Empirical Study for 3D-Printed Robot Design: Dimensional Accuracy of a Hole and Proposal of a New Shaft-Fastening Method

3D printing is currently being studied in many fields and is expected to be applied in the industry. However, previous studies have been based on simple evaluation models, and there have been few studies in which 3D printing technology has been evaluated after being implemented in a system. In this study, first, the existing metal robot arm was duplicated by 3D printing, and the advantages and drawbacks of implementing 3D printing were evaluated. Then, prototyping revealed that dimensional accuracy and shaft-fastening torque are significant drawbacks. Therefore we proposed and evaluated methods to address the two drawbacks of dimensional accuracy and a decrease in the shaft-fastening force of press-fitting. As for the dimensional accuracy, the tendency of the dimensional accuracy was investigated quantitatively by manufacturing several samples of the hole shape and measuring the dimensional accuracy. To address the decrease in the shaft-fastening torque of press-fitting, a new shaft fastening method using hexagonal metal parts and a hexagonal 3D printed hole was proposed. It was experimentally verified that the proposed mechanism could achieve sufficient torque capacity.