Build plate/Z Sensor clearance oddity

I just put my printer back together after replacing the LM8UU bearings that the build plate is running on and adding a drag chain to control the bed heater wires, and ran into something that has me scratching my head.

When I put it together and started to level the bed to get it roughly where it needed to be, with some more fine-tuning later with the bed and nozzle hot, but for now, get it 'in the ballpark'. Homed it to X/Y home and then Z home, and had to adjust the sensor as it crashed then nozzle into the bed, but got it roughly where the nozzle needed to be, if a little high for the moment. Moved over to the far end of X at 192, got the nozzle where it needed to be and so on. The thing that has me scratching my head is all along the X0 axis, from Y0 to the far end of Y at 285, the nozzle and the Z stop sensor ride along the plate perfect, with the nozzle where it needs to be and the sensor also where it needs to be. But at X192, the sensor is touching the build plate, while the nozzle is still roughly the same distance from the build plate as it was at X/Y0. And this remains constant through the entire length of the X192 Axis, from Y0 to the far end.

The sensor is an inductive sensor with an 8mm detection distance, mounted on a spring loaded adjustable mount (found here), but if it was a matter if mis-adjustment of the sensor, the nozzle would be dragging on the build surface before the sensor... The sensor never really would have a real chance of contacting the build plate as the nozzle is lower than the bottom of the sensor by 1.5mm or so.

Does anyone have any ideas why along one side of the build plate, everything's fine, but the other, the nozzle is still fine, but the sensor is dragging on the build plate? This is what has me scratching my head....

Edited 2 time(s). Last edit at 02/23/2020 10:59PM by Cougar281.

A thought.
The 2 x axis guide rods are not vertically aligned at the X max end? This causes the carriage to rotate about the x axis so the sensor hanging out the back goes lower.
The other thought i have is related to misaligned Y guide rods. Is the bed supported on 3 bearings? Which side has the 2 bearings. I can't work this out in my head sorry.

I too was having trouble with the idea that the nozzle was fine but the sensor wasn't, but I think I ended up figuring this out after I got some sleep and revisited it.

To answer your questions, my carriage is running on two 8mm linear rails and four bearings, two on either side.

What I believe it ended up being is cable stress. I didn't have the cable from the sensor secured, so as the print head carriage moved across the axis, it altered the stresses, however 'minor', and as a result, it moved the sensor enough to hit the bed. I have since attached the wire to the carriage, so that the wire to the sensor is totally static regardless of where the carriage is and I haven't had any more issues.

Edited 2 time(s). Last edit at 02/29/2020 10:52PM by Cougar281.

Glad you got it sorted.