Rack & Pinion Systems

Ultra-High Precision Rack & Pinion Drive Systems

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. Positioning accuracy is maintained during acceleration and deceleration, as well as during changes in direction of travel. We have several different different solutions to achieve a zero-backlash drive system:


Split-PinionsSplit-Pinions

The simplest zero-backlash drive system utilizes a split-pinion, which consists of two pinion halves and an axial spring pack. The pinion halves mesh with opposite tooth flanks on the same rack, eliminating the backlash.

One pinion half drives the axis while the second pinion half is "preloaded" to remove the backlash. The preload setting of the second pinion half is fully adjustable on the machine by turning the axial spring pack at the end of the pinion shaft.

The split-pinion shafts mount directly into our High-Torque (HT) & High-Performance (HP) Servo-Worm Reducers.


Dual-Pinion Electrical PreloadDual-Pinion Electrical Preload

Another method to remove the backlash at the rack & pinion is to use two motor/reducer assemblies with dual pinions operating on the same rack in a master/slave setup.

One pinion drives the axis (the "master") while the second pinion is "preloaded" to remove the backlash (the "slave"). The preload is created electronically with a special motor controller; these systems can also be set up to drive together during cycle times when backlash is not critical.

Dual-pinion gearboxes using only one motor are also possible, please consult the factory.

Our Automatic Lubrication Systems are highly recommended for use with these drives, providing continuous grease lubrication to the rack & pinion tooth flanks to preserve the quality and lifetime of the gearing.

These drives are perfect for precise positioning applications, such as traveling gantries and columns, milling machines, CNC routers and material feel axis drives. Two reducers/motors can also be used to eliminate the axis backlash by electrical preload.

  • System Precision
  • Split-Pinion Rack &
    Pinion Drive Systems
  • Electrical Preload Rack &
    Pinion Drive Systems

The system precision, including the pitch error and backlash, can be found below:

System Precision
Level:
Rack Type & Class: Rack Quality
Level:
Rack Pitch Error: Rack & Pinion
Minimum Backlash:*
Ultra-High Hardened & Ground
(UHPR & HPR)
DIN 3 to 6
(~AGMA 12+)
< 0.012 to 0.036 mm
per meter
Zero

*The rack and pinion backlash depends on the alignment of the rack to the linear guides.

There are three levels of precision for the hardened & ground racks, with rack pitch error ranging from 0.012 mm to 0.048 mm per meter length depending on which rack is used. Follow this link for more information on our Precision Racks.

Split-Pinions

The simplest zero-backlash drive system utilizes a split-pinion, which consists of two pinion halves and an axial spring pack. The pinion halves mesh with opposite tooth flanks on the same rack, eliminating the backlash.

One pinion half drives the axis while the second pinion half is "preloaded" to remove the backlash. The preload setting of the second pinion half is fully adjustable on the machine by turning the axial spring pack at the end of the pinion shaft.

The split-pinion shafts mount directly into our Servo 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 reducers have backlash levels down to one arc-minute and ratios from 4.75:1 to 52:1 (higher ratios available with planetary-worm reducers).

The maximum drive force that each system can handle (with safety factor 1.0) is listed below; this should be compared to the application peak force, which can be calculated here, or by filling out our Application Sheet.

Please click on values for PDF specifications:

Reducer Size: Rack
Module:
Split-Pinion: Split-Pinion
# of teeth:
Maximum Drive
Force:*
Maximum Linear
Speed:
HP Size 3 2 74.92.330 30 530 lb. 8,288 in/min
3 74.93.320 20 530 lb. 8,288 in/min
HT size 3 2 74.92.430 30 636 lb. 8,288 in/min
3 74.93.420 20 791 lb. 8,288 in/min
HP Size 4 2 74.92.430 30 636 lb. 6,631 in/min
3 74.93.420 20 1,124 lb. 6,630 in/min
HT Size 4 3 74.93.520 20 1,180 lb. 6,631 in/min
4 74.94.515 15 1,815 lb. 6,631 in/min
HP Size 5 3 74.93.520 20 1,180 lb. 4,973 in/min
4 74.94.515 15 1,815 lb. 4,973 in/min
HT Size 5 5 74.95.615 15 2,447 lb. 6,216 in/min
6 74.96.613 13 3,423 lb. 6,465 in/min
8 74.98.612 12 2,781 lb. 7,957 in/min
HP Size 6 5 74.95.615 15 2,248 lb. 6,216 in/min
6 74.96.613 13 2,248 lb. 6,465 in/min
8 74.98.612 12 2,248 lb. 7,957 in/min
HT Size 6 6 74.96.713 13 3,531 lb. 6,465 in/min
8 74.98.712 12 4,002 lb. 7,957 in/min
HP Size 7 6 74.96.713 13 3,531 lb. 4,246 in/min
8 74.98.712 12 4,721 lb. 5,226 in/min

* Force ratings do not include any safety factors. Drive forces vary depending on gearbox ratio selected.

Dual-Pinion Electrical Preload

Another method to remove the backlash at the rack & pinion is to use two motor/reducer assemblies with dual pinions operating on the same rack in a master/slave setup.

One pinion drives the axis (the "master") while the second pinion is "preloaded" to remove the backlash (the "slave"). The preload is created electronically with a special motor controller; these systems can also be set up to drive together during cycle times when backlash is not critical.

Our new HighForce Planetary Drives, which can handle highly dynamic and heavy loads, are perfect for these applications. These reducers have backlash levels down to one arc-minute and ratios from 4:1 to 100:1.

The maximum drive force that each system can handle (with safety factor 1.0) is listed below; this should be compared to the application peak force, which can be calculated here, or by filling out our Application Sheet.

For dimensions, please click on the "Reducer Size" in the left column.

Reducer Size: Rack & Pinion
Module:
# of Pinion
Teeth:
Maximum Drive
Force:*
Maximum Linear
Speed with 3,000 rpm
Motor:
7 2 23 3,900 lb. 4,528 in/min
2 29 4,200 lb. 5,709 in/min
3 17 5,000 lb. 5,020 in/min
8 3 26 6,500 lb. 7,677 in/min
3 32 6,600 lb. 9,449 in/min
4 20 10,500 lb. 7,874 in/min
5 16 10,000 lb. 7,874 in/min
9 5 20 13,100 lb. 3,281 in/min
6 16 15,000 lb. 3,150 in/min
6 20 17,600 lb. 3,937 in/min
8 15 17,600 lb. 3,937 in/min
10 8 19 20,900 lb. 4,987 in/min
10 15 21,100 lb. 4,921 in/min
10+ 8 19 27,800 lb. 4,987 in/min
10 15 28,200 lb. 4,921 in/min

* Force ratings do not include any safety factors. Drive forces vary depending on gearbox ratio selected.