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Retraction setting: Is that linear speed of filament or the equivalent hotend speed?

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Posted · Retraction setting: Is that linear speed of filament or the equivalent hotend speed?

I'm trying to fine-tune my steps/mm and retraction settings. I'm using Repetier to do the calibration because it gives much better manual control. I'm just trying to get the settings correct. I am confused about the units that Cura lists for retraction. It says mm/s. Is that mm/s of filament? Below is my interpretation of units. Can someone sanity check this?

Cura print speed (mm/s): linear speed of the hotend

Cura retraction speed (mm/s): linear speed of 3mm filament through the drive gear

Repetier speed (mm/min): linear speed of 3mm filament through the drive gear.

 

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Posted · Retraction setting: Is that linear speed of filament or the equivalent hotend speed?

Yes, retraction distance is the distance the filament is moved by the extruder gear in mm. However, this will not be exactly the case on the hot end. Filament will not necessarily move (for example) 4mm on the hot end side when the gears move it 4mm because of things like play in the bowden clamps and slight room in the bowden tube etc.

 

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Posted · Retraction setting: Is that linear speed of filament or the equivalent hotend speed?

It is the linear speed of the filament. However, in the firmware that ships with Cura for the Ultimaker-Original there is a bug that makes retraction slower then entered. Which is why 45mm/s is the default for the Ultimaker. After the fix a value of 20-25mm/s is more accurate.

Repetier lists mm/minute because that's what the firmware is actually reading. Cura uses mm/sec everywhere as those values are smaller and easier to comprehend in my book. mm/minute is a left-over from CNC milling which is much slower in movement then printing.

 

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Posted · Retraction setting: Is that linear speed of filament or the equivalent hotend speed?

After the fix a value of 20-25mm/s is more accurate.

 

Daid means 20-25mm/sec is a more *reasonable* speed as 45mm/sec is too fast for some (most?) Ultimakers and they will skip steps. I use 25.

 

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