Trouble shooting in WEDM using molybdenum wire or brass wire
- Trouble shooting principles
(l) First outside and then inside. The development of wire-cut EDM technology is very mature today. The machine tool structure and the control circuit of the electrical control box are generally free of problems and lead to the failure of spark wire cutting. Therefore, in the process of diagnosis, it is necessary to start from the outside, check the operation process, the conditions of the processing, and the status of each wear part of the movement, instead of unwittingly dismantling the machine parts and the circuit board of the electric control box, change the structure of the machine bed and the internal settings of the control system. Otherwise, the problem will become more and more complicated.
(2) First mechanical then electrical. The wear parts of electric spark wire cutting machines are prone to failure, and they can be seen and touched easily, and they are easy to check; while the electric air traps are not only rarely generated, but also cannot be seen, make it difficult to check. Therefore, in the fault diagnosis, we must first start with the mechanical part, carefully observe and inspect, especially the normal operation of those moving parts and wearing parts, whether there is obvious wear, loose or crack phenomenon. Problems were found during the inspection and they should be excluded. After troubleshooting the mechanical fault, if the fault is still not completely eliminated, check the electrical fault.
(3) First analyze and then implement. After a wire-cut electric discharge machining using molybdenum cutting wire fault occurs, the cause of the fault must be carefully analyzed based on the product description and the schematic diagram, and the inspection plan should be determined based on the relationship between the various modules of the entire system, and then implemented and eliminated one by one. Never blindly repair without analysis.
(4) Simple and complicated first. Some failures are caused by a variety of factors. After careful analysis, we should follow the principle of simple and complicated first, first solve and eliminate those projects that are easy to implement, and then gradually in-depth examination to exclude some of the more difficult projects. In fact, in the face of complex problems, we should also break it down, or “segment it out,” and then we must solve it one by one.。
- Trouble shooting methods in WEDM using molybdenum cutting wireor brass wire.
(1) Routine inspection method. The routine inspection method refers to the routine inspection performed by the maintenance personnel before starting the equipment. Specifically include the following aspects;
① Power supply. Check the input power of the wire-cut electric discharge machine, whether its voltage fluctuation is in the range of 10% or more, whether the high-order harmonics are serious, the size of the power factor, and whether or not a regulated power supply needs to be installed.
② wire cutting working fluid. The role of the wire cutting machining fluid is cooling, washing, chip removal, etc. Therefore, whether the wire cutting machining fluid is qualified or not will directly affect the quality of the workpiece. Check if the thread cutting fluid is too dark and has an odor. If it is, its overall performance will be poor and it will easily lead to broken wires.
③ Electrode wire (molybdenum cutting wire or brass wire). The electrode disc quality, installation, preservation and other factors will directly affect the quality of the workpiece after processing. Check if the wire is selected properly: Use thicker wires when machining thick workpieces or high-current machining. This will facilitate chip removal and increase the cutting speed. Check the tightness of the electrode wire installation: if it is too loose, the electrode wire will be fierce and it will break easily. If it is too tight, the tension will increase and it will break easily. Check if the position of the electrode installation is off center and is not in the same plane. Check whether the preservation of the electrode wire is regulated. If there is moisture, oxidation, and exposure during storage, the electrode wire will become brittle and fragile.
④ control cabinet. Due to static electricity and other reasons, the control cabinet is susceptible to dust. When these dusts are exposed to moisture, they will erode the circuit board, and causes short-circuit or broken-circuit conditions, damage the electronic components, etc., or even the entire circuit board will be scrapped. Therefore, the maintenance must be checked before maintenance.
For example: A cnc molybdenum wire cut machine will break an irregular wire once in a while: sometimes it can run for one day and sometimes it will break several times a day. The inspection revealed that the wire cutting fluid was black, but there was no odor. Careful observation revealed that too much impurities were present in the wire cutting machining fluid, resulting in poor insulation, eventually leading to irregular wire breakage, and troubleshooting after replacing the new machining fluid.。
( 2) Consumables inspection method. The inspection of wearing parts means that after the equipment is started, the maintenance personnel check the faults that have occurred. After C equipment is operated for a long period of time, most of the failures are caused by the damage of thousands of wearing parts. The wearing parts mainly include guide wheels, wire (molybdenum wire china or brass wire) blocking devices, broken wire protection block wires, electric blocks, and cushions and limit switches. The following is a brief description of how maintenance personnel perform consumable inspections.
- guide wheel. The main role of the guide wheel is to reduce friction and locate the aluminum wire. Problems such as the wrong position of the guide pulley and the fact that the guide pulley does not turn on the surface of the guide pulley can cause many kinds of problems. The wrong position of the guide wheel makes it impossible to machine a qualified work piece; the guide wheel does not turn and the surface wear deteriorates, and the surface of the guide wheel will be cut by the key wire very quickly. If the groove is shallow, when the key wire has a large amount of jitter, the aluminum wire will be locally excessively close to the workpiece, so that the discharge current is too large or the wire is burned due to the arc drawing, and the surface quality of the cut surface is deteriorated; The groove is deep and the high-speed movement of the key wire is pinched by the walls of the groove under slight shaking. Therefore, maintenance personnel must carefully inspect the surface of the guide roller in contact with the aluminum wire (not molybdenum wire or brass wire) .
- Wire (molybdenum cutting wireor brass wire) block device. The main purpose of the wire catcher is to position the key wire. When checking, it is necessary to pay attention to whether the thread-receiving column in the wire-blocking device is close to the aluminum wire and whether the thread-receiving column has been cut into a groove. In addition, it is necessary to carefully observe whether there is any phenomenon of overlap on the cartridge.
- broken wire protection block. The main function of the blocking wire is broken wire protection to prevent the electrode wire from being disturbed after wire breakage. During the inspection, measure whether the broken wire protection switch is normally closed. If not, the position of the broken wire protection block should be adjusted so that the broken wire protection switch is normally closed.
- Incoming blocks. The main function of the incoming block is electrical conduction. However, the electric inlet block is easily damaged, such as being cut into a deep groove, the surface being oxidized, etc., which can cause poor contact between the electric block and the key wire(molybdenum cutting wireor brass wire). When the contact is poor, it may cause the high-frequency pulse current to decrease, or even no high-frequency pulse current output.
- Cushion Q The cushion cushions when commutating. During the inspection, listen to the sound produced by the wire removal mechanism, especially when changing direction. If the sound is abnormal, the vibration is very large. In general, the cushion is damaged.
- travel switch. The main function of the travel switch is to reverse or break the high frequency. The winding motor cannot be switched or switched and the high frequency cannot be cut off because the stroke switch is easily damaged or badly contacted after frequent pressing. When the trip switch malfunctions, the contactor cannot be powered off, causing the wire-sweep motor not to switch back to L. There is another pair of trip switches on the wire cutting machine as the control signal to cut off the high frequency. When the trip switch is in poor contact or damaged, it will appear that the switch cannot interrupt the high frequency phenomenon.
For example: When a wire cutter switches (to cut molybdenum cutting wire or brass wire) direction, it cannot turn off the high frequency. The inspection found that the broken wire protection block has been cut into a deep groove, and the control circuit of the broken wire protection does not control the function of the total power supply and only controls the high-frequency circuit. Therefore, when the block is cut into a deep groove, the micro switch is normally closed due to the sag of the iron block, and the high frequency circuit cannot be turned off. Replace the block and the fault can be eliminated.。
- Principle-analysis method. The principle analysis method is to analyze the cause of the fault according to the product specification of the electric spark wire cutting machine and its working principle under the detailed understanding of the fault, and try to find a solution to the problem as far as possible. There are many kinds of such methods, the most commonly used are the following:
Mind the whole heart. According to different functions in the original diagram, it is divided into main circuit and control circuit. The main circuit mainly includes wire feeding motor and water pump motor circuit. The control circuit mainly includes industrial control board, motion control card, interface card, X, Y drive board, UV drive board, high frequency power supply and so on. When a fault occurs, according to the analysis of fault phenomena, it is determined which part the fault belongs to, which gradually narrows down the fault and can eliminate the fault faster.
- reverse analysis method. When it is basically determined that a certain range has failed, reverse analysis can be used. That is, it is assumed that when a circuit somewhere is not connected or a circuit is short-circuited somewhere, what kind of situation will occur will theoretically simulate the state that should be represented when a fault occurs, and determine the cause of the fault.
- circuit simulation method. When the electronic circuit has a large fault, it is common practice to use an oscilloscope to check the output signals of important links, such as voltage and waveform, to determine if the component is damaged. However, after a simple measurement, it is impossible to judge whether the output signal is correct. Therefore, the use of electronic circuit simulation software is the best choice. Through circuit simulation, we can help us to determine more quickly if the electronic circuit component is damaged.
- spare parts replacemet. For thousands of reasons, it is often difficult for maintenance personnel to obtain a complete electrical control schematic. When there is a large failure, only the general cause of the failure can be analyzed. The maintenance personnel can use spare printed circuit boards, fragile electronic components, etc. to replace it, and the equipment can be put into operation as soon as possible.
For example: an electric spark wire (molybdenum cutting wire or brass wire) cutter suddenly increases the frequency, and the high frequency current shows no change, but the speed of the wire cutting process is very slow. According to the integerization, it can be seen that the adjustment circuit has a problem. When the control cabinet is opened, it is found that the contact of the frequency circuit input signal has been virtually connected. No matter what position is adjusted, the output voltage is always zero. After re-welding, the fault is eliminated. 。
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