Slow wire cutting machine tools belong to CNC machine tools with a high degree of mechanical automation.
Slow wire walking, also known as low-speed wire walking, is the use of continuously moving thin metal wires (called electrode wires, usually copper wires) as electrodes to move the workpiece pulse Spark discharge, generating A type of high temperature above 6000 degrees, which can corrode metals and cut into workpieces numerical control machine . The principle of slow wire processing is the phenomenon of continuous discharge to remove metal from the gap between the online electrode and the workpiece.
Due to the fact that the slow wire cutting machine adopts a continuous wire supply method with wire electrodes, that is, the wire electrodes complete the processing during the movement process. Therefore, even if the wire electrodes are lost, they can be continuously supplemented, thus improving the machining accuracy of the parts. The surface of the workpiece processed by the slow wire cutting machine roughness Usually achievable Ra=0.8μm Above and above, the roundness error, straightness error, and size error of the wire cutting machine are relatively low Quick walking silk There are many advantages to wire cutting machines, so slow wire cutting machines are widely used in processing high-precision parts. In addition to early small and medium-sized enterprises, it is also very common in processing factories of large enterprises such as aviation, automotive, and medical.
Slow wire cutting is a type of machining machine tool that uses continuously moving fine metal wires (called electrode wires) as electrodes to perform pulse spark discharge to remove metal from the workpiece and cut it into shape. The phenomenon of loose contact light pressure discharge between the online electrode and the workpiece during slow wire machining. When the flexible electrode wire approaches the commonly considered discharge gap (such as 8-10μ m) with the workpiece, spark discharge does not occur. Even when the electrode wire has come into contact with the workpiece and the gap is no longer visible from the microscope, sparks are often not visible. Normal spark discharge only occurs when the workpiece bends the electrode wire and offsets it by a certain distance (several micrometers to tens of micrometers). At this time, for every 1&mu feed of the wire electrode; m. The discharge gap does not decrease by 1μ m. Instead, the electrode wire increases the tension between the wires by a little, while the workpiece increases the lateral pressure by a little. Obviously, only when a certain slight contact pressure is maintained between the electrode wire and the workpiece can spark discharge be formed. Based on this, it is believed that there is an electrochemical generated insulating thin film medium between the electrode wire and the workpiece
SURFACE QUALITY
( 1) Nanosecond level high peak current Pulse power supply Technology
EDM The erosion of metals can be divided into two types: melting and gasification. The long duration of wide pulse width can easily cause melting processing, resulting in a deterioration of the surface morphology of the workpiece, thickening of the metamorphic layer, increased internal stress, and easy crack formation. When the pulse width is small to a certain value, the action time is extremely short, forming gasification processing, which can reduce the thickness of the metamorphic layer, improve surface quality, reduce internal stress, and avoid crack formation.
Advanced Low speed wire EDM cutting machine The pulse power supply used has a pulse width of only a few tens ns,The peak current is above 1000 A, forming gasification erosion, which not only has high processing efficiency but also greatly improves surface quality.
( 2)Anti electrolysis (BS) pulse power supply
Low speed threading WEDM Using water quality working fluid. Water has a certain degree of conductivity, even after deionization treatment to reduce conductivity, there is still a certain amount of ions. When the workpiece is connected to the positive electrode, under the action of an electric field, OH - ions will continuously aggregate on the workpiece, causing oxidation and corrosion of iron, aluminum, copper, zinc, titanium, and tungsten, And make Hard alloy materials Binder in —Cobalt dissolves in an ionic state in water, forming a surface on the workpiece; Softening layer;. Previously, measures were taken to increase electrical resistivity (from tens of kiloohms? Centimeters to hundreds of kiloohms? Centimeters), aiming to reduce ion concentration as much as possible. Although this has played a certain role in improving surface quality, it still cannot effectively and completely solve the problem; Softening layer; The issue of.
provide against Electrolytic power supply correct Solving workpieces “Softening layer; Effective technical means. The anti electrolysis power supply adopts alternating pulses with an average voltage of zero, which oscillates between the OH - ion electrode wire in the working fluid and the workpiece, without tending towards the workpiece and electrode wire, to prevent oxidation of the workpiece material.
Using an anti electrolysis power supply for wire cutting can control the surface deterioration layer within 1μm To avoid the precipitation and dissolution of cobalt in hard alloy materials, ensure that Tungsten carbide nib and so on Lifespan.
Cutting precision
( 1)Multiple cutting techniques
The multiple cutting technology is the fundamental means to improve the accuracy and surface quality of low-speed wire EDM machining. It is a design and manufacturing technology 、 NUMERICAL CONTROL 、 The scientific integration of intelligent technology, pulse power supply technology, precision transmission and control technology. Generally, it is formed through a single cutting process, with secondary cutting to improve accuracy and more than three cuts to improve surface quality. Previously, in order to achieve high-quality surfaces, the number of multiple cuts needed to be as high as 7～9times,only3～4 times are needed.
( 2)Continuous optimization and improvement of corner machining technology
Due to the lag of the electrode wire during cutting corners, it can cause corner collapse. In order to improve the accuracy of corner cutting, researchers have adopted more dynamic corner processing strategies. For example, changing the wire routing path; Change the processing speed (thin plate); Automatically adjust water pressure; Control processing energy, etc.
By adopting a comprehensive corner control strategy, the shape error of the corners during rough machining is reduced 70%,It can achieve a matching accuracy of 5 μ m in one cutting.
( 3)Using techniques to improve straightness
High precision machining circuits are technologies that improve flatness and are considered to be of great significance for thick part machining.
( 4) machine tool tie More precise construction
In order to ensure high-precision machining, many technical measures have been adopted to improve the accuracy of the host machine: ① Control temperature. By using a water temperature cooling device, the internal temperature of the machine tool is kept the same as the water temperature, reducing the thermal deformation of the machine tool.②use Linear motor . High responsiveness, precise positioning can be achieved 0.1μm Equivalent control, feed without vibration and noise, Increase discharge frequency, maintain stable discharge, and perform two cuts Ry5 μm。③Using ceramic and polymer artificial granite components, its thermal inertia is 25 times greater than cast iron, reducing The impact of temperature changes on cutting accuracy. ④ Adopting a fixed workbench and column moving structure to increase the load-bearing capacity of the workbench, it is not affected by immersion processing and changes in workpiece weight Adopting immersion processing to reduce thermal deformation of the workpiece. ⑥ Motor servo, closed-loop electrode silk tension control 。 ⑦ high-precision tool setting : Using voltage modulation for knife power supply. The precision of knife alignment can reach ±0.005 mm,No damage to the workpiece, regardless of dry or wet conditions 。
processing efficiency
( 1)Maximum processing efficiency
due to ns The development of high peak current pulse power supply technology, detection, control, and anti-interference technology has led to a continuous improvement in the processing efficiency of low-speed wire cutting machines.
( 2)Processing efficiency of thicker workpieces
Mitsubishi Electric Corporation FA-V The series of machine tools can achieve a processing efficiency of 170 mm2/min when cutting 300 mm thick workpieces. This is a very practical technological improvement.
( 3)Processing efficiency of workpieces with varying thickness
Processing efficiency of workpieces with varying thickness
( 4)Double wire automatic exchange technology
ROBOFIL 2030S1-TW The machine tool can automatically switch between two wires using 0.20-0.02mm electrode wires. Using coarse wire for the first cutting, the general wire diameter is 0.25 Mm to improve processing efficiency and enable coreless cutting; Then, fine wire is used for trimming, usually using a 0.10mm fine wire to cut small rounded corners and improve accuracy. Overall, it can save 30% to 50% of cutting time.
( 5)Rapid automatic threading technology
Automatic threading time <15 s; Sadik Corporation of Japan states that the threading time is 13 seconds. Mitsubishi Electric Corporation of Japan states that when the plate thickness is 50 mm, the threading time is 10 seconds, and the total cutting and threading time is 25 seconds.
(Data sourced from Baidu Baike )
