First time PETG - it's a mess!
Hi all. To give you some context, I'm not an expert but with PLA I usually get the print I want.
I bought a spool of PETG from Prusa and this is my first time dealing with this kind of filament. It is driving me crazy. I was expecting that using the PETG defaults in PrusaSlicer to get, at worst, a barely acceptable print. But this isn't even remotely the case.
With the default speed, the plastic almost doesn't stick to the headbed at all, but I was able to get a somewhat decent first layer slowing down the first-layer head speed to 10 cm/s. It isn't as good as the first layer of a PLA print, but it is acceptable and maybe I will improve it later.
The real mess begins with the second layer. Please take a look:
What the hell is happening here? That stringy abominion should be solid infill, according to Prusa Slicer. You can also see problems with the skirt and the outer perimeter.
I slowed down the solid infill speed to 20 cm/s for non-first layers, print time by the way skyrocketed, and this is what I get; with the default speed it is even worse. If I let the print go, the mess continues for the next 3 to 4 layers and then normalizes, and the print continues decently till the end.
Could I have a faulty filament from a bad production batch? Any suggestions?
I'm using the satin powder-coated print sheet, at 85°C the first layer sticks well and letting the print cool to 50°C or lower it comes off nicely. So, I guess, the print sheet is not my problem here.
Thank you for your help.
Best Answer by FoxRun3D:
I don't have a Mini anymore but while I had my Minis I printed a lot of PETG using default settings. From the picture my gut feeling is that your live Z calibration is off. Try a calibration strip like this https://www.printables.com/prints/105404 to get a perfect first layer.
Could I have a faulty filament from a bad production batch?
In all my years I've never seen this happen but sure it's possible. But my money is on bad Live Z.
RE: First time PETG - it's a mess!
I don't have a Mini anymore but while I had my Minis I printed a lot of PETG using default settings. From the picture my gut feeling is that your live Z calibration is off. Try a calibration strip like this https://www.printables.com/prints/105404 to get a perfect first layer.
Could I have a faulty filament from a bad production batch?
In all my years I've never seen this happen but sure it's possible. But my money is on bad Live Z.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: First time PETG - it's a mess!
You were absolutely right!
I printed that calibration strip and landed a -1.78 Z offset. I never thought it might be different from the Z offset for PLA. With PLA I always used -1.33, but I'll check it again next time I'll print with it.
Now I'm printing with all default PETG values, everything is fine. I guess I learnt something today. Thanks a lot!
RE: First time PETG - it's a mess!
There shouldn't be a difference in the z offset between PLA or PETG ( or any other filament) and the same print sheet.
If you change the print sheet you need to readjust the z offset, because they will differ in height.
You can store settings per sheet in the printer, AFIR you can have about 4 presets.
Another option could be a skewed print head, it is very easy in the Mini to twist the printer along the X axis, unfortunately.
See my GitHub and printables.com for some 3d stuff that you may like.
RE: First time PETG - it's a mess!
I definitely changed the print sheet moving from PLA to PETG, but I thought that the bed levelling pass before each print would have corrected for the thickness difference. Now I know that it doesn't.
I can't see any X axis twist, but I'll pay attention to it in the future.
Thank you.
RE: First time PETG - it's a mess!
A few thoughts:
I printed that calibration strip and landed a -1.78 Z offset. I never thought it might be different from the Z offset for PLA. With PLA I always used -1.33
That delta is exactly the -0.4 difference between a smooth and a satin sheet.
but I thought that the bed levelling pass before each print would have corrected for the thickness difference
Mesh bed leveling can compensate for small differences but not the difference between a smooth and a satin sheet.
You can store settings per sheet in the printer
That's the way to go.
There shouldn't be a difference in the z offset between PLA or PETG ( or any other filament) and the same print sheet
True, but PLA is also much more forgiving if the live z is only marginally correct; PETG leaves no prisoners. From the OP's post it wasn't clear upfront if it was a case of badly calibrated first layer or a change of sheets but the right solution in either case was to redo Live z.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: First time PETG - it's a mess!
The PINDA detects the steel of the sheet, not the foil or powder based coating. Those differ in thickness by 0.4 mm.