CNC will only work with nagative coordinates/numbers

[mattyd]

Hi All,

So I'm new to this and I am probably missing something obvious (so sorry in advance)

My cnc, when homed moves to the bottom left - as per this image

but to move it to the right (X axis) I have to use negative numbers. Same with the Y and Z axis.

Logic tells me this is incorrect, and when working up a simple square using positive numbers my cnc is unable to produce this shape. I can of course manually edit the Gcode to add a "-" in front of everything but that seems a little silly and counterintuitive.

As an example, this square has a start point at the bottom left (as per my cnc) but uses positive numbers to make the shape towards the right-hand side. My cnc can only make this shape if I use negative coordinates rather than positive ones.

Does anyone know how I can fix this?

[o_lampe]

@mattyd You could check your endstop-definition: does it home to 0,0 and is that defined as min? Same for the M208 config.
The Z-axis is a different shoe. Some want to have Z0 at the top, others on bed level...

[mattyd]

@o_lampe said in CNC will only work with nagative coordinates/numbers:

@mattyd You could check your endstop-definition: does it home to 0,0 and is that defined as min? Same for the M208 config.
The Z-axis is a different shoe. Some want to have Z0 at the top, others on bed level...

When homed this is what I see via the control panel

No idea why the tool position for X is at 10, but the Machine Position says it's at its max, logically shouldn't that show x:0 y:0 z:0 ?

[o_lampe]

@mattyd I guess it's time to post your config.g

[mattyd]

@o_lampe

; Configuration file for Duet
; executed by the firmware on start-up
; WorkBee Firmware Version 1.1
 
global systemSettingsVersion={1.2}
 
; Configuration files
M98 P"config-network.g"
M98 P"config-drives.g"
M98 P"config-axes.g"
M98 P"config-axes-limits.g"
M98 P"config-axes-calibration.g"
M98 P"config-axes-endstops.g"
M98 P"config-probe.g"
M98 P"config-spindle.g"
M98 P"config-laser.g"
 
; Other Settings
M453 ; Put the machine into CNC Modes
G90 ; Set absolute coordinates
M140 H-1 ; Disable heated bed
M564 S1 H1 ; Disable jog commands when not homed
M911 S21.0 R23 P"G91 G1 Z3 F1000" ; Configure power loss resume
 
; User Configuration files
M98 P"config-user-settings.g"
 
M501 ; Load Stored Parameters 

btw. my "config-user-settings.g" are empty

[o_lampe]

@mattyd said in CNC will only work with nagative coordinates/numbers:

M98 P"config-axes-limits.g"
M98 P"config-axes-endstops.g"

These are the files we are interested in. C'mon, work with me...

[mattyd]

@o_lampe said in CNC will only work with nagative coordinates/numbers:

@mattyd said in CNC will only work with nagative coordinates/numbers:

M98 P"config-axes-limits.g"
M98 P"config-axes-endstops.g"

These are the files we are interested in. C'mon, work with me...

Sorry Here you go

config-axes-limits.g

; Axes Limits configuration executed by config.g
 
M208 X0 Y0 Z0 S1 ; Set axis minima
M208 X270 Y270 Z88 ; Set axis maxima

and config-axes-endstops.g

; Endstop configuration executed by config.g
 
M574 X2 P"xstop" S1 ; Set active low X endstop
M574 Y2 P"ystop" S1 ; Set active low Y endstop
M574 Z2 P"zstop" S1 ; Set active low Z endstop

[mattyd]

@o_lampe

i think've figured it out, and it's all user error!

my mistake was assuming that by homing it the "machine position" should be 0 0 0. This is wrong, the "machine position" SHOULD be 270 270 0.

I totally ignored/forgot about the fact that I can set the "work" position to 0 0 0, which when done so moved the machine to the opposite side, and all the negative numbers become positive and Gcode now "seems" to be working as expected.

At least I think that's correct. More experimantaion is needed

[dc42]

@mattyd to set X0 Y0 to set the bottom left and positive movement to be correct you should do the following:

1. Set the motor directions using the M569 commands in config.g (or in your case, probably in config-drives.g) so that positive X is to the right and positive Y is away from you.
2. Change the M574 commands to set the endstops to low-end (e.g. X1) instead of high end (e.g. X2).
3. Change your homing files to move in the negative direction instead of the positive direction.

See https://docs.duet3d.com/en/User_manual/Machine_configuration/Configuration_cartesian. I am assuming that your machine is Cartesian, not CoreXY.