Thanks Hood,
Appreciate the info, the problem I'm having is that when the machine goes to safe Z (as it is set now) it retracts to the home switch or is supposed to go to the home switch, but it occasionally over travels.

I did slow down the rapid rate to 1/2 of what it was set to before so that may help my situation.

Have a good one,
Ted

the problem I'm having is that when the machine goes to safe Z (as it is set now) it retracts to the home switch or is supposed to go to the home switch

I'm not aware of a setting in Mach that will make a safe Z go to the Z-axis home switch. There are three basic choices, move to a location is work coordinates, move to a location in machine coordinates, or move a certain distance relative to where the Z now is. None of these care about your home switch.

Hi Jeff,
Sorry for the confusion, trying to be precise with a monster head cold is a task.....

When we start up the mill and reference it home 0 Z in machine coordinates is the homing switch.

The Safe Z is set to go to Machine coordinates 0 to it goes up to the home switch position.

This was getting over shot, the 0 position, Hood has said that Mach doesn't support a home and limit, so my assumption is that the mill is over shooting the home position hitting the limit switch but the travel speed maybe to fast and thus it is jamming the ball screw at the top of the travel.

What I'm doing now is slowing the travel down to 1/2 of the prior velocity and also going to set the safe Z to 0.250 above the work coordinates so when someone hits the stop button it doesn't crash again.

Thank you,
Ted

The only way I can see that you would have problems with it overshooting Z=0 is if your Z-axis is loosing steps. If your trying to maximize your Z travel and have your home position set just shy of the axis locking up then your Z may be binding just enough as you approach the home position to loose steps. Once you repeat the safe Z move a few times your Z axis will be off enough to over travel and bind. I like to set my home sensors to go off with at least 0.05" (on a small mill) to 0.5" (on a large router) of travel left in the axis. This gives you a bit of wiggle room and helps prevent problems.

Hi Jeff,
As far as I can tell the Mill is not losing steps, home is a quarter inch ahead of the limit switch, we also use the Z=0 position for tool changing, can change tools all day and not miss a beat, hits the home and stops every time, only time it screws up is when you hit the stop button and the quill makes a hasty retreat.

The other hassle is that if it did it everytime it would be relatively easy to trouble shoot,... it only does it once in maybe 10 to 20 times so it is not a consistant problem just really annoying when it happens. I had read a post from another user that also converted a bridgeport he was having the same issue and he used his limit switch to trip the error line on the servo drive to stop the over travel he said it was the only way he could fix his problem.

Thank you again,
Ted

You have to be really careful with the 'Stop'. When you hit stop Mach just stops outputting pulses, there is no deceleration, it just stops. Chances are you will loose position and your axis could drift on slightly as there will be no deceleration to help slow it. I've not tried to use 'Stop' in combination with Safe Z so I can't say how it works but given how Stop works I can't imagine that the results would be predictable.

If you need to pause the machine while cutting use Feed Hold. The brings things to a controlled stop and keeps you from losing position.