tailieunhanh - Turning and Chip-breaking Technology Part 5

Tham khảo tài liệu 'turning and chip-breaking technology part 5', 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 73 wrap itself around either the tool or workpiece but such a geometry is perfect for machining aluminium or non-ferrous materials. Radial top rake illustrated in Fig. 4 middle and to the left - three grooving insert sizes illustrated . This radial top rake is designed to thin the chip. Such chip thinning eliminates the need to undertake finishing passes on the groove s side walls. Furthermore this type of grooving insert geometry being on-centre enables axial turning of diameters for wide shallow grooves33 or recesses. Raised bumps on top rake see Fig. 27a - left . This sophisticated grooving geometry is utilised for materials where chip control is difficult as it provides an aggressive barrier to the curling chip. The raised bumps force the chip back onto itself either producing a tightly curled watch-spring chip or causes the chip to break. ii Surface speed of the workpiece - in order to obtain full advantage of a grooving insert s chip-forming abilities the chip must be allowed to flow into the chip-former. This chip-flow can be achieved by either decreasing the workpiece s surface speed or increasing the feed - more will be said on this shortly. The former technique of decreasing the surface speed allows the material to move slower across the top rake of the cutting edge and as a result has greater contact time to engage the chip-former. This slower workpiece speed has the benefit of increasing tool life through lower 33 A groove or recess can normally be considered as a straightwalled recessed feature in a workpiece as illustrated in Fig. 40. Typical applications for grooves are to provide thread relief - usually up to a shoulder - so that a mating nut and its washer can be accurately seated or for retaining O-rings. As the groove is produced in the workpiece the tool shears away the material in a radial manner via X-axis tool motion. The chip formed with insert geometries having a flat top rake will have an identical .