1. EDM
1) Basic principles
EDM is a special processing method that uses the electric erosion effect generated by the pulse discharge between the two electrodes immersed in the working fluid to erode conductive materials. It is also called electrical discharge machining or electroerosion machining.
EDM is suitable for the processing of complex parts such as precision small cavities, narrow slots, grooves, and corners. Where complex surfaces are difficult for the tool to reach, where deep cuts are required, and where the length-to-diameter ratio is particularly high, the EDM process is superior to milling. For the processing of high-tech parts, milling electrode re-discharge can improve the success rate, and EDM is more suitable than high and expensive tool costs.
In addition, where EDM finishing is specified, EDM is used to provide a spark patterned surface. Today, with the rapid development of high-speed milling, the development space of EDM has been squeezed to a certain extent. At the same time, high-speed milling has also brought greater technological progress to EDM. For example, high-speed milling is used to manufacture electrodes. Due to the realization of narrow area processing and high-quality surface results, the number of electrode designs is greatly reduced. In addition, using high-speed milling to manufacture electrodes can also increase the production efficiency to a new level, and can ensure the high precision of the electrodes, so that the precision of EDM is also improved.
If most of the machining of the cavity is done by high-speed milling, EDM is only used as an auxiliary means to clear the corners and trim the edges, so that the allowance is more uniform and less
2) Basic equipment: EDM machine tools.
3) Main features
It can process materials and workpieces with complex shapes that are difficult to cut by ordinary cutting methods; there is no cutting force during processing; there are no defects such as burrs and knife marks; the tool electrode material does not need to be harder than the workpiece material; direct use of electric energy processing is convenient for automation; After processing, a metamorphic layer is formed on the surface, which must be further removed in some applications; the purification of working fluid and the treatment of smoke pollution generated during processing are more troublesome.
EDM has the following characteristics
It can process any high-strength, high-hardness, high-toughness, high-brittleness and high-purity conductive materials; there is no obvious mechanical force during processing, and it is suitable for processing low-rigidity workpieces and microstructures: pulse parameters can be adjusted according to needs, and can be used on the same machine Rough machining, semi-finishing machining and finishing machining are carried out on the machine tool; the pits on the surface after EDM are good for oil storage and noise reduction; the production efficiency is lower than that of cutting machining; part of the energy is consumed on the tool electrode during the discharge process, Lead to electrode loss and affect the forming accuracy.
4) Scope of use
Processing molds and parts with complex-shaped holes and cavities; processing various hard and brittle materials such as cemented carbide and hardened steel; processing deep fine holes, special-shaped holes, deep grooves, narrow slots and cutting sheets; processing Tools and measuring tools such as various forming tools, templates and thread ring gauges.
EDM must meet three conditions
1. Pulse power supply must be used
2. An automatic feed adjustment device must be used to maintain a small discharge gap between the tool electrode and the workpiece electrode
3. Spark discharge must be carried out in a liquid medium with a certain dielectric strength (10~107Ω·m).
Not all mold steels can be mirror EDM
The EDM of some mold steels can easily achieve the mirror effect, while some mold steels cannot achieve the mirror effect anyway. At the same time, the hardness of the mold steel is higher, and the effect of EDM mirror surface is better. Please refer to the table below for various materials and mirror finish properties.
2. Wire EDM
1) Basic principles
Using continuously moving thin metal wires (called electrode wires) as electrodes, the workpiece is subjected to pulse spark discharge to etch metal and cut into shapes. English is Wire cut Electrical Discharge Machining, referred to as WEDM, also known as wire cutting.
2) Basic equipment: EDM machine tool.
3) Main features
In addition to the basic characteristics of EDM, WEDM also has some other characteristics:
① No need to manufacture tool electrodes with complex shapes, any two-dimensional curved surface with a straight line as the generatrix can be processed;
②It can cut a narrow slit of about 0.05mm;
③ During processing, all excess materials are not processed into waste, which improves the utilization rate of energy and materials;
④In the low-speed WEDM where the electrode wire is not recycled, the continuous update of the electrode wire is beneficial to improve the processing accuracy and reduce the surface roughness;
⑤ The cutting efficiency that can be achieved by WEDM is generally 20-60 mm2/min, up to 300 mm2/min; the processing accuracy is generally ±0.01 to ±0.02 mm, up to ±0.004 mm; the surface roughness Generally, it is Ra2.5 to 1.25 microns, and the highest can reach Ra0.63 microns; the cutting thickness is generally 40-60 mm, and the maximum thickness can reach 600 mm.
4) Scope of use
Mainly used for processing: various complex and precise workpieces, such as punches, dies, punches and dies, fixing plates, stripping plates, etc. of punching dies; metal electrodes for forming tools, templates, and EDM ; All kinds of tiny holes, narrow slots, arbitrary curves, etc. It has outstanding advantages such as small machining allowance, high machining precision, short production cycle, and low manufacturing cost, and has been widely used in production. At present, wire electric discharge machine tools at home and abroad have accounted for more than 60% of the total number of electric machine tools.
Wire-cut electric discharge machining is a technology to achieve workpiece size machining. Under certain equipment conditions, a reasonable formulation of the processing route is an important link to ensure the processing quality of the workpiece.
The process of WEDM processing molds or parts can generally be divided into the following steps.
Analyze and review drawings
Analyzing the pattern is a decisive first step to ensure the processing quality of the workpiece and the comprehensive technical indicators of the workpiece. Taking the blanking die as an example, when digesting the pattern, it is first necessary to pick out the workpiece pattern that cannot or is not easy to be processed by WEDM, roughly as follows:
1. The surface roughness and dimensional accuracy are very high, and the workpiece cannot be manually ground after cutting;
2. Workpieces with narrow gaps smaller than the diameter of the electrode wire plus the discharge gap, or workpieces with rounded corners formed by the discharge gap of the electrode rigid derrick are not allowed at the corners of the graph;
3. Non-conductive materials;
4. Parts whose thickness exceeds the span of the wire frame;
5. The processing length exceeds the effective stroke length of the x and y carriages, and the workpieces require high precision.
Under the condition of conforming to the wire cutting process, the surface roughness, dimensional accuracy, workpiece thickness, workpiece material, size, fit clearance and punching part thickness should be carefully considered.
Programming Notes
1. Determination of die clearance and transition circle radius
Reasonably determine the die clearance. Reasonable selection of die clearance is one of the key factors related to the life of the die and the size of the burr of the stamped part. The die clearance of different materials is generally selected in the following range:
For soft blanking materials, such as copper, soft aluminum, semi-hard aluminum, bakelite, red cardboard, mica sheets, etc., the gap between the punch and die can be selected as 10%-15% of the thickness of the punching material.
For hard blanking materials, such as iron sheets, steel sheets, silicon steel sheets, etc., the gap between the punch and die can be selected as 15%-20% of the punching thickness.
This is the actual empirical data of some wire cutting punching dies, which are smaller than the internationally popular large gap punching dies. Because the surface of the workpiece processed by wire cutting has a layer of brittle melting layer, the greater the processing electrical parameters, the worse the surface roughness of the workpiece and the thicker the melting layer. With the increase of die strokes, this layer of brittle surface will gradually wear off, and the die gap will gradually increase.
Reasonably determine the radius of the transition circle. In order to improve the service life of general cold stamping dies, transition circles should be added at the intersections of lines, line circles, and far intersections, especially at corners with small angles. The size of the transition circle can be considered according to the thickness of the blanking material, the shape of the mold, the required life and the technical conditions of the punched parts. With the thickness of the punched parts, the transition circle can also increase accordingly. Generally, it can be selected within the range of 0.1-0.5mm.
For the transition circle where the material of the stamping part is thin, the mold fit clearance is small, and the stamping part is not allowed to be enlarged, in order to obtain a good fit clearance of the punch and die, generally a transition circle should be added at the corner of the figure. Because the wire electrode processing trajectory will naturally process a transition circle with a radius equal to the wire electrode radius plus the single-sided discharge gap at the inner corner.
2. Calculate and write processing program
When programming, it is necessary to choose a reasonable clamping position according to the ingredients, and at the same time determine a reasonable starting point and cutting route.
The cut-off point should be taken at the corner of the graph, or at the part where it is easy to remove the convex point.
The cutting route is mainly based on the principle of preventing or reducing mold deformation. Generally, it should be considered to make it easier to cut the graphics near the clamping side.
3. Program tape and proofreading tape for threading and processing
After the paper tape is made according to the program sheet, the program sheet and the prepared paper tape must be checked one by one. After the proofreading paper tape is used to input the program into the controller, the sample can be cut. Simple and sure workpieces can be processed directly. . For molds that require high dimensional accuracy and a small matching gap between the convex and concave dies, it is necessary to use thin materials for trial cutting, and the precision and fitting gap can be checked on the cut parts. If it is found that it does not meet the requirements, it should be analyzed in time to find out the problem and modify the program until it is qualified before formally processing the mold. This step is an important part of avoiding workpiece scrapping.
According to the actual situation, it can also be input directly from the keyboard, or the program can be directly transferred from the programming machine to the controller.
3. Electrochemical Machining
1) Basic principles
Based on the principle of anodic dissolution in the electrolysis process and with the help of a formed cathode, a process method that processes a workpiece into a certain shape and size is called electrolytic machining.
2) Scope of use
Electrochemical machining has significant advantages for machining difficult-to-machine materials, complex shapes, or thin-walled parts. Electrolytic machining has been widely used, such as barrel rifling, blades, integral impellers, molds, special-shaped holes and special-shaped parts, chamfering and deburring. And in the processing of many parts, the electrolytic machining process has occupied an important or even irreplaceable position.
3) Advantages
Wide range of processing. Electrolytic machining can process almost all conductive materials, and is not limited by the mechanical and physical properties of the material such as strength, hardness, toughness, etc., and the metallographic structure of the material after processing basically does not change. It is often used to process difficult-to-machine materials such as hard alloys, high-temperature alloys, hardened steel, and stainless steel.
4) Limitations
The processing accuracy and processing stability are not high; the processing cost is high, and the smaller the batch, the higher the additional cost per piece.
4. Laser processing
1) Basic principles
Laser processing is to use the energy of light to achieve high energy density at the focus point after being focused by the lens, and to melt or gasify the material in a very small time and be etched away to realize processing.
2) Main features
Laser processing technology has the advantages of less material waste, obvious cost effect in large-scale production, and strong adaptability to processing objects. In Europe, laser technology is basically used for welding special materials such as high-end automobile shells and bases, aircraft wings, and spacecraft fuselages.
3) Scope of use
Laser processing is the most commonly used application of laser systems. The main technologies include: laser welding, laser cutting, surface modification, laser marking, laser drilling, micromachining and photochemical deposition, stereolithography, laser etching, etc.
5. Electron beam processing
1) Basic principles
Electron beam processing is the processing of materials using the thermal effect or ionization effect of high-energy convergent electron beams.
2) Main features
High energy density, strong penetration ability, wide range of primary penetration, large weld seam width ratio, fast welding speed, small heat-affected zone, and small working deformation.
3) Scope of use
The range of materials processed by electron beams is wide, and the processing area can be extremely small; the processing accuracy can reach nanometer level, and molecular or atomic processing can be realized; the productivity is high; the pollution generated by processing is small, but the cost of processing equipment is high; micropores and narrow slits can be processed etc., and can also be used for welding and fine photolithography. Vacuum electron beam welding axle housing technology is the main application of electron beam processing in the automobile manufacturing industry.
6. Ion Beam Machining
1) Basic principles
Ion beam processing is to achieve processing by accelerating and focusing the ion flow generated by the ion source on the surface of the workpiece in a vacuum state.
2) Main features
Since the ion current density and ion energy can be precisely controlled, the processing effect can be precisely controlled, and ultra-precision processing at the nanometer level, even at the molecular and atomic level can be realized. During ion beam processing, the pollution produced is small, the processing stress and deformation are extremely small, and the adaptability to the processed material is strong, but the processing cost is high.
3) Scope of use
Ion beam processing can be divided into etching and coating according to its purpose.
1) Etching process
Ion etching is used to process grooves on gyroscope air bearings and dynamic pressure motors, with high resolution, good accuracy and repeatability. Another aspect of the application of ion beam etching is the etching of high-precision patterns, such as electronic components such as integrated circuits, optoelectronic devices and optical integrated devices. Ion beam etching is also used to thin materials and make transmission electron microscope specimens.
2) Ion beam coating processing
There are two forms of ion beam coating processing, sputtering deposition and ion plating. Ion plating can be plated on a wide range of materials. Metal or non-metal films can be plated on both metal and non-metal surfaces. Various alloys, compounds, or certain synthetic materials, semiconductor materials, and high-melting point materials can also be plated.
Ion beam coating technology can be used to coat lubricating films, heat-resistant films, wear-resistant films, decorative films and electrical films.
7. Plasma arc processing
(1) Basic principles
Plasma arc processing is a special processing method that uses the heat energy of the plasma arc to cut, weld and spray metal or non-metal.
(2) Main features
1) Micro-beam plasma arc welding can weld foils and thin plates;
2) It has a small hole effect, which can better realize the free forming of one side welding and two sides;
3) The plasma arc energy density is high, the arc column temperature is high, and the penetration ability is strong. The steel material with a thickness of 10-12mm can not be grooved, and can be welded through and formed on both sides at one time. The welding speed is fast, the productivity is high, and the stress deformation is small;
4) The equipment is relatively complicated and the gas consumption is large, so it is only suitable for indoor welding.
(3) Scope of use
Widely used in industrial production, especially the welding of copper and copper alloys, titanium and titanium alloys, alloy steel, stainless steel, molybdenum and other metals used in aerospace and other military industries and cutting-edge industrial technologies, such as titanium alloy missile casings, aircraft Some thin-walled containers, etc.
8. Ultrasonic processing
(1) Basic principles
Ultrasonic machining is a tool that uses ultrasonic frequency to vibrate with small amplitude, and passes between it and the workpiece
The hammering effect of abrasives free in the liquid on the surface to be processed makes the surface of the workpiece material gradually broken. The English abbreviation is USM. Ultrasonic machining is commonly used for piercing, cutting, welding, nesting and polishing.
(2) Main features
It can process any material, especially suitable for processing various hard and brittle non-conductive materials. It has high processing precision and good surface quality for workpieces, but low productivity.
(3) Scope of use
Ultrasonic machining is mainly used for drilling (including round holes, special-shaped holes and curved holes, etc.), cutting and slotting of various hard and brittle materials, such as glass, quartz, ceramics, silicon, germanium, ferrite, gemstones and jade , nesting, engraving, deburring of small parts in batches, surface polishing of molds and dressing of grinding wheels, etc.
9. Chemical processing
(1) Basic principles
Chemical Etching is a special processing that uses acid, alkali or salt solution to corrode and dissolve workpiece materials to obtain workpieces of desired shape, size or surface state.
(2) Main features
1) It can process any metal material that can be cut, and is not limited by properties such as hardness and strength;
2) Suitable for large area processing, and can process multiple pieces at the same time;
3) No stress, cracks, or burrs, and the surface roughness reaches Ra1.25-2.5μm;
4) Easy to operate;
5) Not suitable for processing narrow slots and holes;
6) It is not suitable to eliminate defects such as uneven surface and scratches.
(3) Scope of use
Suitable for large-area thickness reduction processing; suitable for processing complex holes on thin-walled parts
