G30 travel acceleration and speed

jltx

I am on 3.5.4 SBC. I have a three Z axis bed. I turn down acceleration and speeds with M201,M203,M204, along with motor currents (M913) prior to bed leveling. This used to work way back in 3.2 or thereabouts.

G30 K0 P0 X270 Y25 Z-99999
G30 K0 P1 X30 Y25 Z-99999
G30 K0 P2 X140 Y280 Z-99999 S3

But now I see the travel between probe points is very high speed. It's actually too fast and motors are skipping. I keep dropping the accelerations and speeds but it has no effect. Do I need to change procedure?

jay_s_uk

@jltx the travel speed is set in M558 for the probe. It's the T value

jltx

@jay_s_uk Well, that explains some things. I totally missed that, now and three years ago when I set this up. So curiously, I have to T values specified and M203 appeared to have no effect. I'm wondering if this might be a bug. It seems it was defaulting to some high travel speed and acceleration.

jltx

Yeah, this looks like a bug. I put T10000 on the M558 commands and it slowed down considerably. This matches my M203 X10000 Y10000, which clearly wasn't being honored. Then I changed to T20000 and it went twice as fast, exceeding M203 limits. Kinda two bugs. M203 is not being honored. And with missing T parameter it just made up something? I'm not sure where that speed would have come from. I would expect any machine moves to be limited by the established limits regardless of missing parameters.

jltx

Let me know if I am misunderstanding how these limits are enforced, otherwise I can file a bug.

Are diagonal move limits up to 2^1/2 higher than individual X or Y (which is bad on a coreXY)? Even so, M204 is explicit on "travel".

T3P3Tony

@jltx I see you raised bug report here:

https://github.com/Duet3D/RepRapFirmware/issues/1090

Is this present in 3.6beta4?

jltx1 created this issue in Duet3D/RepRapFirmware

open [Bug]: M558 not honoring M203 #1090

jltx

@T3P3Tony I'm on 3.5.4 currently. I am attempting to move to 3.6 now.

jltx

@T3P3Tony Yes, still present in 3.6.0-beta.4

T3P3Tony

@jltx so to be clear the M558 T value is working as expected, just if you set T higher than the M203 limit, it does not respect the M203 limit?

jltx

@T3P3Tony That is correct, the T value applied to the M558 command does change the travel speed, but it does not honor machine limits. Additionally (I didn't test this part again for fear of damage) if you leave off the T parameter altogether it uses an extreme travel speed. I'm not sure where it would have calculated that based on other settings.