Automatic Bed Leveling with Conditional Gcode Iterations

[fcwilt]

@mwolter said in Automatic Bed Leveling with Conditional Gcode Iterations:

@Phaedrux If the command G90 G1 Z20 is used in one line, does G91 have to be used to return to absolute mode?

G90 is absolute, G91 is relative.

Frederick

[mwolter]

@fcwilt
That’s why I used that command. Pulled that command from another macro and couldn’t remember why it was created. It’s used to move some amount from the current position without needing to bounce back and forth from absolute to relative and back to absolute positioning.

[fcwilt]

@mwolter said in Automatic Bed Leveling with Conditional Gcode Iterations:

@fcwilt
That’s why I used that command. Pulled that command from another macro and couldn’t remember why it was created. It’s used to move some amount from the current position without needing to bounce back and forth from absolute to relative and back to absolute positioning.

But there is no reason not to make use of the two positioning modes, there is no downside to using them.

There is nothing to be gained by emulating relative mode using the object model as you are doing.

Frederick

[Kolbi]

@bearer said in Automatic Bed Leveling with Conditional Gcode Iterations:

optionally you can use push and pop, M120, M121

@bearer I read the gcode manual but these two functions still made little sense to me - best I can derive is a save state / restore state? Could you expand a little on these and give me some use examples?

Many thanks,
Kolbi

[A Former User]

@Kolbi does https://forum.duet3d.com/topic/17854/retrieve-the-position-of-an-axis/5?_=1596130135808 help?

[Kolbi]

@bearer Maybe because I just woke or hadn't gone on my run yet - but it is not completely crystal clear to me. Given the example below:

M120              ;push 
G91               ; relative positioning
G0Z30             ; move Z 30mm
M121              ;pop

I gather that 'M120; push' saves the current kinematic control state, then the user issues G91 & G0Z30 to relatively move the Z axis, and then returns to the previous control state by issuing an M121 - meaning that no M90 command was needed as M121 sorted that out?

[A Former User]

@Kolbi said in Automatic Bed Leveling with Conditional Gcode Iterations:

meaning that no M90 command was needed as M121 sorted that out?

yes - but more importantly if you for reasons unknown already were in relative mode you would not return to absolute in error.

[Kolbi]

@bearer Ah ok - thanks! Besides rel/nonrel state changes - what would be an additional use case?

[A Former User]

@Kolbi ref M120 docs; i only used for absolute/relative and feedrate

[Kolbi]

@bearer Thanks! I'll read the docs again and go for a run to let it soak in.

[Kolbi]

@bearer said in Automatic Bed Leveling with Conditional Gcode Iterations:

already were in relative mode you would not return to absolute in error

If I'm understanding correctly; If you are in currently in relative positioning and then you issue a G91 again - it would toggle, putting you in absolute positioning?

[fcwilt]

@Kolbi said in Automatic Bed Leveling with Conditional Gcode Iterations:

@bearer said in Automatic Bed Leveling with Conditional Gcode Iterations:

already were in relative mode you would not return to absolute in error

If I'm understanding correctly; If you are in currently in relative positioning and then you issue a G91 again - it would toggle, putting you in absolute positioning?

G90 sets the mode to absolute. Sending it again changes nothing.

G91 sets the mode to relative. Sending it again changes nothing.

Frederick

[Kolbi]

Ok, rgr that. So given the following:

M120: Push
Example
 
    M120
Push the state of the machine onto a stack. Called automatically when a macro file is run. It pushes the following values on the stack:
    Current feedrate
    Extruder positions
    Whether moves (and separately extrusion) are relative or absolute
 
 
M121: Pop
Example
 
    M121
Recover the last state pushed onto the stack.

Could use M120 before issuing any homing related current/sensing changes and then instead of changing them all back via individual commands - just use M121? I'm thinking no, but figure it doesn't hurt to ask.

I guess what I'm trying to figure out and ask is, what exactly is saved in the 'stack'? Also, the documentation states that M120 is called automatically when a macro file is run - I assume this means any gcode file that resides in the macros directory and that this would not apply to files in the sys directory?

BTW, @fcwilt & @bearer Thanks for helping me understand this.

[Kolbi]

...Maybe if I get one of these, all will be clear

[fcwilt]

@Kolbi

Hi,

I've never used Push & Pop.

Yes there are places where I switch to relative (G91) and shortly thereafter switch back to absolute (G90) but not that many places, primarily in the homing macros.

If you were to look at all of the .g files in my sys directory the numbers of G90s or G91s would be small in comparison with all the other code.

I've simply never worried about it - I use them as needed.

Frederick

[Kolbi]

Thanks @fcwilt, much like what you have stated - I have never used M120/1 and haven't had any issues.

But on the other side of the coin, it makes me wonder if I could/should be doing things better by employing it's use? It seems to me, with my limited duet experience, that such command would be most usefully employed by a macro being called while performing an actual print, so that the desired settings set by the slicer would 'pick up where the macro leaves off' & not so important while performing homing evolutions before a print is started.

[fcwilt]

@Kolbi

I don't rely on the commands my slicer sets at the beginning of a print.

Here is my "print begin" macro called by the slicer at the beginning of a print.

None of those slicer commands matter because my code overrides them all.

; S3D inserts the following 5 lines of code just before calling this file
;G90                                            ; absolute XYZ moves
;M83                                            ; relative E moves
;M106 S0                                        ; fan off
;M140 S60                                       ; bed temp to 60
;M104 S190 T0                                   ; extruder temp to 190
 
M98 P"test_if_homed.g"				; aborts print if not homed
 
T0                                              ; select tool 0 so extruder commands below will work
M703                                            ; configure selected filament (sets bed/extruder temps)
 
M106 P2 S255                                    ; lights on
M106 P3 S255                                    ; lights on
M106 P4 S255                                    ; lights on
 
G90                                             ; absolute moves
G1 Z75      F1200                               ; position for cleaning
G1 X0 Y-145 F6000                               ; position for cleaning
 
M291 R"Heating Extruder/Bed" P"Please wait..." T0
 
M116                                            ; wait for temps to reach set points
 
M291 R"Priming Extruder" P"Please wait..." T0
 
G92 E0                                          ; reset the extruder logical position
M83                                             ; extruder relative mode
G1  E10 F120                                    ; prime the extruder
M400                                            ; wait for extruding to finish
G92 E0                                          ; reset the extruder logical position
 
M291 R"Clean Nozzle and Bed" P"Click OK to begin printing" S3
 
M98 P"mesh_comp_map_load.g"                     ; load height map based on height map mode
 
 

Frederick

[Kolbi]

@fcwilt Thanks for that info. Could you achieve the same thing by use of start.g? If not the same because timing with regards of being called by the slicer, what does your start.g contain?

Many thanks,
Kolbi

[fcwilt]

@Kolbi said in Automatic Bed Leveling with Conditional Gcode Iterations:

@fcwilt Thanks for that info. Could you achieve the same thing by use of start.g? If not the same because timing with regards of being called by the slicer, what does your start.g contain?

Many thanks,
Kolbi

I haven't gotten around to determining exactly when start.g executes, just too many things on my plate.

My current system works but I imagine converting it to rely on start.g would not be a problem.

Frederick

[Kolbi]

@fcwilt said in Automatic Bed Leveling with Conditional Gcode Iterations:

too many things on my plate

I totally understand that. Thanks again for sharing all the info.

Cheers,
Kolbi