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Machine never raises Z axis to probe while leveling the bed

Posted by Crazor 
Machine never raises Z axis to probe while leveling the bed
September 20, 2018 06:26AM
I have a problem with my recently added inductive probe and Marlin 1.1.9. The probe is connected to the Z min endstop, and works fine for homing. The printer moves in XY to the middle of the bed, raises Z, lowers Z until the probe senses the bed, raises Z again and lowers Z more slowly. So far so good.

I confingured AUTO_BED_LEVELING_BILINEAR, and when I run G29 after homing, the following happens:
The printer lifts Z, moves in XY to the first probing point, lowers Z until the probe senses, but only once. It the moves in XY to the next probe point, but it never lifts Z again. Instead, it quickly drags along in XY to all other probe points, and gives identical numbers for each point.

I tried deliberately skewing the bed, so that it leaves the initial Z height that gets probed on the first point. I notice that when the LED on the sensor goes off, the Z steppers move down a little until the LED is on again, and then the machine continues through the remaining positions without ever moving Z again. The result is that I get two different numbers: one for the first to Y rows, and one for the last two Y rows.
Why does the machine never lifts the Z axis again?

Here's my config: [gist.github.com]
Re: Machine never raises Z axis to probe while leveling the bed
September 20, 2018 09:22AM
After mulling over the code for a bit to find out what exactly it is supposed to do, I stumbled over what went wrong: I had Z_CLEARANCE_BETWEEN_PROBES and Z_CLEARANCE_MULTI_PROBE commented out! Now everything is working as expected.
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