Ok so I no longer have adhesion problems with the PLA,

Ok so I no longer have adhesion problems with the PLA, now I just have this weird problem that I have almost no clue what could be the cause.
My prints start to curl once they are a few layers in, not curl off the bed, the edges just curl up and cause a problem that looks an awful lot like over extrusion, except that my extruder isn’t over extruding at all. I’ve recalibrated all my axis and the extruder, so I know that it isn’t an extruder problem, at least I don’t think it is.
Someone on the forums had a similar problem, and it was suggested that it was the extruded plastic being stretched due to a lower that required heat. I’ve increased the heat up to 230 and it has minimized the problem, but I have a feeling that there is a better way to solve the problem. I’ll post up some pictures of the prints.

Nophead mentioned on his blog that the flow rate for PLA can be significantly different than that of ABS. Could the problem be that the flowrate is wrong?

Did you turn up the bed heat or just the extruder heat? If you don’t have a heated bed you may have to try making changes to the geometry of your part to relieve the stress of the temperature difference between the slices. Adding holes in strategic locations (if possible) may help.

I turned up the heatbed as well, in the pictures that I’ve posted the best one came out with the extruder at 230 and the HBP at 60.

230 for PLA (if that is indeed the temp you’re running at) is too high, generally. PLA should be extruded around 180-190C. A fan directed at the print will also help any kind of curling as well.

It extruded at 175 but as I said the prints were curling near the ends, but the over extruding kind of thing was really prominant. I think it’s a problem with flow, I’ll try and record a video of what’s going on.

well if it’s curling, it’s going to be screwing up the layer height, which causes it to look like it’s over-extruding.
Are the layers separating, or is it coming off the bed?

Curling is an issue with both ABS and PLA when they are printed too hot and too fast.

  1. Increase your fan speed
  2. Increase the minimum layer time in the cool module
  3. Decrease the hotend’s and/or bed’s temperature

If by recalibrated your axes you mean you changed your steps per mm to something other than the calculated, ideal values, undo that and use the proper ones.

I could have written exactly the same post this morning. My prints are now sticking to the tape fine but the force is so strong it’s lifting the tape off the bed! I tried a fan on one side and it just looks to make the problem worse on that side. It’s already a large part so I don’t think a longer layer time is going to help.
Currently printing at 195 so might try cooler.

@Thomas_Sanladerer , I’ll try lowering the speed and setting up a fan. I recalibrated in the sense that I verified that the steps per mm were set to the proper values and reflashed the firmware.

@Jonathan_se5a_Sorens it’s not separating or coming off the bed, on overhangs the edges of the part curl upwards. I only see it in prints where the layers are succesively larger than the previous, like on the Y axis idler for the prusa i3.

Try thinner printing layers (0.2 works very well for me with 0.5 nozzle)

I have just made my very first large print with PLA. It’s about 100x80x5mm. My corners also curl which destroys later layers. I extrude at 190 and my bed is 75. I have no fan. I am using the cool option but have set it faster at 30 secs per layer. That might be to fast. My bed may also be to hot. Eventually I will mount a fan, if I cannot get it to behave…

Great post this one, and many good suggestions.

By the way. Changing layers height as suggested, what are the other options to alter when using skeinforge.

PLA absolutely requires a fan. Get one as soon as possible, printing without one is a fairly frustrating experience.

Oh, and try Slic3r instead. It’s just so much nicer than Skeinforge.

I’m back to wrestling with this as well. Strange thing in my case is that it seems to favor curling on one side (the high end of X); I thought it was a tram thing but I’ve tweaked the tram to the limit of what’s possible with my bed (MG Prusa) and it still curls. I’m using a small fan around the nozzle but I’m going to try a larger stationary one as well, but thanks for the tips and keep them coming :slight_smile:

The other thing i do on large prints is to apply one layer of very very weak pva glue ( about 1:20 with water) on a glass bed. Be warned, to strong and it takes shells out of the glass when trying to lift the part. The parts stick like s#*t and never curl.

You should only need a fan on small parts to help cool down quicker before the next layer… Will post a picture now for you, printing as I speak

@Sandblastcity_Blackp I actually used PVA to improve adhesion until I managed to get a good roll of blue tape. Worked like a charm :wink:
Only problem is that I’m no longer having problems with the print curling off the sheet, its overhangs curling upwards like in the pictures I’ve shown.