Z Probe Logic Seems Opposite (mini rambo)

Mostly Printed CNC - MPCNC Troubleshooting
1

First a huge thanks to the MPCNC dev team, nice work. Really appreciate all your efforts!
I’m 95% complete on my MPCNC and have been testing the z probe function.
Using Fusion 360 with a MPCNC post processor to generate gcode (see below for z probe code).

I’m using unmodified MPCNC firmware.
I have validated stepper movements, I have run gcode to engrave several items and it worked properly.
I’m using the 2 pin endstop cable that was in the mini-rambo box about 14" long.

Work Flow

  1. Power up mini-rambo
  2. Locate head / place probe plate on work piece
  3. Connect 1 z axis min wire to the probe plate and the wire other to the cutter
  4. Run gcode (the head moves 40mm up to the tool change position)
  5. Home position was not updated.

From videos posted I see the logic appears to be:

  • circuit is normally open
  • the G28 Z command should drive the head down until the endstop circuit is closed (tool hits probe plate), the X, Y and Z coords are zeroed to establish physical home position of the head.

My Debug Work Flow

  1. Power up mini-rambo
  2. Short z axis min wire S and - together
  3. Run gcode , the head moves DOWN to the work piece as it should.
  4. Just before the head makes contact with the work piece I unshort the S & - and the head moves 40 mm up to the tool change position. It appears the home position is now set based on me shorting the S & - leads.
  5. Now it appears the z position was captured when I opened the circuit and the machining process starts at this point. So it seems to me the logic is inverted???

So I can test the endstop function of the mini-rambo firmware but it seems the logic is backwards in my setup? Any help is appreciated.

THANKS IN ADVANCE!

Jim

======
;Fusion 360 CAM 2.0.9512
; Posts processor: DIYCNC_Marlin20.cps
; Gcode generated: Saturday, January 9, 2021 7:18:44 PM GMT
; Document: Untitled
; Setup: Setup1
;When using Fusion 360 for Personal Use, the feedrate of
;rapid moves is reduced to match the feedrate of cutting
;moves, which can increase machining time. Unrestricted
;rapid moves are available with a Fusion 360 Subscription.
;
; Ranges table:
; X: Min=-5.707 Max=5.707 Size=11.413
; Y: Min=-5.707 Max=5.707 Size=11.413
; Z: Min=0.5 Max=15 Size=14.5
;
; Tools table:
; T2 D=3 CR=1 - ZMIN=0.5 - bullnose end mill

; *** START begin ***
G90
G21
M84 S0
G92 X0 Y0 Z0
; COMMAND_TOOL_MEASURE
M0 Attach ZProbe
G28 Z
G92 Z0.0
G0 Z40 F300
M400
M0 Detach ZProbe
; *** START end ***

; *** SECTION begin ***
;2D Pocket1 - Milling - Tool: 2 - bullnose end mill
; X Min: -5.707 - X Max: 5.707
; Y Min: -5.707 - Y Max: 5.707
; Z Min: 0.5 - Z Max: 15
; COMMAND_START_SPINDLE
; COMMAND_SPINDLE_CLOCKWISE
M0 Turn ON 12000RPM
; COMMAND_COOLANT_ON
M117 2D Pocket1
; MOVEMENT_CUTTING
G1 X-5.139 Y4.162 Z15 F1206
G1 Z5
; MOVEMENT_LEAD_IN
G1 Z1.5
G1 Z0.0
G1 X-5.135 Z0.753
G1 X-5.124 Z0.707
G1 X-5.106 Y4.16 Z0.664
G1 X-5.081 Y4.159 Z0.624
G1 X-5.051 Y4.157 Z0.588
G1 X-5.015 Y4.155 Z0.557
G1 X-4.975 Y4.152 Z0.533
G1 X-4.932 Y4.149 Z0.515
G1 X-4.886 Y4.146 Z0.504
G1 X-4.839 Y4.143 Z0.5
G3 X-3.424 Y4.566 I0.135 J2.129
; MOVEMENT_CUTTING
G2 X3.424 Y-4.566 I3.424 J-4.566
G2 X-3.424 Y4.566 I-3.424 J4.566
; MOVEMENT_LINK_TRANSITION
G2 X-2.564 Y4.591 I0.448 J-0.597
G3 X-1.709 Y4.495 I0.521 J0.785
; MOVEMENT_CUTTING
G2 X1.709 Y-4.495 I1.709 J-4.495
G2 X-1.709 Y4.495 I-1.709 J4.495
; MOVEMENT_LINK_TRANSITION
G2 X-0.868 Y4.274 I0.266 J-0.698
G3 X-0.078 Y3.912 I0.77 J0.64
; MOVEMENT_CUTTING
G2 X0.078 Y-3.912 I0.078 J-3.912
G2 X-0.078 Y3.912 I-0.078 J3.912
; MOVEMENT_LINK_TRANSITION
G2 X0.648 Y3.405 I0.015 J-0.752
G3 X1.245 Y2.749 I1.058 J0.363
; MOVEMENT_CUTTING
G2 X-1.245 Y-2.749 I-1.245 J-2.749
G2 X1.245 Y2.749 I1.245 J2.749
; MOVEMENT_LINK_TRANSITION
G2 X1.684 Y1.943 I-0.314 J-0.693
G3 X1.849 Y1.04 I1.398 J-0.21
; MOVEMENT_CUTTING
G2 X-1.849 Y-1.04 I-1.849 J-1.04
G2 X1.849 Y1.04 I1.849 J1.04
; MOVEMENT_LINK_TRANSITION
G2 X1.677 Y0.066 I-0.679 J-0.382
G3 X1.023 Y-0.676 I2.319 J-2.705
; MOVEMENT_CUTTING
G2 X-1.023 Y0.676 I-1.023 J0.676
G2 X1.023 Y-0.676 I1.023 J-0.676
; MOVEMENT_LINK_TRANSITION
G2 X0.566 Y-0.537 I-0.208 J0.137
G3 X0.156 Y-0.291 I-0.278 J0.001
; MOVEMENT_CUTTING
G2 X-0.156 Y0.291 I-0.156 J0.291
G2 X0.156 Y-0.291 I0.156 J-0.291
; MOVEMENT_LEAD_OUT
G1 X0.121 Y-0.307 Z0.508
G1 X0.085 Y-0.319 Z0.515
G1 X0.047 Y-0.327 Z0.523
G1 X-0.001 Y-0.33 Z0.555
G1 X-0.05 Y-0.327 Z0.588
G1 X-0.082 Y-0.32 Z0.637
G1 X-0.113 Y-0.311 Z0.685
G1 X-0.134 Y-0.302 Z0.8
; MOVEMENT_CUTTING
G1 Z15
; *** SECTION end ***

2

Which firmware are you using exactly?

Have you checked with M119?

3

Based on your description, it does appear that your logic is backwards. This is the line in configuration.h of the Marlin firmware that set the logic for a normally open connection:

#define Z_MIN_ENDSTOP_INVERTING true // Set to true to invert the logic of the endstop.

A setting of ‘true’ is a normally open.

Note I’m a Fusion 360 user for my CNC work, and I made the choice to move my Z axis probing out of the Fusion 360 generated g-code file and run my Z homing independently. It solves some problems, and is more flexible.

4

jeffeb3,

On boot the screen reports 414 bugfix-2.0.x
Tried the M119 in a .gode nothing on the MPCNC display so I assume I need to connect with repetier-host to see response to M119???

Thanks

jkcnet

5

robertbu,

I checked FW configuration.h , my file reads:
#define Z_MIN_ENDSTOP_INVERTING false

Y and Z are false as well, but that would be OK because I think you want to wire X and Y on a normally closed circuit, so that in case of a switch fault the steppers are disabled, Right ?

BTW what do you use to postprocess the .gcode you don"t mind that I ask?

Thanks

jkcnet

6

I just checked the latest FW is v509 2.0.7.2.
I may have jumped the gun a bit in posting, honestly I spent too long modeling and printing parts and failed to realize the FW has advanced.

It’s great this platform is active.

Let me do an update and see what I get.
Any helpfuls are appreciated!!

jkcnet

1 Like
7

My process is primitive. I use the guffy post processor. If there is a bit change needed, I generate a new g-code file for any tool paths with the new bit. I manually trigger homing for the Z axis between g-code files to setup the new bit. While this process is not as automated as having the tool change in the g-code file, it provides a lot of flexibility. For example I frequently home Z against the spoil board and then adjust the Z height to the top of the stock as specified in Fusion 360, and zero before cutting.

8

Ok. Cool. I don’t remember exactly what was in 414. But one of the reasons we swapped systems to 500+ is that the changes are more automatic and consistent. So hopefully that will work better for you.

9

Just loaded v509, confirmed z probe procedure working properly.
My apologies for not checking the firmware page first.

Thanks again for the help.

jkcnet

1 Like
10

No worries.