PLA prints are curling off the bed

General LulzBot TAZ
1

This is yet another post about bed adhesion difficulties. I searched this forum for advice and tried a few things but my current print is showing the same issue so I’m hoping this will yield some new ideas.

My setup is a KITTAZ w/ standard extruder and hot end and a 1/16" PEI sheet clamped onto the bed. I also have the dual duct fan installed on the hot end to keep air flowing around the heat sink. I have been using the silver PLA from Lulzbot. I like to use Simplify3D for slicing and have tried the following setting combos, all to similar effect:

  • 190º head, 60º bed, 60mm/s default speed, 0.2mm layer height, 30% 1st layer speed, 120% 1st layer height, 100% fan
  • 180º head, 80º bed, 60mm/s default speed, 0.14mm layer height, 35% 1st layer speed, 90% 1st layer height, 100% fan
  • 180º head, 60º bed, 60mm/s default speed, 0.22mm layer height, 50% 1st layer speed, 90% 1st layer height, 100% fan

I’ve carefully checked three times that the bed is level. The prints come off with a gentle pull but seem fixed to the bed well enough. The curling never begins right away, but rather after the first few layers or even later. My (inexperienced) gut feeling is that this is mainly a temperature problem but I don’t know where to go with that hunch. I have made a handful of successful prints, but nearly all of them exhibit this problem to some degree. I’ve also experienced this when printing on the PET surface.

The photos are of a failed print of the Maker Faire articulated robot figure http://www.thingiverse.com/thing:331035.

robot-fail-2.jpg
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2

For me, PLA likes to pull up on corners where there’s a sharp change in direction, just like the arms in your photo. Seems like the head is pulling too much on what it lays down. You might try turning down your fan, or going to 195 C. I was having the problem a lot at 180 C, 60 C bed, GizmoDorks dark blue PLA. It’s much better for me at 192 C, 60 C bed.

I also had a lot of weak layer adhesion at 180 C. Parts were solid, no loose traces, but flexing them produced a lot of crackle. It didn’t take much to pull them apart. At 192 C, they’re very solid, much stronger.
-gj

3

Thanks for the advice. I wouldn’t have thought to try turning down the fan, so I’ll give that a go. I’ve also had good results printing the PLA at 190 vs 180 in earlier prints.

I don’t think, however, that my curling is result of the nozzle pulling up the print. I’ve watched a curl happen – over about 2 seconds while the nozzle is working elsewhere, the print will lift from the bed a few mm and then stay there. I was thinking that this was a temp problem in the opposite way: that the PLA was cooling too slowly.

Anyway I appreciate the ideas and I will try turning down the fan to see what happens!

4

A bit of PVA(watered down (milk-like consistency) white school) glue solution on the bed will help with part adhesion.