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I've recently changed my Ender3's hotend to E3D v6 clone with Titan direct extruder, so I can print faster than on stock. But when I increased the speed up to 70 mm/s for walls and 80 mm/s for infill (PETG, nozzle temperature of 225 °C, bed temperature of 80 °C, 0.2 mm layer height, 0.4 mm layer width), I've faced this kind of issue:

3D printer printing a model with errors

Here's how it looks in Cura:

Screenshot of Cura's preview of model

The printer's head goes from left to right, counter-clockwise and I get issues on both exits from curved shape.

Another Cura preview further into the print with arrows indicating problem areas

First of all, I thought, it is connected somehow with retraction, but according to Cura, both problem places are in the middle of the current layer. Later I thought it could be related to Linear Advance and disabled it on the next test print, but it did nothing:( Slowing the printer down to 60-65 % in mid print solved the issue, but it's not what I changed the hotend for:)

Maybe someone has any ideas, what's wrong with it?

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    $\begingroup$ Petg doesn't like extruding fast. $\endgroup$
    – Perry Webb
    Aug 4 at 17:11
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In my experience, 225 °C is the lower range for PETG, that combined with a higher than normal printing speed of 70 mm/s might be your issue. The lower your print temps the lower the maximum nozzle flow rate. I would recommend increasing the nozzle temperature.

For a point of reference, on my printer with an E3D v6 clone and a generic extruder I print PETG at 235 °C and 60 mm/s and 24 mm/s outer perimeter speed, with a 0.2 mm layer thickness. Though admittedly not optimized for speed.

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  • $\begingroup$ hmmm, maybe it's really the temperature question🤔 Thanks for the tip! I'll try it and come back with results:) $\endgroup$
    – mega.venik
    Aug 6 at 7:38
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PETG can have difficulty printing at higher speeds.

See Why does PETG require slower speed?

Also, if the speed is too slow, it tends to have heat creep.

See What are ways to avoid heat creep?

Higher nozzle temperatures should allow faster print speeds, but will also increase the chance of heat creep and increase the slowest required speed to prevent heat creep.

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  • $\begingroup$ But I don't have such issue printing infill on 70 mm/s - imgur.com/a/8ixtmnP . All the infill lines are clean and even. $\endgroup$
    – mega.venik
    Aug 5 at 7:25
  • $\begingroup$ And also, the most recent and approved answer you gave link to says: "FarO did not specify details of the printer(s) in question, but I found the big limiting factor for my Ender 3 printing PETG was the stock extruder, which presumably was skipping bad to begin with, and even worse with Linear Advance, trying to keep the filament under high pressure to compensate for its compressibility. Since replacing the extruder with a direct drive one, I've had no problem printing PETG at the same speed as PLA, and both can print much faster than I ever could with the stock bowden extruder." $\endgroup$
    – mega.venik
    Aug 5 at 7:25
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    $\begingroup$ If it were a problem of speed, why is the issue appearing when exiting corners, instead of in the middle of long segments, which are printed faster? $\endgroup$
    – FarO
    Aug 5 at 19:30
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In other words, your print exhibits issues when the hotend is accelerating, like if not enough filament were pushed in.

It is advised to calibrate for linear advance after replacing the extruder.

Check https://marlinfw.org/docs/features/lin_advance.html and

and check https://marlinfw.org/tools/lin_advance/k-factor.html

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  • $\begingroup$ Yes, I have a calibrated LA and on the pictures it is enabled. "Later I thought it could be related to Linear Advance and disabled it on the next test print, but it did nothing:(" $\endgroup$
    – mega.venik
    Aug 6 at 7:36
  • $\begingroup$ buuut, of cource, maybe my current settings isn't enough. So I need to calibrate it more $\endgroup$
    – mega.venik
    Aug 6 at 7:40

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