ME 250Nov 15, 2007MachiningMachiningA broad term that refers to the removal of material from a workpiece. Three categories ¾Metal cutting using single/multi point cutting tools¾Abrasive processes e.g., grinding¾Non-traditional processes that utilize methods such as chemical, electrical, hydrodynamic, etc.Metal cuttingA material removal process in which a sharp cutting tool is used to mechanically cut away material so that the desired part geometry remains– Most common application: to shape metal parts– Most versatile of all manufacturing processes in its capability to produce a diversity of part geometries and geometric features with high precision and accuracyNoteCasting and forging can also produce a variety of shapes, but they lack the precision and accuracy of machiningService life Æreplacement partsReplacement Æinterchangeable partsInterchangeability Ædimensional accuracyDimensional accuracy ÆmachiningMachined surfaces on drawingsa) Rotational – axis symmetricb) Non-rotational –Prismatic (mostly flat surfaces)–Free form (spline surfaces)Classification of Machined Parts
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Free form surfacesDie surfaces are free form / complexMachining Operations and Part GeometryEach machining operation produces a characteristic part geometry due to two factors:1.Relative motions between tool and workpiece•Generating– part geometry determined by feed trajectory of cutting tool2. Shape of the cutting tool•Forming– part geometry is created by the shape of the cutting tool(a) straight turning, (b) taper turning, (c) contour turning, (d) plain milling, (e) profile milling.1. Motion generating shape(a) form turning, (b) drilling, and (c) broaching2. Tool (form) generating shapeShape by tool geometry + motionProducing Round Shapes• Turning• Drilling• Boring • Reaming• Tapping