Đang chuẩn bị liên kết để tải về tài liệu:
Machinability and Surface Integrity Part 6

Tham khảo tài liệu 'machinability and surface integrity part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Machinability and Surface Integrity 319 Rth OT - OU r - r2 - f 4ỴA . Rth t2 8r Case I When medium values of the turned feedrate are utilised - as is the situation in Case II Fig. 166a then both the tool nose r and the partial effect of the End-cutting angle Ce must be considered when estimating the deeper Rth value. Assuming that t is equal to JL Fig. 166a and b then the following geometrical conditions are met t JK HE NL Fig. 166a . t r2 - r - Rth T r sinCe r Rth r - 1 cosCe cotCe Case II NB This equation is valid just as long as the t length lies between positions SE and FR . If even larger values of t are utilised i.e. higher feedrates then the three geometrically curved and linear portion s of the cutting insert s profile will affect resultant turned surface topography. Namely this surface topography after machining will now be comprised of the sum of the portions of the end-cutting angle Ce nose radius r together with the side-cutting angle Cs as follows Rth AB - AG r Figs 166a and b D _ tr cos i5-Cc 2-Cs 2 r C.asp III Dth tan Cs cot Ce sin 45-Ce 2 Cs 2 r se The equations given in Cases I II and III can be utilised to produce a non-dimensional graphical plot for various cutting insert approach angles i.e. see Shaw 1984 - p 513 enabling the estimated value of Rth to be found - for any combination of t r Ce plus Cs . Historically it has been well-known that there exists a minimum undeformed chip thickness 57 and if a value is smaller than this actual chip-thickness it is not possible to form a successful chip as a result only rubbing will occur - this being a combination of many interrelated factors. Applying this minimum undeformed chip thickness concept to the insert s secondary cutting edge it was found that a small triangular portion of workpiece material which should have been removed is normally left in-situ Fig. 167 . This fraction of the workpiece left behind has been the subject of intensive interest by previous machinability researchers