Uneven Bed Temperature

Hello,

I’ve been super happy with my mini since i got it but it seems that it’s now having major problems with ABS warping. I’ve tried all the usual stuff:

  • Clean / wipe down the bed with IPA - the bed is clean and flat with no damage
  • Ensure the nozzle is clean
  • Ensure extrusion is calibrated correctly
  • Measure the filament diameter multiple times along its length
  • Up the temps a little - to 245 extrusion and 115 bed
  • Change the model being printed to avoid hard to print parts, e.g. thick bottoms and hollow tops etc.

I checked my bed temperature and i found it varies quite a bit. In cura i have set 115 degrees, and around the edges i see 98-105 which seems low but ok-ish. In the middle of the bed though, i see 85 which for a 115 setting seems well off.

I just experimented with where i placed some prints - i put one on a hot part of the bed and one printing at the same time spanning a hot and the 85 degree part of the bed. That part is sufferring the worst abs curl i’ve seen yet!

So, have i nailed it, is this my cause?

What’s my next steps, can i buy a new bed? I’m in the UK and i think i’ll be out of warranty period now.

You can buy a new bed heater from Lulzbot or IT works https://itworks3d.com/product-category/parts/mini-parts/ . The bed works by heating up concentric loops of metal embedded in the rubber membrane. It is possible for one of those loops to fail without affecting the rest of the bed heater, which will lead to a dead spot. The edges are also generally colder than the interior because the outermost loop has to be a certain distance from the heater edge for safety.

Another option is to replace the glass of the heated bed with a more conductive material, such as a 3/16" thick aluminum plate. You would have to modify the hold downs for that though, which would be a pain. but it really helps adhesion with a Taz!