Rack & Pinion Drives

Welcome to the widest range of standard racks & pinions in the World!  Consisting of both helical & straight (spur) tooth versions, in an assortment of sizes, materials and quality levels, to meet almost any axis drive requirements.

These drives are perfect for a wide range of applications, including axis drives requiring precise positioning & repeatability, traveling gantries & columns, pick & place robots, and material handling systems.  Heavy load capacities and duty cycles can also be easily handled with this drives.  Industries served include Material Handling, Automation, Automotive, Aerospace, Machine Tool and Robotics.

Typical delivery time for these standard components is 2 to 3 weeks, which is ideal for OEM's requiring just-in-time delivery schedules.  Special and/or modified components are always possible - please consult the factory.

Complete Range  |  Selection  |  Ratings  |  Accuracy  |  Lubrication  |  PDF Files  |  Application Sheet
 

There are four basic quality levels of gear racks available, each of which is well suited for certain types of applications:

The quality levels denote the accuracy of the teeth, which affects the positioning accuracy, backlash and noise level of the rack & pinion set.  We always recommend a hardened & ground pinion regardless of the rack type used.

Don't let the rack segment lengths above deceive you - unlimited travel lengths can easily be achieved by mounting the racks end-to-end, using a companion rack to properly space each segment.  What is a Module?  Module is a metric pitch, inversely related to diametral pitch, e.g. Module = 25.4 / Diametral Pitch.

The most recent addition to this range is our Integrated Rack & Rail, for mounting directly to linear guides, simplifying alignment and machining.

Selecting the right gear rack depends on many things, including accuracy and load requirements, design constraints, and cost.  Sometimes it is possible that two different racks would work for the same application, but each having it's own advantages and disadvantages.

Rack & pinions are typically selected based on the peak cycle forces, which usually happen during accelerations and decelerations.  These cycle forces depend on the weight being moved, the speed vs. time profile for the cycle, the friction of the axis bearings, and any other external forces acting on the axis.

Maximum tangential force ratings for the various racks can be seen in the following table:

* Ratings depend on size and material of mating pinion, and are based on fatigue strength; breaking strength ratings are much higher.  Service factors need to be applied to these ratings to make a proper selection.

Helical versus Straight.  There are two styles of gear racks we offer - Straight tooth, where the teeth are perpendicular to rack length, and Helical tooth, where the teeth are at an angle to the rack length.  The helical style provides several key benefits over the straight style, including:

• Helical rack & pinions runs quieter than the straight, especially at high speeds

• Helical rack & pinions has a higher contact ratio (the number of effective teeth engaged) than straight, which increases the load carrying capacity

• Helical rack lengths are nice round numbers, e.g. 500.0 mm and 1,000.0 mm, for easy integration with machine bed lengths; Straight racks lengths are always a multiple of pi., e.g. 502.65 mm and 1005.31 mm.

• In most cases, helical rack & pinions cost the same as the straight rack & pinions!

The only real disadvantage to using helical rack & pinions is it requires more time to set up and align properly.

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.

Rack & Pinion Ratings  |  Rack & Pinion Selection Procedure  |  Application Sheet

When talking about rack & pinion accuracy, it can be broken down into three components:  Backlash, Pitch Deviation and Tooth Quality.

• Backlash is the amount of clearance between the rack & pinion tooth flanks, and will depend on the type of rack selected and alignment accuracy between the rack and pinion.  The backlash can be eliminated completely by using a preloaded split-pinion or dual pinion drive system.
   

• Pitch Deviation is the difference between the theoretical rack length and its actual length.  This varies depending on the rack quality selected and is shown in the catalog as GTf per 300 mm length.  Some servo systems can compensate for this error by using a laser interferometer to map out the errors.  Zero cumulative pitch deviation for long travels is available - please consult the factory.
   

• Tooth Quality is the accuracy that the tooth flanks are manufactured to, which affects the running precision and smoothness of the axis drive.  Soft rack & pinions have a quality level of ~AGMA 9 (DIN 9) *.  Induction-hardened rack & pinions have a quality level of ~AGMA 8 (DIN 10) *, due to deformation from the heat treatment process.  Quenched & Tempered rack & pinions have a quality level of ~AGMA 10 (DIN 8) *.  Finally, Hardened & Ground rack & pinions have a quality level of ~AGMA 12 (DIN 6) *, since the teeth are precision ground.  For high accuracy applications, a precision rack, such as the Hardened & Ground, should be used.
  
  *AGMA quality level numbers increase with higher precision; DIN quality level numbers decrease with higher precision.

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, extending the lifetime and maintaining the quality of the gearing.

For more information on our Automatic Lubrication System, please follow this link: Automatic Lubrication Systems.

• Servo-Worm Reducers are available in four levels of precision to meet any application needs.  Perfect for use in applications that demand high performance, precise positioning and repeatability.  Angular backlash levels down to less than 1 arc-minutes are available as standard.  Optional integral pinion shafts are also available to mount directly to hollow output shaft.
   

• Zero-Backlash Rack & Pinion Drives, for applications requiring ultra-precise positioning and repeatability, the system backlash can be eliminated by using a split-pinion or dual pinions.
   

• 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.
   

• Helical Splined Pinions, are provided with DIN 5480 internal splines to mount directly to popular planetary gearboxes, such as Alpha and Stober.  This interface provides a tight integration of the pinion to the gearbox output, reducing overhung loading and backlash between the components.
   

• 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.