PETG not extruding properly in certain areas of the print

[sketchy984 0]

 

I have a problem with extrusion on these parts. The same issue occurs each time I print. It prints fine with PLA but PETG it doesn't like.

Printer: Ender 5 Plus with a lot of hours on it.

The Slicer is Cura

Hot end is a speedy spider v3

I've tried different retract settings between 1.5 and 3mm, with no effect so I have stuck with 3mm. Retract speed 35mm/s

[Slashee_the_Cow 443]

It's really hard to tell just based on a couple of photos - if you could upload your Cura project file (.3mf, in Cura get it read to print then go to File > Save Project) that would help a lot.

 

The three things that first come to mind are:

1. Make sure it's at the right temperature (it runs a fair bit hotter than PLA), I usually run mine at 240 or 245.
2. Make sure you're retracting enough! PETG is a lot stringier than materials like PLA and ABS. The Ender 5 Plus has a Bowden extruder I think? I'm not sure how much I'd try but it'd be more than 3mm (maybe 6mm?). For a comparison, with the direct drive extruder on my E3V3SE I retract PLA 0.8mm and PETG 2mm (and TPU 3mm, for what it's worth).
3. Probably should have put this first, but make sure it's dry: PETG is hygroscopic (meaning it absorbs moisture from the atmosphere). Some people store it in resealable bags with some desiccant (the kind you can buy a big bottle of changes colour when it's absorbed all it can). I have a filament dryer which I usually pop it in for hour or two before I run a print, depending on long since I last used it and what the whether has been like (Australian summer: great if you enjoy 100% humidity sometimes). The cheat method that you do without either of those is to heat your bed up to about 50°, put your filament on there, cover it with a towel and let it sit there for a couple of hours.

[sketchy984 0]

Hey bud, thanks for the input.

 

Nozzle temp is 145 deg.

Yes it is a bowden extruder but it is running an all metal hotend so if you use 6mm retract you will get a blockage. I used to use 6mm on the standard hotend. Hotend manufacturer specifies less than 5mm for retract.

Yes it is dry - spent 9 hrs in the dryer before printing.

 

I've also cleaned hotend without improvement.

 

I've attached the file

 

The issue starts at the seam. When the nozzle travels to the seam and when it starts to move is when is doesn't extrude.

PETG_BATT.3mf

Edited February 8 by sketchy984

[Slashee_the_Cow 443]

I can't see anything about the model that screams "PETG can't do this" and the settings look about right (other than that I'm not qualified to comment on the retraction distance apparently). I retract a bit faster (45mm/s) with my direct drive extruder but I don't know if that's applicable in your case (but if it's not priming as fast as it can that would explain underextrusion after a retraction).

 

One thing I can suggest is Travel > Retraction Extra Prime Amount. I've never needed it myself (and I have no idea what to set it to, but remember: small scale testing is your friend), but after a retraction it pushes a bit more filament into the nozzle than it retracted to increase the pressure (which makes it easier for it to extrude), which can be useful for stringy materials like PETG because they won't retract or prime as reliably (just be oozy and stick around a bit when you don't want them to).