[thomasz]

Hi!

I have changed the thrust bearings and seals of z-axis from my 4020TH (99).
I use a shim (0.03mm) between the bearings.

The backlash was round about 0.1mm! Okay - i have to adujst the
gibs on z-axis, so the axis-move was very strong. Don't know who made this.

Now the backlash is 0.04-0.05mm (with a little prog measured).

Then i use a second shim between the bearings (total 0.06mm) to test - the backlash was not much better.

Is there a way to improve it and is there a way the backlash of the spindle and the bearing to measure well?

Thanks!

Bye
Thomas

[alex gitzel]

The gibs may be too tight sometimes setting to factory spec. can be too tight,i assume you did it by the maunal.I set gibs by feel,tighten untill snug then back off and tighten untill you just start to get more resitance,then i put the machine in e-stop and turn the screw by hand, loosen your gibs first to get a baseline feel then tighten and feel.it should be just slightly tighter than when loose,but turn freely by hand.another thing to do is realighn the screw it should be done after taking the bearing block off.jog the head up as far as you can and still be able to loosen the bearing block screws it will float into place then thighten the bolts.then do the final gib setting as described before.if the bearing block is thightened with the gibs loose it will not be straight and will bind and cause extra backlash.

[thomasz]

Hi Alex!

Thanks for the tips - I realign the screw and the gibs once again.
"Feel" the thightness and so on. The screw is now turn passably free.
In one orientation more heavy (if z goes +).

But nothing happens: 0.04 mm backlash. I'm afraid, the screw is little damaged.

Bye
Thomas

[alex gitzel]

Test the screw with and indicator,mag base on the head and the tip on the screw tread jog up and down 1 click .010, the backlash should be around .0001-.0003'' more than .0005'' and the screw is worn.

[thomasz]

Hi!

Ballscrew has 2/100mm (0,0008") backlash. So I think the screw is worn.

Bye
Thomas