Z axis re-zeroing during CNC operation, using Fusion

We had the z axis zero value change seemingly at random during CNC operations today. everything was going well and then all of a sudden the CNC machine decided it’s z axis zero value was different than the one it started with. Cad done in inventor, cam in fusion. we can’t think of a way that it is because of the CNC mill malfunctioning. We are wondering if something in the cam process could do this but looked everywhere we could think and could not discover any explanation. Has anyone ever had this happen before when using fusion or perhaps a different cam software?

Make sure the tools on fusion are the same ones you have in your machine. It’s very unlikely the machine is making the mistake.

What machine are you using?
What are your tool numbers in Fusion?
Are they the same offsets on the machine?
Does this re-zeroing happen when you change tools?

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What machine?
Could you be skipping steps on the Z axis?

2 Things I could think of that could have gone wrong that are fixable:

  1. You could have the wrong post processor. When you post, make sure you use the one for your machine. Even though using a different processor is still G-code, it’s a
    “different flavor”, if you will. Tool offsets are one thing I’ve seen change between processors.

  2. It’s possible that you have the wrong tool offsets because they are incorrectly set in the code, or not set on the machine. To check code, go into each tool you use, and check to make sure the tool number matches the tool offset. Once you are on the machine, zero your first tool using the G54 (or G55, etc, just backup WCS sometimes) command. For all following tools, you want to set the offset. G54 adjusts positions for all tools, so that’s why you do it on the first, but not the following ones. The tools you set the offset for, however, you don’t want to affect previous tools. so just use the “tool offset” button (some machines might make you use a command, check your user guide if you don’t have a button).

Comments in some machines might be different. My hass mill Comments the specfic text out that is in () leaving behind the rest of the line

But my router comments the entire line out if it sees () anywhere in a line

So in the hass
(A) G01 X1. Y2. Z2.
would work

But in the router

(A) G01 X1. Y2. Z2.
Would never get processed

The router would require two specific lines.
(A)
G01 X1. Y2. Z2.

What machine controller? Your issue is very likely a line if code containing a G28 being posted from CAM but not being properly interpreted at the machine. It could also be a G43 with an H number that is causing your issue.