Nexen RPS16G-C0070T/360-EP2U 966554 - Manual (Page 5)

5 FORM NO. L-21252-B-1209
SYSTEM DESIGN OVERVIEW
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• Unlike traditional gear systems, the Roller Pinion Gear (RPG) rotary drive system has zero mechanical clearance
and requires a system preload for proper operation. This preload must remain relatively constant around the entire
gear to obtain optimal system performance and life. To achieve this it is crucial that the bearing support system be
as concentric as possible to the ring gear pitch circle diameter and not converge or diverge at any point. If the sys-
tem converges, the pinion preload will become excessive and increase noise, reduce pinion roller bearing life, and
potentially bind the system. If the system diverges pinion preload could be lost causing backlash, a loss of positional
accuracy, an increase in noise, and a reduction in system life. See Figures 1 and 2 for more details.
• Make sure that the machine design is rigid enough to avoid deflection that could affect the RPG system preload.
• The allowed ring gear concentricity variance tolerances shown in Figure 2 are greater than the system preload. This
is not an error. The RPG system has been designed to operate correctly under these conditions.
• The inner diameter and one side of the ring gear must be fully supported. This is best accomplished with a step in
the mounting surface.
• For very large ring gears, a single piece mounting surface will become impractical requiring a segmented one. When
installing the segmented ring gears, their joints should not be near the mounting surface joints but span them as
much as possible.
• The RPG System generates a reaction force that tries to separate the pinion from the gear teeth. Make sure this is
accounted for in the machine design. See product data for pressure angle specifications.
• The RPG System requires a mechanism to achieve proper pinion preload. It is recommended that the pinion be moved
into the gear not vice versa. The recommended method is to mount the servo drive system on a sliding bracket that
has an adjustment to push it into the gear. Another possible preloading method utilizes a bracket with an eccentric
mounting slot pattern. Nexen offers a preloading mechanism that is easy to integrate into your application as shown
in Figure 17. Spring loaded preloading mechanisms should not be used since the spring force required to counteract
the separation forces are much higher than the allowed preloading force and would cause a reduction in pinion needle
bearing life, and increase system noise. See Figure 18 for more details.
• The RPG System requires periodic lubrication and should use the grease offered on Nexen’s website as an acces-
sory to the RPG products or equivalent lubrication as described in the Lubrication section on page 16. For more
information or applications with special lubrication needs consult Nexen.
• Do not use the RPG System in environments with temperature outside of -5 to 40º C (23 to 104º F)‚ or with wide
temperature swings since this can affect the preload and meshing of the system. If you have an application with any
of these characteristics consult Nexen.
• The RPG systems are surface treated with Raydent®, Armaloy®, or Nickel Plating (with the exception of the pinion
rollers that consist of bearing grade steel), and will have moderate corrosion resistance. Pinion roller corrosion will
lead to pinion needle bearing damage and then system failure. Always protect the pinion from adverse conditions.
If the RPG system comes with other coatings, consult the product specifications for performance. Review surface
treatment product specifications for corrosion resistance performance, and determine whether the RPG system is
suitable for your application based on your familiarity with the corrosion resistant surface treatment or thorough test-
ing. Nexen makes no claims for RPG corrosion resistance in any application.
• Nexen can provide additional tapped, untapped or countersunk holes in the ring gear as needed.