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[Solved] Large blob (?) on particular PETG print  

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Florian
(@florian-2)
Active Member
Large blob (?) on particular PETG print

I experience a problem with rather large blobs on one of my prints. I am using a mk3s+ with mmu2s to print petg. I print large cases (ca. 160mm x 160mm). So far everything printed fine. However, I built a model for a solar panel case that fails to print. It fails as the printer detects a collision. The collision comes from a blob of plastic laying on the model (see image above). I use standard prusament PETG settings with prusament PETG filament.

 

At first I thought that the nozzle came loose and is leaking, but this was not the case.  (I unscrewed the nozzle and the thread was clean. I inserted a new nozzle anyways and tightened it with 2.5Nm).

I always get the problem with this model, so I checked printing models that worked and they went through. However, upon close inspection I discovered that during the printing there seemed to be a smaller blob similar to the big one in the model above. This mini blob seems to be small enough to be printed over and not visible in the final result.

 

I am wondering if it could be that the nozzle leaks a bit during the print moves and plastic builds up and then falls down when it gets heavy enough / cooled enough? Should I adjust retraction settings for this? As said all the models I printed so far the end result is excellent quality from what is visible. Any hint on what to try next is appreciated. 

This topic was modified 1 month ago 2 times by Florian
Posted : 13/06/2021 11:02 am
John
 John
(@john-6)
Reputable Member
RE: Large blob (?) on particular PETG print

Unless you have recently changed the nozzle it probably isn’t a leak. Petg can accumulate from the outside on the nozzle during a print. Once it has some petg it loves to stick to itself. Maybe you have done this already but give the nozzle a really good clean and make sure the filament drops straight down as it extrudes and there is no curling as the filament exits the nozzle. ( test with a filament load although the probably is an easier way)

This post was modified 1 month ago 2 times by John
i3 Mk3 [aug 2018]...
Posted : 14/06/2021 12:10 am
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Large blob (?) on particular PETG print

you may be trying to print layers to low with extruder heat to low to allow for the viscosity needed. can you post a .3mf project file?

How-to-save-and-upload-a-project-file

so that we can see your settings as they pertain to your model.

The Filament Whisperer...
Posted : 14/06/2021 12:25 am
Dan Rogers
(@dan-rogers)
Prominent Member
RE: Large blob (?) on particular PETG print

You gotta watch for blobs as you print PETG - especially flat surfaces.  Perfect live Z can help.  Avoid ironing which inherently will create small blobs.

Follow these blobs around with a razor blade on a handle.

 

Posted : 14/06/2021 3:25 am
Florian
(@florian-2)
Active Member
Topic starter answered:
RE: Large blob (?) on particular PETG print

Thanks for all the answers:

1. I attached the gcode as requested: solar_panel_case

2. I also increased retraction and added retraction at layer change and avoid crossing perimeters. I could not determine any effect.

3. As suggested I used live z adjust to tune the first layer while printing. While this removed the blobs it also led to a not perfect first layer (nozzle too high and thus individual strings slightly visible).

Due to the result in 3. I will try to dial in a good first layer that does not blob. However, I am not sure how this is going to work as I dialed in the first layer quite well when the blobs occurred. Is there maybe something I can do with the extrusion rate to help this or is it pure z adjust?

Appreciate the help. I am still rather new to 3d printing with PETG.

 

Posted : 14/06/2021 7:18 am
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Large blob (?) on particular PETG print

@florian-2

 

Solar_thing_Swiss.3mf

 

Try this, I don't know everything you have tried but I made some changes to your profile that may help.

 

Good Luck

 

Swiss_Cheese

The Filament Whisperer...
Posted : 14/06/2021 7:08 pm
Florian
(@florian-2)
Active Member
Topic starter answered:
RE: Large blob (?) on particular PETG print

@swiss_cheese

Thank you very much for your effort. Unfortunately even with your tuning the problem still persisted a little bit. However, I decided to further fine tune the first layer very slightly higher, such that it still squeezes nicely but is a little higher than my initial setting (3 points on the z--adjust) and this made the problem completely go away. Thanks for everyones help.

Posted : 15/06/2021 8:42 pm
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Large blob (?) on particular PETG print

sorry I wasn't able to help.

 

Good Luck in the future

 

Swiss_Cheese

The Filament Whisperer...
Posted : 17/06/2021 4:36 am
Florian
(@florian-2)
Active Member
Topic starter answered:
RE: Large blob (?) on particular PETG print

@swiss_cheese

I am rather considering that it was helpful as it gave me some insight on what to tune when I run in trouble. Even if I the solution to the problem was a little different this is still awesome. So thanks again!

Posted : 17/06/2021 8:52 pm
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