Using molybdenum cutting wire or brass wire
China’s high-speed molybdenum wire-cut WEDM has made great progress, but there has been a tendency for heavy equipment and light processes, resulting in backward technology.
(l) The selection of line cutting process parameters still largely depends on the operator’s experience, or approximate selection based on the process parameter table, and the process parameters are set irrationally, which severely affects the development of the machine capacity.
(2) Molybdenum wire-cutting processing cannot predict the effect of technology based on the addition of T-parameters, and cannot meet the requirements of modern manufacturing environments.
(3) The parameters used in the wire cutting process are many, affect each other, and are complex and random. Our research on the processing mechanism and T-arts law is not sufficient, mainly because there is no systematic development of the process test and there is no innovation in research methods.
(4) The power supply, control system, numerical control system, and instruction code of domestic high speed wire cutting machine tools are all different. The high-speed molybdenum wire cutting process technology depends on the specific machine conditions, and there is no unified standard to follow.
In order to solve the above problems and promote the improvement of the level of our country’s wire-cutting processing technology, it is necessary to establish a simulation system for the prediction of high-speed wire-wound wire-cut EDM processes and the optimization of process parameters. The system can predict the effects of the molybdenum wire cutting process, optimize the selection of process parameters, perform simulation experiments on the computer, and apply to various types of high speed molybdenum wire cutting machine tools.
1. Simulation system structure
High-speed molybdenum wire EDM machining process simulation system structure is shown in Figure f> -13. The main modules included in this system are:
(1) Training model module. Different high speed molybdenum wire or brass wire cutting machine tools, the corresponding actual value of the processing parameter code is different. According to the actual processing conditions, set the corresponding parameters of the processing conditions. For different high speed wire cutting machine tools and processing conditions, the user conducts a complete process test, through the process database management module, to create a new process database or to update the existing process database. Taking the process database as a sample database and training the artificial neural network, a corresponding simulation system can be obtained.
(2) Process effect prediction module. For the set process conditions, the predicted model can be used to predict the process effect of the molybdenum wire cutting process for a given process parameter and analyze the process effect.
(3) Process parameter optimization module. Given the thickness of the workpiece to be machined, input the desired processing technology effects, and the optimization model of the operation satisfies the processing requirements, so that the processing standards are optimized, the surface roughness is minimized, the surface quality is optimized, and the cutting speed is increased as much as possible. .
(4) Process law research module. There are many factors that affect the technological effects, including electrical parameters and non-electrical parameters. Among them, the influence of electrical parameters is very important. This module focuses on the effect of pulse parameters on the process performance.
(5) Help module. This module provides technical support for users. In addition, when the user uses the simulation system, online help is provided to facilitate the user’s learning and operation.
(6) Other functional modules. The system provides functions such as saving files and online printing. The user can save or print process data, running results, etc.
2. Functional modules of the simulation system
(1) Process effect prediction module. Using the BP neural network’s ability to map the input and output, and the ability to perform self-learning, an artificial neural network model of wire-cutting processing was established. Based on this, the prediction of the effect of the rapid wire-cutting process can be achieved. The BP network adopts improved 8 learning rules to learn the learning samples, constantly modify network parameters, connection weights and thresholds, until the network converges, and stores the BP network parameters, connection weights, and thresholds into the data file. The process effect prediction module reads network parameters, connection weights and thresholds from the data file, and uses the built BP network to predict the process effect. For processing conditions set by thousands, the user inputs the processing parameters and predicts the processing effect that the system can give.
The user selects the predictive model and enters the process parameters (workpiece thickness, pulse width t; pulse interval t. and pulse the peak current /;), can predict the corresponding process effect (molybdenum wire cutting speed V..,; and surface roughness Ra). Process effect prediction is divided into two cases: one is the experimental value of process effect, and the other is the experimental value without process effect. If there is a test value of the process effect, the prediction module can compare the test value and the predicted value of the process effect, and give the error analysis result.。
(2) Process parameter optimization module. The goal of optimizing line cutting process parameters is to increase the cutting speed as much as possible, reduce the surface roughness, and improve the surface quality while satisfying the processing requirements. Based on the high-speed molybdenum wire cutting simulation model established by the BP network, the thickness H and the allowable maximum surface roughness Ra of the fly parts to be processed are input. The simulation system uses the simulated annealing algorithm to optimize the selection of processing parameter groups that meet the requirements. (Pulse width t; pulse interval t. and pulse peak current/;), and give the corresponding optimal process effect (cutting speed V..; and surface roughness Ra). Simulated annealing algorithm is not limited by the initial conditions of the network, and it is not easy to fall into the local minimum. The global optimal solution of the problem can be found.
(3) Process law research module. The main evaluation indexes of the molybdenum wire EDM process are cutting speed and surface roughness. The factors influencing the effect of the process are very complex. Pulse power supply, electrode wire, workpiece, working fluid, mechanical transmission, control system, etc. all have an effect on the process effect. The influence of pulse parameters is very important. This module focuses on the study of electrical parameters (pulses width t; the pulse interval t., and the pulse peak current !;) on the process effect. Using simulation methods to study the law of molybdenum wire cutting processing can not only study the mechanism of stable processing, but also extend the research scope to unstable processing areas and processing conditions that are difficult to achieve in actual processing.。
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