Fast then slow Z probe - SOLVED

deckingman

I have a type 1 Z probe ) analogue. It's actually a precision switch with built in LED so the output is normally around 523 but instantly switches to 1,000 (max) when it triggers. I use G30 for Z homing with the offset configured by the G31 command in config.g. The probe speed is governed by the "F" parameter in M558 and is set quite low for better accuracy. This is a bit of a pain when the last print was 300 mm or more tall (I can go to 760mm) as it take a long time for the bed to travel that distance at probe speed.

So ideally, I'd like to do a faster probe to Z zero, then back off a bit and do a slow move - much the same as homing X or Y. I guess one way to do it would be to add an M558 command with high "F" value to my homez, do G30, back of 5 or 10 mm, add another M558 with a low "F" value and repeat the G30 but just wondering if there is a more elegant solution.

dc42

@deckingman, the only alternative solution I can think of right now is to set the Z endstop type as "Z probe" and the Z endstop position as "minimum" instead of "none". Then you could do course homing using a G1 S1 command, then lower the bed 5mm and fine-home using G30.

deckingman

@dc42 Yes, that might be a better way. Thanks.

Phaedrux

I do exactly that with the M558 in the homing files. Works fine.

; Probe the bed
;
M558 A1 F300	; Set single probing at faster feed rate
G30 	; Do a single probe to home our Z axis
M98 P"ZSpeedsSlow.g"	; Set lower speeds for homing
M558 A10 F100	; Set multiple probing at slower feed rate
G30	; Probe again to get a more accurate position
M98 P"ZSpeedsNormal.g"	; Set normal speeds again

deckingman

@phaedrux said in Fast then slow Z probe - SOLVED:

I do exactly that with the M558 in the homing files. Works fine.

; Probe the bed
;
M558 A1 F300	; Set single probing at faster feed rate
G30 	; Do a single probe to home our Z axis
M98 P"ZSpeedsSlow.g"	; Set lower speeds for homing
M558 A10 F100	; Set multiple probing at slower feed rate
G30	; Probe again to get a more accurate position
M98 P"ZSpeedsNormal.g"	; Set normal speeds again

Ahhh. So you can just change the "F" parameter in M558 and not have to input the entire line?

Phaedrux

@deckingman Precisely.

deckingman

@phaedrux Top man!

Phaedrux

@deckingman said in Fast then slow Z probe - SOLVED:

@phaedrux Top man!

That's a new one! I like it.

dc42

It's a general principle of RRF GCode that any parameters you don't provide keep their previous values. So you need only specify the instance that you want to change (e.g. which driver/fan/axis/filament monitor - but there is only one Z probe supported on Duet 2 so this doesn't apply to M558) and the values you want to change.

deckingman

@dc42 Thanks - that's good to know.

deckingman

@Phaedrux , @dc42 ,

Works a treat - thanks guys.

Topenga

@phaedrux said in Fast then slow Z probe - SOLVED:

I do exactly that with the M558 in the homing files. Works fine.

; Probe the bed
;
M558 A1 F300	; Set single probing at faster feed rate
G30 	; Do a single probe to home our Z axis
M98 P"ZSpeedsSlow.g"	; Set lower speeds for homing
M558 A10 F100	; Set multiple probing at slower feed rate
G30	; Probe again to get a more accurate position
M98 P"ZSpeedsNormal.g"	; Set normal speeds again

Hello Phaedrux,

even when it is a very old post i would like to ask something related to this....
Do we have the same situation as well in X/Y positioning during Probing? We are using the same speed as for X/Y referenzing....so to speed up a little the Z-probing positioning is something similar possible? Currently the impact through the mechanic is quite high just because we are using the same Speed "F" Paramenter?!

Many thanks in advance

Danijel

Phaedrux

@topenga I'm not sure which part exactly you're trying to speed up? The travel between probe points during a G29 is defined by M558 T

Topenga

@phaedrux

Hello back,

thanks a lot....yes talked about the speed between the Z-Probs itself. I found the problem...my acceleration was far to low and therfore the speed was not achived. Now i found the compromiss to reduce the probing points as well to increase a bit the acceleration....Many thanks

Danijel