Homing Z Axis Issue

Mostly Printed CNC - MPCNC Troubleshooting
1

Hi. My MPCNC Primo has started acting up regarding homing the z axis.
Sometimes, it will home as it should. Other times and more often, it will raise the z axis a few mm when I press the Home Z button in Repetier host.

I checked the limit switch conditions with M119 and they are all reading open.
I flashed the latest firmware to the board using XLoader and the hex file downloaded from the V1 site.

I saw there was another post on the forum where the OP said his power supply was the issue. What can the power supply contribute to the issue - electrical noise maybe?

I also tried with the router (Dewalt) disconnected from power and that does not resolve the issue.

The output from the M115 command is below:
11:29:16.951 : Printer reset detected - initializing
11:29:16.951 : start
11:29:16.951 : Marlin 513D 2.0.9.2
11:29:16.955 : echo: Last Updated: 2021-09-03 | Author: (V1 Engineering, Ryan, 513D)
11:29:16.955 : echo: Compiled: Oct 24 2021
11:29:16.959 : echo: Free Memory: 3386 PlannerBufferBytes: 1488
11:29:17.162 : N1 M11034
11:29:17.162 : N2 M11536
11:29:17.162 : N4 M11435
11:29:17.172 : N5 M111 S698
11:29:17.175 : N6 T060
11:29:17.175 : N7 M2022
11:29:17.176 : N8 M8019
11:29:19.962 : echo:DIGIPOTS Loading
11:29:19.962 : echo:DIGIPOTS Loaded
11:29:19.970 : echo:DIGIPOTS Loading
11:29:19.970 : echo:DIGIPOTS Loaded
11:29:19.974 : echo:V85 stored settings retrieved (596 bytes; crc 60833)
11:29:23.969 : N9 M220 S100104
11:29:23.969 : N10 M221 S10081
11:29:23.969 : FIRMWARE_NAME:Marlin 513D 2.0.9.2 (Oct 24 2021 13:38:47) SOURCE_CODE_URL:github.com/MarlinFirmware/Marlin PROTOCOL_VERSION:1.0 MACHINE_TYPE:V1CNC 513D EXTRUDER_COUNT:0 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff
11:29:23.969 : Cap:SERIAL_XON_XOFF:0
11:29:23.969 : Cap:BINARY_FILE_TRANSFER:0
11:29:23.972 : Cap:EEPROM:1
11:29:23.972 : Cap:VOLUMETRIC:0
11:29:23.972 : Cap:AUTOREPORT_POS:0
11:29:23.972 : Cap:AUTOREPORT_TEMP:0
11:29:23.972 : Cap:PROGRESS:0
11:29:23.973 : Cap:PRINT_JOB:1
11:29:23.976 : Cap:AUTOLEVEL:0
11:29:23.976 : Cap:RUNOUT:0
11:29:23.976 : Cap:Z_PROBE:0
11:29:23.976 : Cap:LEVELING_DATA:0
11:29:23.976 : Cap:BUILD_PERCENT:0
11:29:23.980 : Cap:SOFTWARE_POWER:0
11:29:23.980 : Cap:TOGGLE_LIGHTS:0
11:29:23.980 : Cap:CASE_LIGHT_BRIGHTNESS:0
11:29:23.980 : Cap:EMERGENCY_PARSER:0
11:29:23.980 : Cap:HOST_ACTION_COMMANDS:0
11:29:23.984 : Cap:PROMPT_SUPPORT:0
11:29:23.984 : Cap:SDCARD:1
11:29:23.984 : Cap:REPEAT:0
11:29:23.984 : Cap:SD_WRITE:1
11:29:23.984 : Cap:AUTOREPORT_SD_STATUS:0
11:29:23.989 : Cap:LONG_FILENAME:0
11:29:23.989 : Cap:THERMAL_PROTECTION:1
11:29:23.989 : Cap:MOTION_MODES:1
11:29:23.989 : Cap:ARCS:1
11:29:23.989 : Cap:BABYSTEPPING:0
11:29:23.989 : Cap:CHAMBER_TEMPERATURE:0
11:29:23.993 : Cap:COOLER_TEMPERATURE:0
11:29:23.993 : Cap:MEATPACK:0
11:29:23.993 : N11 M111 S687
11:29:23.993 : X:0.00 Y:0.00 Z:0.00 Count X:0 Y:0 Z:0
11:29:23.993 : N12 T0*9
11:29:23.997 : echo:DEBUG:INFO,ERRORS
11:29:23.997 : echo:No media
11:29:24.001 : echo:Unknown command: “M80”
11:29:24.001 : echo:Unknown command: “M221 S100”
11:29:24.001 : echo:DEBUG:INFO,ERRORS

I’m using the V1 mini touch plate. Rambo board with dual end stops (purchased from Ryan). All axes move in the correct directions when jogging with Repetier and it cuts fine when I can get the Z axis to zero correctly.

In other cases, I’d just move on and zero it manually, however, this project has multiple passes with different tools and I want the bottom of the cuts to be at the same height.

Is there a sequence I need to follow before homing the Z axis? As in, do I need to home the x and y first? I’ve been using the machine off and on for a year or two now and I’ve never encountered this issue.

2

The two pins we connect to the probe are sense and ground. The sense pin on the Z is looking for ground.

If you attach the sense pin to the router bit, and the router bit is already connected to ground (through the router, and the AC cable and the wall outlet), then it will immediately sense ground, and be triggered.

This has been a common problem. The work around is to either unplug the router from the wall, or swap the sense and ground pins on the Zmin.

The weird thing is, you should have seen triggered (at least sometimes) when looking at M119.

Side note: what would be useful is a print with M119 that showed how long the state has been that way. If it showed ‘open 0.010 s’, then you would know it was being erratic. It would also help with bltouch debugging.

2 Likes
3

Thanks for the insight. I have a job running but when it’s done, I’ll run the M119 command a few times to see if it ever changes and try swapping the sense and ground pins.

As an aside, I tried it several times with the router disconnected from power at the router itself and that did not change the outcome.

The odd/frustrating part is that it’s intermittent. Sometimes after a power cycle, it will home normally. But even when it does that, it only does it once. Afterwards, any other attempts to home the Z only move it up a few mm.

I’m not familiar with bltouch debugging. Is that a separate tool I can get?

3 Likes
4

Just putting this out there… Inused to have the touch plate read as triggered on my old board if I was touching the piece with my skin. I resolved that by using a resistor between the (+) pin and the signal pin, i think 2200 ohm, might have been 4700. The internal pullup resistor should be 4700. Adding this resistor doesn’t consume much current, and wont harm the CPU, but reduces false positives.

So… try the M114 while holding the touchplate, too.

1 Like
5

It isn’t useful here. It was a different use case where that info might be useful.

6

That is the cause - holding the touch plate with my finger. The z homing process works every time when I hold it at the shielded crimp connection and works none of the time when I hold it with my finger directly on the metal of the touch plate.

I’m thinking I’ll just wrap a little electrical tape around the the end of the plate if I don’t have the correct resistor.

Thanks!

2 Likes
8

Adding a resistor between the +5V rail and the signal pin can eliminate that noise. It’s more of a sure thing.