Tool Length Offset between NC Programs

Hello all,

I finally have cncjs setup and working great except for one small thing. For reference I have a Shapeoko 4 Pro XXL which has the BitSetter

I have been using @neilferreri tool change macros referenced here:

My current process is the following:

  1. Create tool paths on fusion and export them into 2 NC Files. First uses a 0.25 flat bit and the second uses a 0.25 ball nose bit.

  2. Set stock 0

  3. Run the Inital Tool Macro

  4. Start Job

  5. Stop router and run New Tool Macro

  6. Change bit while paused and then resume probe

After running the second probe the tool has not updated the stock Z to the new offset. So far it has always been higher but not constantly higher. I have been verifying on part of the stock where I originally set 0.

About how much higher?

One was around 2-3 mm and another run was pretty much exactly 0.43 mm. I used $# to compare the PRB values when it was off by 0.43 mm. I cant fully remember at what stage I took screenshots but below is the results to the best of my memory. I need to run the same two programs again today and I can take better notes. Is there any other debugging commands that would be helpful?

After Initial Tool but before first NC program

[G54:-723.382, -482.791, -63.730]
[G55:0.000,0.000,0.000]
[G56:0.000,0.000,0.000]
[G57:0.000,0.000,0.000]
[G58:0.000,0.000,0.000]
[G59:0.000,0.000,0.000]
[G28:0.000,0.000,0.000]
[G30:0.000,0.000,0.000]
[G92:0.000,0.000,0.000]
[TLO: 0.000]
[PRB: -3.525,-857.000, -81.200:1]

After New Tool Change Macro has probed but before second NC program

[G54:-723.382, -482.791, -63.730]
[G55:0.000,0.000,0.000]
[G56:0.000,0.000,0.000]
[G57:0.000,0.000,0.000]
[G58:0.000,0.000,0.000]
[G59:0.000,0.000,0.000]
[G28:0.000,0.000,0.000]
[G30:0.000,0.000,0.000]
[G92:0.000,0.000,0.000]
[TLO: 0.000]
[PRB: -3.525,-857.000, -81.630:1]

Are those values with the same tool, nothing changed?

Those would be between tool changes and NC programs. I only have the free version of Fusion 360 which doesn’t allow tool changes so I split them into multiple programs. The second set of coordinates is after switching to the 0.25 ball nose and running the new tool macro.

Edit: This is also from my best memory. I didn’t write down notes when I took the screenshots of the results of each $#. I likely need to run it all again with better note taking about the results at each step.

It makes sense that the probe values are different as those are Machine coordinates reported. That’s the distance the Z axis had to move down from your limit switch to reach the BitSetter. The tools have different lengths/stickout.
Are you noticing a height difference on your workpiece?

After running the new tool probe for the second tool I have been verifying against the same section of stock that I originally measured on and its been held down with clamps so I don’t think its moving at all.

And when you compare back to the original stock, what’s the difference?

That’s where the difference is variable. The only time i directly measured it was when I captured the results of $# it seems like it was off by the probe difference amount.

A very uneducated guess it that it seems like the new tool offset is not being recalculate to update the work Z offset.

I have been trying to read more and understand how the different coordinate systems and G10 works. Are you able to point me to some good references material or explain how these macros work under the hood. New to CNC so hopefully I got some of these terms correctly.