Why did my Hall effect switch trigger position changed

[TTalma]

I use hall effect trigger switches for each of my axis. Yesterday I ran my machine and everything ran as normal. Today I noticed that my machine seemed to be cutting deeper. I checked everything out. And I noticed that my Z axis which used to trigger at a point of 6.959 above my table now triggers at 7.0469 above the table. A change of .0879" over 1/16 of an inch different.

I trigger from a steel bolt through the face of my z axis, and a hall effect through the face of the Z mounting plate (Top down pic included, couldn't get a good side view pic). Both the sensor and the bolt are still tight.

So how could the trigger point have changed with nothing else changing?



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[Al_The_Man]

Are you sure the distance from prox sw head to trigger point has not changed?
Al.

[109jb]

Is it a Hall effect sensor or actually an inductive proximity sensor?

A Hall sensor should use a magnet as a target. A proximity sensor can use just a metallic target. For either it is best to have a target that is as large as the sensor face or larger.

[Al_The_Man]

Is it a Hall effect sensor or actually an inductive proximity sensor?

A Hall sensor should use a magnet as a target. A proximity sensor can use just a metallic target. For either it is best to have a target that is as large as the sensor face or larger.

Although technically a proximity sensor is a hall effect sensor, just difference in the construction as to the form the trigger method used. The Prox sensor generates its own magnetic field.
Al..

[DonKes]

Magnetic fields attract chips (which generate more magnetic fields).

Don

[ger21]

They don't attract wood chips.

[PCW_MESA]

They don't attract wood chips.

Ironwood?

[TTalma]

Are you sure the distance from prox sw head to trigger point has not changed?
Al.

While I can't be absolutely sure I checked both the bolt that I have sticking out and the switch (I guess technically it is a prox switch) are tight, There is dust on them, and no evidence that they moved.

This mainly affected my tool changer. I have a Z height depth setter. But a couple of tools are 1/16" above the table and I use G53 (Absolute position relative to homing switches) commands to swap tools. And I first noticed when one of the tools was dragged against the table.

[TTalma]

Magnetic fields attract chips (which generate more magnetic fields).

Don

I haven't cut any metal with this machine. And I did look for metal chips, and didn't find any. I also used my air gun to clean it off, and no difference.

[CL_MotoTech]

I had my Z axis inductive proximity sensor go bad and as a result it was doing what you have described.

At first I just thought the trigger target had moved or maybe that my tool had moved in the collet, but after a few minutes of trouble shooting it was obvious the Z wasn't referencing the same point. I readjusted, remeasured a tool, made some stuff, then the next day it was out of whack again. I replaced the sensor and have been good since.

I'll add, occasionally aluminum chips trigger my Y axis inductive sensor. It's the damnedest thing. Not sure if it's an interaction with my coolant or what, but that should be impossible.

[Al_The_Man]

I'll add, occasionally aluminum chips trigger my Y axis inductive sensor. It's the damnedest thing. Not sure if it's an interaction with my coolant or what, but that should be impossible.

There are also types that operate with non-ferrous metal.
Al.

[davida1234]

I can see only three variables if it worked before:

1. Something with the trigger system has changed (moved, dirt/chips, got magnetic) - You say no.

2. Something has happened with the sensor (hit, got bad, EOL) - Replace.

3. Something has happened with the supply voltage (different sensitivity) - Check.