Need help with PETG on MP Ultimate Maker 2

Hi everyone,

Im new to 3D Print and I have a lot of trouble with my PETG settings in Cura 4.8.0. Im printing on a MP Ultimate Maker 2 (firmware 2.2.8) with a Black Geeetech PETG filament.
I tried a lot of settings in the past days and the prints are getting better and better. Today I decided to get rid of the stringing problem with this "string test". Thingiverse - Digital Designs for Physical Objects - Thingiverse
I also was printing a heat tower today and it looks like 235 - 240 is the best temperature. But if I try to reduce the stringing the rest of the print gets messy.. the two towers are super instable etc.

These are my GCODE Scripts:

;(**** start.gcode for Ultimate2 (150S)****)M140 S{material_bed_temperature_layer_0}; Set bed tempM104 S{ material_print_temperature_layer_0 }; set extruder tempG28 ; Home extruderG92 X200 Y150 Z170G29G1 Z15 F100M109 S{material_print_temperature_layer_0}; wait for extruder tempM190 S{material_bed_temperature_layer_0}; Wait for bed tempM107 ; Turn off fanG90 ; Absolute positioningM82 ; Extruder in absolute modeG92 E0 ; Reset extruder positionG1 X140 Y7 Z0.27 F4000G1 X40 Y7 Z0.27 E23 F1000G92 E0;

(**** end.gcode for Ultimate2****)G1 X170 Y130 F3000G92 E0G1 E-10 F1680 ; Reduce filament pressureG1 Z150 ; Get extruder out of way. Uncomment to use!M107 ; Turn off fanM104 T0 S0G90 ; Absolute positioningG92 E0 ; Reset extruder positionM140 S0 ; Disable heated bedM84 ; Turn steppers off

I hope you can help me a bit with that. :)

what speed are you printing at and what are your retraction settings ?
because pet-g is pretty viscous you can't print it too fast - about 60-70mm/s is the upper limit and nearer 50mm/s is probably better.
Likewise the retraction settings needs to be a little shorter and slower than for pla.

You've got a pretty long bowden tube on an ultimaker - so you'll probably be using fairly long and fast retractions for pla.

It's the main reason they use 3mm filament. Just gives you more control over a long bowden tube.

maybe halve both the length and speed and if you can set cura to perform the retraction during a wipe movement that also really helps.

Thank you!

My current Cura settings: https://imgur.com/a/ihV8crE

If I print with this settings the stringing is almost gone but then the two towers in the test print get really weak and sometimes they just dont get printed or break immediately.
But if I turn off the retraction settings in cura the towers are way more stable , problem is I get a lot of stringing again.I also tried to lower the retraction speed , same result , very poor printed towers like on the pictures in my attachement.
I will try a few prints with much lower retraction and print speed I guess.

well the retraction speed should be fine.
But 5mm ? on 3mm filament and a 0.4mm nozzle.
massive overkill.
try 2 or 3

Apart from the weird changing temp during printing. And I know a olot of people do it - I just have never worked out why.

basically stick to the same temp throughout a print.

It also depends what make and colour pet-g you have.

Like most plastics, white filament works really well. I think it's bacsue a good white filament has a lot of added colourant.

I actually prefer PET to PET-G.
It has most of the same properties, but is almost as rigid as pla and just as bendy as pet-g and really easy to print with.

Hi, thank you for your advises. I tried to print with this settings. You can see here https://imgur.com/a/mSY3eNo there is not much stringing left but for some reason the "right tower" is not printed well looks like the layers are not properly connected. But the other tower is strong and stable. What setting can cause a behavior like this? Or could this be an issue with the .stl file itself?

right - um lol.
Let's start again - for some reason i thought you had an ultimaker - NOT a monoprice.
so ignore much of whatb i said. It makes no sense at all :-)

basically the printbed is most likely not perfectly level.

I know you have all sorts of auto levelling gimmicks on the machine (well i do now !) but is there also a manual bed levelling option as well ?

the layers also look really thick and why are you using a raft ?
Definitely not necessary, I've found pet-g sticks really well to most things.

What extrusion ratio are you using ?

I have leveled the printbed manual before a few times and had to edit the gcode after a firmware upgrade because of some weird auto leveling issues in firmware 2.2.8, but for me it looks now like the leveling is fine.
If I use an index card to test it, it feels good. For the PETG I also use the Z-Offset Plugin in Cura because I read you shall print PETG with a little more offset.
Do I have to adjust this https://imgur.com/a/u0grcWO settings and decrease the layer thickness there?
Im not using a raft, in Cura I use skirt as build plate adhesion and do you mean this https://imgur.com/a/LSnSyCg settings with "extrusion ratio"?

So not to be mean or anything like that.. Just tell how it is. PETG is not hard to print at all. It is NOT PLA it is not going to be docile and look all nice as smooth and pretty no matter what you do. PETG is stringy and sticky and really really cares about how accurate the hardware is and how well you did you basic calibration.
To get it to stick and not gum up the outside of the nozzle you have to have the Z offset correct for the layer thickness you are printing. When starting out use a higher layer rather then a thinner layer. PETG is good for parts that need to be strong and withstand weather. If those are not needed. don use it. It also cares about extrusion multiplier.. There is 1 setting that is correct, it can go .1 over that correct setting and maybe .2 but that is when you start collecting plastic on the nozzle. You do NOT use a fan with PETG. If you have small items you print multiples so they have time to cool. Your little towers will never look like they do with PLA and your temp should be at the low end of the manufacture suggestion, assuming your printers actually is accurate in the temp.. I use a lot of PETG and the setting as the same as PLA and ABS except for bed temp, nozzle temp, cooling and extrusion multiplier, all other things equal (part, nozzle and average filament diameter.) You should never need a skirt or raft with petg, it sticks to glass so tight it will remove chunks and pull a stick on PEI sheet right off. Good luck

PS, you may want to consider PrusaSlicer if Cura is giving you fits..

Hey, thank you.

In the meanwhile I figured out a few things, for example the prints I trigger with Octoprint over the USB-Connection are worse then the prints from the SD-Card itself and also the old Cura 3.3.0 Version from the manufracture seems to work also better then the newer versions of Cura. So there is a high chance that the main problem is not the PETG Filament itself. This 3D Print stuff is very complicated , but at least its fun to troubleshoot. :)

Quote:

---

This 3D Print stuff is very complicated , but at least its fun to troubleshoot.

---

Absolutely :-)

Have a go with prusaslicer - it sounds like the speeds of infill, perimiters etc are probably different in the different slicers and profiles.