(1) nanosecond large peak current pulse power supply technology
The metal erosion in EDM is divided into two parts: melting and gasification. The wide pulse width has a long acting time, which is easy to cause melting processing, which makes the surface morphology of the workpiece worse, the metamorphic layer is thickened, the internal stress is increased, and cracks are easily generated. When the pulse width is small to a certain value, the action time is extremely short, and gasification processing is formed, which can reduce the thickness of the metamorphic layer, improve the surface quality, reduce the internal stress, and avoid crack generation.
The pulse power supply of the advanced low-speed wire-cut wire electric discharge machine has a pulse width of only several tens of ns and a peak current of more than 1 000 A, which forms a gasification erosion, which not only has high processing efficiency, but also greatly improves the surface quality.
(2) Anti-electrolysis (BS) pulse power supply
Low-speed wire-cut EDM wire cutting process uses water working fluid. Water has a certain conductivity, even if it is deionized to reduce the conductivity, but there is a certain amount of ions. When the workpiece is connected to the positive electrode, under the action of the electric field, OH- ions will accumulate on the workpiece, causing oxidation and corrosion of iron, aluminum, copper, zinc, titanium, tungsten, and the binder in the cemented carbide material - cobalt The ionic state dissolves in water to form a "softening layer" of the surface of the workpiece. The measures to increase the resistivity (from tens of thousands of ohms to centimeters per centimeter) have been used to reduce the ion concentration as much as possible. Although it has played a certain role in improving the surface quality, it still cannot be completely solved. Softening layer" problem.
The anti-electrolysis power supply is an effective technical means to solve the "softening layer" of the workpiece. The anti-electrolysis power supply adopts an alternating pulse, and the average voltage is zero, so that the OH-ion electrode wire in the working fluid is in an oscillating state with the workpiece, and does not tend to the workpiece and the wire, thereby preventing oxidation of the workpiece material.
The use of anti-electrolysis power supply for WEDM can control the surface metamorphic layer below 1μm, avoiding the precipitation and dissolution of cobalt in the cemented carbide material and ensuring the life of the cemented carbide mold.
(1) Multiple cutting technology
Multiple cutting technology is the fundamental means to improve the precision and surface quality of low-speed wire-cut EDM. It is a scientific integration of design and manufacturing technology, numerical control technology, intelligent technology, pulsed power technology, precision transmission and control technology. Generally, the cutting is performed by one cutting, the secondary cutting is used to improve the precision, and the cutting is performed three times or more to improve the surface quality. Originally, in order to achieve a high-quality surface, the number of times of multiple cutting needs to be as high as 7 to 9 times, only 3 to 4 times.
(2) Corner processing technology is continuously optimized and improved
Due to the hysteresis of the wire when cutting the corner, the corner collapses. In order to improve the accuracy of corner cutting, the researchers have adopted more dynamic corner processing strategies. Such as: change the wire path; change the processing speed (thin plate); automatically adjust the water pressure; control the processing energy.
By adopting a comprehensive corner control strategy, the corner shape error during roughing is reduced by 70%, and the matching accuracy of up to 5 一次 can be cut at a time.
(3) Adopting techniques to improve flatness
High-precision finishing circuits are techniques for improving flatness and are considered to be of great importance for thick parts processing.
(4) The machine structure is more precise
In order to ensure high-precision machining, many technical measures are taken to improve the accuracy of the host: 1 control temperature. The water temperature cooling device is used to make the internal temperature of the machine tool the same as the water temperature, which reduces the thermal deformation of the machine tool. 2 uses a linear motor. High responsiveness, precise positioning can achieve 0.1μm equivalent control, no vibration, no noise, increase the discharge frequency, maintain stable discharge, and cut Ry5 μm twice. 3 It adopts ceramic and polymer artificial granite parts, and its thermal inertia is 25 times larger than that of cast iron, which reduces the influence of temperature change on cutting precision. 4 The fixed workbench and column moving structure are adopted to increase the weight of the worktable, which is not affected by the water immersion processing and the weight change of the workpiece. 5 Immersion processing is used to reduce the thermal deformation of the workpiece. 6 motor servo, closed loop wire tension control. 7 high-precision tool setting: voltage modulation tool power supply. The accuracy of the tool setting is up to ±0.005 mm without damaging the workpiece, whether wet or dry.
(1) Maximum processing efficiency
Due to the development of ns-level large peak current pulse power supply technology and detection, control and anti-interference technology, the processing efficiency of low-speed wire-cut EDM wire cutters is also increasing.
(2) Processing efficiency of workpieces with large thickness
Japan's Mitsubishi Electric FA-V series machine tools can process up to 170 mm2/min when cutting 300 mm thick workpieces. This is a very practical technological advancement.
(3) Processing efficiency of workpiece with thickness variation
Automatically detect the thickness of the workpiece, automatically adjust the processing parameters to prevent broken wire, and achieve the highest processing efficiency in this state.
(4) Double wire automatic exchange technology
The ROBOFIL 2030S1-TW machine can automatically perform double-wire switching with a wire of 0.20 to 0.02 mm. The first cut is made with thick wire, the general wire diameter is 0.25 mm, to improve the processing efficiency, and the core can be cut; then the filament is used for dressing, generally 0.10 mm filament is used to cut the small round corner, and Improve accuracy. Overall savings of 30% to 50% cutting time.
(5) Fast automatic threading technology
Automatic threading time <15 s; Japan Sodick Company said that the threading time is 13 s. Japan's Mitsubishi Electric Corporation, when the thickness is 50 mm, the threading time is 10 s, the total time of shredding and threading is 25 s. .