hybrid manufacturing ecdm
TRANSCRIPT
Hybrid
Electrochemical Discharge
Machining(ECDM)
Presented by
Ajay Vaishnav
TME15B001
Contents:-IntroductionNeed of ECDMWorking Principle of ECDMMaterial Removal Mechanism in ECDMMain Influencing parametersAdvantages over ECM/EDMDisadvantages over EDM/ECMApplication of ECDMComparison between ECDM, EDM and ECM
• Electro-Chemical processECM
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• Electro-Thermal processEDM
• Hybrid Thermal processECDM
What is ECDM ?
• Material removal due to Erosion of work piece at high temperature and high pressure.
EDM
• Material removal due to Anodic dissolution of work piece. ECM
• Material removal due to Thermal heating/melting and chemical etching of the work piece.
ECDM4
Introduction
Electro-chemical discharge machining (ECDM) is a
hybrid non-conventional manufacturing process which
combines the features of electro-chemical machining
(ECM) and electro discharge machining (EDM). Non-
conducting materials can be machined by ECDM by
employing auxiliary electrodes.
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Need of ECDM
1.High Accuracy and Surface Finish2.High Strength Alloys3.Complex Surfaces4.Technology Advancement5.Machining on non-conducting
materials
.
Material Removal Mechanism
in ECDM :-MRR
Mechanism
Thermal mode
Melting Vaporization
Chemical mode
Etching/E-C Rxn
Mechanism
(auxiliary electrode)
BASIC MECHANISM OF
Electro-chemical discharge machining
(ECDM)
The tool electrode (cathode) and auxiliary electrode (anode) are immersed in an electrolyte solution (typically NaOH or KOH). Both electrodes are connected to a DC power supply, causing hydrogen bubbles to be produced on both electrodes due to electrochemical reactions. The bubbles become dense and coalesce into a gas film (Passivating Film) on the tool electrode. The gas film allows sparking between the tool electrode and electrolyte by isolating the tool from the surrounding electrolyte. If the workpiece is brought close to the tool, material removal occurs.
Main Influencing parameters :-
Electrolyte Semi Dielectric fluids/Electrolyte
Voltage 40-150V, DC & Current 3-4A
Gas Film (Passivating Film)
Spark Generation
Tool Electrode
Auxiliary Electrode
Electrode Gap
Tool PropertiesHigh Electrical & Thermal conductivity
High melting point
Cheapness
Good wear resistance Eg. Steel,Cu
1.Cylindrical Tool (Conventional Tool)
2.Tapered Tool12
Why Tapered Tool Electrode?
Fringing effect
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• Current density is more intense near the rim for
cylindrical tools. Thus, sparks tend to generate
from any point along the rim of the tool electrode,
if not considering any geometrical defects.
By replacing the cylindrical tool with a tapered end tool, we make discharges focus on a concentrated region.
Tapered tool electrodes with different shape
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Some Other Tools
Effect of Voltage
Increase in applied voltage increases the MRR
But Less than 100V is best.
Question: Why Higher voltage is not preferred ?
Ans.: MRR start decreasing due to entrapping of debris in spark gap
Function of Electrolyte
Maintain constant resistance across the gap
Cools the spark region
Removes eroded particles
Avoid welding of tool and work
Examples:- aqu solution of KOH or NaOH, sodium silicate or nitrate
Effect of Electrolyte
Concentration
Concentration MRR
Concentration Smoother Surface finish
But concentration(typically NAOH) < 250g/L
Why ????
Some More Parameters
Effect of machining gap
Effect of inter electrode gap
Effect of tool feed rate
Effect of Electrolyte temperature
Advantages over ECM/EDM :-
• The surface obtained have better finish than EDM and ECM 0.01mm or 10 m
• Suitable for non-conducting materials.
• High accuracy.
• Does not leave any chips or burrs.
• Less power consumption.
Advantages over Traditional
Processes Non conducting materials like glass, ceramics etc can be
machined in this process.
Tool wear is negligible compared to other processes.
Focused spark generation due to the tapered tool.
High machining rates are also possible that increasing the
productivity and reducing the unit production cost.
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Disadvantages over EDM/ECM:-
• Tool is likely to worn out, if the machining time is increased.
• Energy from the spark is not fully transferred.
• Initial cost is high.
• Thickness of ceramic material can be machined is limited to 1.5 mm.
• Radial overcut.
• The process cannot produce internal and external sharp edges.
What is Radial Overcut ?
Application of ECDM :-
production of :
• Through and blind micro-holes
• Micro-grooves
• Micro-slots
• Micro-channels and Complex shapes produced in non-conducting
materials ( quartz, glass, and ceramics) etc.
• Miniature features of turbine blades
• Industrial applications like bearings, computer parts
Comparison betweenECM, EDM and
ECDM ASPECTS ECM EDM ECDM
PRINCIPLE Anodic dissolution Spark erosion Both
POWER 10,000A,2-3V,DC 200A,50-200V,DC 3-4A,40V,DC
WORK
PIECE
Conductive Conductive Conductive &
non- conductive
MRR Less Less 5times faster
than EDM
TOOL
WEAR
Less than both Higher than ECDM Less than EDM
ACCURACY Higher than EDM Dimensional accurate
:+-.03mm
+-.01mm
SURFACE
FINISH
Higher than both Less Higher than
EDM
COST Less initial than ECDM Less initial than
ECDM
High
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…..
Questions
Please