Problem with losing my 0,0, points

[44henry]

I have had this problem surface before, but not often enough that it has been a problem until now. Yesterday when I was cutting a router table top on my ShopBot everything was going fine until it reached the end of the cut and than it moved to the safe Z height of 1" and started to travel back to the home position, unfortunately about halfway there the whole carriage started to jerk and the zero coordinates were lost. It has done similar things before when I was making large signs, it only seems to do this when I start getting further than 2' away from the edge of the table and it generally only does it on the return. I suspect a rough spot in the travel somewhere at this point, but I cannot find it and it does fine it seems when I am manually jogging it around this area. Anybody have any ideas?

[myxpykalix]

This may not be related but do you have adequate grounding? I used to lose 0,0 all the time till i grounded my dust collection system.

[kivimagi]

Are your pinions too tight? Not sure what type of system you are running, but this has been some what of trouble on the buddy machines.

Regards,

[44henry]

It's the basic 4x8' ShopBot. We don't have the dust collection hooked up on it yet, though it does have the accomidation for it. It always seems to do it when it is returning to home position. We have noticed it happening also when we are cutting signs much bigger than 2' long. For some reason it cuts the deeper cuts first and than when it is supposed to return to the home position it goes about half way and resets the zero and starts cutting from the center of the sign. I am kind of wondering if this is happening because the return rate is too fast, I have no idea if the pinions are too tight. Possibly related is the fact that I still cannot get this thing to cut a true circle, though it performs fine on rounded corners and other radius cuts. I like the machine, but we have been having some problems with it.