it put stress on the magnetic bed - which eventually popped up, rocking the piece over enough for the head to hit it. My previous failed pieces were all still firmly attached to the bed - which had been pushed out of position.
It keeps the part at a more uniform temperature thus reducing the shrinkage.