Tormach PCNC 770 - Adjustment Procedure; Determining Proper Angular Contact Bearing Preload

Chapter 9
168
UM10350_PCNC770_Manual_0916A
Maintenance
Figure 9.6 shows how the force of preload is
transmied through the bearings, from the inner
race to the outer race. In a preload pair, this force
is then transmied back to the inner race by an
opposed bearing. It should be apparent that the
correct orientaon of the angular contact bearing is
crical to the operaon.
9.3.4.2 Adjustment Procedure
To adjust the angular contact bearing pair preload,
the following kit is required (see Figure 9.7):
PN Description
35355 AC Bearing Service Tool Kit
There are two nuts: the adjustment nut and the
lock nut. The nut nearer the bearing housing is the
adjustment nut, and the one nearer the axis motor
is the lock nut (see Figure 9.5).
NOTE: When working on the Z-axis, remove any tooling
from the spindle and support the head by resng the
spindle nose on a block of wood.
1. Loosen the lock nut and back it o about two
turns.
2. Hold the ball screw to prevent it from rotang
with a pair of pliers on the coupling and ghten
the adjustment nut unl there is slightly more
backlash than you ulmately want to achieve.
Tightening the lock nut will slightly increase
the bearing preload.
9.3.4.3 Determining Proper Angular Contact Bearing Preload
To properly esmate the torque needed to overcome angular contact bearing fricon, the bearings
must be isolated from the stepper motor detent torque. Use the following procedure:
1. For adjusng the X-axis, posion the table near the right hand end of its travel (i.e., X near to
zero). This ensures that the bearing is near to the ball nut to minimize bending of the screw
during tests.
Figure 9.6
Figure 9.7