In order to use CNC technology and program reasonably, the programming instructions of CNC lathe with similar meaning, similar function, more format parameters and complex trajectory are analyzed. This paper introduces their similarities and differences, difficulties, so as to facilitate rational use.
Numerical control turning; Numerical control system; Programming instructions; Analysis; motion trail
With its advantages, CNC machine tools gradually replace ordinary machine tools and special machine tools and are applied to industrial processing fields. Numerical control system is a real-time multi-task system composed of decoding, tool compensation, interpolation, interface and other relatively independent tasks. It transforms the NC program input by the programmer into the movement of the NC machine tool. The trajectory depends entirely on the input program. A program consists of three parts: program number, program content and program end. As the main content of the program, programmers use numerical control instructions to write according to the shape differences of each part. Every instruction has its own trajectory.
A, the use of NC turning programming instructions (central China system)
(a) the difference between G00 and G0 1, how to use it correctly.
G00 is a fast point positioning instruction. The function is to make the tool move quickly from the current point of the tool to the positioning target point at the maximum allowable speed set by each axis (multiplied by the feed adjustment rate) through point control.
G0 1 is a linear interpolation instruction. This function is to carry out the cutting movement of the straight outline. Sometimes I do short-distance idling.
Both commands can move the tool from the current point to the positioning target point. Therefore, in practical application, it is easy to confuse them. In order to use G00 and G0 1 correctly, it is necessary to find out their differences and distinguish them.
First of all, the format of G00 instruction has no f parameter. Its fast moving speed is set for each axis by the machine tool parameter "fast moving feed speed". Therefore, when executing G00 instruction, because each axis moves at its own speed, the order of each axis reaching the end point will be different according to the actual situation, so the synthetic trajectory of the linked linear axis is sometimes a straight line and sometimes a broken line. Therefore, when running G00 instruction, it is necessary to know the tool path first to avoid the collision between the tool and the workpiece or fixture. G0 1 instruction format has f parameter, and the cutter runs to the end point in linkage mode according to the synthetic feed speed specified by f, and the synthetic trajectory of its linkage linear axis is always a straight line.
Secondly, the use occasions are different. G00 is generally suitable for quick positioning before machining or quick tool withdrawal after machining. During the correct operation, it never comes into contact with the workpiece. G0 1 is generally considered as a straight profile cutting motion. Sometimes short-distance idling is also carried out to prevent inertia overshoot that may occur when G00 commands short-distance high-speed movement.
(B) G02 and G03 direction judgment
G02 and G03 are clockwise arc interpolation and counterclockwise arc interpolation respectively. The way to judge whether an arc is processed by G02 or G03 is to observe and judge from the positive direction of the coordinate axis perpendicular to the plane where the arc is located (interpolation plane). As shown in figure 1.
Figure 1: G02/G03 direction specification for circular interpolation.
CNC lathe machining rotary parts, only need to mark the X axis and Z axis. So its interpolation plane is XOZ plane. According to the principle of right-hand Cartesian coordinate system, we can represent the Y coordinate axis. The y-axis direction is perpendicular to the x-axis and z-axis, and the arrow points inward. According to the judgment method, it can be concluded that (a) the starting point to the end point of the arc in figure 1 is clockwise, and it is processed by G02; (b) In Figure 1, the arc starting point to the arc ending point is counterclockwise, and it is processed by G03.
(3) Determination of command trajectory of rough turning compound cycle G7 1
G7 1 is the instruction of rough turning combined cycle. Its instruction format is: G 71U (△ D) R (E) P (NS) Q (NF) X (△ U) Z (△ W) F (F) T (T) S (S). There are many parameters in this instruction, which respectively represent △D- cutting depth and E- tool withdrawal.
When the program section containing G7 1 instruction is executed, the tool rough machining trajectory depends on the finish machining trajectory given by the program section n (ns) ~ n (nf) and the tool position (cycle starting point) before the G7 1 instruction is executed.
As shown in fig. 2,
Figure 2: Compound cycle of rough turning inner diameter/outer diameter
A is the starting point of the loop, and A → A ′→ B ′→ B is the programming trajectory of the end point. Before the rough machining of G7 1, in order to ensure the finishing allowance in the X-axis and Z-axis directions, the system adds the corresponding finishing allowance to the coordinate values of the cycle starting point A in the X-axis and Z-axis directions, and obtains point C ... First, the tool is moved from point A to point C, and then the rough machining compound cycle is carried out. The roughing route and machining times are automatically calculated by the system according to the specified finishing route, roughing depth and tool withdrawal. It can be seen that when executing the instruction G7 1, the system has scanned, decoded and determined the outline of the finishing program segment. It should be noted that when writing the finishing program, the tool cannot be displaced in the Z axis direction from the program section between A and A→A'. And the cycle starting point a must be a point outside the workpiece. ////The characteristics of NC machining
Numerical control machining, also known as NC(N Shuai ericalConb0 1) machining, is information composed of numerical values and symbols to control machine tools.
The bed realizes automatic operation. After half a century's development, NC machining has become an advanced system applied in various fields of contemporary manufacturing.
Building technology. The biggest characteristics of NC machining are two points: First, it can greatly improve the accuracy, including machining quality, precision and machining.
Time error accuracy; Second, the repeatability of machining quality can stabilize the machining quality and maintain the consistency of the quality of machined parts. also
In other words, the quality and processing time of the machined parts are determined by the numerical control program, not by the machine tool operators. Numerical control plus
Tools have the following advantages:
1) Improve production efficiency;
(2) skilled machine tool operators are not required;
(3) Improve the machining accuracy and maintain the machining quality.
(4) The number of fixing devices can be reduced:
(5) Easy to manage the machining process;
(6) The inspection workload can be reduced;
(7) The rejection rate and defective rate can be reduced;
(8) It is convenient to change the design and process, and the processing setting is flexible.
(9) It is easy to realize the automation of the operation process, and one person can operate multiple machine tools;
(10) The operation is simple, and the physical labor intensity is greatly reduced.
With the increasing numerical control rate of manufacturing equipment, numerical control machining technology has been widely used in China.
With the development of industry, mastering the numerical control technology and the numerical control rate in the process of machining has become the competitiveness of enterprises.
Sign. The key to the application of NC machining technology lies in the quality of computer aided design and manufacturing (CAD/CAM) system.
CAD/CAM has become the key technology to promote the development of national economy and the only way to realize the modernization of manufacturing technology.
How to program NC machining is the key to affect the efficiency and quality of NC machining. Traditional manual programming method
The method is complex, tedious, error-prone and difficult to check, which makes it difficult to give full play to the functions of CNC machine tools. In mold processing, usually,
When encountering parts with complex shapes, their shapes are described by free-form surfaces, and it is basically impossible to compile NC machining by manual programming.
Working procedure. In recent years, due to the rapid development of computer technology, the graphics processing function of computer has been greatly enhanced.
The graphic interactive automatic programming method of CAD/CAM technology is becoming more and more mature.