Cutting surface quality analysis in micro ball end-milling of KDP crystal considering size effect and minimum undeformed chip thickness |
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| Affiliation: | 1. State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China;2. Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001, China;1. Institute of Production Engineering and Machine Tools, Leibniz Universität Hannover, 30171 Hannover, Germany;2. University of Bremen, Center for Industrial Mathematics, 28359 Bremen, Germany;1. Faculty of Mechanical Engineering and Management, Poznan University of Technology, 3 Piotrowo street, 60-965 Poznan, Poland;2. Faculty of Mechanical Engineering, University of Zielona Gora, 4 Prof. Z. Szafrana street, 65-516 Zielona Gora, Poland;3. Faculty of Mechanical Engineering, Opole University of Technology, 76 Proszkowska street, 45-758 Opole, Poland;1. School of Mechanical and Systems Engineering, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK;2. School of Electrical and Electronic Engineering, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK |
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| Abstract: | Potassium dihydrogen phosphate (KH2PO4 or KDP) crystal is a typical soft-brittle optical crystal, and the size effect and brittle cutting mode are easy to appear in micro ball end-milling of KDP crystal. In this paper, micro-grooving experiments are conducted to study the size effect and brittle cutting in micro ball end-milling of KDP crystal with different feed rate and depth of cut. The cutting force, machined groove base quality and chip morphology are collected and analyzed carefully. The size effect is discovered by the phenomena of the existence of oscillations and relaxations in cutting force and hyper-proportional increase of specific cutting force, when the ratio of feed per tooth to cutting edge radius ft/re is less than 1. While the brittle cutting mode is detected through the existence of sharp fluctuations in cutting force and cracks on the groove base when the ratio ft/re is larger than 2. From the further comprehensive analysis of cutting force, specific cutting force, machined groove base quality and chip morphology, the cutting parameters with ratios of the maximum undeformed chip thickness in one cutting circle to cutting edge radius hmax/re around 0.14, 0.2 and 0.4 are regarded as size effect, optimal and brittle cutting points, respectively. The size effect, ductile cutting and brittle cutting zones are divided by the size effect and brittle cutting boundaries (points). Among the optimal points, the depth of cut of 2 μm with the ratio ft/re of 1 is the optimal cutting parameter for micro ball end-milling of KDP crystal. |
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| Keywords: | Cutting surface quality Size effect Micro ball end-milling Undeformed chip thickness Brittle cutting boundary |
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