Bridgeport VMC 1000 z-axis homing down to hard stop instead of up to soft limit???!

Hello,

Machine is a Bridgeport VMC 1000 with tnc426.

Had problems with bad connection to estop relays, fixed and checked distributionboard. Also had the servo to the workbench and tested the servobrake when troubleshooting the problem.

Its now fixed. BUT. When I start it up and press cycle start to home Z,Y,X. The Z axis goes down instead of up until it reaches the hard stop. And now its stuck there. Dunno how to move it since this machine does not have a counterweight for the head.

Why is it going in the wrong direction, I have only disconnected the servo drives and distribution relay bord when troubleshooting the error. I'm quite sure I have not moved the servo engine to its rotation to the ballscrew. And even If i did it should not go down towards the table when homing?

Which parameter sets the limitswitch value?

Does it thinks it is to high from limit switch somehow?

Is there a way to move the axis before homing them in tnc426 ?

Normally on other Bridgeport CNCs, if the axis is homing in the wrong direction it is because the limit switch is stuck. It should be looking for the limit switch to turn off and then it moves one more marker pulse away from the switch for its "home" position.

I am not as well versed with the VMC controllers. Call Aaron or Mark at EMI and they can tell you more. 610-287-4240

Jon
H&W Machine Repair

99 percent, HW has got the answer

Thanks Gustafson, I just dont deal too much with the VMCs. But if its a DX controller, it should be the same.

Jon

If it is a sticking limit switch, which is most likely, make sure you don't leave the machine with the Z all the way up. We had problems with this with a DX32 machine. It just had a bunch of gunk stuck on it holding it in. We cleaned it off and started jogging Z down a bit before shutting down the machine. No more issues so far.