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Hello fellow 3DHubs users,

I have recently had the pleasure to attach and configure an inductive Z-Probe, 12V, 4mm sensing distance (LJ12A3-4-Z/BX), on MK3 aluminium heatbed with BuildTak, to my 3D printer - before it didn’t even feature a Z-Endstop, so this is a huge step up for me.

However, as I had to sadly notice, the inductive probe seems to give precise yet heatbed-temperature-dependent results.

While at 40°C it does not seem to change much, at around 60°C the activation-point of the probe starts to gradually move down by nearly 0.06mm, gravely changing the first-layer Z-Height.
To counteract this I will only probe my bed at specifically 30°C, however this does make me curious:

Has anyone else noticed this before, and maybe found better ways of circumvention?

Or is this a fault in my inductive probe and normal ones should not change by varying heatbed temperature?

How about we start a little discussion on that topic here.

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Things expand and change shape when they are hot, so any calibration work has to be done at temperature the gear is going to be operating at. Otherwise, it is not calibrating really anything.

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Are you sure though that heat expansion would cause a 0.14mm deviation of the distance measured?

Also, the way the probe trigger height changes is a bit counter-intuitive when looking at this theory.
When the heatbed heats up, the height at which the probe triggers actually decreases, which means that either the probe has to have become smaller, or the heatbed must have expanded “downwards”, neither of which sound particularly fitting.

Also it will be rather hard to find “one temp suits it all”, as I run my printer with different materials and, consequently, vastly different required temps, ranging from 0°C for my PLA/PHA to 75°C for ColorFabb nGen
As such I’d much rather prefer a somewhat less temperature dependent calibration, even if it sacrifices a bit of precision.

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If you are using springs on the bed, when they heat up they will contract and the bed will drop. Also, the inductive probe will likely be warmed up by the bed, its component values will drift and it will be slightly off compared to when cold. You are going to have to recalibrate for every temperature range you use if they are vastly different. Or if your printer allows, adjust the Z offset at the start of the print.

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Yeah, seems like this has a lot of complexity in terms of how to get it right …

At the moment, I have decided to run the Z-Calibration, as well as Auto-Bed-Leveling, once per startup of my printer (Using the OctoPrint “On Connect” G-Code script), and run the heatbed at ~30°C to guarantee consistent temps.

We’ll see how this works.