Functional Surfaces Roughness Analysis of 3D Printed PET-G Housings Used for Press-Fitting Steel Ball Bearings

The study examines the impact of mechanical loading on the surface integrity and retention performance of press-fit joints in polymer housings produced by additive manufacturing. Components were fabricated using a thermoplastic material and subjected to controlled assembly and disassembly processes of steel ball bearings. Surface roughness was measured before and after press-fitting to evaluate the effects of mechanical contact. Force–displacement curves were recorded during both insertion and extraction to quantify retention behavior. Three groups of samples were tested: unassembled reference parts, samples with one assembly cycle, and samples with two cycles. Results indicate a reduction in surface roughness and press-fit resistance with repeated cycles. The second insertion in samples exposed to two cycles resulted in a significant decrease in required force compared to the first. Similarly, surface roughness values decreased, suggesting plastic deformation and material wear. The findings confirm that repeated mechanical loading degrades surface texture and weakens the retention capacity of the joint. This study emphasizes the importance of accounting for material behavior under repeated stress in the design of interference-fit assemblies produced by additive manufacturing.