Machine Tools And Devices For Special Technologies

Electrochemical machining

Slovak University of TechnologyFaculty of Material Science and Technology in Trnava

Electrochemical machining 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 machiningElectrolyse 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 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 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 R

a 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 machiningRequests 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

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 + CO

2, 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

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 R

a 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),

Electrolytic soft drilling (ECF) – glass tube

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 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 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.