Why do alloy materials cut slowly? If the speed is fast, it is easy to break the wire. Please kneel down and ask what parameters are set for the fastest uninterrupted line?

1 interrupt line. It has always been a serious problem in WEDM. It stops machining and has to start from scratch, wasting a lot of man-hours, destroying the integrity of the machined surface, increasing the difficulty of realizing unmanned machining and hindering the further development of WEDM. Therefore, it is always an important topic for WEDM research at home and abroad to study the causes of broken wires and the methods to prevent broken wires.

A brief introduction to domestic and foreign research! "In the late 1980s, experts noticed that wire breakage was usually related to the increase of short circuit, and thought that both linear vibration and short circuit would reduce the processing speed and increase the probability of wire breakage. Later, they found that the discharge frequency would suddenly increase before the disconnection. The anti-broken wire control system they designed is in the workpiece degree! " The effect is good in time. Famous professor at the University of Leuven, Belgium; The ratio of left to right is randomly distributed. The designed experimental device for preventing wire breakage has achieved good results. The research shows that different types of pulse power supply have different disconnection signals, and any amount of energy that can reflect the input discharge gap will suddenly increase before disconnection. In principle, it can be used as a precursor signal of disconnection. At present, some foreign WEDM machines take protective measures according to the precursor of wire breakage. After studying the problem of broken wire in the special processing laboratory of Nanjing University of Aeronautics and Astronautics, it is considered that the process of broken wire begins with the instability of the processing process, which leads to the concentration of discharge at one point. The concentration of discharge leads to the concentration of discharge in time, which increases the gap of energy input and concentrates on one point, resulting in local high temperature. The electrode wire is burnt out. This is the whole process of disconnection. "The direct cause of wire breakage is that the heat load of the input gap increases and concentrates at one point, because the processing process is unstable. Because the reason of broken wire is the instability of machining process, it is the fundamental way to overcome the problem of broken wire by taking effective measures to make it enter a stable state as soon as possible according to the unstable signal of machining process.

1, pulse power supply pulse power supply is an important part of WEDM and the most critical setting that affects WEDM. In high-speed WEDM, the electrode wire is reused, which will directly affect the machining accuracy and increase the probability of wire breakage when the loss is large. Therefore, the pulse power supply for WEDM should have the performance of making the electrode wire loss low.

2. Cooling system When the cooling system on the wire cutting machine is not perfect, the cooling liquid splashes around with the movement of the electrode wire during machining, and the electrode wire is not fully cooled, which is easy to cause the electrode wire to burn out. Before actual wire cutting, check whether the cooling system is complete.

3. The vibration of the wire electrode in wire-feeding mechanism appears to be a main shaft, with large amplitude in the middle and small ends. If the difference caused by vibration exceeds the elastic limit of the wire electrode, it will cause wire breakage. Therefore, in order to improve the manufacturing quality of the whole wire feeding mechanism, the electrode wire adopts constant tension.

4. Tightness of molybdenum wire. If the molybdenum wire is installed too loosely, the molybdenum wire will shake seriously, which will not only cause wire breakage, but also directly affect the surface roughness of the workpiece due to the vibration of the molybdenum wire. However, the molybdenum wire should not be packed too tightly. If it is too tight, the internal stress will increase and the wire will break. Therefore, in the cutting process, the tightness of molybdenum wire should be appropriate. The newly installed molybdenum wire should be tightened before processing, and the force should not be too great when tightening the wire. After a period of processing, the molybdenum wire becomes loose due to its own stretching. When the elongation is large, the vibration of molybdenum wire will be aggravated or molybdenum wire will overlap on the wire storage tube. Make the wire run unsteadily, resulting in disconnection. Regularly check the tightness of molybdenum wire, and tighten it in time if it is slack. Install molybdenum wire. Molybdenum wire should be wound on the wire storage tube in the specified direction, and both ends should be fixed at the same time.

When winding, generally, 10mm should be left at both ends of the storage drum, and the middle winding should not overlap, and the width should not be less than half of the length of the storage drum, so as to avoid frequent commutation of the motor, accelerate the damage of parts, and avoid frequent participation of molybdenum wires in cutting broken wires. There is a stop screw at the lead-out of molybdenum wire on the machine tool. The stop rod is a guide column made of two rubies. Unlike the guide wheel, the wire blocking rod does not roll, but directly contacts with the molybdenum wire for sliding friction. Therefore, it wears quickly, and a deep groove will be formed at the place where the cylinder contacts the molybdenum wire soon after use, so it must be checked in time, turned over and replaced, otherwise it will break the wire.

5. Wire conveying mechanism. The wire conveying mechanism of wire cutting machine is mainly composed of wire storage barrel, wire rack and guide wheel. When the precision of wire feeding mechanism (mainly transmission bearing) decreases, it will cause the radial jump and axial movement of wire storage tube. The radial jump of the wire storage cylinder will reduce the tension of the electrode wire, resulting in the loosening of the wire. In severe cases, the molybdenum wire will be pulled out of the guide wheel groove and broken. The axial movement of the wire storage tube will make the wire arrangement uneven, resulting in wire folding. The shaft, bearing and other parts of the storage drum often have gaps due to wear, and it is also easy to cause wire jitter and broken wires, so the worn parts such as shaft and bearing must be replaced in time. If the high-frequency power supply is not cut off when the storage drum is commutated, the molybdenum wire will burn out due to high temperature in a short time, so it is necessary to check whether the travel switch at the rear end of the storage drum is out of order. It is necessary to keep the wire storage drum and guide wheel rotating flexibly, otherwise it will cause the vibration of the wire conveying system and break the wire when moving back and forth. After winding, run the wire with no load, check whether the molybdenum wire is shaking, and if so, analyze the reasons. The limit stop at the rear end of the storage drum must be adjusted to prevent the storage drum from breaking when it rushes out of the limit stroke. The contact friction between the stopper and the fast moving molybdenum wire in the wire blocking device is easy to produce grooves and cause wire breakage, which needs to be replaced in time. The wear of guide wheel bearing will directly affect the accuracy of guide wire. In addition, when the V-shaped groove, the gem block and the conductive block of the guide wheel are worn, the friction of the electrode wire will be too large, and the molybdenum wire will be easily broken. This phenomenon generally occurs when the machine tool is used for a long time, the workpiece is thick, and the wire feeding mechanism is not easy to clean. Therefore, in the use of machine tools, the accuracy of wire feeding mechanism should be checked regularly, and the easily worn parts should be replaced in time.

2. At present, the use of emulsified oil for wire cutting still occupies the vast majority of the market. Emulsified oil for wire cutting is actually an improved product of common emulsified oil. In the case of low cutting requirements, it shows strong versatility. However, with the increase of workpiece cutting thickness, the increase of cutting taper, the decrease of cutting cost per unit area and the increase of the proportion of difficult-to-machine materials (cemented carbide, magnetic steel and copper), the original emulsified oil for wire cutting can not be fully used. Generally, a working fluid with good performance should have the following characteristics:

★ High energy can be used for stable processing. Under normal conditions of machine tools, the average machining current of workpieces within 100mm, such as 60mm, can reach or even exceed 2.5- 3A (ampere). Under this condition, the machining efficiency of unit current should be greater than 25mm2 /min. A, that is, when the processing current is 3A, the processing efficiency should reach 75-80mm2/min. The workpiece with large thickness (200-300mm) can be cut stably with small duty ratio.

★ During the machining process, the electrode wire at the wire outlet of the workpiece will bring out more electro-corrosion products (black ink) and even bubbles, indicating that the cleaning performance of the working fluid in the kerf is good and the cooling is even and sufficient.

★ The cut workpiece should be easy to take off, the surface color should be uniformly silvery white, and the commutation stripes are shallow or almost absent.

The concept of service life of working fluid is not necessarily clear, because most operators use the method of constantly replenishing water and stock solution for processing. This method will shorten the service life of the working fluid and increase the cost.

Generally, the normal service life of a box of working fluid (calculated by 40 liters) is about 80- 100 hours (that is, about one week). Over this time, the cutting efficiency may be greatly reduced, that is, the standard of working fluid life is machining efficiency, which is generally reduced by more than 20% as the basis for replacing working fluid.

Working fluid with good performance will naturally turn black because of its good chip removal performance and high cutting speed, but the blackened working fluid may not reach its service life, so it is inaccurate to take the color of working fluid as the criterion of service life.

WEDM's experience in changing water

Add %20 emulsion. Add %76 water. Add %2 oil. Add% 1 detergent. Add% 1 soapy water`. Exclusion is good. Well done.