Computer control of machine tools has numerous advantages and capabilities.
One distinct advantage is rapid and high-precision positioning of both workpiece and cutting tools. Modern CNC machines can position cutting tools and workpieces at rapid traverse feed rates of several hundred inches per minute to an accuracy of .0001 in. Once programming is complete, and tooling is set up, the machine tool can operate at full capacity 24 hours a day, even in the dark, with only routine service and cutting tool maintenance.
Cutting feed rates and spindle speeds may be optimized through program instructions. This adds greatly to both productivity and consistent dimensional accuracy in parts produced. Modern CNC machine tools have either turret or belt toolholders, some of which can hold more than 150 tools. This gives the machine a vast capability to accomplish many different machining operations. Tool selection and changing is under the program’s control and is therefore extremely productive, as little time is wasted in applying a tool to the job.
Probably the most important advantage of CNC is the ability to program the machine to do different jobs. Once a computer program is developed to accomplish a given machining task, it may be used for a short production run of one or a few parts. The machine may then be set up for a new job and a new program used for a long production run of hundreds or thousands of production units. The machine may then be interrupted, used for the original job or another new job, and then quickly returned to the long production run. This makes the CNC machine tool extremely versatile and productive.
Another computer activity that has become generally accepted technology in the modern era is engineering design. Computer-aided design, or CAD, has become the preferred method of product design and development. The connection between CAD and CNC was logical. A computer
design could go directly to another computer program used to develop CNC machine control information and then use it to drive a CNC manufacturing machine to make a part just designed. Furthermore, the computer is extremely useful for assisting the CNC programmer in developing a program to manufacture a specific part. Thus, computer-aided manufacturing, or CAM, systems have now become the industry standard for programming (Figure M-1).
When CAD, CAM, and CNC technologies are blended, the greatest capability emerges. A modern CNC machine tool can produce parts that would be extremely difficult or impossible to make by manual methods. This capability permits the design engineer to explore designs that
previously could not be manufactured by any manual methods.
With manufacturing capability no longer a constraint for the product designer, this amazing ability of the computer-controlled machine tool is ushering in a new variety of precision-machined component parts and other products.
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