Thin section bearings are being specified for the latest generation of robots. Chris Johnson, managing director of SMB Bearings, examines what design engineers, as well as end users specifying a robot, should know about these bearings.
Robots are performing increasingly complex and precise tasks, faster and more easily than ever before, in industries ranging from production and packaging to surgical environments. In operating theatres, robots can perform complicated surgery; and on the factory floor, collaborative robots and automatic guided vehicles are starting to be used in the open alongside people. In an alternative environment, visitors to CES this year met Lynx, a humanoid robot powered by Amazon’s Alexa, and the Ewaybot MoRo, designed to help out around the house.
Sapporo Precision, however, is supplying EZO bearings to manufacturers of a newer branch of robotics. Robotic exoskeletons are enabling warehouse workers to lift heavier weights and social care workers to lift people with a greatly reduced risk of injury. And, in the food industry, robots are now being used in production environments, as well as packaging and palletising, something that represents genuine evolution in the sector.
These developments have been made possible by advancements in motor, bearing, actuator and sensor technology, as well as software and communications. Hybrid chrome and steel bearings, ceramic bearings and slewing bearings are all common in robot applications, but thin section bearings are the option most commonly chosen by SMB Bearings’ customers.
Thin section bearings deliver higher speed, improved efficiency, and high levels of accuracy, as well as reduced friction and impressive design flexibility. Because there is very little difference in size between the internal and external ring, they also reduce the weight and bulk of an application, making them an ideal choice for robotics.
Because they are so thin, however, you have to pay particular attention to the roundness of the ring itself. If you take a thin section bearing without any lubricant and spin the inner ring, a light squeeze of the outer ring between finger and thumb will stop the bearing in its tracks, thanks to the incredible flex in the device.
As a result, the manufacturing process has to be extremely precise to ensure the highest possible degree of roundness in both rings, as well as good noise levels in the bearing itself. This will normally call for fine grinding and machining, complemented by a very high level of quality in both the process and the raw materials. If the rings are not perfectly formed, even a minute discrepancy will stop the bearing running as smoothly, producing excess noise.
The EZO range of thin section bearings is produced to such a high standard that every item that comes off the production line is individually tested – any tiny deficiency and it is rejected. These thin-section ball bearings can be supplied open, shielded or sealed in SAE52100 chrome steel or 440 grade stainless steel, and are designed to withstand radial loads as well as moderate thrust loads in both directions. Some of the smaller thin-section bearing sizes are available with a fibreglass reinforced nylon high speed synthetic retainer.
Selecting the right grease will result in a free running bearing which, in turn, will reduce the power consumption of the machine itself, as well as the long-term maintenance costs. It is also one of the factors that can contribute to the overall speed of the robot arm.
A low torque, free turning and low noise grease should be chosen, such as those used as standard in the EZO bearings re-sold in the UK by SMB Bearings. A grease with a wide temperature range, perhaps -40 to +150°C, would be most suitable, and allows for the variety of applications in which a robot is most likely to be used – from refrigeration to locations near a furnace. A food grade grease would need to be selected if the robot is going to be used in food or beverage production or packaging.
T: 01993 842555