Application of Electric Spark Forming Machine for Linear Motor, Linear Motor and Linear Motor
time£º2014/1/8 click£º11167
Application of Electric spark molding machine for linear motor
The technology of EDM has been developing for half a century, and it has become an important processing method in the mould processing field with its unique forming performance and "cutting" performance. However, it has also experienced a series of twists and turns. It has been impacted again and again by other processing methods, and it has been improved and perfected again and again, showing its strong vitality.
At the turn of the century, EDM technology has once again been violently impacted by cutting technology represented by CNC machining centers. CNC machining center technology spindle rotation high-speed, tool materials, the main stiffness of machine tools, numerical control track function development and other aspects of progress. This series of technological advances, so that the technology of EDM is facing new challenges. Taking this as an opportunity, the Japanese Sadik company developed a linear servo motor electric spark forming machine. Based on the traditional mature EDM technology, this machine tool is integrated into the advanced technology of linear servo system, which improves the machining performance of EDM. In mould forming, which is a specific processing technology, the main reason for inhibiting the practical processing speed is the deterioration of the processing state caused by complex shapes. The linear servo system known for its high speed of motion is used for high-speed jumping function in EDM, and the process of free-injection fluid processing is derived, which improves the practical processing speed of EDM and shortens the practical processing time of EDM.
2) Technical characteristics of linear servo system
After adopting the linear servo system, the wire bar transmission link is eliminated and the foundation of the shaft high-speed motion is laid. In addition, the control system uses a high-speed 32-bit computer, which greatly increases the speed of axis movement. Sadik's AQ series straight line servo EDM generator and LN series CNC power supply can achieve a shaft motion speed of 36m/min under the condition of 0.0001mm control equivalent, which allows the new generation of EDM to combine high speed and precision machining. conditions.
(1) New processing technology to break through the traditional process indicators
Axial high-speed motion has brought great changes to the traditional EDM forming process. This change is limited to shortening the time required for clamp, correction, and precision positioning due to high-speed motion, and more importantly, realizing high-speed jump(lifting knife) in processing. Jumping(lifting knife) is a key measure in EDM. In complex shape or deep narrow cavity processing, it is almost impossible to process without jumping(lifting knife) and punching. When jumping(lifting knife), there is no discharge phenomenon, which is the phenomenon of "idle work" in EDM, which affects the utilization rate of processing time. Fast jump(lifting knife) reduces the time of "idle work" phenomenon and improves the time utilization rate and processing speed. At the same time, high-speed jumping(lifting knife) also created conditions for increasing the range of jumping(lifting knife), so that the fluid force in the discharge gap during processing was fully improved, and the flushing treatment during processing was eliminated, shortening the processing time to 1/2. Figure 1 is an example of processing of a deep narrow cavity with a fast jumping impulse free liquid(longitudinal dissection after processing). The electrode section size is 1mm ¡Á 38mm, the electrode taper is 1 ¡ã, the cavity depth is 70mm, and the electrode material is graphite., two electrodes. The total processing time is 5H, in which the rough processing time is 160min, and the surface roughness of the workpiece after processing is 2 ¦Ìm. The advantage of linear servo system in deep and narrow cavity processing process index has taken breakthrough progress, the functional field has also widened. Fig. 2 is a typical example of deep narrow cavity processing with Y type electrode. The thickness of the Y-type(three-leaf) electrode is only 0.25 mm. In the traditional concept, such shape processing is quite difficult. Depth exceeding 10mm is considered a restricted area. This processing example has a processing depth of 40mm. It shows that the linear servo system is practical and makes it easy for us to enter the traditional restricted area.
(2) Stable finishing guarantee, high response speed, high stable processing servo system
In the DC servo system, the linear motor and the skateboard form an integrated structure. Skateboard displacement is the direct displacement of a linear motor, and there is no transfer link between the two. In this way, the loss and response lag of the intermediate link in servo motion. Figure 3 shows the relationship between the position of the motion axis instruction and the actual position of the linear servo system. From this, it can be seen that the dynamic response time in the special reversible servo motion of EDM is only in the order of milliseconds. The linear motor high-speed response system is one order of magnitude higher than the traditional rotary DC servo motor driving the ball screw system. As we all know, in the process of fine machining of electric spark processing, the electrodes do not come into contact with the workpieces, and the effective discharge gap between them is only a dozen microns. There are tens to one hundred milliseconds behind the command pulse and the actual position of the traditional servo motor and the ball screw system. It is very difficult to achieve stable and smooth servo and maintain high precision machining discharge efficiency. The advantage of linear servo system has been fully demonstrated in the process of fine machining of small EDM gap. Several milliseconds of high-speed response and greater than 1 g acceleration performance ensure that the micro-process of EDM can be sustained, so that the pulse utilization rate of fine machining can be greatly improved, and then the smooth servo motion of the precision machining speed linear servo system can be improved.
(3) Comprehensive measures to achieve precision control and long-term accuracy maintenance
The motion mode of the linear servo system determines that the servo unit must use the linear position feedback element as the position detection link. The control and drive of the linear servo system can only be a full closed-loop system. The linear displacement of the skateboard is directly detected. There is no screw pitch error, no screw and coupling reverse gap error, and other interference factors such as wear of the transmission chain parts are avoided. Linear motion guidance also adopts rolling guide rails that are adapted to the high response speed of linear Motors. These measures are used in combination to achieve precision control and long-term precision maintenance of machine tools.
(4) Slow micro-feed smoothing
The characteristic of EDM is that the average servo speed is slow. The feed distance is several millimeters per hour during rough processing, and the feed distance is only a few millimeters per hour during finishing. This requires that the EDM servo has excellent dynamic characteristics to adapt to frequent braking, reverse and maintain the small gap between the tool and the workpiece. Then the system is required to have smooth driving characteristics, and the effect of AC motor alveolar effect is usually solved. For this reason, Sadik's linear servo system has a control equivalent and a driving equivalent of 0.1 ¦Ìm. At the same time, a high-density rare earth magnet is used as a magnetic field material when making a linear motor. In the distribution of magnets, a staggered distribution arrangement method is adopted(as shown in Figure 4), coupled with the use of a variable-frequency AC drive system that matches the performance of the motor and can control the various phase currents in a subtle manner. This series of methods ensure that the reasonable magnetic field phase relationship and the reasonable current phase relationship are obtained. The peak limit balances the thrust between the various phase armature windings of the linear motor, overcomes the problem of dynamic load and large-scale rate changes, and reduces the adverse effect of the alveolar effect. Lower, To stabilize the servo movement.
3) Supporting technology with linear servo system
The advent of the linear servo electric spark forming machine and its demonstrated huge functional potential have undoubtedly created a strong attraction for thousands of users and stimulated manufacturers to compete for the development and updating of products to compete for the market. In addition to solving the technical difficulties mentioned above, the commercialization process of linear servo system machine tools also has to solve a series of related technologies supporting linear servo system.
(Information source from network)
Linear motor