Ball Screw Pre-Tension; Pre-Tension Procedure - Makino V55 Maintenance Manual



  
7.6.4

Ball Screw Pre-Tension

The X, Y, and Z ball screws are pre-tensioned (stretched) at installation to
minimize changes in axis positioning due to thermal growth of the screw.
When an axis moves, heat is generated by the recirculating balls in the
nut. The screw is subject to thermal growth by the coefficient of thermal
expansion (12 x 10-6/C°).
The screw shaft grows 0.012/1000mm (0.00047/39.37") with a tempera-
ture rise of 1° C (1.8° F).
The average ball screw temper-
ature rise is 3 to 4° C (5.4 to 7.2°
F). Pre-tensioning places a cold
screw under tension. The ten-
sion decreases or normalizes,
as the ball screw expands
toward its normal operating tem-
perature, minimizing axis posi-
tion deviation.
Table 7-6
7.6.4.1

Pre-Tension Procedure

If the ball screw has been released or removed for any reason, follow this
procedure to pre-tension the ball screw.
Before mounting the X, Y, or Z axis servo motor:
1. Mount the ball screw [1], see
2. Tighten the outboard end lock nut [2], to seat the bearings.
3. Loosen lock nut [2] and run it back in to touch the bearings.
4. Place an indicator [3] and [4] on each end of the ball screw and set the
indicator to zero. (Be sure to load the indicator at about mid-range.)
5. Tighten lock nut [2] until the difference in the reading on indicator B
and indicator A equals the pre-tension amount for the axis,
6. Mount the servo motor, see
7. Check the axis reference points and reset, if necessary.
7 - 28
lists the pre-tension amounts for each axis.
T 7-6
ABLE BALL SCREW PRETENSION
AMOUNTS
X = B-A
Axis
(MM)
X 0.054
Y 0.035
Z 0.035
section 7.6.3
(pg 7-26)
.
section 7.5.1
(pg 7-15)
X = B-A
(INCH)
0.0021
0.0014
0.0014
.
Table 7-6
.