Development and implementation of numerical control programming

In the numerical control lathe, the processing object is mainly various types of rotary surfaces, wherein the processing of the cylindrical surface, the tapered surface, the circular surface, the spherical surface, etc. can be completed by linear interpolation and circular interpolation instructions, and for the ellipse, Some kinds of non-circular curves, such as parabola, have a certain degree of difficulty in processing. The linear interpolation and circular interpolation provided by the numerical control system can not be directly used for the machining of non-circular curved surface. Therefore, the processing of ellipse and parabola on CNC machine tools is mostly based on the method of small straight line or small arc approach. Processing program.

In this paper, the FANUC Oi TC CNC turning system is used, and the method of programming the macro program for turning elliptical contours is discussed.

1 FANUC turning system macro program overview Use variables to program programs that can perform arithmetic or logic operations and control the flow of blocks, called user macro programs. In CNC turning, the user macro program can easily realize the two-dimensional programming processing of the quadratic curve (ellipse, parabola, etc.), the hole chamfering programming, etc., which can simplify the program, improve the programming efficiency, and maximize the manual programming. The advantages. The FANUC 0i system provides two user macro programs, namely user macro program A and user macro program B. User macro program A can be said to be a standard configuration function of the FANUC system, and any configured FANUC system has this function; and user macro program B Although not the standard configuration function of the system, most FANUC systems also support user macros. B. User macro B provides a richer programming function that allows the use of variables, arithmetic and logic operations and conditional branches to make users You can edit the package and the canned program yourself. This article mainly introduces the macro program B function. In a program, the control flow can be changed with GOTO, IF, and WHILE statements. The three branch loop statements are as follows.

1GOTO statement (unconditional branch) function: Turn to the Nth sentence of the program. When the specified sequence number is outside the range of 1 to 9999, an alarm No. 128 appears, and the sequence number can be expressed by an expression. Format: GOTO N; N is the sequence number (1 ~ 9999) 2IF statement (conditional branch: if...) Function: Specify a conditional expression after the IF, if the condition is satisfied, turn to the Nth sentence, otherwise execute the next paragraph. Format: IF [conditional expression] GOTO N.

3WHILE statement (loop statement while...) function: Specify a conditional expression after WHILE. When the condition is satisfied, execute the statement between DO and END. Otherwise, execute the statement after END. Format: WHILE [conditional expression] DO M; (M =1, 2, 3)... END M; M can only take values ​​in 1, 2, 3, otherwise alarm No. 126 appears. The examples in this article use IF statement programming.

2 The basic steps of the formula curve macro program macro program in the actual preparation process, according to the programmer's practical experience, knowledge reserves and habits and other factors will be slightly different, the basic steps of the macro program provided in this article: 2.1 according to the given standard The equation selects the independent variable and determines the range of the variable. 2.1.1 The X and Z coordinates in the formula curve can be selected as independent variables, and generally choose one with a larger range.

As shown, the Z value variable is 12, the X value variable is less than 8, and Z is selected as the variable value. 2.1.2 Select X or Z as an independent variable according to the convenience of the expression. If the expression of the parabolic formula curve is Z=- X 2 /12, it is more appropriate to select X as the independent variable; if Z is selected, the expression transformation is needed, and the second square root expression is not convenient. 2.1.3 After the independent variable is selected, the range value of its variable is also determined. The independent variable is Z. According to the workpiece coordinate system, Z changes from 0 to -12. According to the ellipse center point, Z changes from 13 to 1. In the programming, the variable value is calculated according to the elliptical center point.

2.2 Determine the expression of the dependent variable relative to the independent variable according to the given standard equation. In the equation, the standard equation expression of the ellipse in the workpiece coordinate system is: Z 2 /a 2 +X 2 /b 2 =1, the independent variable is Z, and the dependent variable is X, then the expression of X is: convex ellipse + No., concave ellipse takes the - number.

2.3 Determine the offset from the workpiece coordinate system according to a given standard equation. In the actual machining process, there are many forms of the formula curve position encountered, such as the center point of the formula curve coincides with the origin of the workpiece coordinate system, the center point of the formula curve coincides with the Z axis or the X axis, and the center point of the formula curve is in the workpiece. Any position in the coordinate system, the convex and concave shape of the formula curve, etc., requires that the relative positional relationship between the center point of the curve and the workpiece coordinate system be considered when editing the program. The zero point offset of the ellipse Z to the center point relative to the workpiece coordinate system is negative 13 and there is no offset in the X direction. Therefore, during the editing process, G01 X<2105> Z<103- 13> reflects the Z-direction offset value. .

2.4 Programming procedures. The relevant expression, variable factor values ​​have been determined, ready to be programmed. There is a large margin in the machining of lathe body parts. The G73 cycle command and the macro program are used to complete the elliptical surface machining. The M98 subroutine can also be used to complete the machining.

3 formula curve macro program programming specific application examples analysis 3.1 Z-direction offset convex elliptical parts processing. Task: Using CNC lathe to complete the machining of the parts shown, the blank size is φ30mm×100mm, and the material is 45 steel. According to the pattern, complete the calculation of the part node and base point, set the workpiece coordinate system, formulate the correct process plan (including positioning, clamping scheme and process route), select reasonable tool and cutting process parameters, write CNC machining program, and master the parts. Knowledge and skills in complete work processes such as processing and inspection. Project analysis: The surface of the part is composed of cylindrical surface, conical surface and elliptical curved surface. When machining, the radius of the tool nose radius must be introduced to ensure the size and precision of the machining. The dimension is complete and the contour description is clear. From the given blank size, the workpiece only needs to be clamped once in the process, and can be manually cut off, paying attention to the proper control of the clamping portion and the length of the exposed portion.

According to the above analysis, according to the basic steps of the formula curve macro program, the following reference program is given: N10 G98; set the sub-feed N20 T0101 M03 S800; change the No. 1 tool, adjust the tool offset value, the spindle speed 800r/min N30 G00 X31. Z3.; Quick positioning to the starting point of the cycle N40 G73 U10. W8. R10.; Closed contour compound cycle U: Retraction amount in the X-axis direction, W: Retraction amount in the Z-axis direction, R: Number of rough cuts N50 G73 P60 Q210 U0.4 W0.1 F150; P60: rough machining first block number, Q210: rough machining last block number, U: X-axis direction finishing allowance 0.4mm, W: Z-axis direction finishing allowance 0.1mm , F: rough feed rate 150mm / min N60 G01 X0; N70 Z0; contour machining starting point N80 101 = 13.; ellipse long half axis N90 102 = 8.; ellipse short half axis N100 103 = 13.; elliptical processing Z-axis starting size (calculated starting from the center of the ellipse, the starting point is at the apex of the right half-axis) N110 IF <103 LT 1.> GOTO 170; judge whether to go to the end of the Z-axis, then jump to the N170 block to continue processing N120 104=SQRT<101101-103103>; N130 105=8.104/13.; X-axis variable N140 G01 X<2.105> Z<103- 13.>; ellipse interpolation N150 103=103- 0.5; Z-axis step, 0.5mm N160 GOTO 110 each time; when not going to the Z-axis end point, jump to N110 block N170 G01 X20. Z- 18.; processing cone N180 Z- 28.; N190 X24 ;; N200 X26. Z- 29.; N210 Z- 38.; N220 G00 X80. Z50.; fast retracting N230 M05; N240 M00; N250 M03 S1500 F80; finishing speed 1500r/min, feeding 80mm/min N260 G42 G00 X31. Z3.; Fast forward to the finishing start point, add tool nose radius compensation N270 G70 P60 Q210; execute finishing block N280 G40 G00 X80. Z50.; quick retract, cancel tool radius compensation N290 M05; spindle stop N300 M30; The program ends. The above example has been briefly analyzed. The following extended examples are as follows.

3.2 Both X and Z directions are processed with offset concave elliptical parts. According to the analysis process of the example 1, the example investigates the difficulty in the preparation of the offset program in both the X and Z directions of the ellipse center. When the part is programmed, we can apply the programming format of Example 1. The difference between the two is the convexity and concave of the elliptical shape, the offset position of the center point, and the calculation of the starting and ending points of the variable.

The reference procedure is as follows: ... N10 101=40.; ellipse long half axis N11 102=24.; ellipse short half axis N12 103=12.; ellipse Z direction starting point (relative to the value of the ellipse center) N13 IF <103 LT GOTO 19;; judge whether to go to the Z axis end point, then jump to the N19 block to continue processing N14 104=SQRT<101101-103103>; N15 105=24.104/40.; X axis variable N16 G01 X<84.- 2.105 > Z<103- 44.>; elliptical interpolation N17 103=103- 0.5; Z-axis step, 0.5mm each time N18 GOTO 13; N19...

Conclusion When machining elliptical curves with a CNC lathe, the following points should be noted: a. The accuracy of the workpiece after turning is related to the step size selected during programming. The smaller the step value is, the higher the machining accuracy is. However, the reduction of the step size will increase the workload of the numerical control system, the operation is busy, and the feed speed is increased, thereby reducing the processing efficiency. Therefore, the step size must be reasonably selected according to the processing requirements, and generally a larger step is selected as far as possible while satisfying the processing requirements. b. For parts that do not coincide with the center of the ellipse and the Z axis, the workpiece coordinate system needs to be offset and then processed as described in the example in the text. c. When planning, consider the convexity and concave of the curve. The difference between the two is the X coordinate change in the linear interpolation approximation curve block. d. The elliptical inner contour turning programming is similar to the outer contour, mainly considering the position of the center point, the unevenness and the position of the starting and ending points. The reader can apply it according to the above example.

The examples selected in this paper have been processed and processed in the CNC lathe with FANUC Oi TC system. For the F, S, ap and other parameters in the programming, the parameters can be set according to the actual processing environment. The given values ​​are available for reference. The above program can be used as a formula curve macro program programming template, only need to change the individual parameter values. I hope that readers will give more valuable opinions and exchange learning progress.

(Finish)

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