[JMFabrications]

Hello,

I just recently started having weird problems with my Z Axis home position, due to the problems I cant even use the machine. When I first power on the machine I am required to set all axis to the home position by pressing CYCLE START, the Z is the first one to move from the M92 command in the default program. It would normally move up to the limit switch, then back down about 1/16" of an inch. I have a Kurt power drawbar, and the tools would go in fine at this home position. Now all of the sudden when I set the machine to home, the Z axis moves up, then moves back down about 3/8" of inch. Due to this extra movment I can no longer insert the tool because the air gun will not grab the drawbar to tighten it on the tool holder. Nothing has been change recently, so im not sure what is causing this problem. Here are some specs of the machine:

Acer 10x50 3 axis Vertical Mill
Centroid M10 Control
Kurt Draw Bar
NST 40 Taper

Is there any way to change where the Z axis will stop after hitting the limit switch. At the current home position I cannot move the Z axis up any more, it states that it has reached the limit. Here is a pic of the spindle, and also there is a link to a video of what happens when I CYCLE it to the home position. Any help would be greatly appreciated.

Video:
http://www.jmfabrications.com/misc/HPIM0316.MPG

[Al_The_Man]

I am not familiar with Centroid, but on many controls where the home is the marker pulse on the encoder, after registering the home switch.
A couple of possibilities exist, the home switch has moved or the encoder has changed position on the shaft.
To avoid having to turn the encoder a certain amount, controls generally have what is call a grid-shift, this is a parameter that programabally moves the marker pulse effectively to a different point and is in amount of ± encoder pulses.
Al.

[JMFabrications]

Thanks for the reply, other people have told me that the Gridshift might need adjusting as well. Unfortunately it doesnt say how to do it in the manual. Ill call centroid but most likely they wont help me over the phone, they'd rather send out a tech and charge me $100/hr plus travel time!

[MDLang]

See if you can find a stroke diagram on the machine or in a manual. Find the stroke distance from the table surface to the max z+ distance away from the table surface. This should be the the Z home position. Whatever the machine deviates from this distance is the grid shift correction you need to make. Will be hard to find the parameter without a parameters manual or chart.

of course my first question would be why has it changed. Any crashes lately. Any drive malfuntions, errors?

Mike