Backlash in rack and pinion drives used in machine tools reduces positioning accuracy and can even cause damage to nearby components. An effective way to prevent this is by using a rack and pinion system with two gear reducers whose output pinions are preloaded against the rack. Our previous blog post describes two Redex preloading technologies that enable zero-backlash rack and pinion drive systems — DualDRIVE and TwinDRIVE. In addition to delivering exceptional rigidity and precise motion, they are also easy to set up. This blog post will explain how.
Servo Reducers: The Heart of Preloaded Rack and Pinion Drive Systems
Redex SRP, DRP, KRP and side-mounted KRPX Series rack and pinion reducers are at the heart of the DualDRIVE or TwinDRIVE preload concepts, and they are well-suited for use in CNC applications.
- DualDRIVE is a one-motor drive technology that mechanically preloads the entire system to eliminate backlash. It uses two SRP or two KRP reducers, or one DRP with two units in a single housing.
- TwinDRIVE consists of two electrically coupled SRP, KRP reducers. DRP also becomes a TwinDRIVE when an electrical preload is applied.
A Simple Way To Apply the Preload Torque
Setting the preload is simple, as shown below in the example DualDRIVE system. The gearbox kits come with a locking mechanism that slides into the coupling and holds it stationary. The coupling fastening screws opposite the motor are left loose. The preload torque is applied with a torque wrench on the input shaft opposite the motor, and it goes through a set of spiral bevel gears, a planetary reducer and then to the rack as shown. Both the output pinions contact the rack as the preload is applied, so the preload returns through the other gearbox. At this point, the screws of the coupling are tightened, and the preload is set. The preload torque value is calculated based on the application requirements, and it is controlled by the torque wrench on the input shaft.
Similarly, a TwinDRIVE system is just as easy to set up. Unlike DualDRIVE, the preload is created by fixing a permanent preload gap torque via one pinion electrically braking against the other — driving — pinion. In this manner, the drive controls the backlash.
Achieve Stiffness and Precision
When it comes to eliminating backlash in rack and pinion drives, Redex DualDRIVE and TwinDRIVE preloading concepts not only effectively ensure high rigidity and positioning, they are also easy to implement. Our team stands ready to provide the technical support to help you select an ideal Redex rack and pinion drive system for your machine tool application.
For more information about Redex DualDRIVE, TwinDRIVE and planetary reducer solutions, visit our product page.