According to the different running speed of the electrode wire, EDM wire cutting machine tools are usually divided into two categories: one is the high-speed wire EDM machine tools (WEDM-HS), the electrode wire for high-speed reciprocating motion, the general wire speed of 8 to 10m/s, the electrode wire can be reused, processing speed is higher, but the fast wire walking is prone to cause the electrode wire jittering and reverse when the pause, so that the quality of the process Decrease, is China's production and use of the main types of machines, but also China's original EDM wire cutting processing mode; the other type is a low-speed walking wire EDM wire cutting machine (WEDM-LS), the electrode wire for low-speed unidirectional movement, the general speed of the walking wire is less than 0.2m/s, the electrode wire is no longer used after the discharge, smooth, uniform work, jitter is small, processing quality is better, but the processing speed is lower, is the main types of machine production and use of foreign countries. Production and use of the main types of machines.
Based on the electrode wire trajectory control form of different, EDM wire cutting machine can be divided into three kinds: one is * imitation shape control, which in the wire cutting processing, pre-produced with the same shape of the workpiece * mold, processing of the workpiece blanks and * mold clamped at the same time in the machine tool table, the electrode wire in the cutting process tightly adhering to the * die edge of the trajectory of the movement, so as to cut out the workpiece with the same shape and accuracy of the * mold, so that the workpiece and the * die shape and accuracy of the workpiece. The other one is photoelectric tracking control, which before carrying out wire-cutting processing, firstly depicts a photoelectric tracking map according to the drawing of the parts at a certain magnification ratio, and then puts the drawing on the photoelectric tracking table of the machine tool during processing, and the photoelectric head on the tracking table always follows the trajectory of the inked line graphic, and then with the help of the linkage of electric and mechanical, controls the machine tool table and the workpiece to make similar-shaped movement relative to the electrode wire, so as to cut the blank and the *mould at the same time. Do similar shape of the movement, so as to cut out the same shape with the pattern of the workpiece to; another is the digital program control, the use of advanced digital automatic control technology, drive the machine tool in accordance with the geometric shape of the workpiece before processing according to the parameters of the pre-programmed CNC machining program to automatically complete the processing, do not need to make a * model plate also do not need to draw a magnification of the map than the previous two forms of control has a higher processing accuracy and broad range of applications. Application scope, at present at home and abroad more than 95% of EDM wire-cutting machine tools have been adopted numerical control.
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Introduction of the principle of wire cutting
Introduction of the principle of wire cutting and industrial safety
History of the development of wire cutting processing machine
In the middle of the 20th century, the Soviet Union, the Lazarinkov women studied the phenomenon of the switch contacts corrosion damage by the spark discharge and the reason, found that the transient high temperature of the electric spark can be made to localize the metal melting, The instantaneous high temperature of electric spark can make the local metal melt, oxidize and be corroded off, thus creating and inventing the electric spark processing method, and the wire-cutting discharge machine was also invented in 1960 in the Soviet Union. At that time, EDM was used to manually feed the table left and right in front of a projector to view the contour, and it was thought that although the processing speed was slow, it was possible to process micro shapes that were not easily processed by conventional machines. A representative practical example is the processing of shaped holes in chemical textile nozzles. The processing fluid used at that time was mineral oil (lamp oil). High insulation, small distance between poles, processing speed is lower than today's machinery, practicality is limited.
NCization, in the deionized water (close to distilled water) in the processing of the machine type first by the Swiss electrical discharge processing machinery manufacturer in 1969 in Paris, the exhibition of workhorses to improve the processing speed, the establishment of unmanned operating conditions of security. However, the production of NC paper tapes was very laborious, and it was a great burden to the users if they did not use automatic programming with a large computer. Before the appearance of cheap automatic programming devices (Automatic Programmed Tools APT), the popularity is very slow.
Japanese manufacturers to develop a small computer automatic programming wire EDM machine cheap, accelerate the popularity. The processing shape of WEDM is a quadratic contour. Automatic program device widely used in the simple form of APT (APT language is easier than the official model), the emergence of the simple form of APT as an important factor in the development of wire-cutting discharge machine.
WEDM basic principle
WEDM uses copper wire as the tool electrode, and applies 60~300V pulse voltage between the copper wire and the processed material such as copper, steel or super-hard alloy, and maintains a gap of 5~50um, and the gap is filled with insulating medium such as kerosene, pure water, etc., so that spark discharge occurs between the electrode and the processed material, and each other is consumed, Corrosion. Electrode on the surface of the workpiece countless small pits, through the NC control monitoring and control, servo mechanism implementation, so that this discharge phenomenon is uniform and consistent, so as to achieve the processed material is processed, so that it becomes the size and shape of the required precision products.
The physical principle of EDM is as follows:
In order to produce EDM between two electrodes, the voltage between these two electrodes must be higher than the gap (electrode-workpiece) breakdown voltage depends on:
1) the distance between the electrode and the workpiece;
2) the dielectric fluid insulation (water specific resistance);
3) the pollution condition of the gap (water specific resistance);
3) the dielectric fluid (water specific resistance). The contamination status of the gap (corrosive waste).
Discharge occurs first at the point where the electric field is strongest, which is a complex process; free positive ions and electrons accumulate in the field
and soon form a conductive channel that is ionized; at this stage, a current is formed between the two plates. Numerous collisions take place between the conducting
particles, forming a plasma zone, which soon rises to a high temperature of from 8000 to 12000 degrees
, instantly melting some of the material on the surfaces of the two conductors, and, at the same time, owing to the vaporization of the electrodes and of the dielectric fluid,
a bubble is formed, and its pressure rises regularly until it is very high; the current is then interrupted, and the temperature is suddenly
lowered, causing the current to flow. p>
Decrease in temperature causes an inward explosion of the bubble, and the resulting momentum throws the dissolved material out of the crater, and then the corroded
material is recondensed in the dielectric fluid into small spheres, which are discharged by the dielectric fluid; for the corrosion of the electrodes and of the workpieces
The problem of asymmetry of corrosion
pairing is dependent on electrode thermal conductivity, the melting point of the material,duration, and the density of discharge
degree, which occurs at the electrodes is called loss. The problem of asymmetry depends on the thermal conductivity of the electrode, the melting point of the material, the duration and the density of the discharge.
Industrial safety
In order to ensure that the operator and the machine tool are in the best safety conditions, as well as the health of the personnel in the same plant and have a comfortable working environment, so that the machine and equipment can maintain the original machining performance and accuracy for a long time, and prolong the service life, it is necessary to comply with the rules of safety of wire-cutting discharge machining.
I. Environment:
The choice of environment has a direct relationship with the WEDM equipment and its operators, and the good or bad choice of environment has the following influences: firstly, it damages the performance and accuracy of the equipment and shortens the life of the machine tool; secondly, it influences the accuracy of the workpiece processing and causes the quality to be poor; and thirdly, it jeopardizes the operator's safety and physical health. Therefore, please refer to the following matters in the selection of the environment place:
1. Meet the space size required by the WEDM machine tools;
2. Select the place that can bear the weight of the machine tools;
3. Select the place where there is no vibration and shock incoming.
WEDM is a high-precision processing equipment, if the place where it is placed has vibration and shock, it will
cause serious damage to the machine, which will seriously affect its processing accuracy, shorten its service life, and even lead to the scrapping of the machine.
4. Choose the place without dust and avoid the place next to the channel with many streams;
(1) The characteristics of the WEDM machine itself, there is dust in the air, which will make the machine's
screws suffer serious wear and tear, thus affecting the life of the machine;
(2) The WEDM machine belongs to the computer control, and the disks used in the computer are very sensitive to the dust in the air, which will cause serious damage to the machine.
Requirements for dust in the air are quite strict, when there is dust inside the disk, the disk will be damaged, and also damage the hard disk;
(3) WEDM discharge machine itself emits a lot of heat, so the electrical cabinet needs to be frequently exchanged, if there is too much dust in the air, it will be deposited on the electrical components during the process of exchanging the air, which will result in the poor heat dissipation of the electrical components, and thus cause the circuit boards to be burned out. Circuit boards are burned out. Therefore, the machine dust net should be cleaned frequently.
5. Choose a place with small temperature change, avoid direct sunlight through windows and top window glass and close to heat flow
Place
(1)The products of high precision parts processing need to be carried out at a constant temperature, generally 20C room temperature;
(2)Since the wire-cutting discharge machine itself generates considerable heat when working, if the temperature change is too large, it will cause damage to the machine. is too large, it will have a serious impact on the service life of the machine.
6. Select the shielded house: because the wire-cutting discharge process belongs to the arc discharge process, in the arc discharge process will produce strong electromagnetic wave, which will cause harm to human health, and at the same time will affect the surrounding environment.
7. Choose good ventilation, spacious plant, so that the operator and the machine can work in the best environment.
Transportation:
1. Selection of transportation: wire-cut electrical discharge machining equipment with forklift and roller type, in special cases when the choice of crane type movement;
2. Locking before transportation: before transportation, must use special random fixed parts of the bed table and each axis lock.
To prevent damage to the equipment during transportation, thus affecting the accuracy of the machine or even make the equipment scrap.
Three, operation safety:
In order not to make the machine tool and personnel damage and harm, in the operation of wire cutting processing equipment need to pay attention to the following matters.
1. Only personnel who have been trained on this type of machine and equipment are authorized to use it.
2. In order to avoid overheating of the processing fluid and the electric cabinet, the cooling system must be in continuous operation;
3. In order to avoid direct contact with the energized electric wires, the protective door of the machine must be closed;
4. It is not permitted for two people to operate the same machine at the same time, and in the operation of the running screen, you should try to reduce the luminance of the screen and choose to observe the screen in a diagonal view to reduce the harm to your eyes caused by radiation from the screen;
5. Radiation to the eyes to bring harm;
5. The processor should be proficient in the operation panel of the specific functions of the keys and the use of the state, in the operation of the machine in the process of flexible use, familiar with the conversion of the screen, in particular, several important screen (such as the preparation screen, observe the screen) has the function, to avoid the processing of unfamiliar with the operation panel caused by a variety of abnormalities, and another due to the keys (especially) the high density of commonly used keys. Another reason is that the keys (especially the common keys) are easy to be damaged by high-intensity use, so when operating the panel, a layer of plastic paper should be attached to the surface for protection, in order to prolong the service life of the operating panel;
6. The same as the operating panel, the processor should be familiar with the specific use of the remote control, the keys of the remote control should be protected by a layer of plastic paper on the outside of the remote control, and the remote control can be detached from the operating panel to operate over long distances. In addition, the reason why the remote control can be operated far away from the operation board is to utilize a wire for conduction, so the protection of the remote control should also include the protection of the wire. In the use of the process can not vigorously pull the wire, so as to avoid remote control failure, the part of the wire column should be placed in a circle, after use, must be put back to the original place to hang up;
7. In the machine tool or machine head movement, never put your hand can be placed in the fingers of the machine head and the work between the object, by preventing the wrong instruction or the direction of the key to press the wrong, resulting in security accidents;
8. When the workpiece, should pay attention to whether the clamping method will hurt the processing platform, in the use of the machine should be blown dry platform, long-term non-use should be on the anti-rust oil to protect the machine tool;
9. In the process of setting up the workpiece, should pay attention to the cutting whether it will hit the upper and lower head, for the processing of small holes should be used in a special processing technology, to avoid the waste can not be taken out of the card material caused by the material, affecting the accuracy of the machine tool;
10. workpiece clamping in order to facilitate and solid as a principle, when setting up the workpiece compression force to the workpiece is not washed by the water as a principle, so as not to cause the screws to slip and can not be unloaded;
11. in the daily work, often encountered the use of general set up the mold method can not be processed by the workpiece, in this case it is necessary to use a special clamping fixtures:
(1) small workpiece - the pressure plate is unable to When set up can consider the use of positive angle or wheat stone processing;
(2) In the case of large inclined type of workpiece - can not be tilted processing, should be used sinusoidal table or inclined pads to assist tilting of the processing method of processing;
(3) multiple pieces of processing - can be considered to use the positive angle or wheat stone for the overlap of the processing
(4) in the process of the fixtures should be ensured that the fixture not be damaged.
(such as: for the convenience of rack mold and in the cutting of the jig and other actions are not feasible)
12. Processing should pay special attention to the equipment: voltmeter voltage in the standard range of provisions;
13. Processing can not directly touch the workpiece and copper wire with your hands, the drop should pay attention to the phenomenon of the head of the head of the machine card head, the head of the difficult to take out the equipment and be careful to take care of fingers from injury;
13. When it is difficult to take out the material head, we should be careful that the equipment and fingers will not be hurt;
14. When cleaning the processed material, oxalic acid cleaning liquid will be used, when using it, we should use the brush to wash the processed material, and we should not use our hands to touch the oxalic acid cleaning material directly, so as to reduce the corrosion of the oxalic acid opponents, and we should not get the oxalic acid into the eyes, and we should use the water to wash the material if we get it into the eyes;
15. The operator of the wire-cutting machine should be careful about the washing of the hands diligently after processing, especially before the meal, we should wash the hands. The operator of the wire cutting machine should wash his/her hands after processing, especially before eating, to avoid harming his/her body by ingesting processing fluids with more impurities;
16. When carrying out all kinds of maintenance and testing inside the power cabinet or on the electrical parts of the machine tool, the main switch must be set in the OFF position and a sign must be set up (do not turn on the power during maintenance);
17. When carrying out maintenance and testing, safety instructions must be observed and the corresponding chapters in the manual must be consulted prior to any maintenance work;
18. Must consult the corresponding chapter in the manual;
18. Only when the control cabinet cut off the power supply, you can touch the electronic components;
19. When you take the components, you can only grasp the handles, do not touch the gold-plated wires of the printed circuit board;
20. Components that have been damaged must be put into a protective device, in order to rest assured of the removal of the device;
21. wear parts of the equipment should be replaced in a timely manner in order to maintain accuracy.
Four, safety devices:
A, machine and equipment safety equipment of the introduction:
1. Buzzer settings (can be in the event of a stop or anomalies in the automatic alarm);
2. Screen protection settings (can be in the screen for a long time not to be used when the screen is automatically shut down to reduce radiation);
3. Emergency braking key settings (can be in the event of sudden abnormalities in the emergency brake);
3. Emergency brake key (can be used in the event of sudden abnormality emergency brake);
4. Cooling fan installation (mainly responsible for the ventilation of the main chassis cooling);
B. Safety equipment operation and use of methods:
1. The use of the buzzer, the use of the buzzer has only two statuses: when the function selected for the "ON", buzzer will automatically alarm for the emergence of anomalies. When the function is selected as "ON", the buzzer will automatically alarm the abnormalities; when the function is selected as "OFF", the buzzer does not work. When the function is selected as "OFF", the buzzer does not work. The buzzer is mainly used as a reminder to remind the processor to continue processing when the machine is paused;
2. The use of screen protection: The screen protection of Shadick models can be set up using the modification of the parameters to choose whether or not to enable the screen protection and set the time to enable the time, such as not in use when it is off;
3. The use of the emergency brake button: When a sudden abnormality occurs, the processor is unable to immediately stop the machine, and the machine is not able to stop. Emergency Brake Button: When there is a sudden abnormality in the machine, and the processor can't think of a correct solution immediately, the machine can be braked by pressing this button;
4. Heat dissipation fan will be enabled when the main power supply is turned on;
First Aid and Escape:
1. Fire: In case of a fire, the fire should be dealt with correctly and reported to the supervisor immediately, and call the fire police to report the fire to the police. "119" telephone (must have received a senior supervisor's order), to make clear the name and address of the unit on fire, fire material, fire size and the alarm's name and phone number, and actively participate in fighting the initial fire, to prevent the spread of fire, when the fire is difficult to control, we must calm down and try to escape. When surrounded by smoke, to cover the mouth and nose with a wet towel, low-position walking and creeping through the scene, when the escape route is blocked by smoke and fire, can be used to wet quilts and other drapes on the body stooped to rush through the fire. When the escape route is blocked, you can escape through the balcony drainpipe, etc., or in a fixed object on the rope, along the rope to escape from the fire, if the above measures do not work, should be returned to the interior, close the doors and windows leading to the fire area, and pouring water out of the window to slow down the spread of the fire, and at the same time to the window to send out a signal of distress, in short, in any case, do not give up hope of rescue;
2. When found that some people Electrocution, first aid work should be carried out quickly, move quickly. Accurate methods are the most critical. Whenever and wherever found critical patients or accidents, can call "120" phone, request first aid center for first aid. First of all, should quickly cut off the power supply, if the power switch is far away, can be used to insulate the body of the person electrocuted to pull open the wire, or with an insulated handle of the tool to cut off the power supply, do not use metal materials or wet objects as a rescue tool, and can not be contacted by the body of the person electrocuted, in order to prevent their own electrocution. When the electrocuted person from the power supply, should be based on its specific circumstances, rapid treatment of symptoms. The injury is not serious, conscious people, should be made to rest quietly for an hour, and then sent to the hospital for observation; on the more serious injuries, but also unconscious, but the heart beat and breathing still exists, it should be comfortable, quiet lying down, and quickly ask the doctor or sent to the hospital, on the seriousness of the injuries, respiratory arrest or the heart stops beating, or both have been stopped, artificial respiration should be carried out immediately and the chest squeezing and sent to the hospital quickly for treatment.