Electrochemical Machining A non-conventional metal machining technology
Metaalbewerking middels alternatieve technieken vereist alternatieve kijk op materiaaleigenschappen SIG Material Analysis November 16th 2010
Hans-Henk Wolters
ECM
What is ECM? Fundamentals of ECM/ theory Process description Process animation Material characteristics Advantages and disadvantages of ECM Photo gallery Introduction of ECM Technologies
What is ECM? •Electrochemical machining is a metal machining technology based on electrolysis where the product is processed without contact and thermal influence. The metal work piece is partially dissolved (Machined) through electricity (Electro) and chemistry (Chemical) until it reaches the required complex 3D end shape. •Unlike previous ECM techniques, the current ECM technique benefits from pulsating power supplies and vibrating axis. This concept enables processing products with a minimum processgap varying by single micrometers. The shape accuracy of the end product depends on the size of the gap.
Fundamentals of ECM
Fundamentals of ECM •ECM Electro Chemical Machining •AM Anodic Machining •ECP Electro Chemical Processing •ECP Electro Chemical Polishing •ECP Electro Chemical Plating •CE Chemical Etching •PP Plasma Polishing •ECD Electrochemical Deburring •ECD Electrochemical Drilling •ECG Electro Chemical Grinding •ECM Electro Chemical Milling
Process description
Proces animation For a computer animation copy the following link into your browser http://www.youtube.com/watch?v=Z_U_ZZty5Ns
Material characteristics •Conventional machining •Hardness •Toughness •Sintered •Electrochemical machining •Electrical conductivity •Chemical composition •Heat treatment •Existence of metal carbides •Structure/ homogeneous/ phases
Fundamentals of ECM Electrochemical machinability coefficient Kv , specific charge Qspec en velocity of dissolution Vf for various materials Specific charge Qspec: (C/g) F = Faraday constant ( =96485 C/mol) x = fraction of element i n = valence of dissolution of element i Mw = molecular weight (g/mol) Ti 6-4
element
percentage
Oplosvalentie
Molgewicht (g/mol)
Ď (g/cm3)
Qspec (C/g)
Vf / j (Âľm/s)/ (A/cm2)
Ti Al V
90 6 4
4 3 5 (2)
47.90 26.98 50.94
4.5
8274 0.267 (8047)
Kv (mm3/C)
0.0267
Material characteristics •Electrical parameters •Current (density) •DC, pulsed, bipolar •Pulse length •Pause length •P/P ratio •Electrolyte parameters •Temperature •pH •Conductivity •Salt type (single/ mixtures) •Passivating/ non-passivating •Measurements •Efficiency •Surface quality •Surface roughness •SEM analysis
Anode reaction :
Me → Men+ + ne-
Anode reaction :
6H2O → O2↑ + 4H3O+ + 4e-
Phase 1: high speed machining, v ≈ 2,5 mm/min at 150A/cm2 DC
Phase 2: accurate machining
Fundamentals of ECM Machining strategy in passivating elecrolyte High current density, high MRR
Optimal current density, accurate machining
Phase 3: polishing range
Non passivating electrolyte
Fundamentals of ECM
Increasing concentration
Fundamentals of ECM
Decreasing temperature
Advantages of ECM •The product is free of burrs after processing •No-contact process - The process does not cause thermal or physical strain on the product - Unlike other machining techniques, no upper-layer deformation occurs •3-Dimensional products can be processed in one single step •High quality level attainable (Ra < 0,05 µm) depending on material •High dimensional accuracy attainable •Material stress which releases during the process will be compensated where possible •Stainless steel in the upper-layer will be affected through various machining techniques, as a result of which local rust formation can occur. This is not the case with ECM •Due to the ECM application it is possible to generate more design of freedom for the product •ECM is a technique with high machining speed at relatively low costs
Advantages of ECM •The hardness, toughness and thermal resistance do not affect the material removal rate (MRR). For the machining of the product it is also irrelevant if it is processed before or after a heat treatment (hardening) step. •MRR is high, approx. 1,5 cm3/min by 1000A DC. •MRR is almost independent on the type of material - Hard and tough alloys are machined as “quick” as for instance aluminum •Low running and tooling costs •Initial investment in process design and electrode construction are high, however the recurring costs are low •“No” electrode wear
Disadvantages of ECM •ECM was previously known as a environmental unfriendly process. Through developments in the treatment of electrolytes, the process has become less harmful to the environment. The sludge can be re-used depending on the machined material. •Each product and material requires new research •Higher production numbers are essential, as a special electrode must be developed for each product. The ultimate best depends on complexity and material. •High power consumption but in general lower than other nonconventional machining techniques. •Design of electrode is complex and initially expensive, however “the electrode will not wear”. •ECM requires relatively high skilled staff.
Watch case Process time: 25 min
Turbine wheel Process time: 12 min
Sportscar logo Process time: 22 min
Polished part Ra< 0,05 Âľm Process time: < 1 min
Microstructure Diameter pilar 60-70 µm Centre centre distance 200 µm Height pilar 250 µm Process time: 12 min
Thin wall profile Thickness=60, 45, 30 & 15 Âľm Length=7mm Height=1,5 mm Process time: 45 min
Heat exchanger cell Process time: 6 min
1 mm
Introduction of ECM Technologies ECM Technologies offers research on the feasibility of applying electrochemical machining on metal products. Consultancy and research (fundamental and application based) is being offered for realizing new or optimizing existing ECM processes. The results from the research are used to design and specify an electrochemical machining process to be implemented at customers location. Founded March 2003
Introduction of ECM Technologies When a customer requires a research, small series production/ prototype production and a customized machine then it is possible to define the following phases. • Phase1: Fundamental research on the specific material. •Phase 2: Application research •Phase 3: Small series production to optimize the process and to analyze the parts. • Phase 4: Implementation of the application at the customers location.
Introduction of ECM Technologies ECM Technologies is a small company with high skilled ECM specialists on board. ECM Technologies equipment; •PEM Tec machine for application research •ECD equipment developed by University of Eindhoven •FCC research cell for fundamental research •Plasma polishing research set up •VMB deburring/ polishing equipment •Micro ECM machine
Introduction of ECM Technologies ECM Technologies is working for customers in different industries: •Automotive •Aerospace •Space •Medical •Steel industry •Energy market e.g. fuel cells •Offshore industry •Consumer products •Watch industry •Hygiene market •etc
Introduction of ECM Technologies
Customers Representatives
Thank you for your attention For more info please visit www.electrochemicalmachining.com