Z-Stage not going all the way down

[znib 2]

I just noticed that my Z-Stage does not go all the way down until it hits the lower z-endstop switch. To actuate the lower z switch, it would have to go down until the arms almost touch the ground plate right? But about 5cm before this, it becomes very hard to turn the leadscrew, even by hand, and by motor it just blocks. What am I doing wrong?

 

[joergen 2]

the lead screw and the 2 linear bearings are probably misaligned and prevent the Z stage from going further. if you force it down, you'll probably break something.

 

[znib 2]

the lead screw and the 2 linear bearings are probably misaligned and prevent the Z stage from going further. if you force it down, you'll probably break something.

 

That's what I figured out too, but how do I align them? The position of the vertical axes is fixed by the wholes in the top and bottom. The position of the lead screw is fixed by the wholes user to mount the motor. There is no was to adjust this without drilling new wholes, which I don't like to do because all the other laser cut parts were very precise and I'm not sure if the real problem isn't something else.

[illuminarti 18]

Can you post some pictures of the zscrew, coupler at the bottom, and the block where the screw attaches to the bed?

 

[znib 2]

Can you post some pictures of the zscrew, coupler at the bottom, and the block where the screw attaches to the bed?

 

Sure. The first one is the bottom, coupler and z-screw, the second is the back of the bed seen from below, and on the last you see how far I can move it down. If I try to move it down further than that, it need lots of force, and the motor blocks below this point.

 

[owen 19]

Hi znib

The height at which it stops looks like possibly the wood at the bottom of the z stage is hitting the top of the coupler where the coupler should go up inside that part.

Not sure why it would be hitting it as nothing looks out of whack in the photos.

To see which part is sticking otherwise you could undo the to 2 top grub screws in the coupler and unscrew the screw right back up through the top (if it will go) then see if the z stage will slide all the way down.

Also I can't see grease on the screw thread though it may be there. It shouldn't stop it but it does need to be greased.

Owen

 

[znib 2]

The height at which it stops looks like possibly the wood at the bottom of the z stage is hitting the top of the coupler where the coupler should go up inside that part.

Not sure why it would be hitting it as nothing looks out of whack in the photos.

To see which part is sticking otherwise you could undo the to 2 top grub screws in the coupler and unscrew the screw right back up through the top (if it will go) then see if the z stage will slide all the way down.

Also I can't see grease on the screw thread though it may be there. It shouldn't stop it but it does need to be greased.

Owen

 

I also thought the wood of the z-stage would touch the coupler somehow, but I checked that. Also, I remember when I inserted the vertical axes but not yet the z-screw, the table was going all the way down without any problems.

And yes, there is grease on the screw. It was actually kinda hard to turn it manually because it was so greasy. :-)

 

[owen 19]

I remember when I inserted the vertical axes but not yet the z-screw, the table was going all the way down without any problems. :smile:

 

In that case it sounds like there is something on the screw that is stopping it going through the nut at that height.

 

[calinb 11]

Haha--perhaps that's a good reason to slot the top end of the lead screw so a screwdriver can be used to turn it through the top hole! When there's enough room under that stage, you can grab the coupler, of course.

 

And yes, there is grease on the screw. It was actually kinda hard to turn it manually because it was so greasy. :smile:

 

[znib 2]

I finally found the time to look into this again. I read in another thread, that the drive nut should have some play in the wood to allow the lead screw to wobble. Mine was very tight, I remember it used some force to fit it into the wooden parts. So I losened the screws in the coupler and took the lead screw out of the coupler. The I grabbed the lead screw above and below the z-stage an moved it left and right, back and forth a few times, too loosen a bit the nut in the wood. Now I can lower the z-stage all the way down until it hits the end switch.

 

[illuminarti 18]

Aha! This is good to know. I guess it proves the value of the 'loose nut' design. :-)