Engineering Considerations for Greases Used in Robotic Applications Michael D. Holloway, 5th Order Industry, LLC Highland Village, TX 75077 | 214-450-7864, holloway@5thOi.com Adam M. Smothers , Aerospace Lubricants, Inc. Columbus, OH 43228 | 614-620-5823, adam@aerospacelubricants.com Rich Wurzbach , MRG Laboratories York, PA 17401| 717-843-8884 rwurzbach@mrgcorp.com
Multi-axis robotics are a relatively new application in the world of manufacturing assembly lines. Often when a piece of equipment is brought on line, its lubrication requirements are not readily understood until failure occurs and reliability data are established. Guess work combined with fundamental concepts are used until the overall reliability entitlement and product performance criteria are established. This paper describes the logic of how a grease is selected and then maintained to meet the challenges of robotic applications. The information in this paper will help end users select and maintain lubricants for their robotic devices and avoid failure. Industrial Robotics The use of robotics and automation continues to grow more prevalent across industries, particularly in manufacturing, as companies are realizing the full potential of its ability to reduce costs, boost production, and deliver greater efficiency and competitiveness. Typical industrial robotic applications include welding, painting, assembly, product inspection, and testing. As the technology has progressed, automation has demonstrated exponential improvements in endurance, speed, and precision, and more sensitive applications in medical and other high-tech sectors are becoming common. With highly choreographed, programmed movement on two or more axes, bearings play a major role in the motion control aspect of this technology. The use of high-precision bearings is an integral consideration for those tasked with designing and maintaining these applications. Bearing life and performance demand that the correct type, material, and lubrication are specified. The advantages of robots are precision, speed, and strength. These demands challenge the bearings and, ultimately, their lubricants. Industrial robots provide precise motion in multiple dimensions, from single axis to multi-axis applications. The arm connections of a robot determine the number of axes. For example, an arm with a 2-axis configuration travels in an x-y plane in a Cartesian coordinate system (Fig. 1). The device on the end of a robot’s arm, sometimes referred to as an ‘end effector’, performs work. Robots with 2-D configurations are commonly used with end effectors that pick and place parts, dispense a fluid such as ink or adhesive, insert screws or rivets, and perform inspections. Devices that insert screws or rivets or perform inspections can be fitted to robot arms with 2-axis configurations. Often, the arms are controlled by motor-driven rack-and-pinion gears, chains and sprockets, or guide wheels with wires or bands. There have been advances in hydraulic and pneumatic applications for 2-axis configurations. Robotic arms with 3-axis configurations (Fig. 2) are utilized in applications that require fast and intricate movements. An arm with a 3+axis configuration (Fig. 3) can work in 3 dimensions. In multi- 10 NLGI Spokesman | VOLUME 85, NUMBER 2 | May/June 2021
