Cross-scan Error Evaluation of Large Size Polygon Mirror Based Laser Scanning System for Industrial 3D Printing

This paper analyses and evaluates the cross-scan error of a large-size polygon mirror-based laser scanning system for industrial stereolithography (SLA). The polygon mirror (PM) is often used for fast scanning applications due to its superior scanning speed and large scanning angle. However, PM-based laser scanning systems are prone to cross-scan errors, restricting scanning precision. The facet tilt and scanhead dynamics are considered as two primary sources contributing to cross-scan errors. The datum-to-shaft error by manufacturing imperfections is modeled as the main cause of the facet tilts in the investigated PM-based scanner. This datum-to-shaft error varies due to radius expansion by the PM at high-speed rotations, leading to a 10μm variation in the cross-scan error. The scanhead dynamics are measured by a vibrometer and characterized by non-deterministic vibrations and the deterministic periodic excitation. The total scanning precision of the large-size PM-based laser scanning system is approximately 160μm mainly due to the datum-to-shaft error, limiting the precision of the PM based industrial SLA printer without any compensation.