Comparative Study of the Geometric Accuracy of 3D-Printed Polyamide CF15 and Injection-Molded POM Spur Gears

The accuracy of gears is a determining factor for their functionality, reliability, and durability in various mechanical systems. Two widely used technologies for producing plastic gears are injection molding and 3D printing, each having its own advantages and limitations. Injection molding is a traditional method for mass production that offers high productivity but is sensitive to parameters such as temperature, pressure, and cooling, which can lead to shrinkage and dimensional instability. On the other hand, 3D printing is gaining popularity due to its flexibility, rapid prototyping capabilities, and the possibility of producing small series without the need for expensive tooling. In the present study, the accuracy of plastic gears with module 2 and module 3, manufactured using both technologies, was investigated and compared. Measurements were performed on three main parameters: span measurement, chordal tooth thickness, and measurement over pins. The obtained data were statistically analyzed and classified according to the DIN 3962/3963 and ISO 628 accuracy standards. 3D-printed gears demonstrated lower standard deviation (0.0079-0.0083 mm) and improved repeatability compared with injection-molded gears (0.0131-0.0189 mm), achieving DIN 10-14 accuracy classes. Unlike previous studies that compare different materials or technologies separately, this work directly compares both simultaneously under controlled conditions, revealing that material selection (CF-reinforced vs. unfilled POM) may influence dimensional outcomes as strongly as the manufacturing method. These findings provide practical guidance for selecting production routes for low-to-medium precision polymer gears under the tested conditions.