Effects of Lattice Parameters in Material-Extruded PLA Crank Arms on the Kinematics and Bearing Vibrations of an Inverted Slider-Crank Mechanism

This study investigates the kinematic and vibration performance of an inverted slider-crank mechanism incorporating poly(lactic acid) (PLA) lattice crank arms fabricated by material extrusion (MEX). Gyroid, Schwarz-D, X, and 2.5X topologies with 5 and 10 mm cell sizes and nominal infill densities of 25%, 50%, and 75% were compared with aluminum and fully solid PLA reference crank arms. All 25% specimens failed before steady-state operation; comparisons therefore covered 16 configurations at 50% and 75%. Output-link angular acceleration, slider relative linear acceleration, and vibration levels at bearings A0 and B0 were measured. A rigid-body dynamic model solved using the fourth-order Runge–Kutta method provided a theoretical baseline. Increasing nominal infill from 50% to 75% reduced the average angular and linear acceleration root mean square error (RMSE) relative to aluminum by 66.2% and 76.0%, respectively; average bearing vibration reductions were 28.6% and 29.6%. Cell size showed no systematic trend. At 75% nominal infill, X and 2.5X crank arms combined low kinematic deviations and bearing vibration levels with approximately 55% lower mass than aluminum. These findings identify promising PLA lattice configurations for lightweight moving components under the investigated manufacturing and operating conditions.