In the operation of CNC lathe, to reach the level of senior workers and technicians, we must solve several difficult problems, including the following four aspects: 1 profiling; 2 trapezoidal thread processing; 3 non-circular curve processing; 4 assembly Processing. Take SIEMENS 802S as an example to solve them separately.
1. Profiling processing As shown in the handle parts, the main structural features are the forming surface and the concave shape of the contour. The sharp knife can be used, and the profiling process can be used. The route is as shown, from large to small layered cycle cutting until the final completion. . Here are two programming methods: G91 incremental subroutine loop cutting method and G158 coordinate shift command program loop cutting method.
1. G91 incremental subroutine cycle cutting method (1) processing analysis. Since each path is the same as the contour, a cyclic cutting method is used. After the outline is shifted outward by a certain distance, the absolute coordinate X of each point increases. Although it is difficult to calculate and determine the coordinates because of the point, the relative position between the points is fixed, and the coordinate increment does not change. That is, the relative coordinates are not changed, so only the relative coordinates can be used in programming. As long as the starting point of the cycle is close to the workpiece, layered profiling can be achieved.
In the operation of CNC lathe, to reach the level of senior workers and technicians, we will certainly encounter a series of difficult problems. This paper selects several aspects and analyzes and solves with examples, hoping to improve the skills of CNC car.
The efficiency of CNC machining technology is largely related to the company's own technology management model. The standardization and standardization of NC machining program embodies the application level of CNC machining technology to a certain extent. It regulates the diversification of NC program by standardization and improves the quality of tool path. For example, the positioning reference is specified in the process documentation. Tool reference, coordinate system, tool parameters and cutting parameters; program programming can be standardized from 2D contour machining, 3D surface machining, fixed cycle, tool compensation and tool path machining strategy; On the basis of experience, the establishment of standardized and standardized NC program templates can greatly improve the programming quality and product processing efficiency. For the successful product processing technology and CNC machining experience of the enterprise, it can be saved in the form of template, which is beneficial to the reuse of resources and also as a resource for technical exchange. Therefore, the effective CNC machining process and the use of CNC programming templates and corresponding specifications can greatly reduce quality accidents, reduce costs and improve processing efficiency.
In order to focus on the preparation and application of the subroutine, the outer dimensions are not processed. It is assumed that the blank of Φ30mm is directly selected, and the concave forming surface is processed by the T4 sharp knife.
(2) The reference procedure is as follows (using point A as the programming origin).
Main program SKG91.MPF M03S600 T04D01 G90G0X30Z2 G01X30Z0F0.1 L91P15 (call subroutine) G90G0X80Z80 M5 M30 subroutine L91.SPF G91G01X-2F0.1 (increment to point A) G3X17.5Z-5.16CR=10 (to point B) G3X1.8Z-46.71CR=50 (to point C) G2X3.33Z-13.28CR=12 (to point D) G3X7.37Z-9.85CR=15 (to point E) G1Z-5 (to point F) X2 (X Direction retracting) G0Z80 (Z direction rewind) G1X-32F0.1 (X direction infeed) M17 (or M02) (subprogram end) (3) A few points about the main program.
First, the format of the calling subroutine: L xx P n n. The subroutine name can be represented by the letter "L" followed by the number xx in addition to the command method specified by SIEMENS, Lxx is the subroutine name, and Pnn is the calling subroutine. The program nn times, such as L91P15, means that the subroutine L91 is called a total of 15 times.
Second, the absolute coordinates G90 must be used before and after the subroutine is called. Generally, it cannot be omitted.
Third, the determination of the number of times the subroutine is called. 1 First determine the maximum machining allowance, the diameter of the blank can be reduced by the minimum size of the part. In this case, the blank diameter is 30mm, and the minimum dimension of the part is 0 at the starting point of the contour, so the maximum machining allowance is X max = 30mm-0=30mm. .2 determine the depth of each layer t, this example takes t = 2mm.
3 number of cycles n=X max /t=30m m/2m m=15.4 Calling the start point of the subroutine X s, Z s coordinate calculation: X s =X 0 +Δd×n (where X 0 is the starting point of the contour The X coordinate, Δd is the depth of cut for each layer, and n is the number of times the subroutine is called. The Z s coordinate of the cycle start point is the same as the Z o coordinate of the start point of the contour. In this example, the starting point of the contour is point A, coordinate (0,0), so X 0 is 0, Z o is 0, Δd is 2, n is 15, then X s =X 0 +Δd×n=0 +2×15=30, Z s =Z o =0, so the loop starting point is set to X30Z0.
(4) G91 incremental subroutine writing instructions.
The structure of the subroutine follows the "six steps and two principles". The six steps are: the first step is to determine the X direction feed (G91 incremental coordinate calculation, each layer depth 2mm), to the starting point of the contour; the second step, Step forward along the contour until the end point of the contour; in the third step, retract the tool in the X direction (note that the highest point is exceeded); in the fourth step, the Z direction quickly retracts to the starting point; the fifth step, the X direction re-feeds , to the X starting point; the sixth step, the subroutine ends (M17). The two principles are: 1 algebra of all X coordinate values ​​(with sign) in the subroutine and algebras satisfying ZX=-2; 2 Z coordinate values ​​(with sign) in the subroutine and satisfying ΣZ=0. “-2†is the depth of cut of each layer, and its size can be modified in programming according to the actual situation.
As a result, after the subroutine is executed one cycle, the tool stops at a position of the cutting depth in the X direction from the start of the previous cycle. If ΣX=0, it means that the amount of feed in the X direction after the cycle is 0, and the part will not be cut in the X direction; if ΣX>0, the tool will retract outward in the X direction every cycle, and it is farther away from the workpiece. .
If ΣZ is a positive number, the tool will retreat to the right while trimming; if ΣZ is negative, the tool will cut to the left and not to the Z-start. These are not correct.
2. G158 zero offset command program cycle cutting (1) command function. Program zero offset for all axes, also used for profile offset machining, or for machining multiple identical structures in a part. The following G158 instruction replaces the previous programmable zero offset instruction; when only the G158 instruction is entered in the block and the axis name is not followed, the current programmable zero offset is canceled.
(2) Instruction format: G158 X_Z_ (where X_Z_ is the new programmed origin position, where X is the radius value. The coordinates in the block are all the positions in the new workpiece coordinate system). There are two special forms of format: G158 X_ (X-direction zero offset) and G158 Z_ (Z-direction zero offset). The G158 instruction requires a separate block. In order to achieve cyclic cutting, subroutines and macro programs are often used.
The format is: R1=maximum unilateral cutting thickness+finishing allowance value MA1:G158 X=R1 Z0 (establishing zero offset) L158 (call subroutine, subroutine is programmed with absolute coordinate value)R1=R1-per knife One-side cutting amount IF R1>=finishing allowance value GOTOB MA1 G158 Description: The cutting amount per knife = single-side cutting thickness / number of cuttings, the thickness can be slightly modified, so that the number of cuttings and the amount of single-side cutting are moderate. The number of cycle cuts is determined by the IF conditional statement. If the condition is met, the MA1 sentence is returned and the loop is continued. If the condition is not met, the next sentence G158 is executed, and the zero offset is canceled.
(3) The machining route is the same as the G91 incremental subroutine cycle. The subroutine is generally programmed with absolute coordinates, as shown.
(4) Reference procedure.
Main program SKG158.MPF M03S600 T04D01 G90G0X30Z2 R1=15.1 (parameter R1 assignment) MA1: G158 X=R1 (establishing zero offset) L158 (call subroutine L158) R1=R1-0.5 (cut depth 0.5) IF R1>=0.1 GOTOB MA1 (conditional sentence) G158 (cancel zero offset) L158 (finishing) G0X80Z80 M5 M30 subroutine L158.SPF G01X0Z0F0.1 (absolute coordinate, point A) G3X17.5Z-5.16CR=10 (point B) G3X19. 3Z-51.87CR=50 (point C) G2X22.63Z-65.15CR=12 (point D) G3X30Z-75CR=15 (point E) G1Z-80 (point F) X32 (X-direction retraction) G0Z0 (Z direction fast Retract) M17 (sub-program end) Second, trapezoidal thread processing (1) parts processing trapezoidal thread Tr36 × 6.
(2) Processing analysis. Because the trapezoidal groove is deeper and the bottom of the groove is wider, the processing methods include straight-forward method, oblique-forward method, left-right cutting method, straight groove method and layering method. Here, the layered and left-right offset cutting method is better. , can be programmed with subprograms.
If a high-speed steel cutter is used, the width of the trapezoidal thread edge is ground to 1.7 mm, and the layered and left and right cutting method is adopted, that is, a knife is cut in the middle during processing, and then the offset is 0.114 mm. The left and right offset distance algorithm is the width of the groove bottom minus half the width of the tool tip, (1.928mm-1.7mm)/2=0.114mm.
(3) Reference procedure.
Main program SKG33.MPF M03S180 T01D01 G90G95G0X38Z3 M8 G1X36F0.1 L33P35 (call subroutine) G90G0X80Z80 M9 M5 M30 subroutine L33.SPF G91G1X-0.2F1 (incremental X feed) G33Z-38K6 (straight cut thread) G1X9F5 (retraction) ) Z38.114 (returned, right 0.114) X-9 (X infeed) G33Z-38.114K6 (right cut thread) G1X9F5 Z37.886 (returned, left 0.114) X-9 G33Z-37.886K6 (left) Cut thread) G1 G1X9F5 Z38 (return to the middle) X-9 M17 III. Non-circular curve machining 1. Non-circular curve Non-circular curve mainly refers to the contour of an ellipse or a parabola shape, and is programmed by macro programming. The following is an example of processing the ellipse "X 2 /144+Z 2 /400=1".
2. Processing analysis (1) roughing. Cutting from large to small in roughing, the route is as shown. The coordinates of the end point of each pass are determined: the parameter variable is used to determine the length of the long and short axis direction by two parameters, and then the relationship between the point coordinates X, Z and the parameter is analyzed. If the short axis is represented by the parameter R 1 , then X = 2 × R 1, the maximum value of R 1 is 24 mm / 2 mm = 12 mm; if the long axis is represented by the parameter R 2 , then R 2 = 20 × (1-R 1 2 / 144), the programming expression is R 2 = 20 × SQRT (1-R 1 × R 1 / 144), and the corresponding coordinate Z = R 2 -20 (is a negative value). Because it is roughing, retain 0.2mm finishing allowance, take Z=R 2 -19.8.
Therefore, the coordinates of the end point of each layer are (2 × R 1, R 2 -19.8), and the value of R 1 is from 12 mm to 0, which is continuously reduced by delamination.
(2) Finishing. Finishing along the contour from the right end to the highest point, using parametric programming to subdivide the contour into hundreds of interpolation points. The point coordinates are determined to be the same as the roughing.
(3) Rough finishing reference program.
Program name TY.MPF M03S600 G90G95 T1 (roughing) G1X25Z2F3 R1=12 MA1:G1X=2R1 F0.15 R2=20SQRT(1-R1R1/144)G1 Z=R2-19.8 F0.15 G1X=(2R1+1) G0 Z2 R1=R1-1 (one cut per side 1) IF R1>=0 GOTOB MA1 (note the space!) G0X80Z80; T2S800 (finishing) G0X0Z1 R1=0 MA2:R2=20SQRT(1-R1R1/144 ) G1 X=2R1 Z=R2-20 F0.06 R1=R1+0.05 IF R1<=12 GOTOB MA2 G1 X24 Z-20 (without omission) G0X80Z80 M5 M30 IV. Assembly of parts such as parts 1 and parts 2. After the processing is completed, it can cooperate with each other: the convex end of the right end surface of the part 1 is matched with the groove of the left end surface of the part 2, and the left end of the part 1 and the inner and outer threads and the circular arc surface of the right end of the part 2 can cooperate with each other. Show.
(1) Processing analysis. Many such assemblies need to make full use of the cooperation between them to solve the clamping problem during processing. The difficulty is that the clamping at the right end of the workpiece 1 is screwed into the inner hole of the member 2. Therefore, it is important to arrange the processing sequence correctly, which can reduce the number of clamping, improve the accuracy, save time and improve efficiency.
(2) Processing sequence. The processing sequence of the assembly is as follows: 1 the clamping member 1 blank Φ45mm left end, flat right end surface, the right end step is machined, the head is machined to the total length; 2 the right end step is clamped, and the left end processing of the finished piece 1 is completed (shape, undercut And thread); 3 total length of workpiece 2; 4 left end of workpiece 2 (drilling, inner hole contour, inner end groove and contour); 5 right end of workpiece 2 (inner hole profile, internal thread, profile and outer groove) ; 6 The external thread of the piece 1 is screwed into the inner hole of the member 2, and the right end of the workpiece 1 is processed (the inner groove is processed first, and the shape is processed). Note that after roughing the shape, remove the part 1 and screw it on again, and then loosen it once after semi-finishing, so that after finishing, the thread can be loosened directly by hand.
In short, in the operation of CNC lathes, we must constantly analyze and solve the difficult problems in practice, and diligently think and learn and use them in order to continuously improve our skills and become the leader in the industry.
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