Unable to retract faster than 200mm/s

[joleeh 0]

Cura refuses to slice above 200mm/s

[gr5 2,167]

I get the same thing.  I've printed at 500mm/sec just fine but never tried to retract that fast.  You must have a very fast extruder?

 

I'm not sure where this value is coded.

[GregValiant 1,248]

That's a smokin' extruder gr5!

 

Many extruders are geared to provide more torque and push power.  I didn't know of any of them were geared for that kind of speed.

 

This is in the base definition file for Creality printers.  It will either show up in your base definition or in the actual printer model definition file under "overrides".

"machine_max_feedrate_e": { "value": 50 }

You can carefully change the 50 to something else.

This also might carry back to fdmprinter.def.json where the retract speeds are noted.

"retraction_speed":
                {
                    "label": "Retraction Speed",
                    "description": "The speed at which the filament is retracted and primed during a retraction move.",
                    "unit": "mm/s",
                    "type": "float",
                    "default_value": 25,
                    "minimum_value": "0.0001",
                    "minimum_value_warning": "1",
                    "maximum_value": "machine_max_feedrate_e if retraction_enable else float('inf')",
                    "maximum_value_warning": "70",

 

Whatever you set it to will be affected by E-Accel.  At the generic default of 5000mm/sec² on the E - it takes 4mm to get up to 200mm/sec.  That means your retract distance would need to be at least 8mm to get up to speed.  A retract speed of 175 takes about 3mm to get to speed so I would call that the max possible for a 6mm retraction.  Average speed in that case would be 87.5.

 

There may also be a max set in M203 in your printer or possibly in the firmware.

 

Edited June 12, 2021 by GregValiant

[joleeh 0]

>Whatever you set it to will be affected by E-Accel

I only retract about a mm, perhaps I'm not getting up to speed? 200mm/s did seem awfully high. I have acceleration control disabled in Cura. I'll try retracting something like 20mm to see if I can see it accelerating.

 

I installed the Printer Settings plugin and changing the "Maximum Feedrate" there does not remove the error. Decreasing it does not affect print time until around around 15mm/s, down from 50mm/s.

[GregValiant 1,248]

You are accelerating for 1/2mm and decelerating for 1/2mm.  Things are not instantaneous even with Accel turned off.  You could set Retraction Speed to 1,000,000 and it wouldn't have any effect on the speed.

Now, you could possibly raise the Maximum Accel on the Extruder but there WILL be a point where the machine will hurt itself when it tries to hit that number.

 

Set the Retraction speed to 30 and forget about it.

Edited June 13, 2021 by GregValiant

[nallath 1,120]

Certain machines have a firmware limit of 150 mm/s, I guess you are slicing for one of those.

[joleeh 0]

I have decided to use firmware retraction instead, thanks for your help.