Bizarre probe start crashes

LowRider CNC Troubleshooting
1

I cut most of a cabinet yesterday on my machine (woohoo!) but today when I went to cut the back I started having trouble probing.

When I start a job, it has me attach the probe (all good) and then the bit slowly starts moving downwards. After 5-10mm of downward travel, I get the following error message in my FluidNC terminal:

[MSG:INFO: ALARM: Probe Fail Contact]
ALARM:5
Probe fail. Probe did not contact the workpiece within the programmed travel for G38.2 and G38.4.

and the Z-axis crashes down to the work top. The really weird part is that if I retry (re-home Z, and move even closer to the tabletop) it claims it’s starting to probe, but actually moves upwards and will even move up so high that the z-limit stubs are pushed slightly upwards (if I let it, I only did that once.)

So the bad initial probe breaks something in the machine that stays broken until I reboot FluidNC. I was cutting just fine (including probing) on this machine less than 12 hours ago, so I have no idea what could be happening here. Any tips?

2

What version of FluidNC? There were some 3.8 versions that had issues like that.

What are you running for a probe command? That error is normal if you don’t specify a long enough max distance in the command.

3

Firmware is v3.9.1.

I am using the same prelude from EstlCAM as worked fine last night: G38.2 Z-80 F200 P0.5.

The initial probe failures I could chalk up to some loose wiring (maybe something happened overnight) but the reversed second probe seems really bizarre.

I did check my wiring and it all seems fine.

4

If this is on an LR4, that Z-80 should be Z-110. The Z-80 was for the LR3 but the LR4 has more Z travel. So, depending on Z position before you start probing, that could fail on a LR4.

Reversing the direction is still weird and wouldn’t expect that on v3.9.1.

5

I will update the postprocessor, but even when I start well within 80mm of the top surface, this happens.

How should I start debugging this?

6

How is the probe attached? What kind of bit are you probing? A picture might help.

Is this something you can easily reproduce or does it seem random?

7

I am using the tiny touch place from the V1E store and a 1/8” single flute upcut bit. The probe has its clamp on the bit and the touch plate against the top of the material.

I’ve confirmed by tapping the plate on the bit and seeing the light on the Jackpot illuminate that it can actually detect the bit.

This reproduces 100% of the time with this file. I’ll try a different file and see if it’s 100% overall, as well as just a plain probe from the UI.

It feels like somehow one of the electrical components is malfunctioning here but I don’t know how to check them.

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8

All right, I came home, ran a standalone probe on the machine (worked) and then tried to cut the same file again and it ran just fine. No idea what happened, the bad behavior before lasted through 4 restarts/attempts to cut this file.

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9

Glad you got it working.

If it misbehaves again grab the output of $SS in the terminal so we can see what’s up.