Gantry type Lapping Manipulator toward Unmanned Lapping Process for a Large Work Surface
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Gantry type Lapping Manipulator toward Unmanned Lapping Process for a Large Work Surface Sangki Park1 · Daegwon Koh1 · Jaeyoon Shim1 · Jong‑Jae Kim1 · Sun‑Kyu Lee1 Received: 12 February 2020 / Revised: 9 July 2020 / Accepted: 14 September 2020 © Korean Society for Precision Engineering 2020
Abstract This paper presents a developed manipulator and control method for automatic lapping process applied to a large work surface. A lapping machine consists of a newly designed parallelogram-type 5-axis manipulator and a conventional 3-axis gantry machine. The gantry machine is utilized to precision positioning over a large work area, and the manipulator is controlled by a separate controller for lapping operation in the local surface area which is provided by the CNC controller of gantry machine. The lapping process is, as a first step, needed to remove milling tool marks without injuring original shape, and then to correct the shape error. Wheel compliance becomes different in accordance with the special purpose such as tool mark removal and shape correction. Both processes require high stiffness of the manipulator. In this study, newly designed joints are adopted to secure the stiffness of the joints in both normal and lateral directions. Deadweight of manipulator including wheel motor as well as feed-forward torque control are adopted to suppress the vibration caused by abruptly dynamic cutting force. It was confirmed that the lapping operation was successful in wiping the curved contour without the structural vibration, and that the feed-forward torque control produces twice higher machining efficiency as well as 30% higher surface quality in comparison with the existing compliance control method. The experiment investigated the effects of the abrasive wheel compliance and the dynamic cutting force. In results, the smooth surface was achieved within a satisfied quality level of less than Rz 0.5 μm. It is considered that the proposed manipulator has great potential to be applied in unmanned lapping systems for a large work surface. Keywords Lapping · Surface finishing · 5-axis manipulator · Robotic machining · Compliance
1 Introduction Surface finishing is a critical process for the final products of molds or 3D-printed parts. The finishing affects quality in terms of machining accuracy and surface roughness, and in special cases, this quality also affects the performance of products [1, 2]. To date, most surface finishing operations have been regarded as manned work, which requires a long process time and high cost. However, as the demand for high-quality large-sized molds and 3D printing products increases, the automation of surface finishing has attracted global attention [3–6]. At the same time, labor issues, such
* Sun‑Kyu Lee [email protected] 1
School of Mechanical Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi‑ro, Buk‑gu, Gwangju 61005, Republic of Korea
as the need to recruit highly skilled workers and the adv
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