The electric current is of the order of 50 to 40000 Ampere at 5 to 30 V D.C. for a current density of 20 to 300 Ampere/Square cm, across a gap of 0.05 to 0.70 mm between the tool and the work piece. The electrolyte flows through this gap at a velocity of 30 to 60 meter/second forced by an inlet pressure of about 20 kgf /square centimeter. Suspended solids are removed from the electrolytes by setting, centrifuging, or filtering, and the filtered electrolyte is recirculated for use. It is interesting to note that the salt is not being consumed and the metal is being machined at the expense of electrical energy and with a small amount of water. The electrolyte acts as a carrier of current. The common electrolytes used are sodium chloride, sodium nitrate, potassium chloride, sodium hydroxide, sodium fluoride, sulfuric acid, and sodium chlorate. These solutions on reaction produce an insoluble compound in the form of sludge. The electrolyte carries the current between the tool and the work piece. It removes the machined products and other insoluble products from the cutting region. It dissipates the heat produced in the operation. The electrolyte should posses good electrical conductivity, non-toxicity, chemical stability, non-corrosive property, low viscosity, and high specific heat. The most commonly use electrolyte is the solution of sodium chloride in concentration varying from 0.10 to 0.25 kg / litre of water.
The general requirements on the tool material in ECM are mentioned below:
- The tool material should be a good conductor of electricity.
- It should be rigid enough to take up the load due to fluid pressure.
- It should be chemically inert to the electrolyte.
- It should be easily machinable to make it in the desired shape.
- Copper, Brass, Titanium, Copper-Tungsten, and Stainless steels are most commonly used electrode materials when the electrolyte is made of sodium or potassium.
- The other materials which can be used as tool materials are aluminium, graphite, bronze, platinum, and tungsten carbide.
- The cavity or hole that is made, exactly reproduces the tool shape. Thus the accuracy of the tool shape directly affects the work piece accuracy.
Factors govern the accuracy of parts produced by ECM:
- Machining Voltage
- Feed rate of the electrode (tool)
- Temperature of the electrolyte
- Concentration of the electrolyte
Now, electrochemical machining systems are available as numerically-controlled machining centers with the capability of high production rates, high flexibility, and the maintenance of close dimensional tolerances. The electrolyte in flowing through the machining gap creates a thin boundary layer of slowly moving fluid next to the anode. Ions of work material leaving the metal surface must traverse this slowly moving boundary layer primarily by a process of diffusion. The rate at which ion can move through the boundary layer influences the rate of metal removal. The ideal electrolyte would provide a uniformly thin layer over the entire surface of the work piece, irrespective of pressure and fluid velocity variations. High velocity flow (30 to 60 meter /second) over the electrode surface is one of the key factors in ECM. This is necessary in order to prevent crowding of hydrogen gas and debris of machining. If this is not fulfilled, bubbles of hydrogen gas will fill the machining gap and machining will stop in that area. It also flushes the metallic particles suspended in the electrolyte, leading to local heating or arcing, and ultimately damage of the tooling and the work piece.
Metal removal rate (MRR) is an important parameter in ECM. The overall machining rate is governed by Faraday’s Laws of Electrolysis. Because of the tendency for the electrolyte to erode away sharp profiles, electro chemical machining is not suited for producing sharp square corners or flat bottoms. Controlling the electrolyte flow may be difficult, so irregular cavities may not be produced to the desired shape with acceptable dimensional accuracy.
Designs should make provision for a small taper for holes and cavities to be machined. The shaped tool should be either in the form of a solid or tubular form, and generally made of brass, copper, bronze, or stainless steel. The tool should be rigid enough to take up the load due to fluid pressure. The tool should be easily machinable to make it in the desired shape. The accuracy of the tool shape directly affects the work piece accuracy. Under ideal conditions with properly designed tooling, ECM is capable of holding tolerances of the order of plus or minus 0.02 mm and less. In general, tolerance can be maintained on a production basis in the region of plus or minus 0.02 to 0.04 mm. As a general rule, the more complex the shape of the work, the more difficulties to hold tight tolerances.
The main applications of ECM process are in machining of hard-heat-resisting alloys, for cutting cavities in forging dies, for drilling holes, machining of complex external shapes like that of turbine blades, aerospace components, machining of tungsten carbide and that of nozzles in alloy steels. Almost any conducting material can be machined by this method. The material removal rate by this process is quite high for high strength-temperature-resistant (HSTR) materials compared to conventional machining processes. Tool wear is nearly absent and extremely thin metal sheets can be easily worked without distortion. It is also used to machine automotive components like engine castings, and gears. It is also used for machining and finishing forging-die cavities (die sinking) and to produce small holes. Versions of this process are used for turning, facing, milling, slotting, drilling, trepanning, and profiling, as well as in the production of continuous metal strips and webs. More recent applications of ECM include micromachining for the electronics industry.
About the Author
Dr.Thoguluva Raghavan Vijayaram, currently working as Senior Lecturer in the Faculty of Manufacturing Engineering at UTeM, Universiti Teknikal Malaysia Melaka, Malaysia. He hails from India and he has completed his PhD Research Degree in Mechanical Engineering (Metal Matrix Composites: Materials Engineering) from the Faculty of engineering, Universiti Putra Malaysia. He has published quality research papers in reputed International journals, National journals, International conference proceedings and in the Malaysian broadsheet. He has a wide range of work experience, both in academics and as well as in industry, consultancy, and teaching and especially in research and development work. His areas of expertise include: Metallurgical Engineering, Mechanical Engineering and Manufacturing Engineering and his special areas of research interests are in the field of advanced casting technology and techniques, composite materials and processing, powder metallurgy, Ferrous and Non-Ferrous foundry metallurgy, solidification science and technology, solidification processing of metals, alloys and composites, microgravity solidification, squeeze casting, die casting die design, heat treatment, Metallography, microstructure-property correlation ship, new materials and process development, aerospace engineering materials, computer simulation of casting solidification, FEM analysis and advanced engineering mathematics. Besides, he is a prominent writer and possesses wider experience in editing technical papers, theses and dissertations.
Metallurgical Aspects of Powder Coating Technology
Electrical Discharge Machining (EDM) of Metals and Alloys
Application of Chemical Milling, Chemical Blanking and Photochemical Blanking in Metal Working Industries
歡迎來到利豐行的世界，首先恭喜您來到這接受新的資訊讓產業更有競爭力，我們是提供精密表面處理的代理商，應對廠商高品質的表面處理需求，我們可以協助廠商滿足您對產業的不同要求，我們有能力達到非常卓越的表面處理品質，這是現有相關技術無法比擬的，表面處理技術皆集中於精密研磨,拋光, VTD PVD工具鍍膜, 光學鍍膜 optical coating, 金屬濺鍍 metallization, absolute chemie 精密CVD/PVD退鍍工藝和EMAG Precision Electrochemical Machining 精密電化學加工技術(ECM / PECM)取代放電加工), EMAG 硬車削/乾式車削 hard turning, Koepfer 滾齒(齒輪加工製造) 技術, Reinecker, KARSTENS 內外圓研磨外圓+內圓曲面磨削, Naxos-Union曲柄軸研磨, 凸輪軸, KOPP非圓研磨, SW中心加工機, EMAG 雷射焊接, 自動化設備. oelheld 超高性能研磨切削油/EDM 放電加工液等。我們成功的滿足了各行各業的要求，包括：精密需求高的軸承盒、射出成型的模具、高壓空氣閥、航太零配件、超高硬度的切削刀具、醫療配件及汽車用精密五金等等。我們的產品涵蓋了從桌上型到工業級的生產設備；從微細零配件到大型五金配件；從小型生產到大型量產；從半自動到全自動整合；我們的技術可提供您連續生產的效能，我們整體的服務及卓越的技術，恭迎您親自體驗.
另外有EMAG ECM GmbH (ECM/PECM) 精微電化學加工技術在未來各種細微加工應用中佔有極大的優勢。該技術之優點係在於其加工能力與材料硬度無關，且能加工出微細及形狀複雜之表面結構，經由該製程加工後之產品表面具有粗糙度佳、無殘留應力及無裂縫產生等優良特性，常應用於航太、光電半導體、醫療器材、綠色能源、模具等產業上，本次研討會中特別邀請國內外知名學者及專家，介紹於精微電化學領域內之各種加工技術，可應用於燃料電池雙極板、生物晶片、微流體動壓軸承、微噴嘴、次世次流體分配閥元件、模具等產品加工上，機會難得，精彩可期。PECM為精密電化學切削的工程公司，其領先的技術，已在精密電化學切削領域達到量產化的水準。供顧客PECM精密電化學切削生產技術和客制化的製程設備。Electrochemical machining / pulse electrochemical machining / precise electrochemical machining. Electro chemical machining (ECM) is a method of removing metal by an electrochemical process. It is used for working extremely hard materials or materials ...
利豐行著重於表面處理之前後製程技術，提供客戶individual & total finishing solutions 的整合作業，協助產業提升效能並降低成本。
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本館專門提供 OTEC 表面處理技術皆集中於精密研磨,拋光, deburring, smoothing and polishing. 還有VTD PVD 超硬工具鍍膜 tool coating, 精密光學鍍膜 optical coating, 真空金屬鍍膜 metalization 和 absolute chemie PVD/CVD 退鍍工藝和 EMAG ECM / Precise Electrochemical Machining 精密電化學加工技術, EMAG 硬車削/乾式切削 hard turning, Koepfer 滾齒加工製造技術, Reinecker, KARSTENS外圓研磨+內圓曲面磨削, Naxos-Union曲柄軸研磨, 凸輪軸, KOPP非圓研磨, SW中心加工機, EMAG 雷射焊接, 自動化設備. oelheld 超高性能研磨切削油/EDM 放電加工液等, 其它非相關資料純粹供同好分享.