The French transmission equipment specialist Redex Andantex has developed an alternative to ballscrews for rack-and-pinion applications which, it says, provides high positioning accuracy and repeatability at a relatively low cost. In many applications, the PDP (preloaded double pinion) can eliminate the need for two coupled planetary reducers.

The device (above) consists of two ground pinions connected through a patented preload system to reduce rack-and-pinion mesh backlash dramatically. It includes gear teeth that mesh precisely with each other when the coupling is engaged.

Mounted on the output flange of a planetary gearhead, the PDP is said to deliver a precision and repeatability of better than 0.1mm. It provides high torsional and radial rigidity and tilting moment levels. It can handle input speeds up to 1,200 rpm, and torque levels up to 2,840Nm.

The PDP is available in eight reduction ratios and in four different modules, with straight or helical teeth. There are also angle drive versions.