Problems with PETG

[Yisonco 0]

After printing parts for weeks with PLA and having a lot of luck, I needed to begin printing with a material that has more rigidity and stability at higher temperatures. I have been trying to print parts varying in complexity with PETG for some time now, and the printer always seems to jam and mess the whole print up. I printed hundreds of calibration blocks and concluded with the following configuration:

• Door and Cover to stabilize the temperature
• Part Fan's 0% -  little or no bridging necessary
• Build Plate 80C - this helps to keep chamber around 40C
• 3m glue on glass build plate
• Nozzle temperature 150C
• Flow 100%
• Retraction 4mm @20mm/s - minor stringing, but better than getting molten material in heat break 
• Extruder tension tight to prevent slipping and grinding, but not to deformation of the filament
• Printer Speed is 100% - calculated to about 40mm/sec

 

I have used several filaments with similar results. I use a printer dryer to ensure the filament is dry which made the print nicer but did not resolve the problem.

 

The image is of a part that failed during the first two layers, but it is random in the part which makes me think its irregularities in the filament. I tried every temperature from 240C to 270C before settling on 250C. The tests at 260C+ had too much oozing and 240 the filament would not adhere to anything. When the jam occurs, it appears to almost zig-zag as the plastic comes out of the nozzle. Your help is much appreciated.

[Yisonco 0]

I disassembled the unit for the 32nd time (I've kept count) and used a length of filament that I cut off during one of the jams to determine the ideal printing temperature. By hand, I applied pressure to the filament until it began extruding. Interestingly, it got more difficult as temperature exceeded 155C. When I manually retracted the filament, I noticed it would catch when pressed back down, almost impossible to re-extrude. I used a drill bit to carefully clean the rig without scratching the heartbreak, little improvement.

 

Reading one of the other forums, I learned people have been applying a drop of olive oil to PETG with a lot of luck. Already having the head disassembled I figured it wouldn't be that difficult to clean if things went wrong, plus I have a spare of virtually every part.

 

What happened next surprised me. After applying the drop of olive oil, the extruder felt like I was extruding PLA. When manually retracting, the catch slowly resolved itself until it was completely non-existent.

I reassembled the rig with an aluminum tube around the Bowden tube to ensure the filament approached the head perpendicular to the build plate and began my test print. 

 

Everything initially looked promising, the initial purge coiled into a perfect stack on the left front of the plate. Though the victory was short-lived, the print failed halfway through the first layer. I remain hopeful and restarted the test at 90% printing speed.

[Yisonco 0]

The second print was a success. Still, a lot of cleanup and the top designed for minimal bridging came out really rough. But it appears it minor setting tweaks from here.