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1、Unit 6 Part Programming,6.1 Lesson 11 Manual Part Programming,A part programmer is very essential in any NC manufacturing system. After getting the part drawing, he decides the sequence of operations, the speeds and feeds for the various operations and determines the magnitude of various motions des
2、ired. Therefore, it is important that he should be familiar with the various operations and machine tools to be used and ought to carry out calculations based on geometry and trigonometry.,In manual part programming, the machining instructions are recorded on a document, called a part-program manusc
3、ript (Table 6-1)by the part programmer. The manuscript is essentially an ordered list of program blocks Because a part program records a sequence of tool motions and operations to produce the final part geometry, one must prepare a process plan with setups and fixtures before writing the program. Th
4、e work-piece location and orientation, features (holes, slots, pockets) to be machined, tools and cutting parameters used need to be determined. We will use an example to illustrate how a part is programmed.,6.2 Lesson 12 Example of Manual Part Programming,The part drawing shown in Figure 6-1 is to
5、be machined from a 5in.4in.2in. workpiece. The workpiece material is low-carbon steelWe will use a hypothetical 3-axis CNC machining center for the process. The process plan for the part is as follows: Set the lower-left bottom coner of the part as the machine zero point (floating-zero programming).
6、 Clamp the work-piece in a vise., Mill the slot with a 3/4in. four-flute flat end mill made of carbide. From the Machinability Date Handbook, the recommended feed is 0.005 in/tooth/r and the recommended cutting speed is 620 fpm. Drill two holes with a 0.75in. diameter twist drillUse 0.18ipr feed and
7、 100fpm speed Figure 6-2 shows the setup，fixturing，and cutter path. All dimensions in inches. All tolerance A0.001 inch. The program for the example part is shown in Table 6-2.,6.3 Reading Materials 11 Format of Programming Language,A program format is a system of arranging information so that it is
8、 suitable for input to a CNC controller. Several different types of formats exist. The format to be used in this text is known as the word address. It was originally developed for use with NC tapes and has been retained for CNC programming. Programming of CNC equipment involves the entry of code to
9、a CNC machine for the purpose of precisely controlling all machine movements. Programming language is similar to the English language and is divided into the following parts (Table 6-3).,It is important to mention that there are different programming language “dialects”. Each CNC controller is desig
10、ned to accept a particular dialect. Thus, the format that works on one controller may have to be slightly changed when running it on another controller. It would be impractical and most likely impossible to describe all the different codes for each controller. Thus, in this text we will give the mos
11、t general coding pattern that can be followed for any type of programming application. Point-topoint as well as contouring programs will be written for a CNC machine with a Fanuc controller.,Many of the same commands can be used on other controllers but some may not. Variations even exist within the
12、 same family of Fanuc controllers. In each case, the programming manual of a particular CNC machine must be consulted before attempting to apply the programs presented here to that machine.,6.4 Reading Materials 12 Terminology of Programming Language,The following terminology is important when using
13、 the word address format. Programming characters A programming character is an alphanumeric character or punctuation mark. For example, the following are programming characters: N G, Addresses An address is a letter that describes the meaning of the numerical value following the address. For example
14、, the G in the codes G00 and the X in the codes X3.75. It is important to note that a minus () sign may be inserted between the address and the numeric value. Positive values do not need a plus sign. Words Characters are used to form words. Program words are composed of two main parts：an address fol
15、lowed by a number. Words are used to describe such important information as machine motions and dimensions in programs., Blocks A block is a complete line of information to the CNC machine. It Is composed of one word or an arrangement of words. Blocks may vary in length. Thus, the programmer need on
16、ly include in a block those words required to execute a particular machine function. For example: N0020 G90G00X2.5Y3.75S1000 the block is composed of the following words: N0020, G90, G00, X2.5, Y3.75 and S1000., Programs A program is a sequence of blocks that describe in detail the motions a CNC machine is to execute in order to manufacture a part. The MCU executes a program block by block. The order in which the blocks appear is the order in which they are processed.,
