Did I wreck my stepper motor?

[Atomic_Sheep3]

Hi, I had a look finally at what might be the issue. I took off the spindle assembly and then powered on the unit to see which part was slipping... everything was fine to my surprise. I didn't dismantle anything other than taking off the spindle mind you. I then tried to control the Z axis with jog and putting as much pressure on the unit as possible with my hand both up and down but it was tight as a whistle. So I assembled it back up... i.e. simply attached the stepper motor back and tried it again thinking that maybe it was some sort of software issue that caused the issue. Anyway... initially it was all going well and then all of a sudden it began to slip again.

Except the slipping I think is for a different reason... the screw itself isn't seated correctly and its moving around up and down. You can see it in the video if you look closely. Pretty sure the threads are all fine.

EDIT: Looks like the video I'm trying to upload is too big .

EDIT 2: "http://www.youtube.com/watch?v=lHHZ3B3fJWw&feature=channel_video_title"]09102011.wmv - YouTube

[Atomic_Sheep3]

Hmm, I unscrewed the whole thing and it seems that the screw moves around in its housing as I showed in the video, not sure if that's a major issue or not but apart from that... where the motor attaches to the screw... I think the screw itself has either been stripped or shortened... basically the screw which you use to tighten the joint with... doesn't even reach the thing... might have to call the guy that sold it to me and see what he says... will be interesting what the customer service is like after the sale has been completed!

[Atomic_Sheep3]

Hi guys, haven't called the guy that sold it to me yet as I'm still trying to figure out what is wrong with it.

I had another look at it and it looks like the screw came undone as the motor was free spinning over the screw attachment... well I think that it simply shredded the screw allowing it toturn freely, I tightened it up a bit more and now it's got proper contact again, however the original problem remains although to a lesser extent.

I had a read about what backlash is and the definition is pretty broad. Going off this

"Backlash has a variety of causes. The most common is play between the leadscrew threads and those of the nut. ACME screws can have considerable backlash of this kind, while ballscrews may have almost none. Another source is any tendency for the screw to move axial in the bearings that hold it"

I think that I certainly have the latter i.e. as I showed in the video, the screw has quite a bit of movement as a result of a poor seal or whatever it might be, maybe because of this problem, I get the former problem of b/w leadscrew nut movement although it 'looks' pretty good. I think that what is happening is... the play of the screw gives it enough room to rotate around the nut until it gets jammed either at its upper or lower limit at which point the Z axis begins to move.

As you can see in the diagram, there are two screws with overhanging hats which don't appear to be doing anything at the moment so I'm thinking to find a washer of an appropriate diameter and insert it at the top of the screw to remove the gap and eliminate the play and then screw it down in place with the screws, how does this sound?

EDIT: Looks like I was wrong, it's not the axial movement of the screw within the bearings that hold it which is being observed, I'm pretty sure the problem is to do with the housing.

[Atomic_Sheep3]

Well I ended up swapping over the gantry... similar problem... although I haven't looked at it closely yet to determine if the problem is exactly the same, but I imagine it has to be.

I did a test run with the standard cruddy drill bits so they contributed to the poor results but its pretty obvious that the Z axis is creating varying depth cuts.

P.S. Sorry for the poor video... had to reduce the quality to comply with max 500kb.