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PETG printing = a lot of frustrations

Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
I just wanted to document some of my trials of PETG printing, everyone says "it's just as easy as PLA..."
I am not finding that to be the case.

Couple things I learned: (using Amazon Basic filament)
Print temperature: marked 230-240C, I'm printing at 235
Bed temp: I tried several temps, I think my best print so far has been at 100C bed.
Speed: this is THE BIGGEST IMPACT. I had to slow down my initial layer to 10mm/s so that it would lay down a good first layer.
First layer height: second biggest impact. I think this needs to be ~0.3 or so. I started at 0.25 and had to baby step up the Z offset as it was printing the brim.
Bed surface: I tried blue tape with bed temp of 70C and 80C, failed every time. Went back to glass bed, windex, then isopropyl alcohol to clean the glass.

I have had a heck of a time with 0.1mm layer height. I think I might back this down to 0.15mm
Currently I'm printing a new fan mount to replace the part cooling fan, and to install a BL touch sensor. I'll know more in a couple hours if these settings worked.

I checked the print about 10min ago and the supports aren't printing the best, but the main part seems to be doing OK.


Thanked by 1Samuel Pinches

Comments

  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    edited March 25
    The print last night went well until the top skin. Either the infill wasn't enough to close the top, or it was moving too fast. I woke up this morning to this.
    I may try again tonight, or just print this piece at work on our ultimaker with ABS...

    I will look into the top/bottom speed and see if I can adjust it so that it prints better. I might even try a gradual infill so the top layer has more surface to adhere to. At least I didn't have a wad of plastic on the heat block, it all fell off...
    Post edited by Laser8302 on
  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    I'm priniting that piece pictured above in ABS on another printer...
    I started a new print, same roll, for a stepper driver cooling channel.
    Initial layer went well, then on the 2nd layer it started to under-extrude. I bumped up the temperature from 235C to 240C and that seems to have solved that mid-print.
  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    edited March 26
    Ugh. Seems to be stringing too much. It got 1/3 of the way through the print and the nozzle picked up some of the plastic and jammed itself.
    So 240C for the first layer or two, then 235, maybe 230 for upper layers.
    I may need to increase retraction by 1 more mm, I just don't want to risk gumming up the microswiss throat.
    My biggest problem seems to be plastic sticking to the nozzle. I ordered some silicone socks just now I'll see if that helps. I also order some stainless steel nozzles, maybe a different material will help too?

    I also ordered some feeler gauges... I think leveling the bed with a 0.2mm gauge will be better than a piece of printer paper. I seem to be grinding my nozzle on the bed with the paper so every time I start a print it grinds across the bed.

    This last print was at 0.15mm layer height. Maybe PET just wants bigger layers? I might try a print with 0.2mm height next.
    Post edited by Laser8302 on
  • Der_MuckDer_Muck Posts: 257🌟 Super Member 🌟
    Thats all very strange. I print my ABS with 265Β°C 70m/s works fine and looks very good. (2,5mm retraction)
    I was printing my PETG with 0.2 that worked without a problem to.
    Usualy its not normal that the nozzle jams itself while picking up filament. Maybe you overextract to much? But even with that, is stays weak. What do you use Cura or SP3D?
    SS nozzles are only good when you want to print food save stuff. Brass should be good enough. Set the extraction rate down to 0,95
    Thanked by 1Laser8302
  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    edited March 27
    I'll try going back to 1.5mm retractions.
    The infill isn't flowing/sticking well to the parts and that's what causes the glob to collect on the nozzle. When the temperature changed from 240 for the initial layer to 235 for the 2nd layer, it started under-extruding. So I might try 245-250C even though the spool says print temp should be 230-240. I just hope I don't get a bunch of stringing.

    I'm still using the thermistor. I haven't gotten a good reading of the heat block when it's fully hot, maybe it's inaccurate? I am using the community firmware.
    Post edited by Laser8302 on
  • Samuel PinchesSamuel Pinches Posts: 1,761Administrator
    Sometimes, a certain colour filament can be a massive pain... if you really and truely have no luck, try a different spool!
  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    Further experiments have been slow because of my day job.

    I installed a new part cooling fan and finally printed a new part cooling duct.
    The material seemed to under-extrude so I had to bump up the speed of the extruder to 125%... Seems a bit high. I'm going to try adjusting it or print a test with different multipliers and/or different temperatures to see if I can improve my prints.

    Another item I found was a problem with my build plate. Seems when I got my printer it was glued to the bed heater. Because of all the thermal cycling I've done trying to get this PETG to work the glass started to separate. I used a pair of vice-grip pliers in one corner last night and I finally had a semi-successful print of a round part fan duct that was fairly complex.

    Tonight I might try for a stepper motor cooling duct. I got in some TMC2208 drivers and I want to print the duct before installing them in legacy mode, then I might move to UART mode later.

    I also got a BL touch knock-off that I need to install as well. My plan for auto bed leveing will be to heat the bed to ~50C, probe the bed, then do the preheat/print.

    I also had an old Rpi model B+ lying around, I installed octopi on it and found an old webcam that seems to meet the requirements.

    Once I get everything set up I'll take pictures and maybe post a tutorial.
  • Samuel PinchesSamuel Pinches Posts: 1,761Administrator
    @Laser8302 - sounds good! Don’t let this stuff get you down, it’s no fun when a hobby becomes a chore. I like to take a break for a week and come back with fresh eyes :smile:
  • Laser8302Laser8302 Posts: 36Member, 🌟 Super Member 🌟
    I think I now know why the printer is under-extruding. I think my extruder motor is skipping steps. I've got my case opened up to install some LEDs, some TMC2208s on X and Y and a cooling fan for the steppers. I'm going to increase the VREF on the extruder motor but keep it an A4988 driver.

    If all else fails, time to get a titan or BMG extruder...
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