Bowden - PETG How to reduce stringing?

Scachi

@pro3d Same length of bowden here. e3d hotend with https://www.thingiverse.com/thing:1318849
I use
Retraction 6mm ,
Retract Speed 90
PA S0,4
Not sure about my other values.. modifying the printer hardware at the moment.

pro3d

@scachi

Wow those values are high. What do you use for PLA? What extruder? - edit got the extruder thanks

Scachi

@pro3d
Forgot to mention that my print speed is lower: 30 - 50.
For some petg brands I need to use a speed of 30 , for other ones I can go to 60 and lower PA to 0.3

For PLA is can use a bit higher printing speed 50-70 and reduce PA to 0.2 and retraction to 4.5 - 5mm

deckingman

@pro3d said in Bowden - PETG How to reduce stringing?:

Do I increase retract or PA parameter? or both to reduce stringing

This is a long bowden 750mm with e3d Titan extruder printing PLA great at R 3,5mm / PA S0,15

This is what I tried so far
Retraction 4 - 4,5 mm
PA S0,15
Retract Speed 60
Prime Speed 30
Travel Speed 150
Accel 1500
jerk 15
Printspeed 60-75

Tips to reduce stringing please

Jerk of 15? Is that extruder or carriage? That's really low. Does pressure advance work for you? Do arcs print really slowly? That aside, extruder jerk won't be applied to retract moves (according to DC in another thread) but it will have an impact on pressure advance which in turn might have an impact on blobs and stringing.

I've also found that running high travel speed helps, if your printer is capable of it. The less time the print head takes to do travel moves, the less time there is for the filament to ooze. I run 350mm/sec but of course, the actual speed depends on if the non-print move is long enough for the head to accelerate up to that speed.

Having said all that, I've never been able to completely eliminate fine "hairs" when printing PETG - but a hair dryer or careful use of a hot air gun sorts them out

pro3d

@deckingman

15 jerk on all axis except Z so E as well yes - What is recommended?

PA works after long painful tuning on PLA. I dont know if it works on PETG (Actually CPE) and wonder if it need retuned and what to tune

I dont know how quick I can travel. Have run 300 in dry runs, I thought 150 was good travel but anyway when distance is so short it never will reach anything close to it if accel is 1500 so makes little sense going to 300?

I can manage the hairs but would like to decrease them to what I used to have which was close to nothing so wonder about tuning in general for different materials

pro3d

You can see it printing here
https://www.facebook.com/vking3d/videos/448935422531033/

JamesM

I hope you realize that on the Duet, both the accel and jerk values are mm/min not mm/sec so if you have your jerk set at 15 it is way too low.

pro3d

@jamesm
OH sorry yes I mean 900 in jerk... 15 mms

deckingman

@pro3d 900 for extruder jerk makes a bit more sense that 15 but you might find PA is easier to get right if you use something like 3600. Also try 1200 to 1800 for your X and Y. Then the carriages won't slow down quite so much which can help.

Have you tried different temperatures? This can make a great deal of difference to blobs and stringing. Also, for sure anything that affects the viscosity of the filament will have an effect on the pressure advance you need. So you'll likely need a different setting for PET-G but establish the best (lowest) temperature first, before attempting the tune PA.

Phaedrux

You could use M204 Pn Tn to separately tune your print acceleration and your travel acceleration. That could help speed up your travel moves quite a bit which could help with the stringing.

Also, I find that with PETG temperature has a large impact on stringing. A few degrees lower is usually enough to eliminate the majority of it.

DocTrucker

PETG is intollerant to over extrusion too. Slightest overbuild and you're likely to pick up strings as the nozzle drags and periodically dump lumps of oxidisted plastic onto your print.