Retraction Speed?

I am wondering what retraction speeds do you guys use to minimize oozing and bumps.

I am running 200mm/s with 3.5mm retraction. With that said, oozing is nearly non existent, but I have some very very fine micro bumps on my curved prints. At this point I may change my retraction speed to 250mm/s to 300mm/s. The extruder at this point should have the same retract characteristics as direct drive being that it is belt driven.

So what are you guys using for retraction speed? The length of retraction does not seem to matter much after 3.5mm for me.

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The retraction speed setting is irrelevant as long as it is high enough, because over a short length such as 3.5mm it will not reach that speed because of limited acceleration. For example, with 2000mm/sec^2 acceleration and 3.5mm retraction length, the peak retraction speed will be just under 120mm/sec.

What matters is the acceleration setting. Too low and the retraction will be slow. Too high and the extruder will either miss steps or lose its grip on the filament.

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Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
The retraction speed setting is irrelevant as long as it is high enough, because over a short length such as 3.5mm it will not reach that speed because of limited acceleration. For example, with 2000mm/sec^2 acceleration and 3.5mm retraction length, the peak retraction speed will be just under 120mm/sec.

What matters is the acceleration setting. Too low and the retraction will be slow. Too high and the extruder will either miss steps or lose its grip on the filament.

I will take a look into my aceleration settings, time to test this out. I was wondering what people here were doing.

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Modicum V1 sold on e-bay user jaguarking11

Mine is set for 6.5mm @ 100mm/second with a long Bowden tube and geared stepper motor extruder, and yes, I upped the acceleration settings.

Are you sure that the bumps are not from water absorbed in your filament?????

I am using abs. The Environment is annoyingly dry Actualy and the roll is less than 1 week old. I will measure my filament as well. The bumps are less than 1/10 of a mil. Can't feel them by hand but barely visible via naked eye. However macro lens picks them up.

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Modicum V1 sold on e-bay user jaguarking11