Prusa PETG Orange, small prints fine, large prints have issues
I am a newbie. I have had the printer for a few weeks. My PLA prints have been great. This is my first stab at PETG. I am using an out-of-the-box MK3 kit with the 0.4mm nozzle.
i am printing an enclosure for my MK3 using Prusa PETG. I started with the door handles, and they printed great. I did a test print of 2 bottom corners and they printed great. I am using the default settings in Slic3r for Prusa PETG. Latest firmware installed. For the smooth PEI Sheet, I prep with Acetone, the 99% ISPA, then WIndex. I also make sure the nozzle is clean. THe initial calibration goes fine and the first layer calibration with PLA looks great.
I use a Live Adjust Z of a change of about -0.1 for PETG (-0.745 to -0.610). I base the value on the shape of the PETG being laid down when drawing the border line before the parts start to print.
When I print the larger file with all of the bottom corners and the hinges (which uses most of the PEI Sheet area), most of the parts print fine but a couple have issues where a the PETG is pulled up when the print head changes direction. The subsequent layers are fine and the end results seem ok, but is there something I should do to get a perfect first layer like I do with PLA?
The default speed for the first layer in PETG is 30%, the bed temps 80C, and the default temp for the first layer is 230C. Maybe slow it down tp 20%, or try 225 for the nozzle, or 70C for the bed? Are these the general directions to solve this problem?
Re: Prusa PETG Orange, small prints fine, large prints have issues
good morning Raymond,
have you checked whether your printer is printing well at the edges of the bed?
if not, you can use 'Bed level correction' to adjust them
I print a large square with concentric infill, and this shows what is going on around the edges of the board
two copies attached, one for petg and one for pla.
a couple of laps is usually enough to show where adjustment is required!
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Prusa PETG Orange, small prints fine, large prints have issues
Thank you. I will try printing that this weekend.
Additionally, I did another large print this morning with a 20% first layer speed and a starting temp of 35 degrees and I got a perfect first layer with no issues, so maybe it is fine now anyway.
Re: Prusa PETG Orange, small prints fine, large prints have issues
joan.t is certainly much more experienced than me, but I want to add my experience.
I have been printing quite a lot with PETG in the past months and hadd issues with first layer adhesion as well in the beginning.
With the right first layer height it actually sticks very well and I didn't use even IPA for cleaning, instead I gently wiped off the dust froom the PEI sheet with my bare hand, using the skin oils as a release agent.
I adjusted the first layer height to about -50 to -60 units in the Z-level correction from PLA for good adhesion (e.g. PLA: -450, PETG: -510)
I did that printing a small 20x20 square, which also shows if the perimeter and infill connect well.
For releasing the print from the PEI sheet I am making sure that the flex plate is quite warm. Either get it off immediately after printing, letting it cool a bit (still warm!) and then flexing it. If the printer is cold already, I pre-heat and extract the filament (for storage) and by that time also the print bed is warm enough to easily release the PETG. It's much easier to get it off than from the cold sheet.
BTW, I also noted bubbles and stringing with wet PETG, so keep it dry.
Hope that helps!