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DMG MORI EVO 60 problem ?

GeorgiMirov

Plastic
Joined
Jan 28, 2020
Hello ,

I recently bought an used DMU EVO 60 2015 with iTNC 530.
The machine had a lot of hours on it ( 38000) but I got it for a good deal.
Everything is working , there are no errors and it's overall a working machine.

I've decided to change the probe stylus with a smaller one ( 3mm ) and when I recalibrated it for diameter it showed weird numbers on the screen ( attached picture ).

When I measure the ball with a digital micrometer it shows 2.98mm.
After the calibration the control calls it R 1.41 in the offset page and also in the calibration page. So it basically measures it 2.82mm with 2microns offset on X and 0,078mm offset in Y.
I've adjusted the runout of the tip to be around 1 micron ( needle of the 2micron indicator barely moves).

Another issue :
Removing material with adaptive strategy around a plastic cylindrical stock , and the cutter starts to chatter when it reaches Y+ and Y- strokes , and no chatter when in position X+ and X- strokes.

When jogging the machine in Y direction with more than 30% rapids( moving the hole column ) it shakes the machine. No such observations in X and Z.

I suspect a major wear on the Y axis ballscrew/nut. Any other suggestions ?
 

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DrimJohn

Aluminum
Joined
Jul 12, 2017
Hello,i would first check the brakes on the servos if they working properly (disengage when servos on).The machine has linear encoders, if you apply a force to the y axis with the servos not enabled you will see the reading change, for say 10 Kgr of force you must see a deviation of few microns, compared this with the x axis.
 

GeorgiMirov

Plastic
Joined
Jan 28, 2020
Hello ,

Today I did this check. I've lowered the Z axis and put a micron indicator on the spindle nose.
I applied as much force as I can in Y+ and Y- direction. The indicator was had less than 0,01 deviation in both directions and on the screen I could see a +/- 3-4 microns changes ( this with the servos enabled ). I don't know how to perform the same test with the servos disabled ? Probably push the E-Stop ?
 

DrimJohn

Aluminum
Joined
Jul 12, 2017
Hello, sorry for the late replay, the problem as you describe it looks like a worm ballscrew as you mentioned or the brake in the axis is not disengage fully or partial, so when it reverses the direction the relise of friction makes those spikes, find a place in the circuit to measure the voltage going to brakes and the impedance of the brakes when not powered. The motor can easy overpower the brakes.
 

DrimJohn

Aluminum
Joined
Jul 12, 2017
Yes you have to push the estop and apply force to the axis and watch the screen. with the servos powered you should not see any change in the screen as they make corrections very quickly.
Regard John
 

DrimJohn

Aluminum
Joined
Jul 12, 2017
The servos have zero backlash brakes, when they are disengage the servo is not moving at all. open the machine cover and put the indicator between the base casting and Y axis casting, in this way you remove any deflection and problems in the rest of the machine. the problem may be in the ball-screw or in the support bearings or some screw in the linear encoder may be loose.
Regards John
 

Bad.Cyborgh

Plastic
Joined
Jan 11, 2022
Location
Auckland - New Zealand
While the axis is moving at speed >=30% find a safe spot to stand and push against the column in the direction of movement and if the shuddering stops then the complete ball screw + angular bearing with adjusting nut needs to be replaced because the preload on the ball screw no longer exists. If you need to be "safe" then hook some bungy cord onto the column which would have the same effect as pushing on the column. If the ball screw is kaput then the B-axis pre-load will also need to be checked. Hope this helps

Regards
 








 
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