Zero-Backlash Rack & Pinion Drives

For rack & pinion applications requiring ultra-precise positioning and repeatability, the system backlash can be eliminated by using two pinions - one to drive the axis and one to "preload" the axis to remove the backlash.

The simplest zero-backlash rack & pinion drive utilizes a split-pinion.  A split-pinion consists of two pinion halves and an axial spring pack.  The pinions halves mesh with opposite tooth flanks on the same rack, eliminating the backlash.  The axial spring pack is used to preload the rack & pinions to insure that no backlash develops during the operating cycle.

The split-pinion shafts mount directly into our Servo-Worm Reducers and are fixed in place by means of a compression coupling.  This provides rigid support and tight integration of the split-pinion shaft into the reducer.  The end result is a compact and ultra-precise positioning axis drive.

These drives are perfect for precision positioning applications, such as traveling gantries and columns, milling machines, and material feel axis drives.  Two reducers/motors can also be used to eliminate the axis backlash by electrical preload.  For more information on this solution, please consult the factory.

The split-pinions are available in 6 sizes, from module 2.0 to module 8.0.  To view a PDF catalog page for the split-pinion, as well as the servo-worm reducers and racks that they mate to, please click on the sizes in the table below:

* The above ratings is based on using the split-pinions with a hardened & ground rack; it is possible to use different rack, but the ratings will be reduced.  The maximum torque and force values are without preload setting; the rating of the Servo-Worm reducer should also be checked for limitations.

Selecting the right split-pinion depends on many things, including load requirements, the duty cycle, and design constraints.  Typically, the peak cycle torque can be used to make a preliminary selection, however, the amount of preload required by the application must be carefully selected to insure no backlash develops.  The preload setting can affect the final split-pinion selection.

For application & selection assistance, please call us or fill out our Application Sheet.  Your application data will be reviewed by our engineers, who will recommend the best solution for your application.

With open gearing such as rack & pinions, lubrication is critical!  A thin film of grease or oil should always be on the contacting tooth flanks to ensure there is no metal-to-metal contact, which can damage the teeth.

It is recommended to use our Automatic Lubrication System, which pumps grease through a felt gear applicator and meshes directly to the pinion or the rack.  This provides continuous lubrication at the tooth flanks, extended the lifetime and maintaining the quality of the gearing.  For more information on this system, please follow this link: Automatic Lubrication Systems.

• Servo-Worm Reducers are perfect for use in applications that demand high performance, precise positioning and repeatability.  Available in four levels of precision to meet any application needs.  Optional integral pinion shafts mount directly to hollow output shaft.
   

• Helical Flanged Pinions, are provided with ISO 9409-1 flanges to mount directly to our High-Torque (HT) Servo-Worm Reducers and popular planetary gearboxes, such as Alpha TP, Stober PH, Apex AD and Neugart PLF.  This interface provides a tight integration of the pinion to the gearbox output, reducing overhung loading and backlash between the components.  The pinions are easily mounted and replaceable if future repair is needed.
   

• Integrated Rack & Rail mounts directly to most standard linear guides (HIWIN, IKO, INA, NSK, SKF, Star, THK, etc.), eliminating the need for additional machining and alignment, saving time and money.