畢業(yè)設(shè)計(jì)-數(shù)控銑削編程與加工設(shè)計(jì)-在線瀏覽
2024-08-01 03:48本頁面
【正文】 machining processing that is carried out by means of a multi edge rotating tool known as a milling cutter. In this process, metal removal is achieved through bining the rotary tool motion of the milling cutter and linear motion of the work piece simultaneous. Milling operations are employed in producing flat, contoured and helical surfaces as well as for thread and gear cutting operations. Each of the cutting edges of a milling cutter acts as an individual single point cutter when it engages with the work piece metal. Therefore, each of those cutting edges has appropriate rake and relief angles. Since only a few of the cutting edges are engaged with the work piece at a time, heavy cuts can be taken without adversely affecting the tool life. In fact, the permissible cutting speeds and feeds for milling are three to four times higher than those for turning or drilling. Moreover, the quality of the surfaces machined by milling is generally superior to the quality of surfaces machined by turning, shaping, or drilling. A wide variety of milling cutters is available in industry. This, together with the face that a milling machine is a very versatile machine tool, makes the milling machine the backbone of a machining workshop. As far as the direction of cutter rotation and work piece fed are concerned, milling is performed by either of the following two methods. Up milling (conventional milling).In up milling the work piece is fed against the direction of cutter rotation. The depth of cut gradually increases on the successively engaged cutting edges. Therefore, the machining process involves no impact loading, thus ensuring smoother operation of the machine tool and the longer tool life. The quality of the machined surface obtained by up milling is not very high. Nevertheless, up milling is monly used in industry, especially for rough cuts. Down milling (climb milling). In down milling the cutter rotation coincides with the direction of feed at the contact point between the tool and the work piece. The maximum depth of cut is achieved directly as the cutter engages with the work piece. This results in a kind of impact, or sudden loading. Therefore, this method cannot be used unless the milling machine is equipped with a backlash eliminator on the feed screw. The advantages of this method include higher quality of the machined surface and easier clamping of work piece, since the cutting forces act downward. Milling machine There are several types of milling machines employed in industry. They are generally classified based on their construction and design feature. They vary from the mon general purpose types to duplicators and machining centers that involve a tool magazine and are capable of carrying out many machining operations with a single w
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