Contact Issue with the Y-limit Switch and the Y-Axis Nut Mounting Bracket

Hi everyone -

Alright, this is probably going to fall into that "stupid question" category, but this has happened to me twice now. The first time I thought I had understood the issue, but now I'm pretty convinced I'm just doing something wrong -- operator error -- but I just can't figure out what.

Twice now, after turning the Handibot on it's side to either do something to the base or change a bit, I've ended up in this situation where somehow, the Y-axis has "slipped" in such a way that the limit switch no longer makes contact with the Y-axis Anti-Backlash Nut Mounting Bracket. (I'll just call it the "bracket" from here on out.) See the attached picture.

The first time this happened was after doing the Y-axis backing plate upgrade and squaring the base. I figured I must have slipped the exoframe in relation to the base during the upgrade, so I disconnected the bracket from the base, moved the exoframe about 3/4" by rotating the drive screw, then reattached. Problem solved.

However, today, I was simply changing bits. When I starting preparing the machine to cut and did the XY-zeroing, Y-axis again ran forever, and looking below, I could see the limit switch was again not making contact with the bracket before the end of the ball screw was reached. Since I had not disconnected the bracket from the base this time, I can only assume that something is slipping when the Handibot is being turned on its side. But despite looking at this for quite a while, I can't figure out how it's happening and thus how to fix it.

Any suggestions for how to resolve this and, perhaps more importantly, what I'm doing that is so stupid?!?

Thanks!

Eric (Moron in California)

Alright, upon further examination, it appears I'm even dumber than I thought. I tried what I thought was the solution previously -- disconnecting the bracket from the base and turning the screw manually -- but wasn't able to resolve the issue. After thinking about it a little more, I realized there was no way that that could have been the solution because both the bracket and limit switch are attached to the exoframe. D'oh! (In my defense, I used to think much more clearly before I had toddlers running around the house.)

So now I'm baffled. I'm not sure how I managed to resolve this issue before but clearly not the way I thought I did.

So in short, it seems I need to find a way to reposition the bracket on the Y-axis ball screw so that it can contact the Y-limit switch. And I can only assume that this occurring because I'm slipping on the Y-axis ball screw.

Thoughts, anyone?

Thank you,

Eric

Hey Eric--I know we just resolved this one over email but I wanted to share here in case anyone else has a simliar problem. It turned out that the blue pointer that plugs into the handibot base was protruding a bit, blocking the full motion of the Y axis.

Motion issues like that can be pretty tough to diagnose--but the first thing I always check on my own tool are things like "is the tool colliding with something inside or outside of its work area?" After making sure that the axes are not hitting anything, then I'll look for damage to the motors--severe impacts on the tool can break motor shafts or anti-backlash nuts...or the axis could just neat a little bit of re-alignment maintenance. If all of that checks out then I start to suspect a wiring issue--in the new handibot you can see clearly through the back of the tool to the driver board where you should see 4 wires plugged into the X, Y and Z terminal blocks.

Hi Brian,

Thanks for the follow up here. You beat me to it.

To elaborate, the blue pointer on the base had gotten slightly dislodged vertically -- just enough to stop the Y axis movement by blocking the carriage from traveling the last 1/2". However, whenever this happened, it was with exoframe all the way forward, effectively blocking the pointer from view. It wasn't until I got down to eye level with the rails on a different surface -- the large material jig clamped to my work surface also interrupted my view -- that I could see the slight elevation of the pointer.

To others who might have a similar issue, Brian's advice is very good. The compact design of the Handibot is one of its greatest features, but it does mean you have to look much more closely when an issue occurs. Though my issue turned out to be a little silly -- as I had said was possible in my original post -- smaller objects in less obvious locations could easily cause similar issues.

Thanks again, Brian and Tom!

Eric