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Repeated PETG Failures After Past Successes

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* Posting on behalf of a member*


I have to admit that I didn't join this site to learn all there is to know about 3D printing - I just need to be a pro at PETG, and I am close to putting my 3D printer out by the trash can.  Maybe some other senior citizen with too much time on his/her hands can make something of it.

I have gone back to the basic settings, forgetting about all of the fine-tuning details and simply settled on the temperature.  At too low a temp (225), I get a lot of stringing and fuzz from the lines that make up the support.  At a higher temperature (245), I get blobs and crunchy prints that I can force my finger through.  It didn't seem to be like this at first.  I just started another print with a new steel nozzle and 240/65 on the temperatures.  The first layers are sticking and the support lines are stacking but the deposited plastic looks dried and somewhat pitted, not glossy.  More on this in an hour, or so . . .  OK, I am back and with default settings except for 235/65, I am printing trash.

I am using a Longer Pro4 3D printer and the Longer slicer which is just a modified Cura slicer except for one important feature - supports can be generated for ceilings.   This allows me to slice my project upside down for balance.  When everything was, otherwise, working properly, all I had to worry about was a bad lower 45 degree face.  Now, though, if I successfully print a device, it is globby or frail or both.

While I know that all printers and slicers are different, they all work with similar core features and settings.  Would you be so kind as to provide me with a link to your best PETG settings, at least concerning temperatures, speeds, Z-hops, etc.  along with anything you think I should check my printer for and I will start there.  Attached are some pictures of my failures.  I only need to get this perfect once (assuming I write down the settings) because all I want to do is print one object repeatedly.

18497955 1617586787U9iBad Support

Here are line supports that have deformed at 225 degrees printhead temperature.


18497982 1617586941eoQBad Start at 235

This is a bad start at 235 degrees.  Contrary to what I have heard, I DO need to squish PETG onto the (painter's tape) print bed or I just drag around filament.


18498000 16175870266rhBad Texture on Switch Face

This is the switch face of my project and it prints upside down at 45 degrees.  Supports haven't helped the quality.  Any ideas?

18498029 1617587146uk6Overall Disaster

I know what happened here - I switched from 100% flow to 98% flow and I think that is where the rip occurred.  I have had no reason, in the past, to use less than a 100% flow rate.


So, besides fine-tuning settings, does this sound like I am having printer issues and, if so, what might they be?  The filament loads and unloads cleanly.  The only thing I have been experiencing a lot of is molten filament accumulation on the nozzle. 

I thank you in advance for reading this diatribe of misery and for any help you might lend to get me printing again.  One last thing, all my filament is stored in 5-gallon buckets with "Damp-Rid" crystals . . . and I live in the desert!

Topic starter Posted : 06/04/2021 1:05 pm
Member Moderator

Hi there!

It is sad to hear that you are having some disappointments with your printings. But we will figure it out and get back on course…

First of all, since you configured the initial settings, the ones you had good results, I guess that you might be having issues with your printer. I have made several prints with PETG, having excellent results; mostly, I use PETG when I am making appliances spare parts due to the characteristics of this material. You already have experienced good results, but there are some key points to bear in mind. 

When you mention you find molten filament on the nozzle, this might be the result of a problem in the extruder, causing the problems you show from your model. This could be the cause of the nozzle too close to the model, which causes the material to stick in the nozzle, instead laying down on the model. 

While printing, does the extruder motor make a strange noise when pulling material? This means the filament is not flowing correctly from the nozzle, the causes could be the following:

  • Low Hot End Temperature.
  • Nozzle too close to the Bed.

In both cases, you will notice a strange noise in the extruder pulling gear, like skipping. Therefore, there will be parts of the layer missing in the model.

Before, I have some questions that could help narrowing the causes:

  • Have you printed with PLA previously? This might sound awkward, but if you have PLA debris in the Bowden tube or in the nozzle (but you changed it already), your print will be affected; since both materials have different characteristics. Try to check if there is any old filament placed on the extruder system.
  • What cooling speed did you set up? For PETG I normally set it up at 30%, this helps with adhesion between layers. Even with the first two layers, I recommend you turn off the cooling fan in order to enhance the bed adhesion. If the fan is running too high, you will notice some delamination, meaning the layer didn’t stick to each other.
  • What is your printing speed? After some experiments, I have found that 40 mm/sec works fine for me. In this first stage, I wouldn’t recommend you to change the flow rate, since we are adjusting the speed. When making changes, remember to make one or two (if they are nor related) at the time, in order to know how that change affected the outcome. If printing too fast, this will affect the layer adhesion.

Resuming, this are the main characteristics I configure for PETG:

  • Nozzle Temperature: 220°C (while printing, increase it in 5°C steps and see the results). Remember, if it is too cold, the gear from the extruder will skip, making an extrange noise.
  • Bed Temperature: 70°C
  • Flow: 100%
  • Print Speed: 40 mm/sec
  • Initial Print Speed: 15 mm/sec
  • Retraction: 6 mm @ 25 mm/sec
  • Regular Fan Speed: 30%
  • Initial Fan Speed: 0 (until layer 3).
  • Supports: In this case, you could start adjusting the following settings (there are many more):
    • Overhang Angle: Above 45°.
    • Pattern: Concentric works fine.
    • Support Density: 20%
    • Support Z Distance: 0.2 mm (distance between roof/top of the support and the model). If it is too close, it will be hard to remove; but, if it is too far, won’t help much as a support.
    • Support Thickness: Should be a multiplier of the model layer.

But, have in mind that every machine and brand of material has its own characteristics and could be different to mine. But, take it as a starting point.

Sorry, but when you mentioned: “Contrary to what I have heard, I DO need to squish PETG onto the (painter's tape) print bed or I just drag around filament”, what did you refer to?

I hope the explanation could help you to get back on track.

Please, keep me updated with your results, and let me know if you have other questions…



Posted : 06/04/2021 7:27 pm

Just a thought.  PETG can be sensitive to moisture.  I have seen all these problems cured by drying the filament.  Best way would be a food dehydrator if you have one.   You can also use an oven.   With both of these be careful setting the temp too high or you will melt the filament together(or melt the spool completely if you way overshoot). Especially the oven.  Most ovens really struggle to be at all accurate at temps this low.

The numbers here can be some guidance but start 5-10c lower so it doesn't overshoot too high:

Here are two other tricks I've used for drying when oven or dehydrator weren't an option:

Drying at the bottom.

Posted : 04/06/2021 5:32 pm

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