【正文】 deal procedure – either temporarily, for a given job, or permanently, to reflect a particular CNC programming style. Remember, there are no ideal procedures.第六章：制定編程計劃編寫任何CNC程序都必須經(jīng)過周密計劃后開始。From Peter Smid, CNC Programming Handbook: A Comprehensive Guide to Practical CNC Programming, Second Edition, Industrial Press, Inc. 200 Madison Avenue, New York, 2003. CHAPTER 6: PROGRAMMING PLANNINGThe development of any CNC program begins with a very carefully planned process. Such a process starts with the engineering drawing of the required part. Before the part is machined, several steps have to considered and carefully evaluated. The more effort is put into the planning stage of the program, the better results may be expected at the end.STEPS IN PROGRAM PLANNINGThe steps required in program planning are decided by the nature of the work. There is no formula for all the jobs, but some basic steps should be considered:* Initial information / Machine tools features* Part plexity* Manual programming / puterized programming* Typical programming procedure* Part drawing / Engineering data* Methods sheet / Materials specifications* Machining sequence* Tooling selection* Part setup* Technological decisions* Work sketch and calculations* Quality considerations in CNC programmingThe steps in the list are suggestions only a guideline. They are quite flexible and should always be adapted for each job and to the specific conditions of the work.INITIAL INFORMATIONMost drawings define only the shape and size of the pleted part and normally do not specify data about the initial blank material. For programming, a good knowledge of the material is an essential start mainly in terms of its size, type, shape, condition, hardness, etc. The drawing and material data are the primary information about the part. At this point, CNC program can be planned. The objective of such a plan is to use the initial information and establish the most efficient method of machining, with all related consideration – mainly part accuracy, productivity, safety and convenience.The initial part information is not limited to the drawing and the material data, it also includes conditions not covered in the drawing, such as pro and post machining, grinding allowances, assembly features, requirements for hardening, next machine setup, and others. Collecting all this information provides enough material to start planning the CNC program.MACHINE TOOLS FEATURESNo amount of initial information is useful if the CNC machine is not suitable for the job. During program planning, programmer concentrates on a particular machine tool, using a particular CNC system. Each part has to be setup in a fixture, the CNC machine has to be large enough to handle the size of the part, the part should not be heavier than the maximum weight allowed. The control system must be capable to provide the needed tool path, and so on. In the most cases, the CNC equipment is already available in the shop. Very few panies go and buy a new CNC machine just to suit a particular job. Such cases are rather rare and happen on if they make economic sense.* Machine Type and SizeThe most important considerations in program planning are the type and the size of the CNC machine, particularly its work space or work area. Other features, equally important, are the machine power rating, spindle speed and feed rate range, number of tool stations, tool changing system, available accessories, etc. Typically, small CNC machines have higher spindle speeds and lower power rating, large machines have lower spindle speeds available