Making precision robotics a reality

The Consumer Electronics Show (CES) often highlights consumer trends towards robotics and this year, the spotlight remained on robot personal assistants. Inspired by the show, Chris Johnson, managing director of precision bearings provider SMB Bearings, explains what design engineers, as well as end users specifying a robot, should know about thin section bearings.

Visitors to last year’s CES year met Lynx, a humanoid robot powered by Amazon’s Alexa, and the Ewaybot MoRo, designed to help you around the house. The idea of personal robots assisting with the housework seems great, but we’re a long way away from this technology being effective and affordable enough to see any uptake on a large scale.
 
Nevertheless, the precision and accuracy required by consumer robots has become possible thanks to the research and development conducted in industrial automation, particularly in the last decade.
 
From production and packaging to surgical environments, robots are performing increasingly complex and precise tasks, faster and more easily than ever before. In operating theatres, robots are now capable of performing complicated surgery with dramatically reduced impact on patients, improving recovery time.
 
On the factory floor, collaborative robots and automatic guided vehicles are breaking out of the cages that have traditionally confined automation and are beginning to be used in the open alongside people. For example, Sapporo Precision is now 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 greatly reduced risk of injury. 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 Bearing’s 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, where both footprint and weight are premium items.
 
However, because they are so thin, one has to pay particular attention to the roundness of the ring itself. If we 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, complimented 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.
 
For example, the EZO range of thin section bearings is produced to such a high standard that every single 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.
 
You should choose a low torque, free turning and low noise grease. An overly stiff grease won’t deliver the best results as it could increase bearing torque to unacceptable levels for a thin-section bearing.
 
A grease with a wide temperature range, perhaps -40 degrees centigrade to +150 degrees centigrade would be most suitable. This allows for the variety of applications in which a robot is most likely to be used, from refrigeration to locations near a furnace. It’s also important to select a food grade grease if the robot is going to be used in food or beverage production or packaging.
 
The right grease choice 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.
 
So, while humanoid robots may not be cleaning our homes any time soon, it does seem likely that their impact on industry will continue to increase apace. The technology presented at CES, which clearly draws on developments from industry, acts as robust evidence for the continued march of the robots.