CoreXYU second extruder offset and stuttering

sharctic

I finally found the cause for the stuttering:
When controlling jerk by Cura (eg 12mm/s) it adds a "M566 X720 Y720" command.
However for it to work on a the second carriage of a CoreXYU it has to be "M566 X720 Y720 U720 V720".

At the same time I noticed that in Cura you set jerk in mm/s while the M566 needs a mm/min value, or so I think. So my jerk setting in config.g was totally wrong all the time...

Phaedrux

Be sure to set Cura to reprap flavour gcode.

sharctic

Yes, I had it set to reprap flavor, however Cura does not know about any U or V axes of the machine. I add the correct jerk settings for U and V manually when a print starts, but maybe there is a better solution? (but I assume this has to be dealt with on the Cura side...)

Tool offset:
After further testing I noticed that the tool offset does not work, when the print starts with the second extruder (T1). I can see it immediately from the Z offset.
Prints that start with the first extruder (T0) work fine, first layer sticks to bed perfectly and when the second extruder (T1) comes into play next, it also has the correct position.
However when a print starts with the second extruder (T1) the first layer is too high and does not stick to the bed. (Maybe I can work around by babystepping down the Z offset, but thats not a real solution)

These are my current tool settings in config:
M563 P0 D0 H1 ; Define tool 0
G10 P0 X0.10 Y0 Z0 ; Set tool 0 axis offsets
M563 P1 D1 H2 X3 ; Define tool 1 and bind it to U-axis (X3)
G10 P1 X0 Y-0.40 Z0.4 ; Set tool 1 axis offsets
In the homing files for first layer height:
G1 S1 Z-310 F100 ; move slowly to Z axis endstop once more (second pass)
G92 Z0.7 ; set Z to axis minimum

dc42

You would normally set the M566 jerk settings in config.g, not in the slicer.

sharctic

@dc42 Yes I set the max jerk in cofig. But I can't get the benefit of slicer jerk control (eg for different materials, detail grades, travel vs drive moves, etc)

I find it curious that XY speed and XY accelleration applies to a UV tool, but XY jerk does not

dc42

@sharctic said in CoreXYU second extruder offset and stuttering:

But I can't get the benefit of slicer jerk control (eg for different materials, detail grades, travel vs drive moves, etc)

Do you really think there is any benefit in that?

sharctic

@dc42 said in CoreXYU second extruder offset and stuttering:

@sharctic said in CoreXYU second extruder offset and stuttering:

But I can't get the benefit of slicer jerk control (eg for different materials, detail grades, travel vs drive moves, etc)

Do you really think there is any benefit in that?

I have to admit I was writing this as I was having a hard time getting PVA to stick on PLA, especially line ends and corners, thinking that smoother movement might be the key. So being able to go fast with PLA while going buttersmooth with PVA is definitely an application for this kind of thing, or so I think
Now after some testing and tweaking rather than jerk I found low accelleration to be the better solution, which is something I can control via Cura.

On the tool offset:
For prints that start with Tool1 I found out that at least the Z height works when I add the Z offset to the homing file. You would think that T0 then bumps into the bed, as it should now sit double the offset lower, but actually both tools are level, the offset flipped?!.....I dont even know what happens to XY offset on those prints. When I get a print that starts with T0 I have to modify the homing file back again. This cant be the right way?
Do you know anything about this offset matter? Or do you at least know that it SHOULD work firmware-wise and that the error is somewhere else?

deckingman

@sharctic Just out of curiosity, does Cura add U and V values to the M201 commands? It just seems odd that you can control accelerations for all axes via Cura but not the instantaneous speed threshold (jerk).

sharctic

@deckingman said in CoreXYU second extruder offset and stuttering:

@sharctic Just out of curiosity, does Cura add U and V values to the M201 commands? It just seems odd that you can control accelerations for all axes via Cura but not the instantaneous speed threshold (jerk).

No, it does not use M201 at all, but M204 which works independently from axis names. AFAIK, since T1 (U&V) is mapped to X and Y, the M204 command applies to T1 movement in that moment

Apparently , the M566 command works differently. Cura spits out M566 commands but only for Y and X axis. For Cura jerk control to work on my machine it would have to generate something like M566 X720 Y720 U600 V600 for example. However Cura does not even know what axis I'm using, there is no setting to enter the axis setup. I guess Cura just expects a single carriage with 2 nozzles, like the Ultimaker

deckingman

@sharctic Ahh OK. Make sure you set the values for M201 high enough in your config.g because M204 will still respect those limits.