Printing with PETG

Wonder if anyone has any experience printing with PETG?

I've got a spool, but so far I can't get it to print normally. At some point the filament invariably bends before the tube, and I end up with a clog. Almost like it's not stiff enough. This happens even when trying to print in air, so it's not an issue of pressure from the print bed. Pretty sure my feeds are properly calibrated too, i.e. 100mm command extrudes 100mm.

Should I try reducing the print speed until it stops bending? Wouldn't be the perfect solution as I'm not printing that fast to start with, so hoping somebody has a workaround.

It's hard to know what changes to recommend without knowing where you're starting...Speeds, temperatures, what kind of hot end...

I've had no problems with it starting with my ABS settings except running the hot end at 255C and the bed at 70C. Going that hot does take an un-lined hot end.

I've got an MK8 hotend, speeds are 30mm/s for printing, 60mm/s for travel. Temperatures: I've tried both 240C and 250C. Bed is unheated (PETG supposedly does not warp much).

I never had a problem with ABS, which is why I'm wondering if PETG behaves differently.

Try searching for "PET or PETG" in this forum to read a lot of experiences and tips from other users.

On the mk8 the throat needs to be as close as possible to the drive gear without fouling the idler. People sometimes place the throat level with the top surface of the aluminium block and the resulting large unsupported gap causes problems. 30mm/s and 250C is what I use with a 0.4mm nozzle and .2mm layers, but there's a lot of machine to machine variation (and filament to filament) so experimentation is always the order of the day.

Edited 1 time(s). Last edit at 06/26/2016 06:36PM by JamesK.

Nothing I could find on my issue.

I'll try printing a support tube for the filament for before it enters the tube and see if that helps, will update when that's done. Regular MK8, not too much leeway for how big to make that unsupported gap otherwise.

I've started printing with PETG, and so far it's been as simple as PLA for me. I'm using a bowden setup on my CoreXY from Thingiverse. This one works with the MK8 gear (despite the thingiverse page saying MK7) and I've had no issues between PLA or PETG with it. If you notice, its encapsulated the filament the entire path which I contribute to my non-issues. I had another bowden that used to coil and screwup printing, but with this one I've yet to have an issue.

As far as printing, the settings for PLA worked with retraction and speeds, I only had to increase my bed temp to 80C and the genuine E3D V6 hot end at 240C. I've had crappy luck with the knockoffs, so I spend the extra for the real ones. Not had any issues with the E3D V6 once I wrapped the heater block in kapton tape.

Word of caution, I tried 70C on the bed, and it didn't stick for me on one part, and 90C stuck too well as it brought a small shard of glass with it when I pulled it off after it cooled. The glass was supposed to be borosilicate glass, but I'm not so sure these days. It was from a kit I bought.

Edited 1 time(s). Last edit at 06/26/2016 06:42PM by PDBeal.

Thanks for the good tips.

I have an aluminum bed so breaking it is a non-issue, hopefully.

Just tried using a supporting tube, doesn't help. The filament keeps bending up within the gap...

Edited 1 time(s). Last edit at 06/26/2016 07:11PM by anvoice.

I had a similar issue till I switched to the Thingiverse bowden extruder. When I put it together, there is almost no gap between the filament coming into the MK8 gear and then almost no gap going out to the bowden tube (and I didn't bother with the MR105ZZ bearing either as I wanted to be able to see the MK8 gear moving). At first glance, I wasn't even sure there was a path for the filament, but it works. I had what I think was similar issues when I first started with PLA with the filament getting kinked after the MK8 before it entered the tube to the hot end, and this extruder design solved that issue. When I went to PETG, I didn't even have to adjust the tensioner, just retracted the PLA, and stuck in the PETG and off I went with the higher temps. This bowden extruder design also claims to be able to do Ninjaflex, although I have a spool, I have not yet tried it but with the clearance of the MK8 and the filament path I have no doubt it should be capable.

Edited 1 time(s). Last edit at 06/26/2016 07:37PM by PDBeal.

Well I seem to have partially solved my problem by cleaning my hotend, then using a long piece of teflon tubing that acts as a support for the filament (e.g. an approximation of 0 clearance).

Now onto the second issue, which is the PETG not sticking well to cold Kapton or aluminum. Will have to get my heated bed going now (not working yet).

I've been using PET-G for some time now. I use a glass bed on both of my printers, heated to 70 deg C, with the hot ends running at 200. It sticks well and I usually have to wait for the bed to cool a bit before the job will release. I've not had the 'filament bending' issue but the hobbed nut on both of my extruders is quite close to the tops of the hot ends.

Harvey

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HarveyC
I've been using PET-G for some time now. I use a glass bed on both of my printers, heated to 70 deg C, with the hot ends running at 200. It sticks well and I usually have to wait for the bed to cool a bit before the job will release. I've not had the 'filament bending' issue but the hobbed nut on both of my extruders is quite close to the tops of the hot ends.

Harvey

I didn't think PET-G would melt at 200, the side of my spool says 240-260C as temperatures. I run PLA at 70/200, but 200 for PETG doesnt seem high enough from everything I've read. What brand is the spool, as you have my curiosity to run PETG at a lower temp.

No trouble with Pet-G at 245 degrees with bed temp at 70 degrees. I use Makergeeks brand which seems to be the best over others. They now have a higher temp PLA which I extrude at 240 degrees with o degrees on bed. Works a lot better than Pet-G. Also can be annealed to make the part stronger.

Interesting comments, thanks everyone.

I use 230-240C for the nozzle, and 60-70C for the bed. I also print at half the speed I use for other filaments, otherwise it doesn't come out very well.

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David J
I use 230-240C for the nozzle, and 60-70C for the bed. I also print at half the speed I use for other filaments, otherwise it doesn't come out very well.

Do you change anything with your retraction settings? When I print, I sometimes get a lot of very tiny strings, almost hair like, but I didn't change any speeds only temps.

I use PETG almost exclusively. Attached is my configuration that I use with SLIC3R. I hope this helps you. My setup uses a Geeetech MK8 printhead and an aluminum build plate with a Keenovo silicone heater on the bottom. I put blue painter's tape on the plate then smear glue stick on the tape. I get great results.

Edited 1 time(s). Last edit at 07/04/2016 12:54PM by Lymphomaniac1.

Thanks!

Just to mention this, I get great results with the Kapton clone and 75 C on the heated bed. No warping whatsoever. Good z calibration of course.

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PDBeal

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David J
I use 230-240C for the nozzle, and 60-70C for the bed. I also print at half the speed I use for other filaments, otherwise it doesn't come out very well.

Do you change anything with your retraction settings? When I print, I sometimes get a lot of very tiny strings, almost hair like, but I didn't change any speeds only temps.

Sorry I haven't replied sooner - this forum software is messing me about!

I do get some stringing, but I mostly solved that by slowing down the print speed a lot, to around 30mm/sec.