Rotary indexing tables have been a mainstay of automation systems for decades. They are simple, precise, reliable and durable. They can output a lot of product in a relatively small footprint with a minimal number of parts fixtures. A rotary indexing table consists of circular steel plate and a drive for turning it. Parts rest in nests spaced equally along the table’s circumference. Self-contained machines and tooling for specific tasks are arrayed around the perimeter. As the table rotates, it stops intermittently to “dwell” for a fixed period of time, so that an operation can be performed at each station. Rotary indexing tables work well with machines that perform simple, fast, vertical operations, such as presses, screwdrivers, riveters, dispensers, pad printers, SCARA robots, pick-and-place units, and ultrasonic welders. Parts can be loaded and unloaded manually or automatically.
Considering All Options
There are many options for driving a rotary indexing table. Options include pneumatic cylinders, belts, cams, worm gears, direct-drive systems, and the newest precision ring drive system technology. Pneumatic tables are best-suited for small loads, slow speeds and low production volumes. Belt-driven rotary tables offer the advantages of high speed and low cost, however due to the potential for elongation of the belt, positioning accuracy of belt drives is often inferior to other technologies. They also have limited load capacity, limited rigidity and relatively poor life in general. Low maintenance and superior life are among the biggest benefits of cam-driven indexers, but you cannot overlook their inflexibility. If additional indexing positions are needed the cam must be changes, which can be a significant expense. Worm gear systems have speed limitations and periodic backlash adjustment may be required based on use and accuracy requirements. Worm gear systems are less efficient than other drive systems. When considering direct-drive systems keep in mind that the output torque is typically low, the expense is high, and they generate a lot of heat so a cooling system may be required.
Ring Drive Systems
Nexen’s Ring Drive System is based on the innovative Roller Pinion System (RPS) for linear motion. Ring Drives come complete with a precision-grade, high-capacity bearing and drive mechanism in a rigid housing. with options for high speed, high torque, and zero backlash, Ring Drives can be optimized for any application. Ring Drives provide more productivity while boasting low maintenance, high efficiency and long life.
The RPS is a patented linear drive concept that combines the best attributes of existing technologies while eliminating most of their shortcomings. Instead of the sliding friction of traditional rack-and-pinion system,s the rollers provide smooth rolling friction that converts rotary motion to linear motion with 99 percent efficiency.
Download the Ring Drive Systems whitepaper from Nexen to learn how CBT and Nexen can help you select the optimal equipment for your application.
