LR3 with SKR Pro 1.2 and TFT35. I’m using the “start” code from the Milling Basics page:
G92 X0 Y0 ; Set Current position to 0 on the X and Y axes.
M0 Attach probe ; Pause to connect touchplate
G38.2 Z0 ; Probe down to touchplate
G92 Z0.5 ; Set new Z position to thickness of touchplate
G1 Z2 F900 ; Lift off touchplate
M0 Remove probe ; Pause and wait for touchplate removal
M106 ; This will turn on an IOT relay to start a router or vacuum
For some reason, the probing sequence goes wonky “sometimes” - I start the program, the first M0 message comes up, I attach the clip to the mill and position the touch plate under it. Tap the “Continue” button on the LCD.
Sometimes, the sequence continues as it should - Z moves down to the touch plate, then back up 2mm and the next M0 message comes up. Exactly as expected.
But sometimes (and I haven’t been able to figure out why), Z will move for only an instant and the second M0 message comes up and I’m screwed - the only thing to do at that point is reset the board, home again and start all over.
My take from your questions is that sometimes the Z probing stops “early” meaning just after it started. I can think of three possible reasons:
Intermittent grounding
Electrical noise
Known issue with some SKR Pro boards
The possible intermittent grounding can be addressed by making sure the signal pin from your control board goes to the plate not the clip.
Electrical noise is addressed by either firmware settings, or by adding a capacitor to the circuit.
The issue with the SKR Pro boards is addressed by either adding a pullup resistor to the circuit, or by disconnecting the LED for the probing. Disconnecting involves cutting the trace to the LED, or removing the LED.
I would start with no. 1 since it only requires rotating the plug if you have it “wrong.” Sometimes you can see no. 3 issue if you examine the LED for the problem at the time you are probing. The board will have the opposite state to LED.
I assume you have to reset your board is that you are including your homing code as part of your job. One way to help the situation (not a fix) is to pull out the homing code and execute it separately…separate job on the SD card, connected to an options button in Repetier-Host, etc. If the problem occurs, then all you have to do is execute homing again. This would also help with debugging the problem.
Thanks for the quick reply! I’ll bet its #1 - I’m sure I didn’t pay any particular attention to how I plugged in the lead for the touch plate. I’ll check it out.
Also thanks for the suggestion of moving the homing code to a stand-alone job. Not sure why I didn’t think of that…
In my opinion, this is the least likely cause. It is only an issue of somehow the router bit is grounded. In 99.99% of the cases, the router bit is not grounded, so polarity does not matter. To me, the fact that your router moves just a bit makes this even more unlikely. But it is such an easy fix, it is not something to be ignored. And it may change things electrically that helps address the other two possibilities.
I finally figured out what was going on with the touchplate issue.
Turns out it only happens after G91 (relative positioning) has been executed. The G38.2 Z0 doesn’t do anything because it’s already at 0, relative to the current position…
Fixed it by adding a G90 at the top of my probe macro to make sure it’s set to absolute positioning.
Hey there just a curious question whats was the symptoms that you were receiving I’m looking to fixing mine.
It’s not probing to the touchplate correctly(8.98mm thickness)
