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Turning and Chip-breaking Technology Part 4

Tham khảo tài liệu 'turning and chip-breaking technology part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Turning and Chip-breaking Technology 63 a Profiling - a spherical component with a large nose-radiused turning insert having an efficient chip-breaking action. NB Cutting forces continuously vary as the contoured profile is cut. b A large tool nose radius may generate a machined surface R which can deviate A from the theoretical T . Ci Tool wear A creates dimensional deviation which is also affected by the size of the nose radius rt . Cii Flank wear creates a changed cutting edge position A this results in some dimensional deviation A and frequently deteriorated surface finish on the workpiece diameter. Figure 31. The cutting insert s tool nose radius when either profiling or general turning will modify both the profile and diameter as flank wear occurs. Courtesy of Sandvik Coromant 64 Chapter 2 ously as the insert progresses i.e circular interpolates with the X- and Z-axes of the machine tool around the curved profile. If the geometry of the tool was not itself of round geometry then the point-contact could not be maintained leading to significant variations in chip formation. If this lack of tool-work contact were not to occur then the machined profile would be compromised and due to insufficient chip control the actual cut surface profile would not have a consistent and accurate surface texture. The machined surface texture generated by the passage of the cutting insert s geometry is to a large extent the product of the relationship between the nose radius and the feedrate and to a lesser degree the cutting speed and its tool wear pattern. The size of the tool nose radius will have quite an effect on the surface texture produced if the feedrate is set then a small nose radius will create a different workpiece surface texture to that of a larger one see Fig. 31b . Moreover if a large nose radius is selected for a lighter DOC or if the feed is equal to the nose radius then this larger nose geometry will be superior to that of a smaller tool nose radius. This is .