Question Z axis binding

Hi all,

I just finished assembling my SC420 and I am having a really hard time trying to level the Z axis.

I followed the instructions on the manual and in the videos. If no tool is installed in the tool holder, the SC homes all of the axes and moves smoothly.

However, when I install the Kress 800 spindle it binds on the Z axis. Is the weight of the Kress too much for this router?

I disassembled the portal twice and checked for possible problems, but I can't find what is going wrong.

Any suggestions will be greatly appreciated.

Frank

No, it's not too heavy, we have users that also have a 800 or even the 1050 running on their SC.

Is it binding the whole way along the Z -axis? Or does it move in the middle and get stuck on the beginning and the end? Then there might be some misalignment in the threaded spindle and the nut ( for example the nut might be twisted just a bit ).
Maybe you tightened the rollers too much. When I build my machine there was a step, where they asked to pull with a force equivalent to 1kg on the z-axis and it should just be on the edge of not moving. I simply placed a bottle of water on the spindle holder.
If the z-axis is not moving easy enough, you would run into this problem when adding weight. In this case it should be possible to move downwards but it stalls upwards.

BTW: Welcome to the forum.

The Z axis is the one people tend to have least problem with.

Assuming that the top and bottom plates are aligned and the track rollers move freely, you could try removing the orange powder coat from the bottom plate bearing seat to allow some float.

Kress 1059 spindles weigh about 2 kg but should not cause a problem. Mine weighs about 1.6 kg.

As for actually levelling the plate to the machine bed, try this method:

https://www.stepcraft-systems.com/en/forum/assembly-and-maintenance/3367-spindle-bed-tramming-840-supports#42414

Doug

I have tried different tensions on the rollers and got better results if the rollers are tight. Yesterday I got a point where the z axis can move all the way up and down, but not at full speed. However, if I loosen the screws by 1/4 of a turn then it starts binding. If I thighten them 1/4 on the opposite direction it binds.

Doug,

as soon as I solve this issue I was planning on levelling the plates and trying to get the spindle into tram.

I will try to remove some of the painting.

I´m using a 2.4kg China spindle with no problem...and in addition to the weight comes the pressure when milling down in Z-direction!
But I have reduced all axis maximum speed and acceleration to preserve the machine.

I've seen videos of the router moving a Kress spindle, but now that you mention that yours is equiped with a 2.4kg spindle, I know that is not the problem.

Do the bottom plate bearing should fit tightly? From Doug's comments it seems that it shouldn't. This will be my next test, removing some of the painting.

Frank,

Why not assemble the Z-axis with the bottom bearing temporarily removed - this way you will be removing the effects of possible misalignment at the bottom end of the leadscrew.

Move the Z-axis to its lowest position before tightening the two upper screws (part #42) This done, you should be able to turn the stepper motor by hand (with power off of course) - it will be quite stiff but manageable. The lower end of the leadscrew should be central in the hole where the missing bearing fits when tightening these upper screws.

When you rotate the stepper, the end of the leadscrew should not move laterally - if it does then either the leadscrew is bent or the thread is not concentric with the machined end (this was the case on my SC420/2). Either way, your chances of getting full free Z axis movement are pretty slim unless the leadscrew is changed for a good one.

When replacing the lower bearing, it should not be a tight fit in the bottom plate - remove some of the orange powder coating if necessary.

Finally, when refitting the lower plate (part #3) with the bearing in situ, ensure that the leadscrew is not pinched between the lower and upper bearings. Slacken off the setscrews on the coupling sleeve to just remove any endfloat.

Hope these adjustments sort your problem.

Peter

Just an addendum to the bottom ball bearing theme, Version 1 machines did not even have those. My screw ends some mm above the plate.

My laptop has decided that it was time for an OS update. So I have to wait until the update finishes before trying your suggestions.

Thanks a lot guys. I will let you know the results.

O.k. Frank. Let us know how you get on.

Regards.

Doug

Hi guys,

after a trial and error procedure, I think I have solved the issue.

Not completely sure what I made different this time. I was going to unscrew the bottom plate to remove the coating, but suddenly the problem was solved.

This weekend I will try to tackle my first project: drilling a small aluminium base.

Once again, thank you guys. Hope this problem does not occur again.