Drives & Controls March 2023

38 n BELTS, BEARINGS AND CHAINS March 2023 www.drivesncontrols.com Better robots need thinner bearings I ndustrial robots and automation have a proven ability to cut costs, boost productivity and deliver greater efficiency and competitiveness. Every year, robots are becoming more collaborative with humans and capable of delivering the same functions in smaller footprints. Robots have typically been used for monotonous handling and assembly tasks. However, it’s predicted that software and firmware platforms, and robots connected to them, will become more integrated in manufacturers’ERP (enterprise resource planning) and MES (manufacturing execution systems). Robots are becoming smaller, faster and are performing more complex and precision tasks, from production and packaging to surgical environments, as well as large-scale applications in warehouses. Whatever the application, the improving speed, manoeuvrability and precision of robots relies on precision bearings. Hybrid chrome and steel bearings, ceramic bearings and slewing bearings are all widely used in robots. Then there are thin-section bearings, which are allowing robots to perform tasks with increasing precision and accuracy. But what are they? As the name suggests, thin-section bearings are very thin and compact, available in a limited number of widths and thicknesses. They are designed to withstand radial loads as well as moderate thrust loads in both directions, and to offer high accuracy in a low- profile design. SMB, for example, supplies thin-section ball bearings as either open, shielded or sealed in SAE52100 chrome steel or 440 grade stainless steel. Thin-section bearings have cross-sections that don’t change as their bore sizes increase. There is very little difference in size between the internal and external ring, so there is no change in the space requirements. These bearings can contribute to downsizing, weight saving and reducing torque losses in robots. However, the thinness of the bearings also presents design challenges. For instance, if you spin the inner ring of a thin-section bearing without any lubricant, and then squeeze the outer ring lightly between your finger and thumb, the inner ring will stop spinning. This demonstrates the incredible flex in these devices. If the rings are not perfectly formed, even a tiny discrepancy will stop the bearing running smoothly, generating heat and noise, and increasing the risk of bearing failures. As a result, the manufacturing process has to be extremely precise to ensure the highest degree of roundness in both rings, as well as low noise levels. One area where thin-section bearings are being applied is in medical robots that can perform complicated surgery with a dramatically reduced impact on patients, improving their recovery times. They are also used in robotic exoskeletons that allow warehouse workers to lift heavy weights, and social care workers to lift people with reduced risk of injury. The UK’s Shadow Robot Company (SRC) designs and manufactures anthropomorphic robot hands to perform nimble tasks in areas such as scientific research. The company also makes a smart grasping system for industrial applications. Designed to be robust and reliable, the system uses AI to help it pick up many types of object, reducing the need for human hands in a factory. Torque sensing ensures that the robot hands can grasp almost any object accurately and reliably. The system relies on bearings with tight tolerances in dimensional accuracy. SRC approached SMB Bearings, which recommended its EZO thin precision bearings. Importantly, these bearings are manufactured to a consistent shape and size because any inconsistences could affect the accuracy of the joint positions, and thus the robot’s behaviour. Tests by the Shadow Robot Company determined the correct friction coefficient and its corresponding grease fill, needed to optimise performance. The thin-section bearings gave the right levels of quality, tolerance and consistency. These properties ensure that friction in the bearing is predictable – essential for controlling the robot’s movements accurately. SRC expects the easy-to-install bearings to outlive most other parts of its grasping system. Smart technologies and Industry 4.0 are high on the agenda for every manufacturer and supply chain manager. While many people may not regard bearings as a smart technology, they are nevertheless critical components that are essential to the optimal performance of many automation technologies, especially robots. n Thin-section bearings are a specialised type of bearing with particular characteristics. Chris Johnson, managing director of SMB Bearings, explains why they are vital to achieving the full potential of compact, speedy, precision robots. Thin-section bearings can help robot equipment such as grippers to achieve high levels of performance and consistency.