3 Z axis and homing

kb58

Duet3 6HC
Firmware 3.3
CoreXY

Finishing construction of a 3D printer and am testing the 3 Z-axis bed steppers, and am having two issues while testing the Z homing function.

First, I've been assuming that the positive Z direction is upward, with 0 at the top, and -350mm at the bottom. Is that correct? The reason I ask is because I set the endstop switched to be at the "low" end, thinking that's at zero Z position, at the top of travel.

I originally had a negative Z target in HomeZ, but instead of traveling upward as expected, the three traveled downward. As a test, I changed the target to +355, and they then rose, which is what I want, but I don't understand needing a positive target polarity.

Lastly, while the three steppers are at least homing in the desired upward direction, and they're stopping properly at the endstop switches, I get the error, "G28 Z Error G0/G1: insfufficient axes homed." Why is that appearing and what's causing it?

I'm wondering if I'm getting confused by the usage of "lifting" the Z axis. In one context, that would mean raising it, but I can also see how it could mean "move Z away from the bed", which is exactly the opposite!

Thanks

HomeZ:

G91 ; relative positioning
G1 H2 Z5 F10000 ; lift Z relative to current position
G1 H1 Z355 F1800 ; move Z down until the endstop is triggered
G90 ; absolute positioning
G1 X-34.3 Y5 F10000 ; go to location that places the Z sensor in the center of the bed
G30 ; home Z by probing the bed
G91 ; relative positioning
G1 Z5 F100 ; lift Z relative to current position
G90 ; absolute positioning

Config.g:

M574 Z1 S1 P"io3.in+io4.in+io5.in" ; endstop switches at the "low" end

fcwilt

@kb58

Z=0 is when the bed is touching the nozzle.

Moving the bed away from the nozzle is moving the bed in the positive Z direction.

Please post your config.g file and your homing files using the </> tag for each file.

Thanks.

Frederick

kb58

; Configuration file for Duet 3 (firmware version 3)
; executed by the firmware on start-up
;



================ General preferences ============

G90                                                	; send absolute coordinates...

M83                                                	; ...but relative extruder moves

M550 P"Bobo"   	                                	; set printer name
M669 K1                                            	; select CoreXY mode

;


================ Network ========================

;M552 P0.0.0.0 S1                                   	; enable network and acquire dynamic address via DHCP

M552 P192.168.2.2 S1					; set hard address to P192.168.2.1 and enable ethernet port
M553 P255.255.255.0					; assign subnet address
M586 P0 S1                                         	; enable HTTP

M586 P1 S0                                         	; disable FTP

M586 P2 S0                                         	; disable Telnet

;


============== Set motor direction ==============

M569 P1 S0                                       	; physical drive 1 - X

M569 P2 S0                                       	; physical drive 2 - Y

M569 P3 S1                                       	; physical drive 3 - Z1 left

M569 P4 S1                                       	; physical drive 4 - Z2 rear

M569 P5 S1                                       	; physical drive 5 - Z3 right

M569 P0 S0                            			; physical drive 0 - extruder;



============== Set drive mapping ================

M584 X1 Y2 Z3:4:5 E0 					; Drive 1 - X
							; Drive 2 - Y
							; Drive 3 - Z1, left
							; Drive 4 - Z2, rear
							; Drive 5 - Z3, right
							; Drive 0 - Extruder;

================ Drives settings ================

M350 X16 Y16 Z16 E16 I1                            	; configure microstepping with interpolation

M92 X200.00 Y200.00 Z640.00 E917.444               	; set steps per mm
M566 X700.00 Y700.00 Z24.00 E2000.00               	; set maximum instantaneous speed changes (mm/min)

;M203 X35000.00 Y35000.00 Z1200.00 E5000.00         	; set maximum speeds (mm/min)

M203 X10000.00 Y10000.00 Z1200.00 E5000.00         	; set maximum speeds (mm/min)
M201 X6000.00 Y6000.00 Z400.00 E2500.00            	; set accelerations (mm/s^2)

M906 X1600 Y1600 Z1600:1600:1600 E500 I30              	; set motor currents (mA) and motor idle factor in per cent

M84 S60                                            	; Set idle timeout

;


=========== Independent Z leveling ==============

M671 X-215:0:215 Y-120:210:-120 S5 			; Define Z leadscrew positions relative to origin: front left, center rear, front right;


================ Axis Limits ====================

M208 X-165 Y-165 Z-350 S1                              	; set axis minima

M208 X165 Y165 Z0 S0                             	; set axis maxima

;


================ Endstops =======================

M574 X1 S1 P"io1.in"                               	; configure active-high endstop for low end on X
M574 Y1 S1 P"io2.in"                               	; configure active-high endstop for low end on Y
M574 Z1 S1 P"io3.in+io4.in+io5.in" 			; Z axis with 3 motors, individual min endstops, active high
M574 E0 S1 P"io6.in"                                 	; configure extruder Z-probe endstop for low end on Z

 - io0 reserved for PanelDue;


================ Z-Probe ========================

M558 P5 C"^!io7.in" A2 H5 F120 T15000              	; set Z probe type to unmodulated and the dive height + speeds 
G31 P50 X34.3 Y5 Z1.035		                   	; set Z probe trigger value, offset and trigger height Z1.023

M556 S50 X0 Y0 Z0                                  	; set orthogonal axis compensation parameters

M557 X30:270 Y30:270 P4                            	; define mesh grid

;


================ Heaters ==============================================
M308 S0 P"temp0" Y"thermistor" A"Bed" T100000 B3950 	; configure sensor 0 as thermistor on pin temp0

M950 H0 Q10 C"out1" T0                                  ; create bed heater output on out0 and map it to sensor 0 (if NOT SSR, delete Q10)

M307 H0 R0.928 C350.9 D6.77 S1.00 V24.0                 ; disable bang-bang mode for the bed heater and set PWM limit

M140 H0                                            	; map heated bed to heater 0

M143 H0 S100                                     	; set temperature limit for heater 0 to 100C


M308 S1 P"temp1" Y"thermistor" A"Hotend" T107537 B4725 C7.06e-8
							; configure sensor 1 as thermistor on pin temp1

M950 H1 C"out2" T1                                	; create nozzle heater output on out1 and map it to sensor 1

M307 H1 R1.953 C374.1 D8.85 S1.00 V24.0       		; disable bang-bang mode for heater and set PWM limit
M143 H1 S280                                       	; set temperature limit for heater 1 to 280C

; 


================ Fans & Lights ==================

M950 F0 C"out7" Q500 				        ; create fan 0 on pin out7 and set its frequency

M106 P0 S0 H1 T35                                  	; set fan 0 value. Thermostatic control is turned on

M950 F1 C"out8" Q500                               	; create fan 1 on pin out8 and set its frequency

M106 P1 S0 H-1 C"Layers Fan"                       	; set fan 1 value. Thermostatic control is turned off 

M950 F2 C"out9" Q500                               	; create fan 2 on pin out9 and set its frequency (lights)

M106 P2 S0.2 H-1 C"Lights"                         	; set fan 2 value. Thermostatic control is turned off (lights)

;


================ Tools ==========================

M563 P0 D0 H1 F0:1                                 	; define tool 0

G10 P0 X0 Y0 Z0                                    	; set tool 0 axis offsets

G10 P0 R0 S0                                       	; set initial tool 0 active and standby temperatures to 0C

;


================ Miscellaneous ==================

M575 P1 S1 B57600                                  	; enable support for PanelDue

M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" 	; set voltage thresholds and actions to run on power loss

; homez.g
; called to home the Z axis
;



G91               		; relative positioning

G1 H2 Z5 F10000     	 	; lift Z relative to current position

G1 H1 Z355 F1800 		; move Z down until the endstop is triggered
G90                		; absolute positioning

G1 X-34.3 Y5 F10000 	 	; go to location that places the Z sensor in the center of the bed
G30                 	 	; home Z by probing the bed


G91              		; relative positioning

G1 Z5 F100       		; lift Z relative to current position

G90              		; absolute positioning

kb58

; bed.g
; called to perform automatic bed compensation via G32
;



M561				; clear any bed transform

G28 				; home all

G30 P0 X-165 Y-165 Z-99999 	; probe near left front leadscrew

G30 P1 X-34 Y160 Z-99999 	; probe near rear center leadscrew

G30 P2 X130 Y-170 Z-99999 S3	; probe near left front leadscrew
, then perform a 3-point calibration
G29  				; probe the bed and enable compensation

M291 P"Leveling finished" R"Probing..." S1 T2

kb58

; homex.g
; called to home the X axis
;


G91                ; relative positioning

G1 H2 Z5 F10000    ; lift Z relative to current position

G1 H1 X-375 F10000 ; move quickly to X axis endstop and stop there (first pass)

G1 X5 F10000       ; go back a few mm

G1 H1 X-375 F360   ; move slowly to X axis endstop once more (second pass)

G1 H2 Z-5 F1000    ; lower Z again

G90                ; absolute positioning

kb58

; homey.g
; called to home the Y axis
;

G91               	; relative positioning

G1 H2 Z5 F10000    	; lift Z relative to current position

G1 H1 Y-375 F10000  	; move quickly to Y axis endstop and stop there (first 

pass)

G1 Y5 F10000      	; go back a few mm

G1 H1 Y-10 F360   	; move slowly to Y axis endstop once more (second pass)

G1 H2 Z-5 F1000   	; lower Z again

G90               	; absolute positioning

kb58

; homeall.g

; called to home all axes
;

G91                     ; relative positioning

G1 H2 Z5 F10000         ; lift Z relative to current position

G1 H1 X-355 Y-355 F3000 ; move quickly to X or Y endstop and stop (first pass)

G1 H1 X-355             ; coarse home X

G1 H1 Y-355             ; coarse home Y

G1 X5 Y5 F600	  	; go back a few mm

G1 H1 X-10	        ; move slowly to X axis endstop once more (second pass)

G1 H1 Y-10  	        ; then move slowly to Y axis endstop


G1 H1 Z-355 F360        ; move Z down, stopping at the endstop
G90                     ; absolute positioning
G92 Z0                  ; set Z position to axis minimum (may need to adjust)

; Uncomment the following lines to lift Z after probing
G91                    ; relative positioning
G1 Z5 F100             ; lift Z relative to current position
G90                    ; absolute positioning

kb58

Endstop switches are at the physical top end of the Z stepper travel, meaning near the nozzle.

kb58

Some of my confusion is coming from what "high end" and "low end" mean for stop switches on the Z axis. If zero is at the nozzle, does putting the switch there make it the high end because it's physically high, or is it considered the low end because of the numerical value of zero at that location?

fcwilt

@kb58 said in 3 Z axis and homing:

Some of my confusion is coming from what "high end" and "low end" mean for stop switches on the Z axis. If zero is at the nozzle, does putting the switch there make it the high end because it's physically high, or is it considered the low end because of the numerical value of zero at that location?

Yes the terms "high end" and "low end" can be confusing.

In this case low means near the axis min and high means near the axis max.

Perhaps they use those terms because endstop sensors are not required to be exactly at axis min or max.

As mentioned when a G1 H1 move triggers the endstop sensor the axis position is set to axis min or axis max. I believe the endstop sensor setting of low or high controls this.

Frederick

fcwilt

@kb58

In my option when you have multiple Z endstop sensors, as you do, it makes more sense to home using G1 H1 moves rather than the Z probe.

The homing "levels' the bed to the degree the Z endstop sensors trigger at the correct point to achieve a level bed. The firmware moves each Z axis until the associated endstop sensor triggers. When all Z endstop sensors have been triggered the homing is finished.

Then you can use G32 and the bed.g file to use the Z probe to "fine tune" the bed leveling.

This is the way my triple Z printer works.

Here is a quick and dirty video showing the "rough leveling" achieved during homing with the multiple endstop sensors and then the "fine leveling" achieved use the Z probe.

I have intentionally put the bed seriously out of level to more clearly show the "leveling" action of the multiple endstop sensors.

triple Z homing video

Frederick

fcwilt

@kb58

Here is the basic Z homing code from that printer:

G1 Z-399 F1200 H1 ; move up until endstop switch is activated
G1 Z20   F1200    ; move down a bit
G1 Z-25  F600  H1 ; move up until endstop switch is activated

which is then followed by a G32 to run bed.g to auto-level the bed using the Z probe.

Here is the essential code from bed.g:

M671 X-180:0:180 Y-65:130:-65 S3 ; positions of lead screws

; --- level bed ---

while true
  ; run leveling pass

  ; --- probe near lead screws ---

  G30 P0 X-145 Y-65 Z-99999
  G30 P1 X0    Y100 Z-99999
  G30 P2 X145  Y-65 Z-99999 S3

  ; check results - exit loop if results are good

  if move.calibration.initial.deviation < 0.02
    break

  ; check pass limit - abort if pass limit reached

  if iterations = 5
    M291 P"Bed Leveling Aborted" R"Pass Limit Reached"
    abort "Bed Leveling Aborted - Pass Limit Reached"

; --- finish up ---

G1 Xaaa Ybbb ; move Z probe to center of bed - aaa and bbb would be determined for your printer

G30          ; set Z=0 datum

kb58

I'll look into using G1 H1. Keep in mind that I gathered the information on creating these files from multiple sources. Some of it hasn't been tested yet and is no doubt completely wrong, but for the purposes of this thread, I'll stick to just Z homing.

What you're describing is my end goal, to have the three steppers home to the switches, then do a three point probe to do fine leveling. As mentioned, I very likely have lines of code that are either wrong or have no business being there, but I'm slowly coming up on the learning curve for all of this.

fcwilt

@kb58

Some folks don't use Z endstop sensors and rely on the Z probe.

I always install Z endstop sensors.

As you can see from the video, multiple endstop sensors can cope with a bed way out of level - a Z probe can have serious problems trying to do that.

You did watch the video, didn't you?

I use the Z probe for:

auto-leveling the bed
creating the height map needed for mesh bed compensation
setting the Z=0 datum which I always do with the probe at the center of the bed

Note that setting the Z=0 datum:

needs to always be done at the same XY location
needs to be done after auto-bed leveling
needs to be done before creating/loading the height map

Frederick

kb58

Thanks, and yes I watched your video... actually saw it several days ago while looking on YT for just this setup. As mentioned, as it is right now, all three Z steppers are driving to the endswitches, so now it's a matter of following that by probing for fine leveling. The Pinda probe isn't yet connected or calibrated, so there's still a long way to go.

fcwilt

@kb58 Glad to hear you are making progress.

Let me know if you need more input.

Frederick

kb58

@fcwilt Oh I will! I grew up using assembly language on 1802 and 6800 microprocessors, and it's pretty amazing what's out there now. As I head toward retirement, it's nice to get back into coding and hardware.

fcwilt

@kb58 said in 3 Z axis and homing:

@fcwilt Oh I will! I grew up using assembly language on 1802 and 6800 microprocessors, and it's pretty amazing what's out there now. As I head toward retirement, it's nice to get back into coding and hardware.

I never worked with those - started on the 8080 and then the Z80 and then the 8085.

I tried a few others but the 8085 did everything I needed.

The first eprom chips I used were only 256 bytes and I didn't have the "luxury" of an assembler.

Just coded in hex (knew the commands by heart) which was punched to tape, loaded on another machine and then burnt to the eprom.

Didn't care for the 8086 design and by the time the "sensible" designs came out I was no longer doing hardware.

Those early days were fun.

Frederick

kb58

@fcwilt yup, bytes, all entered by hand, no assembler. I tried working with some of the Intel processors but just connected better with Motorola processors, 6800, 6802, 6809, and the 68HC11. That was, oh, 50 years ago... good times.