Heat effects the z-offset when using Capacitive Sensor

I made a custom prusa i3 and added Capacitive sensor for Auto bed leveling. If I heat my print bed before priting, the z-offset just changes each and every time. Especially when printing Ngen my print bed goes to 70 to 80 degree. And if I want to print the second print z-offset changes upto 1 mm. But if I print without heating the print bed, it prints the perfect 1st layer without any problem each and every time. It is just when the print bed is hot the z-offset is way off(print bed is heated before auto leveling) than what I calculated and wrote in Marlin.

How do you guys solve this problem? I am thinking of using BLtouch or microswitch.

Capacitative sensors are affected by heat, and humidity.

Inductive sensors are not but then you may not have metal within the sensing range.

You can use BLtouch but its only repeatable to around 50 microns, a microswitch is much more repeatable, if you have it fixed (which you can't or it would hit the object your printing) you have to deploy/stow it, so it might vary between deployments.

My recommendation would be a fixed, accurate probe with high accuracy (10 microns) and repeatability deviation (2-7 microns), no offsets in x or Y. This can fit on to the groovemount of an i3. (Mk2 version coming soon)

www.precisionpiezo.co.uk/shop

Also see these threads
[forums.reprap.org]
[forums.reprap.org]

A massive amount of work has gone into this and it has proved its worth time and again.
This is what one customer said:

"Just have to post back here after probing lots of times and doing many prints. First layer height is now always the same and I'm not even using baby steps to correct anymore this sensor is just bang on each time. No way back to the IR sensor after trying this! I'm designing my other printer to run with piezo probes also now since this is so stable to use. Great product guys!"

Edited 1 time(s). Last edit at 09/04/2017 07:03AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

@methesoul use edge ruler to verify that your bed is not warping as it heats up.

If the capacitive sensor is affected by heat, then try and keep it away from the heat? Move to Z max or if possible on your printer move it in y/x off the heat bed while heating up. Probe when hot and make sure your probing sequence is optimised for speed before the probe can heat up itself.

I print on glass. I I decided to buy 4mm aluminium as print bed and buy a new inductive sensor. I hope it helps.

Edited 1 time(s). Last edit at 09/05/2017 04:57AM by methesoul.