How to write the learning report of EDM machine tool?

How time flies! How time flies! Five weeks of WEDM have passed in a blink of an eye. Although the internship time is not long, it has gained a lot. Although I am very tired and bitter during my internship, I feel very happy! It's my first time to attend an internship processing class, and I feel very excited! Moreover, in the colorful technical school career, such opportunities will not be too many, so from the beginning, I felt that such opportunities were very rare, so I should cherish such hard-won opportunities! Now the five-week WEDM practice is over.

Near the end, recalling the dribs and drabs of five weeks, I feel a lot, and even have a feeling of wanting more!

Our first exercise was wire cutting. After the patient explanation and demonstration by the masters, we also learned how to cut some simple metal workpieces. This is strange to us, because of its magical and accurate operation, we have a great interest. A tiny molybdenum wire, with his persistent disdain, twisted and cut out what people want. The teacher told us about safety first. Tell us how to do it is dangerous, then the masters begin to teach us some basic problems, and finally teach us to program on the computer and control the direction of the machine. In this way, the morning passed unconsciously, although tired, but the psychological feeling is very sweet. In the next two days, we will repeat the first day. Although I feel bored, considering that the masters work in the workshop every day and are not bored, we are nothing these days. Under the careful teaching of the masters, I quickly completed the task and said goodbye to the masters soon.

1.WEDM is an electro-machining machine tool, which cuts metals (especially hard materials and linear complex parts) with molybdenum wire through electro-corrosion.

Wire cutting (WEDM)

Cutting EDM (WEDM), sometimes called WEDM. Its basic working principle is to use thin metal wire (called electrode wire) which moves continuously as electrode to remove metal and cut workpiece by pulse spark discharge. It is mainly used to process various complex and precise workpieces, such as punches, dies, punches, fixed plates, discharge plates, etc. Forming tools, templates, metal electrodes for EDM, all kinds of fine holes, grooves, arbitrary curves, etc. It has the outstanding advantages of small machining allowance, high machining precision, short production cycle and low manufacturing cost, and has been widely used in production.

WEDM machine tools are usually divided into three categories according to the different running speed and processing quality of electrode wires:

The first one is WEDM-HS, whose electrode wire reciprocates at high speed. Generally, the speed of electrode wire is 8 ~ 10 m/s, and the electrode wire can be reused, so the machining speed is high. However, the electrode wire will easily shake and stop in the opposite direction, which will reduce the machining quality. It is the main model produced and used in China and the original WEDM processing method in China.

The second type is WEDM-LS, in which the electrode wire moves in one direction at a low speed, and the linear speed is generally lower than 0.2m/s, and the electrode wire is no longer used after discharge. It works smoothly, evenly, with little jitter and good processing quality, but its processing speed is low, so it is the main model produced and used abroad.

The third medium-speed WEDM machine tool should be accurately called "multi-speed WEDM". It is original in China, and the principle is to cut the workpiece repeatedly. At the beginning, it was cut with faster spool speed and stronger high frequency, just like the current high-speed wire cutting, and the last knife was polished with slower spool speed and weaker high frequency current, thus improving the machining smoothness. Moreover, after the linear speed is reduced, the jitter of the guide wheel and bearing is smaller and the machining accuracy is improved;

In addition, the first knife has the fastest cutting speed, and the subsequent cutting and grinding amount is very small. Therefore, the total time of three-knife cutting is generally faster than that of one-knife cutting of fast-moving line.

According to the different control forms of electrode wire trajectory, WEDM can be divided into three types:

One is profiling control, in which a die with the same shape as the workpiece is made in advance before on-line cutting, the workpiece blank and the die are clamped on the workbench of the machine tool at the same time during processing, and the electrode wire moves close to the edge of the die during cutting, so as to cut the workpiece with the same shape and precision as the die;

The other is photoelectric tracking control. Firstly, according to the part pattern before wire cutting, the photoelectric tracking diagram is drawn according to a certain amplification ratio. During machining, the pattern is placed on the photoelectric tracking table of the machine tool, and the photoelectric head on the tracking table always follows the trajectory of the ink line pattern. Then, with the help of electrical and mechanical linkage, the machine tool workbench and the workpiece are controlled to do similar movements relative to the electrode wire, so that the workpiece with the same pattern shape can be cut.

The other is digital program control, which uses advanced digital automatic control technology to drive the machine tool to automatically complete the machining according to the NC machining program pre-programmed according to the geometric parameters of the workpiece before machining, without making templates or drawing enlarged drawings. Compared with the first two control forms, the machining accuracy is higher and the application scope is wider. At present, more than 95% WEDM machine tools at home and abroad have adopted numerical control.

WEDM belongs to the category of electrical machining and was invented by the former Soviet Union. China was the first country to be used in industrial production. On this basis, we developed a fast WEDM system (HS) in China and a slow WEDM system (LS) in Europe, the United States and Japan.

The main differences are: 1, tungsten-molybdenum alloy wire is used for electrode wire in China, and brass wire is used abroad; 2. Soap chemicals are used at home and deionized water is used abroad; 3. The linear speed in China is about 1 1 m/s, and it is about 3~5 m/min abroad. Our electrode wire is reused until it is broken, which is not reused abroad. 5. Our accuracy is not as high as that of foreign countries.

Second, the principle of EDM.

Electrical discharge machining (EDM) is a special machining method to remove conductive materials by electrical corrosion generated by pulse discharge between two electrodes immersed in working fluid. It is also called electrical discharge machining or electrical corrosion machining, or EDM for short.

During EDM, the tool electrode and the workpiece are connected to the two poles of the pulse power supply respectively, and immersed in the working liquid, or the working liquid is filled into the discharge gap. The gap automatic control system controls the tool electrode to feed the workpiece. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied to the two electrodes will break through the working fluid and generate spark discharge. A large amount of heat energy is instantly concentrated in the micro-channel of discharge, the temperature can be as high as 10000 degrees Celsius, and the pressure changes sharply, so that a small amount of metal materials on this working face are immediately melted and gasified, and explosively splashed into the working liquid, which quickly condenses to form solid metal particles and is taken away by the working liquid. At this time, tiny pits were left on the surface of the workpiece, and the discharge stopped for a short time, and the working fluid between the two electrodes returned to an insulating state. Then, the next pulse voltage breaks down at another point where the two electrodes are relatively close to each other to generate spark discharge, and the above process is repeated. In this way, although the amount of metal etched by each pulse discharge is very small, more metal can be etched due to the action of thousands of pulse discharges per second, which has a certain productivity.

Through this internship, we learned about the production mode and technological process of modern machinery manufacturing industry. Familiar with the main molding methods and processing methods of engineering materials, the working principle and typical structure of the main equipment used, the use of fixtures and measuring tools and the safe operation technology.

It is said that eyes can't deceive themselves, but sometimes eyes can deceive people. What seems simple may not be done well. Only by personal practice can we know the mystery and make an ideal product. Practice is the truth of learning! If I have another chance, I will take part in such an internship. I will use practice to improve my knowledge and ability, so that I can have a higher ability to adapt to society when I leave campus. Thanks to the school and teachers for giving us this opportunity to hone ourselves and improve ourselves!