I know Lulzbot is working on a new heated bed (which I’ll definitely buy as an upgrade when it’s available), but the current bed has relatively uneven heating across the surface. Has anyone found any way to mitigate this when you have very large prints?
I’m about 11 hours into a ~20 hour print of what is basically a 200mm x 200mm box - so it covers 3/4 or so of the TAZ bed. I just noticed all four corners are starting to warp upwards a bit. The printer is in an enclosure (unheated, but it retains the heat reasonably well) and smaller parts that are close to the center of the bed print wonderfully with zero warping. The bed had a fresh coat of ABS glue before starting the print.
I may look into using a heater to keep the build enclosure actively heated to a certain temperature, but I’m trying to avoid that since the electronics are in the enclosure with the printer right now and I’d like to avoid rewriting things if possible.
A thin aluminum or copper plate under the heater will spread the heat a bit. You can also use PET or packing tape to close off the edges of the build plate between the aluminum and the glass to try to keep a pocket of heated air under the bed.
I don’t have easy access to any aluminum or copper plating, but I do have a roll of PET tape I’m going to try, so thanks for that suggestion.
After looking at my print, it looks like the bed itself isn’t causing the problem as much the ABS shrinkage is. Some corners of the box I printed warped upwards and left the box walls more or less solid. The walls above the corners that did NOT warp ended up cracking open…so it looks like the ABS is going to relieve the pressure from shrinking by either warping or cracking. So more consistent bed heating may have held all corners down, but that would have likely caused more cracking elsewhere. This is all with an enclosure too.
It looks like I just can’t print big, reasonably solid objects in ABS, so I’m going to break the model into smaller sections and reassemble them with ABS glue afterwards.
Sounds like a plan. Have you tried adding a ~4-6mm brim to your part? That will also do wonders for keeping things stuck, but require some cleanup afterward
I haven’t tried a brim yet, but I’ll get that a try if I attempt a big print again. I’ve wasted lots of time and a couple of kilograms of plastic trying these huge prints, so it’ll probably be a while before I try again. I can definitely see the brim helping though.
Is it true Lulzbot is going to offer an improved heatbed? Setting aside my gripe that the original heatbed should provide even heat, this upgrade would be a must buy. I print almost exclusively large prints and have learned from experience all the trouble spots on my bed. This effective build area is much smaller than the advertised print area.