Transcript Document 133509

Slovak University of Technology
Faculty of Material Science and Technology in Trnava
Machine Tools And
Devices For Special
Technologies
Electrochemical machining
Electrochemical machining
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Using only for conductive materials,
independence of hardness, toughness,...
Anode melding – machining material is anode
and tool is cathode,
Is not originated thermal and mechanical
damaging of material,
Little worn-down of tool,
The quality is influenced by homogeneity of
structure,
In comparing of photochemical machining are
achieved higher rates of removing of material,
shape and dimension accuracy are higher
Electrochemical machining
Electrolyse is takes place in gap between tool and
material where is flowed electrolyte in pressure.
High pressure using of electrolyte is accelerated
removing of material and quality of surface too.
Material removing is most intensive where is the
gap smallest – with highest flow intensity.
Tool has the shape of asked workpiece.
Electrochemical machining
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electrolyt – solution of HCl,
Pressure of electrolyte is 0,5 – 1,5MPa,
Speed of electrolyte flowing is around 50 m/sec,
Flow intensity is to 1000 A/mm2,
Voltage to 30V, with higher is possible to origin the
discharge,
Speed of removing is 1 – 3,5 mm3/min.A,
Feeding till 2 mm/min
Particular phase components are impregnated by
various speed, that everyone phase components
have minimum voltage is that process is stopped.
Electrochemical machining
Electrochemical machining
Largeness of the gap is 0,1 – 0,3 mm.
Higher gap – more slow removing of material and
quality of the surface,
Lower gap – increased possibility of the short circuits
and damaging of material and electrode.
Constant gap – it achieved by continuous regulation
and from time to time is measured the size of gap
and changed the speed of feed (adaptive directing).
Electrochemical machining
Tool is Cu electrode.
Economical is in series production of difficult shape
of workpieces.
Parts of tool that are not attended in the machining
that are isolated.
Machines and tools are expensive and that is why
used only in the reasonable cases.
Electrochemical machining
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Power of electrochemical machining is amount
of melted metal directed by Faraday laws,
Removing speed is main factor of
electrochemical machinability,
Accuracy of machining is depend on between
electrode distance generally IT 8 till IT 10,
Quality of surface (roughness) depend on the
machined material, on concentration of
electrolyte, on electric hydraulic parameters,
achieved Ra 0,2.
Electrochemical machining
Electrolyt is most often solution of acid or of various
salts.
Electrolyt is used in concentration 10 till 20%,
temperature is around 35 °C.
Electrolyt assuring:
 Direction of electricity,
 Takes away originated heat and impurities,
 Melted machined material
Electrochemical machining
Requests of electrolyte::
 High electric conductivity,
 Is not possible to outflow cations of metal that make
to possible to settled in the tool.
 Must contains ions that melted anode
 Reaction products that are to possible remove from
electrolyte,
 Low kinematics viscosity to no become useless
hydraulic losses,
 Must be aggressive with respect to machined
material and must equally melted all his phase
components.
Electrochemical machining
During machining is acidity of electrolyte fast
increased and can become passivation of
anode (Fe and Ni alloys).
Here is added nitrous acid that is like
stabilisator of ph.
Removing of waste products from electrolyte.
Electrochemical machining
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Machining by homogeneous electrolyte – gap
between electrodes around 0,2 mm, lower that
accuracy machining, needed correction of
activate part of tool.
Machining by mixture electrolyte – substance of
electrolyte and air, electrolyte + CO2, gap can be
under 0,1 mm (usually 0,05 – 0,08 mm), higher
quality and accuracy of surface in the difficult
shapes too.
Kinds of electrochemical
machining
By kinds of removing of melting waste parts we can divided:
 With flow electrolyte:
 Inside,
 outside,
 Cross,
 By mechanical removed products of reactions.
In the low flow intensity (under the limit of creation of passivity
layer) is not possible to removing of waste parts.
Kinds of electrochemical
machining
ECM deeping of holes
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High flow intensity (1000 A/cm2),
High flow speed of electrolyte (around 60/sec),
Feed of the tool electrode 0,5 – 10 mm/min,
Mixture electrolyte,
Roughness of surface Ra lower than 2
Hard machining, hard and high strength materials.
Voids of dies, turbine vanes, ...
ECM void deeping
ECM void deeping
ECM void deeping
ECM drilling
We know three base kinds of hole production by
ECM:
 Deeping by form tube (STEM) – tube of form
section (shape hole),
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Electrolytic soft drilling (ECF) – glass tube
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Electrolytic drilling by flow of electrolyte
(ESD) – glass tube with capillary
Deeping by form tube
Electrolytic soft drilling
Electrolytic drilling by flow of
electrolyte
Electrochemical dividing of
material
We know the next kinds of ECM dividing of
material:
 By rotary disk – disk electrode has sides
covered with isolation, stabile stock removal
 Slot tool – tool is a tube in that is slot from which
is flow out electrolyte, complicated shape cuts.
 By wire tool – electrode is wire, into the place of
cut is directed the electrolyte by hose, thickness
to 20mm,
ECM dividing material by slot
tool
ECM dividing material by wire
tool
Electrochemical machining
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Removing the burrs – electrolyte is directed to
burrs, in the sharp rims is highest intensity,
burrs are melted by anode.
grinding – combination of anodic melting and
mechanical grinding, into electrolyte is mixing in
abrasive,
polishing – at the top of these raggedness is
highest flow intensity, little stock removal, flow
intensity around 0,7 A/cm2, voltage till 12 V,
cathode is of plumbum, big gap, macro
raggednesses can be increased.
Electrochemical machining
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marking – electrode has the shape of mark,
marked place is different of background of
deeping about 0,003 to 0,1 mm, marking
lasted only some seconds, the force is not
influence, heat and deformation too, it used
for thin foils, strong and brittle materials.