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Application of "R" parameter programming in NC milling process

Abstract NC machine tool is the basic equipment of advanced manufacturing technology and a typical mechatronic product. Mastering numerical control programming technology is the key to making full use of this kind of equipment, and it is also an important sign for us to improve the training and teaching level of numerical control milling engineering. Key words NC machine tool NC Milling Machining NC programming "R" parameter programming "NC milling technology training" is a newly opened engineering training subject with strong theoretical significance in our center. In terms of teaching form, it is different from the traditional and mechanical "Metalworking Practice" in the past. The purpose of the training is to understand today's advanced machinery manufacturing methods, give full play to the characteristics of today's college students with new knowledge, fast response and strong creativity, and combine specific practical teaching to widely cultivate students' practical ability, comprehensive application ability and innovation ability

due to the limitations of objective conditions and teaching time, automatic programming (computer programming) has not been popularized in engineering training in Colleges and universities at present. In order to understand the basic principles and methods of programming, manual programming is still one of the most commonly used basic training contents

for parts with simple machining shape, it is the "master" of quality control. The calculation is relatively simple, there are few programs, and it is easier to complete manual programming. Therefore, manual programming is still widely used in point positioning processing and contour processing composed of straight lines and arcs. However, for parts with complex shapes, especially those with non-circular curves, tabular curves and curved surfaces, it is difficult to use general manual programming, and there is a high probability of errors, and some of them can't even program. The "R" parameter programming can solve this problem well

there are many kinds of non-circular curve contour parts, but no matter which type of non-circular curve parts, the mathematical processing done during programming is the same. One is to choose the interpolation method, that is, first of all, we should decide whether to use the straight line segment to approximate the non-circular curve or the circular arc segment to approximate the non-circular curve; The second is the calculation of interpolation node coordinates. Using straight line segment to approximate the contour curve of the part, the general mathematical processing is relatively simple, but the calculated coordinate data is more. The equidistant method is to make the increment of one coordinate equal, then calculate the corresponding nodes on the curve, connect the adjacent nodes into a straight line, and replace the original contour curve with the broken line composed of these straight line segments (see Figure 1). It is characterized by simple calculation and convenient selection of coordinates. The selection of material increment can be large or small. The smaller the selection, the higher the machining accuracy. At the same time, the number of nodes will increase, and the corresponding programming cost will also increase, Using "R" parameters, the contract price of blow molding grade HDPE in February is 83.4 cents/pound (1 programming can just make up for this shortcoming.

nowadays, CNC milling machines generally have "R" Parameter programming functions, such as Siemens 802D numerical control system, make it convenient to manually program some complex graphics. As shown in Figure 2 and 3, when processing sinusoidal lines of one cycle, the usual method is to use automatic programming. If manual programming is used, it is simpler to use "R" parameter programming. How many coordinate points are selected on the curve depends on the machining accuracy

the essence of "R" parameter programming is to write "subroutine" with variable "R", and call "subroutine" many times according to the condition of "R" value to simplify programming. For example, the variable R1 is used to represent from 0 to 2 in the above figure л Radian value of each point; Use [x=100*r1/2 л， Y=25*sin (R1)] indicates a subroutine. If you want to select 1000 coordinate points on the sinusoidal line, you can only call the subroutine 1000 times. Reasonable selection of "R" parameter programming can improve the machining accuracy (multiple nodes) and programming efficiency of some parts. It is also one of the main methods of manually programming complex parts. This method is often used when there is no computer automatic programming. Programming example: (Siemens 802D system) try the method of "R" parameter programming to program the whole circle (as shown in Figure 4)

analysis: if circular interpolation is not used, the circles can be divided into 360 parts and then connected by linear interpolation. The variable r1=50 represents the radius, r2=360 represents a total of 360 parts, r3=1 represents an interval of 1 part, and r4=0 represents the initial angle. The procedure is as follows: o0001 N10 g54 G42 G90 G00 X50 Y0 Z100 N20 G01 F20 S600 M03 Z-10 N30 r1=50 r2=360 r3=1 r4=0 N40 aa:x=r1*cos (R4) y=r1*sin (R4) N50 r4=r4+1 r2=r2-r3 N60 if R2> = 0 gotob AA N70 G00 Z50 N80 G40 m export more than 100 million tons 2 note: in the procedure, N30 program section is a condition

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