Home » Redex Andantex Uses Mechanical Preload System to Increase Drive Capacity
Redex Andantex Uses Mechanical Preload System to Increase Drive Capacity
June 12, 2007
The new DualDrive from REDEX ANDANTEX eliminates backlash and increases the rigidity of rack and pinion drives using a patented mechanical pre-load system and reinforced output bearings. This gives a 100% increase in drive capacity together with ideal precision. Thus in machine tool design, wherever linear movement exceeds four meters, ball screws are sometimes replaced by linear motors (a very expensive solution that is not always easy to put into practice) or, more and more often, by rack and pinion drive systems. DualDRIVE rack and pinion drive systems are constructed of two parallel mounted planetary servo reducers that are coupled mechanically or electrically. Extreme rigidity is provided in all directions by an integral output pinion shaft supported by reinforced output bearings. In addition to providing torsional stiffness characteristics,DualDRIVE also has improved rigidity along the other axes. According to the company's press release, this often enables use of up to twice the acceleration rates or weight capacities of other solutions. Its design, combines strongly reinforced output bearings with pinions integral to the output shaft (chill cast, case hardened and ground, and the same diameter as the shaft) whose pitch diameter is optimized to ensure the best ratio between the torque transmitted and rigidity at the rack. The bearing arrangement consists of two tapered roller bearings, preloaded and oversized. This bearing arrangement is designed to support the pinion as close as possible to the force applied, with only the thickness of the locknut separating the pinion from the output bearing. In particular, this design provides a considerable reduction in radial deflection. DualDRIVE can increase the natural frequencies on the axes of machines with high dynamic capacity, and hence meet the most crucial requirements of machine manufacturers. Mechanical preload allows use of just one motor to power both reducers. The mechanical preload is obtained by applying torsion into the system to lock the two pinions against the rack in a mechanical closed loop. To do so, each reducer is supplied with an input right angle drive and the preload is mechanically applied (torsion bar principle) using a torque wrench. This solution simplifies the electrical control system because it does away with the necessity of electrical control of the opposing torque between the two output pinions (the torque is absorbed by the mechanical preload) or through electrical preload. Another option offers a design specifically adapted to suit preload systems based on electrical control. This solution provides an alternative for machine designers who prefer to centralize all the motion controls. The electrical preload system consists of using a separate servomotor to drive each reducer, providing opposing torques between the two output pinions (taking up backlash) and a resultant torque that drives the system as a whole. This solution provides increased flexibility of assembly. The servomotors can thus be fitted on in-line flanges, or set at 90° using high-quality right angle gearboxes. Applications include those in the machine tool industry(gantry and column milling machines, multi-task machines, high capacity lathes, etc.), as well as robotics, and any machine requiring precise dynamic movement of heavy loads over long distances (laser cutting, high speed punching, winding, composite coating).