Characteristic study of multiple air beam approach for in-process measurement with coolant condition

• Published in: Journal of manufacturing processes 2024-09, Vol.126, p.487-500
• Main Author: Li, Ruipeng
• Format: Article
• Language: English
• Subjects: Applicator; Bubble generation; In-process optical measurement; Opaque coolant barrier
• ISSN: 1526-6125
• DOI: 10.1016/j.jmapro.2024.07.123

The optical in-process measurement is especially important for machining error compensation, to improve machining quality and increase machining efficiency. However, coolant would cover the workpiece surface and block the optical measurement beam. Several coolant displacing approaches could help to solve the coolant opaque layer problem and the multiple air beam approach is the most practical one. However, the characteristics of multiple air beam remains unknown. This paper aims to assess the performance of multiple air beam approach and study its characteristics. A silicon wafer and an aluminum free form workpiece were measured by a Wyko NT3300 interferometry profiler for reference, and then measured by the developed measurement system without and with coolant condition for comparison. The experimental results show that when the step height is about 110 μm and the coolant thickness was Tc = 5 mm, the measurement error induced by the multiple air beam approach is ΔeIw∈ [0.006, 0.348] μm, while for the free form workpiece with PV value of 130 μm, the point-by-point measurement error induced by multiple air beam approach is ΔeIa = 1.431 μm and the relative measurement error is 1.1 %. The relations between measurement condition and measurement error are also studied and analyzed. The multiple air beam approach could displace coolant of Tc = 15 mm with air flow rate of Qa = 6 L/min, and the induced measurement error is ep = 0.092 μm. It is noted that the vibration induced by multiple air beam approach would influence the measurement results. Enhancing the robustness of measurement system would help to reduce measurement error, from 0.092 μm to 0.057 μm. The multiple air beam approach could be used for optical in-process measurement with coolant condition, and carefully selected measurement parameters would decrease the induced measurement error.