Z-axis homing reversed?!

[Baldur Norddahl]

Hello

My Pocket-NC v2 suddenly attempts to home the Z axis in the reverse direction. That is, it moves the spindle forward until it hits the limit (or the work piece), then continues to try to move it forward (producing bad skipping noices) for a while before giving up. Manually hitting Z+ will move the spindle in the right direction (away from the table). WTF?

I tried rebooting and downgrading the software to 3.2.0 but it still does this. Obviously I can't use the machine now because the Z axis can not be homed. Homing the other axis works fine.

Anyone seen this before or have any idea to what I can do to resolve it?

Regards,

Baldur

[Jonathan]

Baldur,

The problem that you are describing sounds like it could be caused by a faulty Hall sensor circuit. There are a number of things that could cause this issue. I will email you directly with some troubleshooting ideas. 

Jonathan

[ke...@pocketnc.com]

This post has been resolved, chips were shorting out the Hall sensor on the Z/spindle circuit board and vacuuming up the chips fixed the issue (sometime these chips can creep under the cover plate). Here are the troubleshooting steps to take to determine if this is the issue:

If you have been cutting any conductive materials, this could be caused by a chip shorting out the hall sensor. 

In order to check this, please remove the cover plate from the Z/spindle circuit board compartment. It is located on top of the X carriage behind the spindle. You will need to remove the 4 M3x5 button head fasteners with a 2 mm hex driver. Look under and around the wires for any chips. 

Pay special attention to the black component sticking up about 3/8 of an inch above the board on the spindle side. This is Hall effect sensor. Take care not to disturb its position. Look for any chips under or around its 3 leads connecting to the board.