Large flat print in PETG HF - Getting slight warping at the corners

[MikeP1951]

I’m printing a fairly large (230x180x68mm) flat model in petg hf on my P1S. With quality settings, it took 11h last night. I’m getting a little warping at the corners (see photo). It’s not horrible, but I’d like to improve it. Here’s some relevant info:

• Layer height .20, Initial layer speed 50, 2 wall loops
• Increased initial bed temp from 70 to 75 (tried 80, too)
• Lowered max vol speed to 18 from 21
• Flow ratio set by calibration test - prints other prints very well
• Aux fan off (other cooling at defaults)
• Door closed, top open about 4 inches (concerned about heat creep.)
• Cryogrip Glacier build plate (leaves nice finish on what will be the top of piece).
• No glue tried, yet (trying to avoid it)
  
  

[Olias]

Unfortunately, there is no magical formula here. Three remedies quickly come to mind, listed in order from best suited to your needs to least suited.

1. Use brims. They will hold down the edges better.
2. Use Glue(I realize this defeats the cryogrip benefits)
3. Increase the plate temp(ill-advised for the cryogrip plate)
4. Give up and use a different plate altogether but even with a smooth engineering plate, lifting will occur with a model that sized. You simply cannot ignore the shrinkage.
5. Try slowing down the first layers using either the first speed function or you could use a layer modifier and try that.

Right-click on the model and select height range modifier.

Then select that in the Objects menu and navigate to the speed section. Change the outer wall from the default to some fraction of speed.

[MikeP1951]

@Olias

• Use brims. They will hold down the edges better.
• Use Glue(I realize this defeats the cryogrip benefits)
• Increase the plate temp(ill-advised for the cryogrip plate)
• Give up and use a different plate altogether but even with a smooth engineering plate, lifting will occur with a model that sized. You simply cannot ignore the shrinkage.
• Try slowing down the first layers using either the first speed function or you could use a layer modifier and try that.

Those are all good suggestions.

In troubleshooting, I know that one must not “shotgun” the problem, rather try changing one variable at a time so you know what actually fixes it.

Yep, I think that I’ll try brims next (it had crossed my mind). I hate waiting 11h (and 380g) to find out, but I know if I take a slice of the model, say only 20mm high (approx 3.2h), that doesn’t prove anything as the cooling dynamics of a 68mm high model over a much longer time are very different. If the problem persists, I will try some glue as I’ve read that really helps big flat prints. I may be printing this model a few more time, so I’d like it to look its best.
(BTW, the plate is clean:)

Thanks for the reply and good input.

[bill.m.davis]

One thing I tried once when having a similar issue (PC, not PETG) was turn off the cooling for the first few layers. I had all fans/cooling off for the first 7 layers and my issue went away.

[MikeP1951]

Alright, I put large brims on this model and the print still lifted some at the corners (shown upside down for clarity in photo). It’s acceptable, but perplexing. So, I’ll buy some glue and use it next time.