Ball joints are automotive products that perform reciprocating sliding motion of metal and resin components with grease lubrication between them. Understanding the effects of temperature on the characteristics of product components and their elements is necessary to design ball joints that are applicable to a wide range of temperatures. The viscosity of the grease base oil has the most effects of temperature. To investigate the applicability of PDMS base oil grease, which has a smaller viscosity dependence than the current PAO base oil grease, the lubrication properties of PDMS oil and PAO oil between resin (POM) and metal (chromium molybdenum steel) were studied by reciprocating sliding friction test. Seven PDMS oils with a wide range of viscosities were used in the experiments, assuming that the viscosity of the oil changes over the temperature range required for practical use. Lower viscosity PDMS showed an increase of contact areas in mixed lubrication mode but effect on the friction coefficient was small while higher viscosity PDMS caused lubrication starvation in the latter half of the test. These results indicate that there is an upper limit of viscosity where lubrication can be maintained.

In recent years, advances in Additive Manufacturing (AM) technology using 3D printers have been remarkable, and the manufacturing of lightweight parts using Generative Design (GD) is attracted attention. The implementation of these technologies in industrial robots used to automate manufacturing sites is being considered. The authors have been using aluminum alloy robot arm extensions manufactured by cutting for industrial robots to adjust the reach of the robot arm, but their large weight has been a problem. In industrial robots, weight reduction of various components is desired to improve work efficiency through high-speed operation and to reduce the motor load. In order to further reduce the weight, optimization design using GD was performed, and the results of manufacturing components by AM and mounting them on the robot were examined. As a result, a 77% weight reduction was achieved compared to conventional robot arm extension components, and the motor load and arm vibration during robot operation were reduced. GD was shown to be an effective method for designing lightweight components.