Drives & Controls Magazine May 2023

n LINEAR MOTION The more load-bearing balls in the load zone, the greater the load handling and durability. Deploying two ball tracks in a conforming floating track, for example, can increase the load capacity six times and bearing life 216 times over precision bearings. This configuration is also optimal for rails 12–38mm in diameter and with dynamic loads up to 5.3kNm. When high load-handling, speed and precision are priorities, a self-aligning bearing can maintain a low coefficient of friction while maximising bearing lives. Some manufacturers accomplish this by designing the bearing plate so that the radius of its outer surface is smaller than that of the inside radius of the hardened precision ring. This allows the bearing plate to roll against the ring, distributing the load evenly on each of its two ball tracks. The bearing designs also allow the bearing plates to rock 0.5 degrees about the hardened precision ring to ensure smooth ball entry and exit in the load-carrying zone, and optimum ball loading from end to end. This self-aligning structure compensates for torsional misalignments that might result from inaccuracies in base machining or machine deflection, with little increase in stress to the components. Once a self-aligning bearing is mounted in an adjustable housing, designers can achieve a selected preload. The design allows the bearing plates to move radially, which helps to achieve close bearing/linear race fit-ups for precision applications. Furthermore, although ball bearings are not necessarily as environmentally-resistant as polymer plain bearings, actions can be taken to protect their high load handling and durability in corrosive environments. These include specifying stainless steel, nylon or nylon-coated rolling elements. If applications requiring low cost, smooth and quiet operation, or reliable performance in corrosive environments, are more critical to your operation than high load-handling, precision or speed, you should consider plain bearings. If your shaft requirements are incompatible with traditional ball-bearing materials, you should consider polymer materials. If durability and maintainability are most important to you, self-lubricating plain bearings would suit your needs best. Otherwise, you will need a ball bearing, in which price, precision and load handling will vary depending on the number of balls , whether the ball track is fixed or floating, or whether the assembly is self-aligning. n Thomson’s online LinearMotioneering sizing and selection tools can help to optimise bearing selection for round-rail applications. This table can help to choose the best type of linear bearing for an application. Small & precision brushed and brushless motors, stepper motors, frameless torque motors Stepper motor drives, intelligent & integrated stepper and servomotor drives - StepSERVOtm Integrated AC servo- and stepper motors - MAC motor® & ServoSteptm Robust incremental and absolute encoders for speed and posi琀onal feedback Harsh industrial, vacuum and UHV, cryogenic and space rated stepper motors and gearboxes Small & precision stepper, brushed and brushless motor applica琀ons Precision resolvers, AC and DC servomotors, high-precision sensors, IMUs and gyros High performance, mul琀-axis mo琀on control technology Planetary and spur gear units Slip ring assemblies Geared DC motors Vacuum and harsh industrial posi琀oning systems Applica琀on-speci昀c mo琀on control +44 (0) 1252 531444 Custom engineered mo琀on systems Servo motors & drives Stepper motors & drives Feedback devices Gearboxes Mo琀on controllers & so昀ware Mechanical components As a leading supplier of precision mo琀on control products for over 40 years, we have a commitment to technical excellence and customer service and adopt a partnership approach to business. We o昀er our customers a professional speci昀ca琀on and design & build service, backed up with quali昀ed and experienced technical sales and applica琀ons support sta昀. The Place For Precision Mo琀on Control Challenge Us To Provide You With A Complete Solu琀on