Nexen HGP25 969053 - Manual (Page 12)

FORM NO. L-21277-B-1213 12
APPLYING PRELOAD
If the machine design does not already have provisions for a
preloading mechanism, Nexen offers a high precision lifting
and jacking screw style preloading system onto which the
HGP is fastened. It can simplify machine design and help
achieve the best possible system performance. A suitable
mounting surface and the correct mounting hole pattern
is required to add the Nexen preloading system to the
customer machine frame. See Figure 14. P
reloadinG
P
rocedure
Note: Exercise care when engaging the HGP with the rack
to avoid damaging the rack teeth or pinion rollers.
1. With a dial indicator mounted on the movable carriage,
measure the height of the tooth peaks. Move the
carriage down the run taking frequent measurements
to locate the high spot in the run. This is where the
pinion preloading should be done to prevent excessive
preload from occurring elsewhere in the run.
2. Install the HGP onto the preload system’s sliding
member. Apply a serviceable threadlocking compound
to all fasteners which perform the function of locking
down the position of this sliding member. Assemble
the HGP assembly onto the machine, ensuring that
the preloader lockdown fasteners are left just loose
enough to allow the pinion rollers to be pulled in
and out of mesh with the rack teeth. For the Nexen
Preloader System, this is approximately 0.2 – 0.3
Nm [2-3 in-lbs]. If sufficient travel within the preload
system exists, the pinion can be initially engaged with
the rack by adjusting the pinion until the OD clears
the rack tooth tips.
Nexen precision preloader system product numbers
and dimensional information, and customer machine
frame mounting hole requirements can be found at
www.nexengroup.com on any of the HGP pages under
“Accessories” in the left-hand column.
To ensure optimal meshing of the pinion’s roller pins with
the rack teeth, the HGP must be preloaded to 0.010
– 0.015 mm [.0004 - .0006 in] beyond full roller/tooth
engagement.
NOTE: Do not apply excessive preload. Preloading
beyond 0.015 mm [0.0006 in] will decrease product
life, increase noise, and cause vibration. When the
RPS is properly preloaded, there will be no tangential
play between the rack and pinion when pinion rotation
is restrained and the carriage assembly is manually
forced back and forth in the direction of travel.
Refer to Figure 15 for other suggested preload methods.
Gearhead
Nexen Precision
Pinion Preloader
Customer
Machine Frame
Figure 14
Figure 15 Customer Designed Pinion Preloaders
Adjustment by Elongated Slots
(Preferred Method)
Adjustment by Eccentric Slots
Part #
Part #
Preload Adjustment
Screw
High Point In Rack Teeth
High Point In Rack Teeth
HGP e
nGaGement witH
rPS r
ack
(
continued
)
• If sufficient travel within the preload system exists, the
HGP can be initially assembled to the machine. Adjust
the position of the preload system’s sliding member
until the pinion OD clears the rack tooth tips.
From it’s side face, the rack can then be slid beneath
the pinion flanges and into position. The preload
adjuster’s position can then shift to attain initial
engagement of the pinion rollers and rack teeth.