Changing end mills results in a an x/y offset

After having my Shapeoko for over a year this weekend was my first time trying multiple bits, I’m a simple man. :slight_smile: I got a 90 degree vbit to add some chamfers and this is when I noticed it. After the pocket operation I changed the end mill, homed the machine and then told it to go back to the offset and it appeared to be correct but after the operation ran it was off by a little (1-2mm). I tried another toolpath just to make sure it wasn’t that and when that was off I made a test model. The test model was a simple pocket circle. I cut it once, shut the machine off, didn’t touch the end mill and then proceeded to home, set z and run again. I noticed that in the +x/y there was a little movement as I could hear it grabbing new wood when it was in this direction only and so small it didn’t even make dust but I could hear it. I did this two more times and when looking at the pocket it was visually noticeable it was off a little so it appears after a reset (or just movement) it’s drifting in the x/y? What should I check first, what’s the best way to test this going forward? Thanks

Try not to home on end mill changes…

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Why shut the machine off? For a bit change I just turn off the router, jog it to a convenient location, change the bit, re-zero Z and run the new file. I know the controller “should” hold the offsets, but why take that chance? If the limit switch differs by even a tiny amount, the new path will be off by that tiny amount as well.


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That’s how I did it the first two times actually, and when it wasn’t lined up o figured I did something wrong and some other threads explained how you should home it between changes because it’s likely to move it while changing end mills so I started doing it that way. Both ways end it offsets after the tool change.

did you remove power to the steppers (e.g. the CC board) when changing tools?
Once you do that and you then touch the machine, it’s likely to move…

The last couple of times I did while testing but originally I did not, I would shut the router off and change the bit in place but because the process was finished the machine would always home itself after it was done so I was changing the bit in the top right which made it hard.

I tightened all the belts and tried my test again this morning and it appears better but I can still /hear/ the router hitting the left side. Is this normal, the tone definitely changes when it’s touching the left pocket vs the right every time but I don’t see it cutting and I marked it with a pencil and it didn’t remove it.

hmm if you take out a bit and put it back in, there will be a very small tolerance on that depending on how good your collet is… but … odd.

I don’t get that. Unless you’re shutting Carbide Motion down after a toolpath, or turning the machine off, there should be no re-homing of the router. After my first (or second, or third, etc) file completes, the router moves to the rear of the machine while keeping the X location. I then bring it to center. After loading a new file for a different bit and hit run, the router moves to the current X - Y offset and begins the new toolpath.

It seems odd that yours would home after a file run

As mentioned by others in this thread, not a good idea to home or shut off the machine during a job. The reason is that the mechanical “limit” switches that come with the SO3 are not particularly accurate. Perfectly fine for what most of us do with our machines, just need to understand the limitations.
If, however, you make as many mistakes/are interrupted as much as I am thus causing the need for shut downs and/or re-homing you should look into proximity switches. Magnetic rather then mechanical. @Luke (formerly Mr Beaver) used to sell them. Many references here in the forum.

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Ah, you’re right, it moves to the back right and I just assumed it was homing but the switches are not touching. Close though.

So, I guess the best way is to wait until it finishes, let it move to the back, shut off the router and then using the quick move commands bring it to the front and change out the tool then just load up the new file and start. Sound about right?

I think tightening the belts helped, the last job I ran I changed tools and it seemed to be better.

That’s exactly what I do and so far it’s worked well for me. I’m in the process of upgrading my machine (HDZ, steel belts and bitsetter) so that workflow will change some (due to the bitsetter), but right now that’s it.

In your process above you omitted the portion where you need to reset Z0 with your new endmill before starting with the new file

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