【文章內(nèi)容簡(jiǎn)介】 ied performance of the tool.2) The part c) is made from normal medium carbon steel, 5 pieces are required。 the part d) is made from wrought aluminum, 10,000 are required. Please choose suitable process methods to machine the part, and arrange the process routing for it. a) b) c) d)Fig. 31) a) It is a turning tool (left offset tool). The tool shank is made from medium carbon steel and there is a rhombic carbide insert clamped on the shank by a clamp screw. The insert is indexable and has four cutting edges, when one of its edge bees dull, another sharp edge can be indexed to use. The tool has a positive working rake angle and clearance angle, and a sharp corner, it can be used for external cylindrical or taper surface turning or facing. The tool has a 90176。cutting edge angle, so it can be used to turn 90176。stage surface. The tool is suitable to cutting cast irons or steels at higher cutting speeds and larger back engagements of the cutting edges, but had better to avoid cutting discontinuously。 it is suitable for dry cutting or turning with cutting fluids, but should avoid cooling discontinuously. Because carbide insert is hard and brittle, special attention should be given to proper mounting and using the tool in order to prevent from impact and vibrating as well heat stress.b) It is an end milling cutter and made from HSS. It has a solid structure and flat end, four helical cutting edges. It can be holden by a collet or special chuck, cut workpiece with its circumferential cutting edges. It can be used to mill plane, side surface and curved surface as well slot, but is not suitable to feed in axial direction. It is suitable to cutting nonferrous alloys, also ferrous alloys such as cast irons and mild or medium carbon steels. Because its hot hardness is low relatively, it is suitable to cut at lower cutting speeds and needs cooling continuously. However, it possesses good impact toughness, so, it can be used to cut discontinuously. 2) c) The part has a stepped cylindrical shape, so it can be produced by turning. Only 5 pieces are needed, we can choose an energy lathe to make it with Ptype carbide insert or a HSS solid tool, and choose a rolled stock as the blank. Because the part has a severe shape and position tolerance, so the left end face and cylindrical surface should be pleted in one setup of the part. The through hole has a higher finish requirement, after drilling a finish turning is needed. In addition, screw threading and chamfer are needed. Machining routing: Sawing the blank (longer than 5 times of the part)——holding the blank with a three chuck in lathe, let the overhang be little longer than the final length of the part——facing one end——roughturning external surfaces——medium finishturning theФ50 external cylindrical surface to the dimension for threading M50——finish turning the Ф44 segment to dimension accuracy and the step face with a left offset tool——coring——drilling the through hole——internal turning the hole——chamfering——grooving in theФ50 external surface——screw threading——parting——turning around the workpiece and chamfering another end.d) The part is made from wrought aluminum alloy, a quantity of 10,000 pieces and a roughness of Ra is required, so some economic processes such as extrusion should be used to produce the blank and a semifinishmachining, finishmachining process should be applied. The through hole should be performed in the blank, then, the final dimension including the keyway may be broached optimally. There is no finish requirement for its external cylindrical surface and side surfaces, so these surfaces do not need to be machined. The three end faces marked can be are produced with end milling cuter (the left end face and right cylindrical end face also can be produced with face milling). In order to obtain a high machining efficiency, a special fixture should be designed for fixing the workpiece on milling machine.Machining routing: fixing the workpiece on a vertical milling machine, milling the left end face——turning around the workpiece, milling the right plane and cylindrical end face——mounting the workpiece on a broaching machine, broaching the through hole and the keyway.5 Comprehension and discussion (10 marks)As you can appreciate, the cost of machining centers is considerably higher than more traditional machine tools. In view of the fact that many operations performed by these centers can also be done on conventional machines, how would you go about justifying the high cost of these centers? Do you think under what condition we should purchase a precise and expensive machining center, and when we should use an economic machining center, even traditional machine tools only?Answer outline: Machinine efficiencyMachining accuracy and roughnessAutomationMultiple functionsMachining time, labor, workshop area《Manufacturing Engineering and Technology—Machining》Test Paper(20050614)Name: Student No: Score:1. Drawing and marking (Close Test. 15 markings) Fig 1a) shows a turning tool. Please mark its major cutting edge and minor cutting edge, rake face and major flank, cutting edge angle, rake angle and clearance angle. ( markings) Give the process method name, mark the main motion and feed motion(s) for each illustration in Fig 2. ( markings) There is a poor design consideration for each of the following workpieces, mark it and give your correction (5 markings).(a) to be threaded (b) to be shaped (c) gear to be generated (d) to be drilled (e) cavity to be milled (by end milling cutter)2. Judging. Mark √ for true and for false. (Close Test. 30 markings, 2 markings for each) It is always advisable to increase cutting speed in order to increase production rate. () L