【正文】 , but their power rating is higher.* Control SystemThe control system is the heart of a CNC machine. Being familiar with all the standard and optional features available on the control is a must. This knowledge allows the use of a variety of advanced programming methods, such as the machining cycles, subprograms, macros and other timesaving features of a modern CNC system.A programmer does not have to physically run a CNC machine. Yet, the programs will bee better and more creative with good understanding of the machine and its control system. Program development reflects programmer’s knowledge of the CNC machine operation.One of the main concerns in program planning should be the operator’s perception of the program. To a large degree, such a perception is quite subjective, in the sense that different operators will express their personal preferences. On the other hand, every operator appreciates an errfree, concise, welldocumented and professionally prepared part program, consistently and one after another. A poorly designed program is disliked by any operator, regardless of personal preferences.PART COMPLEXITYAt the time the drawing, material and the available CNC equipment are evaluated, the plexity of the programming task bees much clearer. How difficult is to program the part manually? What are the capabilities of the machines? What are the costs? Many questions have to be answered before starting the program.Simple programming jobs may be assigned to a less experienced programmer of the CNC operator. It makes sense from the management perspective and it is also a good way to gain experience.Difficult or plex jobs will benefit from a puterized programming system. Technologies such as Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) have been a strong part of the manufacturing process for many years. The cost of a CAD/CAM system is only a fraction of what it used to be only a few years ago. Even small shops now find that the benefits offered by modern technology are too significant to be ignored. Several programming systems are available various puters and can handle any job. For a typical machine shop, a Windows based programming software can be very beneficial. A typical example of this kind of application is the very popular and powerful MasterCAM, form CNC Software, Inc. Tolland. CT. There are several others.MANUAL PROGRAMMINGManual programming (without a puter) has the most mon method of preparing a part program for many years. The latest CNC controls make manual programming much easier than ever before by using fixed or repetitive machining cycles, variable type programming, graphic tool motion simulation, standard mathematical input and other timesaving features. In manual programming, all calculations are done by hand – with the aid of a pocket calculator – no puter programming is used. Programmed data can be transferred to the CNC machine via a cable, using an inexpensive desktop or a laptop puter. This process is faster and more reliable than other methods. Short programs can also be entered manually, by keyboard entry, directly at the machine. A punched tape used to be the popular media of the past but has virtually disappeared from machine shops.* DisadvantagesThere are some disadvantages associated with manual programming. Perhaps the most mon is the length of time required to actually develop a fully functioning CNC program. The manual calculation, verification and other related activities in manual programming are very time consuming. Other disadvantages, also very high on the list, are a large percentage of errors, a lack of tool path verification, the diffic