I'm running Mach3 to run a router. When I home the machine all axes move to the zero position with z at the top. When a program encounters a g28 g91 z0 (any time it needs a tool change for example) the z rises up to the limit switch but triggers an e stop rather than a limit and the program must be reset. Any guidance on settings? Thanks

Tripping the limit switch is an e-stop condition.
If you are using the limit switch as a home switch as well it could be problematic but I am not sure.
Try G28 Z0. You can also look at the config, homin/limits and verify that the G28 positions are set to Zero. If it still goes up and hits the switch and estops, you could always try setting the G28 position for the Z axis as -.5 to see if that helps.

FYI G28 is different in Mach4 vs Mach3. Mach 4 is more Fanuc in nature IIRC.



Mike

I can't say for the mill but G28 / Mach3 can behave in way that's not what you are expecting for the lathe depending on
current configuration / modes. Still not done testing ..........
Read the description of the command in the manual very carefully.

FWIW,
RICH

 

I'm running Mach3 to run a router. When I home the machine all axes move to the zero position with z at the top. When a program encounters a g28 g91 z0 (any time it needs a tool change for example) the z rises up to the limit switch but triggers an e stop rather than a limit and the program must be reset. Any guidance on settings? Thanks

You must also set up soft limits even though you have physical limit switches.
For home position, soft limits and limit switches are set identical - all set to zero.
For the other end of the x and y axis make the soft limits 1 mm before hitting  the limit switches. I have remove the bottom limit switch for z and use only soft limit because z is always zeroed using the probe to the material surface and soft-limit can be easily changed to avoid cutting the table or even too deeply on the spoil board. It also helps if the auto Z probe fail.
I found that the presence of soft limits help avoid "e-stop" conditions. The limit switches if really triggered must "e-stop" to avoid physical damage to the machine.

Get rid of the G28 G91 Z0 line.
Are you using Fusion 360? I see this question asked a lot from Fusion 360 users.