Kossel seems to have z height hysteresis

I have a slightly modified FLsun Kossle with linear rails that used to be a great performer. Lately I have noticed horrible first layers.
When I zero the bed with pronterface, I get a nice repeatable height. When I user CURA to print, I see that the head, instead of going to 0.18mm seems to go to about a .5mm and I have to use baby-stepping to put it in the correct place.
I am using CURA 3.6 and Marlin 1.1.8.

Has anyone seen and fixed this? This version of CURA has worked fine and I have used it for a while, so I do not suspect CURA. I recently updated my Marlin from to 1.1.8 and this is when the fun began. Initially the head stopped about 5mm off of the bed, but I found a bed level setting that I didn't disable in the configuration.h file (I do not use bed leveling.)

I started with the FLsun Kossel configuration files BTW.

thanks,
DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

Did you heat up the bed first before leveling? It may warp going from room temperature to print temperature. Do you use bang/back or bed PID? Bang/bang may rhythmically move the bed up and down, a bit like breathing

Check the custom gcode sections to see there's any offsetting pre programmed there. Something like
G92 Z0.5
or something similar.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Quote
imqqmi
Did you heat up the bed first before leveling? It may warp going from room temperature to print temperature. Do you use bang/back or bed PID? Bang/bang may rhythmically move the bed up and down, a bit like breathing

Check the custom gcode sections to see there's any offsetting pre programmed there. Something like
G92 Z0.5
or something similar.

I heat the head and the bed, the bed does use "bang-bang", I have let that default operate on all of my printers, and bang-bang was what I used before.
I think that I may have found what was going on. When I moved to 1.1.8 I went to the example_configurations and pulled out the FLSun Kossel one to customize. I did this because the mechanics of my Kossel are based upon that FLSun kit - But I tossed everything but the linear rails and the 2020 extrusions. I used my own corners, end effector, extruder, hot end, bed, etc. I figured by starting there I'd at least get the pulley teeth right. Well... Hidden in that configuration file set were the settings for the piezo auto bed-leveling algorithms. I have since changed to a generic Kossel with no hidden assumptions where the default is no firmware bed-leveling. I will see if this makes the difference.

Also, for better or worse, I do my own custom gcode sections. Usually I don't mess them up. But when I do, it ISN'T subtle!

Thanks for the ideas, I had never considered the "breathing" thing. I may PIDTUNE my beds to see if that changes other odd things that I have seen over time.
DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

Well. I gave up.
I was simply unable to get Marlin 1.1.8 to put the nozzle close enough to the bed to be able to print decently when using CURA gcode...
Until...
I realized that I had goofed the DELTA_RADIUS setting. Now it is working as it should. The first assumption that a person can never make, is that they did everything correctly the first time.

Bad assumption, no biscuit.
DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.