Multi Tool Paths

I have had some concerns with roughing and finishing passes.
I have found that when I run multi tool cutting routines, during the tool change process the router and slip or jump from home position. That scares me because I eyeballed x0y0 on first pass, and no have to replicate a new X0Y0 for a VBit tool bit. I am wondering what is best practice for X0Y0 for using Multiple tools. If router moves.

Thanks in advance for any input.


if your machine is tuned properly the motors should have enough torque for holding position during tool changes.

In my experience holding both wenches with one hand and loosening the chuck this way, you’re less likely to push the spindle out of position than when you would use both hands.

I have homing switches on my CNC and I use them when I change bits.

I usually locate the work piece close to the center of the CNC. I do this by homing the CNC and then precisely jogging to a location which I use to fix the work piece down. Once that is done, any bit I put in will find the same location once I home and jog by the same amount. The only thing I have to watch out for is the Z height.

Since I don’t have a touch plate, I use the paper method and I keep a spot on the work piece un-machined so that the bits can all start from the same height.

This system is also useful when you break a bit. The new bit goes in, you home and the jog, you set the Z and the new bit will follow where the old bit cut. Usually I edit out some of the G-code to skip what was already milled.

1 Like

To reduce the risk of manually shift the machine position during tool change make sure GRBL parameter $1=255 and that the Xcontroller “Idle current reduction” switch is set to OFF.

If you have homing switched installed you can:

  • Home the machine once when powering up your CNC
  • Jog only using the jog commands to where you want your work zero to be
  • Click “Confirm Home Position” - this store the work zero relative to machine home (switches)

Now you have a stored work zero position, relative to machine zero.

This allow you to:

  • If manually pushed or steps lost, reset your machine by rehoming, and “Use previous home”
  • Do 1st tool job today, power the CNC down, restart tomorrow with 2nd tool etc.
  • Restart an aborted or otherwise interrupted carve
    Re-zero of Z may be required if something bit related have changed.