Electrochemical grinding

ELECTROCHEMICAL GRINDING: Meaning, Considerations & Parameters

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MEANING

Electrochemical grinding is a cycle that eliminates electrically conductive material by grinding with an negatively charged abrasive grinding wheel, an electrolyte liquid, and a positively charged workpiece.

Materials eliminated from the workpiece stay in the electrolyte liquid.

Electrochemical grinding (ECG) joins electrochemical machining with regular grinding.

Electrochemical grinding process
Fig. 1 Electrochemical grinding process

The gear utilized is like an ordinary processor.

The wheel is a pivoting cathode installed with grating particles.

The wheel is metal bonded with diamond or aluminum-oxide abrasives and turns at a surface speed from 1,200 to 2,000 m/min (4,000 to 7,000 ft/min).

The abrasives have two function:

To serve as insulator between the wheel and the workpiece to precisely eliminate electrolytic items from the working region.

A progression of electrolyte arrangement (normally sodium nitrate) is accommodated in the electrochemical machining period of the activity.

Current densities range from 1 to 3 (500 to 2000).

Most of the metal evacuation in ECG is by electrolytic activity, and regularly, under 5% of the metal is taken out by the abrasive activity of the wheel.

Thus the wheel wear is low, and the workpiece remains cool.

Completing cuts normally are made by the pounding activity, however just to create a surface with great completion and dimensional precision.

The ECG cycle is suitable for applications like those for milling, grinding, and sawing, but it is not adaptable to cavity sinking operations.

ECG can be applied effectively to carbides and high-strength alloys.

It offers a particular benefit over conventional precious stone wheel grinding in preparing exceptionally hard materials where wheel wear can be high.

ECG machines are available with mathematical controls, which improve dimensional accuracy and repeatability and increases productivity.

Electrochemical honing combines the fine abrasive action of honing with electrochemical activity.

Although the equipment is expensive, this process is much quicker than conventional honing and the tool lasts as much as 10 times longer.

Electrochemical honing is utilized principally for completing inner round and cylindrical surfaces.

DESIGN CONSIDERATIONS FOR ELECTROCHEMICAL GRINDING

In addition to those design consideration previously listed for electrochemical machining, ECG requires two more:

Designs should avoid sharp inside radii.

If flat surfaces are to be created, the electrochemically ground surface should be smaller than the width of the grinding wheel.

PROCESS PARAMETERS

The removal rate for ECG is administered by the current density just as in ECM.

Standard machines are available with current rating ranging from 50 to 3000 amp.

The current density frequently utilized relies on the material being pro­cessed and can range from 77 to 620 amp/cml (500 to 4000 amp/in2).

As with ECM, the higher the current density the futer the evacuation rate and better the surface completion.

The voltage utilized for ECG can range from 4 to 15 VDC relying on the application and is generally set as high as conceivable to boost the evacuation rate.

Obviously, this greatest breaking point should not be high to such an extent that it debases the nature of the machined surface, and it should be predictable with surface completion and instrument requirements.

Ordinarily ,voltage is adjusted by expanding it until fine red sparkles become noticeable at the exit side of the wheel.

An excessive amount of voltage is indicated by the arrangement of brilliant blue, perceptible sparkles at the front of the wheel.

The ECG electrolyte is kept up at a temperature somewhere in the range of 15 and 32°C (60 and 90°F) and is separated as in other ECM processes.

As referenced before, the electrolyte being forced through the gap produces a wheel pressure.

In practice this can range from 0.3 to 1.4 MPa (50 to 200 psi) and is held consistent by either a steady feed rate or a water powered chamber that permits the wheel to one or the other give or feed depending on the dissolution rate.

When a feed rate have been established for a specific application, it can be changed by as much as 4 mm/sec without inconveniently influencing the pro­cess.

If the feed rate is running too slowly for the application, a large overcut will be delivered that will bring about helpless surface completions and tolerances.

On the off chance that the feed rate is too quick, the grating particles will be rashly constrained into the workpiece, bringing about unnecessary wheel wear.

The gap between the work surface and the conductive wheel bonding agent is typically 0.25 mm (0.001 In.) on a newly dressed wheel.

Wheel speeds are typically somewhere in the range of 1200 and 1800 surface meters each moment (4000 and 6000 SFPM).

CYCLE CAPABILITIES

Electrochemical grinding shows material expulsion rates that are up to 10 times quicker than ordinary grinding on materials harder than HRc 60.

Three phases of ECG process
Fig. 2 Three phases of ECG process

It is consid­ered cost on materials harder than HRc 45.

Regardless of how hard, intense, or weak a material is, ECG produces surfaces liberated from any grinding scratches.

Electrochemical pounding will likewise create a preferred surface completion over traditional crushing in non-homogeneous materials.

When grinding intense composites are used then the ECG metal expulsion rates might be five to multiple times those of ordinary grinding techniques.

In the wake of taking wheel wear into con­sideration, absolute creation has been accounted for to be multiple times that of ordinary grinding.

ADVANTAGES

There is no thermal damage to workpiece.

Long lasting wheels.

No distortions.

Single pass grinding.

No burrs.

DISADVANTAGES

High capital cost.

Corrosive environment.

High preventive maintenance cost.

Not economical for soft materials.

APPLICATIONS

Grinding turbine blades.

Grinding honeycomb metals for aerospace application.

Sharpening hypodermic needles.

Machining carbide cutting-tool inserts.

ECG is used to remove surface defects from parts where excessive material removal and residual stresses are undesired, such as re profiling locomotive gears.

CONCLUSION

We have covered all the important concepts related to electrochemical grinding process. Hope you all are crystal clear with understanding all the concepts mentioned here. If you have any questions please use the comments section to get in touch with us. Till then have fun and always keep reading!

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