【正文】 床的運動。這意味著，一旦程序被驗證是正確的，可以很容易地加工出 2 個、 10 個或 1000 個相同的零件，而且它們的精度高，一致性好。這里是數(shù)控設(shè)備提供的比較重要的幾個優(yōu)點。t first centerdrill the hole. Find the problem first Many mechanics tear into things before they understand the problem, hoping that it will appear as they go. We know this from the fact that more than half of all warranty returned parts are in good working order. If the spindle doesn39。s petition is to sell products on the value of novelty. The average product life cycle on cars today is 4 years, puters and accessories years, hand phones 3 months... One of the prerequisites of this development of fast design changes and rapid product development time is the HSM technique. Complex products There is an increase of multifunctional surfaces on ponents, such as new design of turbine blades giving new and optimized functions and features. Earlier designs allowed polishing by hand or with robots (manipulators). Turbine blades with new, more sophisticated designs have to be finished via machining and preferably by HSM . There are also more and more examples of thin walled workpieces that have to be machined (medical equipment, electronics, products for defence, puter parts) Production equipment The strong development of cutting materials, holding tools, machine tools, controls 畢 業(yè)設(shè)計（外文翻譯 ） 8 and especially CAD/CAM features and equipment, has opened possibilities that must be met with new production methods and techniques5. Definition of HSM Salomon39。s justintime (JIT) product requirements. Motion control the heart of CNC The most basic function of any CNC machine is automatic, precise, and consistent motion control. Rather than applying pletely mechanical devices to cause motion as is required on most conventional machine tools, CNC machines allow motion control in a revolutionary manner2. All forms of CNC equipment have two or more directions of motion, called axes. These axes can be precisely and automatically positioned along their lengths of travel. The two most mon axis types are linear (driven along a straight path) 畢 業(yè)設(shè)計（外文翻譯 ） 2 and rotary (driven along a circular path). Instead of causing motion by turning cranks and handwheels as is required on conventional machine tools, CNC machines allow motions to be manded through programmed mands. Generally speaking, the motion type (rapid, linear, and circular), the axes to move, the amount of motion and the motion rate (feedrate) are programmable with almost all CNC machine tools. A CNC mand executed within the control tells the drive motor to rotate a precise number of times. The rotation of the drive motor in turn rotates the ball screw. And the ball screw drives the linear axis (slide). A feedback device (linear scale) on the slide allows the control to confirm that the manded number of rotations has taken place3. Refer to . Though a rather crude analogy, the same basic linear motion can be found on a mon table vise. As you rotate the vise crank, you rotate a lead screw that, in turn, drives the movable jaw on the vise. By parison, a linear axis on a CNC machine tool is extremely precise. The number of revolutions of the axis drive motor precisely controls the amount of linear motion along the axis. How axis motion is manded understanding coordinate systems It would be infeasible for the CNC user to cause axis motion by trying to tell each axis drive motor how many times to rotate in order to mand a given linear motion amount4. (This would be like having to figure out how many turns of the handle on a table vise will cause the movable jaw to move exactly one inch!) Instead, all CNC controls allow axis motion to be manded in a much simpler and more logical way by utilizing some form of coordinate system. The two most popular coordinate systems used with CNC machines are the rectangular coordinate system and the polar coordinate system. By far, the more popular of these two is the rectangular coordinate system. The program zero point establishes the point of reference for motion mands in a CNC program. This allows the programmer to specify movements from a mon location. 畢 業(yè)設(shè)計（外文翻譯 ） 3 If program zero is chosen wisely, usually coordinates needed for the program can be taken directly from the print. With this technique, if the programmer wishes the tool to be sent to a position one inch to the right of the program zero point, is manded. If the programmer wishes the tool to move to a position one inch above the program zero point, is manded. The control will automatically determine how many times to rotate each axis drive motor and ball screw to make the axis reach the manded destination point . This lets the programmer mand axis motion in a very logical manner. Refer to , 3. All discussions to this point assume that the absolute mode of programming is used6. The most mon CNC word used to designate the absolute mode is G90. In the absolute mode, the end points for all motions will be specified from the program zero point. For beginners, th