Nexen RPG25A-GE486T 966740 - Manual (Page 15)

15 FORM NO. L-21235-G-0413
Table 6
Screw
Tightening Torque
Nm [in-lb]
Preloader Screw
All Models - 1.7 [15] Max
Shoulder Screws (Mtg. Plate)
RPS-PRE-064 M8 x 1.25 40 [350]
RPS-PRE-090 M8 x 1.25 40 [350]
RPS-PRE-110 M8 x 1.25 40 [350]
RPS-PRE-140 M8 x 1.25 40 [350]
RPS-PRE-200 M12 x 1.75 120 [1060]
Gearhead Screws (Mtg. Plate)
RPS-PRE-064 M4 x 0.7 5.3 [47]
RPS-PRE-090 M5 x 0.8 10 [88]
RPS-PRE-110 M5 x 0.8 10 [88]
RPS-PRE-140 M6 x 1.0 17.5 [155]
RPS-PRE-200 M8 x 1.25 40 [354]
Preloader Mtg. Screws (2x)
All Models M6 x 1.0 17.5 [155]
3. Verify pinion rotational axis is as close to 90° from the
rack run axis, the pinion rotational axis is also parallel
with the tooth tops or rack mounting surface, and the
rack is centered between the pinion bearing flanges
as shown in Figure 1.
4. Rotate the preload adjustment screw clockwise to
separate the pinion from the rack. This will ensure
that clearance is initially present. Then seat the pinion
into contact by turning the preload adjustment screw
counterclockwise until a slight resistance is felt and
then back the screw off 1/8 of a turn. This step is
critical to prepare for preload settings.
5. Place a magnetic base dial indicator on the movable
carriage, and locate its probe on the OD of the pinion
flange such that it measures in the direction of preload
travel.
6. Apply the preload of 0.010 - 0.015 mm [0.0004
- 0.0006 in] with the preload application screw(s)
and then tighten the preload lockdown bolts to
their recommended torques. See Table 6 for Nexen
Preloader System torque values. Typically the preload
will change slightly when the preloader lockdown bolts
are tightened. If tightening the preload bolts causes
the amount of preload to fall outside of specifications
record how much it changed when tightening the
preloader lock down bolts then loosen the preloading
system and repeat the preloading procedure but
adjust the initial preload (more or less) by the recorded
preload deviation. This procedure will ensure that
when the preloader lockdown bolts are tightened the
amount of preload should fall within specifications.
7. With the pinion preloaded to specifications manually
traverse the carriage down the run by hand (if possible)
checking for smoothness and uniformity of resistance.
If manually applied motion is not possible, use the
servo motor to traverse the carriage along the run, with
just enough torque output to move it while looking and
listening for resistance to motion.
Proper roller to tooth meshing is critical and can be verified
by two methods depending on which you find easier to
interpret:
Option 1: Apply a slow drying machinists dye to the pinion
rollers and move the RPS system back and forth over a
short distance (about 1/2 meter). It is important the dye
remain wet so it transfers to the rack teeth and is not
depleted. Analyze the dye pattern transferred to the teeth.
If the meshing geometry is good the dye will be spread
evenly all the way across the tooth face over the middle
2/3 - 3/4 of the teeth with none at the top and bottom. If
this section is properly aligned clean off dye residue and
repeat as necessary to verify the RPS alignment over the
entire length of travel. See Figure 20.
Option 2: Apply a small amount of high contrast grease
to each rack tooth face over 1/2 meter of rack. Operate
the RPS system back and forth over this 1/2 meter of
travel. If the meshing geometry is good the grease will be
Good Alignment Poor Alignment
Contact Pattern Contact Pattern
Figure 20
completely wiped away all the way across the tooth face
over the middle 2/3 - 3/4 of the teeth with some remaining
at the top and bottom. If this section is properly aligned
clean off grease with a solvent and repeat as necessary
to verify the RPS alignment over the entire length of travel
as shown in Figure 20.
SYSTEM ALIGNMENT VERIFICATION
If the dye or grease contact pattern indicates a meshing
problem, diagnose the problem, correct it, and then repeat
the Applying Preload and System Alignment Verification
procedures.