Retraction speed
Hi guys
From looking at other people's retracting settings as well as Josef' himself, it seems that it is common to set the retraction speed to 35 mm/s with the MK3. Besides my MK3, I've had a delta printer for several years, and I am used to seeing retraction speeds in the range of 100-110 mm/s.
Wouldn't it be beneficial to up that speed? Is the MK3 extruder motor not able to handle that? Is there a downside to retracting faster with a direct drive extruder?
Best regards
Hansen > Greetings from Denmark <
Re: Retraction speed
I think it is because of the e3d hotend. It needs much less retraction than many other hotends.
Too much retraction can lead to jams.
Re: Retraction speed
Too much retraction can lead to jams, but I'm not clear that a higher retraction speed will.
With the e3dv6 hot end and direct extruder attach (no bowden), I would expect on the order of 0.25-1mm of retraction. I suspect that due to acceleration limits, your 100mm/s and the lower 25-35mm/s end up with exactly the same effect. With that distance, it may be the extrusion is over before either speed is actually reached.
The only downside of actually getting faster retraction would be the extruder being unable to pull the filament that fast, and the bonden gears slipping/grinding the filament. In parts with many/repeated retracts, that could lead to ground down filament and therefore extrusion problems.
Try both, see if you notice a difference, and let us know.
Re: Retraction speed
If the delta was bowden, it needs faster/more retraction to avoid stringing as the hysteresis (which can be thought of as lag for the filament at the nozzle doing what the gears are doing) is a function of length between the extruder gears and the nozzle.
This is why the multi-material on the MK2 uses faster retraction settings, it's a bowden setup.
Re: Retraction speed
With the e3dv6 hot end and direct extruder attach (no bowden), I would expect on the order of 0.25-1mm of retraction. I suspect that due to acceleration limits, your 100mm/s and the lower 25-35mm/s end up with exactly the same effect. With that distance, it may be the extrusion is over before either speed is actually reached.
Assuming I have the correct, basic understanding of how Marlin calculates speeds, I did some math on it. I believe that the MK3 will reach about 63 mm/s when doing a 0.8 mm retraction with acceleration = 5000 mm/s^2 and jerk = 2.5 mm/s. With my delta, which has "slightly" more aggressive parameters (acceleration = 6500 mm/s^2 and jerk = 45 mm/s), the speed when doing a 4 mm retraction would be about 165 mm/s if it weren't limited by a max of 100 mm/s.
So... I think that the MK3 should be able to reach higher speeds, even with very short retraction values.
The only downside of actually getting faster retraction would be the extruder being unable to pull the filament that fast, and the bonden gears slipping/grinding the filament. In parts with many/repeated retracts, that could lead to ground down filament and therefore extrusion problems.
I agree. The extruder on my delta was quite good, but I think that the Bondtech extruder is even better at gripping the filament.
Try both, see if you notice a difference, and let us know.
Yes, I'll have to setup some tests when time allows 🙄
If the delta was bowden, it needs faster/more retraction to avoid stringing as the hysteresis (which can be thought of as lag for the filament at the nozzle doing what the gears are doing) is a function of length between the extruder gears and the nozzle.
Yes, but do you see any reason for the MK3 to not use the same high retraction speeds?
Best regards
Hansen > Greetings from Denmark <
Re: Retraction speed
Yes, but do you see any reason for the MK3 to not use the same high retraction speeds?
There will be a point where there's no real benefit to going faster, which would require some experimentation.