Ball screw backlash compensation.

[Guest]

Could ball screw backlash compensation cause spermatic errors on a part, depending the operation sequence of a program? For example spot drilling in a zigzag pattern verses a straight line pattern. Also does anyone know the setting that is used on a Fanuc control for X axis backlash compensation?

Thank you,

[MACHINEMASTERG]

yes bepending how loose it is on critical positions on holes we cdrill drill bore ream going same direction not zig zaging

[Guest CNC Apps Guy 1]

Eric,

 

Yes backlash compensation can cause sporadic issues. Un-round circles, holes out of position paralellograms instead of squares are all symptoms. Zig-zag can cause holes to be out of position but the heart of the matter is not Mastercam, it's the machine, so things you can do within Mastercam to alleviate hole position errors is to always go the same direction, look into seeing if you have the positining option for canned cycles, this can help. What it does is ivershoot the hole then pull it back far enough to take out any slop that was present. Kind of a nice feature.

 

The parameter you're looking for depends on the model of your control. So what model is it?

[Vector]

Hi Eric

 

M46 - Turn on Positive Approach

 

M47 - Cancel Positive Approach

 

We have 2 Fadals, and use M46/M47 all the time for drilling.

 

T3 M6 (.25 CNTR DRILL )

S4500 M3

G17 G90 G0 X-2.4375 Y0 E1

Z1. H3 M8

M46

G81 G98 X-2.4375 Y0 Z-0.055 R+0.15 F7.

X1.9967 Y1.3981

Y-1.3981

M47

G80

G0 G90 M5 M9

G53 Z0

M1

T4 M6 (11/64 DRILL )

S4500 M3

G17 G90 G0 X-2.4375 Y0 E1

Z1. H4 M8

M46

G81 G98 X-2.4375 Y0 Z-0.1 R+0.1 F10.

X1.9967 Y1.3981

Y-1.3981

M47

G80

G0 G90 M5 M9

G53 Z0

M1

 

Good luck

 

Vector

[Allan]

Backlash... Never seen "real" backlash over .002" if you have more than that it is more than likely a loose bearing or nut on the screw.

 

You can check it out by puting an indicator in the spindle MPG it up to the edge of a block. Then push as hard as you can on the table in the direction you want to check. You will see some movement but it should return to the zero point when the pressure is relesed. Push on the other side of the table and check again.

 

HTH

Allan

[J Coulston]

Check the coupling between the servo and the ball screw. I had one come loose once. I located the part why didn’t it cut the Y in the right position; I must have entered the wrong offset. Ok, reindicate it WTF I know I used the right offset but now it is off a different amount. Either on accel of decel the coupling would rotate small amount and change the position of the ball screw. I tightened the coupling everything has worked fine since that time.

 

John