CNC Knowledge: Comparison of quick thread and slow thread

Methods of analysis and treatment for the breaking of wire interrupted in the cut of slow wire:

The cutting of electric sparks can be divided into fast wire and slow wire depending on the cutting speed. 0. 16 microns.

Given that the slow wire trip adopts the thread power method as a function of wire electrodes, that is to say that the wire electrode is treated during movement, even if the wire electrode is undergoing A loss, it can be completed continuously, so that the precision of treatment of parts can be improved, but the wire of electric sparks which cuts the broken thread has become an obstacle to these advantages, and it is very necessary to solve This problem.

Wireless mechanism:

It is generally believed that the breach of the wire is mainly caused by the concentration of electrical spark discharge and that the electrode wire is merged and broken, which is consistent with the precursor of a wire rupture detected. Consequently, the study of the temperature distribution of electrode wires from the theory of thermal conduction has become the main means of studying the mechanism of the breaking of the wire. Research results show that the thermal load before breaking the wire exceeds average value; The rinsing is very important to avoid breaking the wire; Joule Heat The effect of vibration of silk can be relatively neglected.

For equal energy pulse power supplies, research shows that there are two important signs of wire break: 1. The sparkling discharge frequency suddenly increases in a short period of time. Too high, which leads to the breakdown of the wire; 2. Normal sparkle The probability decreases and the gradual increase in the probability of abnormal sparks is also a sign of the broken thread. As the loss of wire increases, the electrode wire becomes thinner and eventually removes. Kprajurkar and others pointed out that the sudden change in the thickness of the room during treatment is one of the main reasons for the discharge concentration. Therefore, it is necessary to detect changes in the thickness of the online part, adjust the corresponding process parameters, control the supply speed and the discharge frequency of the electrode wire and obtain Better cutting speed under a constant thread.

Since the precursor of the broken thread is short and the real -time control of the prevention of the broken thread is high, the selection of control parameters is very important. In online cutting treatment, the amplification of the pulse interval will increase time to eliminate electrocorrosion products in the discharge deviation, effectively improves the phenomenon of discharge concentration and considerably reduces the risk of rupture thread. Prevention control.

1. Wireless break -up factors linked to the electrode wire

1. Characteristics of the electrode wire material

The electrode wire requires good discharge characteristics and high tensile resistance. The electrode wire is in famous molybdenum thread, with great precision, strong tensile resistance and good quality. The low -temperature treatment of the electrode wire is also one of the measures to reduce the risk of thread. A company in Ohio, in the United States, compared the electrode wire that has cooled 24 hours at a low temperature temperature and the electrode wire which has not undergone low temperature treatment.

During the processing process, the size of the transport and discharge capacity of the electrode is determined by the size of the diameter of the electrode wire, so that the size of the wire directly affects the rupture speed. To real needs, the diameter must be selected, the surface of the coating is smooth and there is no oxidation.

2.

In the low -speed electric cutting treatment, the cutting of electric sparks, the highest and most stable voltage can be maintained at the maximum resistance limit of the electrode wire, so that the wire can keep the elbow Minimum hysteresis under the explosion force of discharge during rough treatment without breaking without breaking the wire. The appropriate tension can effectively reduce the amplitude of wire vibrations and maintain the stable wire during treatment.

3. Movement speed of the electrode wire

Since the diameter of the electrode wire in the treatment of the wire cut is small (generally 0.1 to 0.3 mm), if the electrode wire moves too slowly, a certain point on the wire D ‘Electrode can cause several discharges, which makes the amount of withdrawal of corrosion too large. Easily under the action of the metal tension and the explosive force of the spark discharge. Consequently, in the condition that the wire allows a little continuous number, the speed of the wire must be adjusted as a function of the discharge frequency in combination with the thickness of the part. The discharge frequencies of rough treatment and the treatment of the finish are different and the metal flow speed is also different. If the electrode wire is low diameter, thick in the room, rough treatment and discharge frequency is necessary, the speed of the wire is relatively faster. In the real treatment, the speed of movement of the electrode wire given by the process database provided by the electric cutting machine at low speed can be mentioned.

4. Driver block

The conductive blocks are mainly in silver tungsten alloy, which has a good conductivity and resistance to wear. During the treatment, the conductive block and the moving electrode wire remain in contact, resulting in wear of the driver’s block. Generally, the conductive blocks used in low -speed electric cutting machines should be checked over time, removed and the sticking dirt must be swept away by the cleaning fluid. Or update the driver’s block.

5. Treatment of waste wire

The treatment of the cutting of electric sparks at low speed is a movement of one -way wire and a large amount of waste wire will be generated during treatment. If the waste wire is not removed over time, an additional capacity will be easily generated between the electrode wires and can be directly connected to the electrode threads in the treatment area, thus generating a concentrated energy release , causing broken wires or even short circuits, and even not to treat normally. Currently, high-end machine tools have automatic waste treatment devices. There are two ways to face it: one is to place the thread cutting device in the port of waste waste;

2. Wirelessness -related factors linked to work fluid

Currently, most of the low -speed electric sparks are used pure water and distilled water, which is inexpensive and without pollution. There are two main functions to use work fluid: insulation and cooling. Therefore, the work fluid must have good heat absorption, heat transfer and thermal dissipation functions.

When the performance of the work fluid worsens, this means that the impurities and ions present in the work fluid increase considerably and that the dielectric performance of the work fluid is considerably reduced. On the one hand, it will result in an increase in the probability of contact discharge caused by conductive bridges made up of dielectric particles; , the characteristics of the treatment wave wave are a series of almost no open circuits and breakdown. Currently, the entry of energy density away from treatment is very high, which is very easy to cause a break by wire. The work fluid must be replaced at this time.

The treatment chips generated during the discharge are also one of the factors that cause a wire break. A micro-circuit state state formed by chips of machining fleas or occasionally meets net points on the two poles, which occurally meet, have great contact resistance. Due to the movement of the electrode wire, this micro-short circuit is easily separated to form a spark discharge. Consequently, the entry of energy density of the pulse power supply to the treatment space is much higher than that during normal treatment, which leads to an impulse energy in a concentrated manner in The adhesive part of the electrode wire, causing cracks in the electrode wire, which can cause a wire break. In order to effectively wash the solid particles, when there is no restriction on the geometry of the room, you must also try to choose a tight treatment to allow the water to rinse in the cutting joints to better improve the erosion condition. If the direction of spray water is inaccurate, it is easy to break the wire. Since the direction of water spray is inaccurate, the work fluid cannot be sprayed in the cut and the electrode wire cannot be cooled, causing a sudden increase in the local temperature of the wire of electrode, causing the burn of the wire. The water spray position should be covered with a water column to cover the electrode wire, and the upper and lower spray pressure should be comparable.

3. Factors of rupture of the wires linked to the control of the servomotor

The supply speed of the servo must be maintained in a certain relationship with the speed of elimination of the corrosion of the part, that is to say that the machining deviation must be maintained at a certain value. Because when the speed of the servo exceeds the engraving speed, frequent short circuits occur, which will increase the possibility of breaking of wire; will also occur due to an open circuit during treatment, causing the cutting of cutting speed and surface roughness increases. Consequently, the servo must be uniform and stable to avoid crawling, the overtaking must be small, the rigidity of transmission must be raised, there should not be obvious gap in the transmission chain and the capacity of anti- interference should be strong. The frequency of discharge treatment is very high and the state of the discharge difference changes rapidly, which requires that the supply adjustment system can adapt quickly as a function of the low signal of the state space. Consequently, the requirements of inertia for the insensitive area, the time constant and the mobile part in the entire process must be low, the magnification must be sufficient and the excessive process must be short.