Frage Still have z Axis issue

After replacing the brass leadscrew nut because of wear which caused the whole z axis to move up and down.
I have the same issue again after doing a few jobs.
Im now getting fed up with it. Im wondering if the Kress spindle is to heavy for the cnc at 1.7kg.
In the posted video you can hear the friction with the brass nut and leadscrew. I've adjusted the track rollers and lined everything up a dozen times. Without the kress attached the z axis will do 5000 velocity with no noise/friction. Any ideas as im now thinking of getting rid of the cnc.

mmm it looks like the axis sometimes accelerates and then goes back again to normal speed. It may be a faulty connection or cable.

No I'm using the shift key to start and stop acceleration, all electronics are fine, its mechanical.

Remove the small screw on the motor shaft and the spindle from the support mount. Turn the rod by hand. If you don't detect any problem, then the mechanics are ok.

I hade the same problem before i adjusted the roller tighter. After that I have no problem.
Try little, by little...

/Mika

The problem is the brass lead screw nut has play because it has worn due to friction between it and the leadscrew. If i support the weight of the spindle like in the video it does not bind.

I have just replaced the brass nut 10 days ago and its worn again after milling some aluminium and another job.

Ive adjusted the rollers with the 2 screws loosening them and tightening them and cant find something that works.
I see you have the HF spindle, this is less than half the weight of my kress 1050FME which should be easier on the z axis. Im at at loss what to do at the moment. I'll get in touch with Rory and see if i can get another brass lead screw nut, but i'm guessing i'll get the same issue

REGARDS.

I´m happy that it worked out for you too.

/Mika

mikath schrieb: I´m happy that it worked out for you too.

/Mika

Mika... you miss read, Ive tried adjusting the screws but makes no difference as i think the 1.7kg weight of the kress puts strain on the leadscrew nut and spindle.

jonalm schrieb:

mikath schrieb: I´m happy that it worked out for you too.

/Mika

Mika... you miss read, Ive tried adjusting the screws but makes no difference as i think the 1.7kg weight of the kress puts strain on the leadscrew nut and spindle.

Okay, I´m sorry. Hope you find what´s wrong. It could be the heavier Kress.

/Mika

Just remembered that I had to tighten the small screws more than what was in the description.

/Mika

I use the Kress 800 and I don't have problems with my Z axis.

May be your rollers are too tight? I never heard of that brass screw friction thing. Mine just works ok.

I even attached a custom dust extractor device to the spindle, adding more weight and no problem at all.

jvalencia schrieb: I use the Kress 800 and I don't have problems with my Z axis.

May be your rollers are too tight? I never heard of that brass screw friction thing. Mine just works ok.

I even attached a custom dust extractor device to the spindle, adding more weight and no problem at all.

This is what happened the first time with the the brass lead screw nut worn, the lead screw is loose in the nut to the point you can lift up and down the whole z axis (see vid)

I have made a bit of headway though by positioning the z axis in the middle of the gantry dead center. I then loosen the orange stepper motor holder for z and loosen the bottom tool holder at the same time, i adjusted both slightly and carefully tightend up all the bolts and set all accelerations to 750 in uccnc. i Ran a job without any lost steps.

The Kress 1050 is heavier than the kress 800 by 300grams i think when the z axis is fully down there is a lot of leverage on the z axis of the stepcraft. i may invest in the HF500 as its a better power to weight ratio just my opinion jvalencia.

The kress 1050 works with the Stepcraft. See here:





This is my video with the dust extractor. It should weight like a 1050.

You'll need to disassembly the bridge and see what's going on with all the rollers. Something must be wrong there.