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stuttering hot-end?

Posted by shadowphile 
stuttering hot-end?
June 05, 2021 06:53PM
Don't know why I'm having problems lately, although redesigning the entire effector might have something to do with it smiling smiley
In this case that doesn't matter.
I'm printing a 10" single filament circle for calibration purposes. I'm generally running it at 50mps (1st level).
The skirt runs fine all the way around but the path along the object itself stutters badly when rounding the curve where the X and Y axis are swapping %s. That sounds like code starving but I've never encountered it before with the driver board and that doesn't explain the skirt printing ok.
Re: stuttering hot-end?
June 06, 2021 02:59AM
Stuttering on curves is typically caused by XY jerk being set too low.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: stuttering hot-end?
June 07, 2021 04:17PM
I discovered that I've been adding incorrect gcode to the slicer to set acceleration and jerk for that particular print.

I've been using, with out a problem, these two statements in my slicer:
M566 X500 Y500 Z300 E:40:40
M201 X5000 Y5000 Z3000 E120:120
(note: my extruder is a Zesty Nimble with a 30:1 gear ratio so those weird extruder values are suggested by Zesty)
I realized that they set the machine's max acceleration and jerk, not what to use for the current job.
Plus, M566 uses seconds, not minutes, so that should have been more like M566 X10 Y10 Z5.

So I set those correctly in config.g and put M204 and M205 in my slicer using values as desired. (including mm/sec for the jerk)
Here I my current settings in config.g:
M203 X10000 Y10000 Z4000 E2:2
M201 X8000 Y8000 Z3000 E120:120
M566 X800 Y800 Z300 E:40:40
M204 X5000 Y5000 Z2000 (Zesty says don't change the recommended accel or jerk from the machine settings)
M205 X5 Y5 Z2

I set the slicer for 50 mm/sec but the nozzle is now moving at a glacial pace on the current print (7mm/sec) although the travels are fast like normal.
When I run a job that ran ok in the past, it prints at ok speeds but is constantly taking long (a few seconds) pauses throughout the job, constantly..
So my logic says I've messed up my machine settings in config.g but at a lost now what is actually wrong. Unfortunately I am not in the habit of backing up my config.g so I can't revert to what used to work.
Re: stuttering hot-end?
June 09, 2021 06:14PM
M566 in RepRapFirmware accepts speed parameters in mm per minute, which is the standard way of expressing speeds in GCode as defined by the NIST standard.

Unfortunately, some other firmwares such as Marlin use a mixture of mm/min and mm/sec. Worse than that, even though M203 was defined as taking speed parameters in mm/min for many years before Marlin implemented it, Marlin expects M203 speeds to be given in mm/sec. This has led to the current sorry state that if you don't tell your slicer what firmware you are targeting, it may provide parameters in the wrong units.

Accelerations (e.g. in M201and M204 commands) are always quoted in mm/sec^2.

The M566 X800 Y800 settings that you quoted are reasonable for a lot of 3D printers.

Pauses when printing using RRF are not normal. Can you confirm that you are printing from SD card?

Edited 2 time(s). Last edit at 06/09/2021 06:15PM by dc42.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: stuttering hot-end?
June 09, 2021 08:48PM
I discovered that my extruder was set to 2 in the max feedrate but needs mm/min, not per sec. The pauses went away and it seems like the jerky moves too after I changed it to 300 (mm/min)
Another question: why is there a M204 but not a jerk equivalent?
BTW, while I'm here, what config commands can be input immediately and which ones require a reboot?
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