How to best implement the Eddy sensor and EddyTap function

General Discussion
1

Basic Information:

Printer Model: Voron 1.8
MCU / Printerboard: SKR mini e3 v3
Host / SBC Pi4
klippy.log

klippy.zip (24.3 KB)

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Describe your issue:

I have an BTT Eddy Coil sensor, and have been using the EddyNG setup with good results. I decided to migrate back to mainline klipper now that Eddy Tap funcions are integrated.

I did encounter a few problems setting up the ldc sensor and calibrating the sensor, which I had to workaround(and did not document) and ultimately have a succssful tap with adequate accuracy and can rapid_scan.

I am curious about how to best implement the Klipper Tap function into my print start macro and how to use the macros supplied in the Eddy Config doc.

-do I use the command “Probe method=tap” to set the final z offset, when the printer is warmed up right before printing?

-what is the use case for the macros in the Eddy Config doc?

Thanks for your time

2

Shortly speaking, Eddy coil does not have thermistor, so to make use of data not from the tap at different temperatures, you have to somehow cancel the thermal drift.

Technically you have now at least 2 probes, one probe, probes with the nozzle, second one does proximity estimation based on the “scan” and calibration data from the config.

Tap allows to get some reliable/repeatable point in a space, so one can compare PROBE, PROBE METHOD=scan, PROBE METHOD=rapid_scan against it.

In ideal world, all probe modes would output the same value at the same spot.

PROBE commands does not alter anything, including the z_offset, probe commands, well, do the probe.

How I think, it should work:

  1. You configure tap to get some reliable “tap”
  2. You print with SET_Z_FROM_PROBE METHOD=tap + BED_MESH_CALIBRATE MEHTOD=tap, to get the idea of tap offset, if it is here.
  3. One can automate setting of G-Code Z Offset after the tap, because it would be a constant value at a specific speed.

Then, when you have reliable tap data, and you know that tap provides you with the TRUE zero reference plane.

One can proceed here: probe_eddy_current: runtime calibration curve adjustment by nefelim4ag · Pull Request #7179 · Klipper3d/klipper · GitHub

And with knowledge of “tap” offset,
one can then set kinematic state to the correct “zero” reference, and by measuring the second (scan) probe at the same spot, measure the thermal drift offset.

Hope that helps,
-Timofey

3

Do you mean here to use that Tap method to generate a bed mesh? I am hoping to continue with a rapid_scan bed mesh and utilize the Tap function to set a final z-offset when the printer is at printing temperature, which I think is what you are describing otherwise.