Non-circular parts CNC turning software control system

The piston is an important part of the internal combustion engine and is a typical non-circular part. The degree of cooperation between the piston and the cylinder is an important criterion for measuring the quality of the engine. Nowadays, the medium-convex and elliptical pistons are commonly used. Many manufacturers use the mastering method. However, since the hard-module system uses mechanical or hydraulic pressure to realize follow-up profiling, it is difficult to further improve the accuracy and efficiency. Difficult to process and expensive to manufacture, it is required to design a new type of CNC lathe to meet the special processing of the medium-concave variable-round piston. The development of linear motor technology with 篼 frequency response characteristics makes this requirement possible. When machining, the machined parts are mounted on the machine tool spindle and rotate with the spindle. The tool is mounted on the linear motor and is opposite to the linear motor. The machined part reciprocates radially. Due to the extremely complicated shape of the convex and convex cylindrical piston, the amount of data to be processed during interpolation is large, and the response speed is also required to be high. In addition, when machining the piston, it is necessary to simultaneously control two different types of motors, one is position servo, and the other is a special servo linear motor for machining non-circular cross sections. General CNC software does not meet this special requirement for machining pistons. The software system introduced in this paper is a mixed programming of C language and assembly language. It adopts independent modular design, which better solves the relationship between spindle rotation and tool linear feed.

1 The overall design of the system The system host adopts the industrial control 586 machine, the system software is stored in the microcomputer hard disk. After the system is started, the user can perform various operations through the menu. The system has CNC functions such as reading machining program, compiling, simulation, generating piston machining data, controlling linear motor, interpolation, M, S, T in-position detection. The block diagram of its system is shown.

The system software adopts a hierarchical and modular design. The system software can be divided into several modules according to functions, and each module can be edited and compiled separately. The information is transmitted between them through parameters or data files. The addition, modification, deletion, etc. of one module do not affect other modules. The system software is divided into interface layer, compilation layer, control layer and auxiliary layer, and the operations of each part are relatively independent. Its overall structure is as shown.

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The real-time 'system I number compensation 丨I in place' measurement 丨 2 system composition and characteristics from the system can be seen that the system consists of six modules, and has a real sense of control on the 糸 糸 糸 糸 糸 糸 砝氙 砝氙Yan Lixin, Yang Yong (56 Mailbox, College of Agricultural Engineering, Nanjing Agricultural University, Nanjing 210032, China) Date: 2000-07 CNC lathe is a typical mechatronic product, widely used in machinery manufacturing. However, the price is generally 5 to 10 times that of a conventional lathe. If a collision occurs during processing, the lighter will damage the accuracy of the product and cause waste. In severe cases, the machine tool will be damaged, causing major economic losses and personal injury.

After observation and analysis, the author summarizes several possibilities for collision on CNC lathes, and proposes a method to avoid collisions when programming CNC lathes.

1 When using the G00 command, there is a high possibility of collision. As shown, the workpiece requires a slot, the workpiece origin is at the right end, and the tool change point is when the slot is finished. To save time, you want the tool tip to start from the starting point. Arriving at the tool change point >1, using the N150G00X80Z50 block to complete the retraction. If the track is considered to be a sinuous connection, it seems that there is no problem, but the actual tool nose trajectory is B and the line (as time help function. In this system, the user can Firstly, according to the specific requirements of the part pattern, the input and the operation of each data are performed at the interface layer in the manner of human-machine dialogue. At the compilation level, the information input by the user is compiled to generate the target code, which includes Format conversion, coordinate conversion, error detection, calculation of control data, interpolation of list curve, coarse interpolation, etc. of NC source program; at the control layer, issuing instructions for controlling system operation, coordinating functions of various parts of the system; Provides a variety of auxiliary functions that facilitate system operation and user-friendly operation. The whole system is controlled by keyboard and mouse. Users want to select a menu, just press the cursor and heat. In addition, the system also has a strong graphics function, providing a graphical display of the piston input data, a dynamic simulation function of the tool trajectory, and displaying the input data and the tool in an intuitive form. ) It is obvious that the tool must collide with the step surface of the workpiece during the movement process, and the workpiece and the tool must be damaged, and the accuracy of the machine tool must be seriously damaged.

The difference between the point positioning command G00 and the linear interpolation command G01 is not only the speed of the speed, but more importantly, the trajectory of the former is generally not a straight line, and the latter must be a straight line reaching the end point. If you mistakenly believe that G00 is also a straight line to reach the end point is very dangerous. The trajectory of the tool tip moving from the original position to the point position commanded in the G00 block is generally a straight line segment with two different angles, that is, a curve is to be turned during the traveling, and the tool holder X and Z directions are respectively set according to the respective positions. Speed ​​travels, each to the end of the child in this direction.

To perform the retraction, the trajectory of the tool is shown in Figure lb, so that collisions can be avoided.

The running track enables the user to find operational errors in time.

3 Summary The system adopts a top-down design method, friendly interface, real-time help function, graphic simulation function, alarm function, etc., which can save a lot of time spent on machine tool over-the-air inspection and trial cutting inspection. The efficiency of the machine tool is reduced and the production cost is reduced. The system has been successfully tested in several machine tool plants.

Lin Yuhong. Machine Tool Numerical Control Technology and Its Application M. Beijing: Mechanical Industry Press, 1994. (Editor Enlightenment) Born in 1966, lecturer, the main winter research direction is: CADfCAM and related fields.

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