Grinding

Grinding is a metal cutting process in which the material is removed from the workpiece by the abrasive action of rotating cutting tool known as a grinding wheel which rotates at a high speed (v= 10-80 m/s) while the work is fed past the wheel at a rate of 0.2 m/s to 0.6 m/s. It has some similarity with up milling operation except that the cutting points are irregularly shaped and randomly distributed.

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Grinding operation is performed to:

1. Machine hard surface

2. Impart better surface finish

3. Sharpen the cutting tool

4. Finish the workpiece within the close tolerance.

Classification of Grinding Machine

1. Rough grinders: These grinders are used for removal of a large material rather than for accuracy.

2. Precision grinders: These grinders are used to finish the workpiece within close tolerances obtaining desired dimension accurately.

Working principle of Grinding Machine:

In a grinding machine, there is an electric motor which supplies the motion power to the grinding wheel with the help of a belt and pulley.

So when we start the electric motor the motor rotates at a certain rpm (150-15000 RPM, it may change according to the types of grinding machine) with the help of v-belt and cone pulley the grinding wheel also starts rotating and we perform the operation.

Types of Grinding Machine

1. Rough Grinders:

Floor or bench grinders
Portable grinders
Abrasive belt
Swing frame grinders

2. Precision Grinders:

Surface grinders
Cylindrical grinders (plain, universal and centerless grinders)
Tool and cutter grinders
Internal grinders (chucking, planetary and centerless grinders)
Special grinding machine

Floor or bench grinders:

Floor or bench grinders is a small type of machine used in the labs where a small workpiece has to grind. For example, when we manufacture a single point cutting tool for a lathe machine we use to manufacture by floor or bench grinder.

Portable grinders:

As the name indicates portable that means it is not fixed at one point. The portable grinders is used for cutting tiles.

Abrasive grinder:

The abrasive grinder is a similar type of these grinders but the main difference is here abrasive is used while cutting and finishing the job. This is more costly than the floor and portable grinder.

Swing frame grinder:

The swing frame grinder is a complicated type grinder machine and it is used for the heavy workpiece.

Surface grinder:

A surface grinder consists of an abrasive wheel, a chuck (a workpiece holding device), and a rotatory table. The chuck is used to hold the material in place while the wheel and object are rotated to produce a smooth finish.

Cylindrical grinder:

A cylindrical grinder is used for shaping the outside of a workpiece. These machine accept workpieces in a variety of shapes as long as they can be rotated through a central axis.

In a cylindrical grinder, both the workpiece and grinding wheel are simultaneously rotated.

Centerless grinders:

A centerless grinder is a type of cylindrical grinder which uses two rotatory wheels to secure the workpiece in place. Unlike a centered grinder, a centerless grinder does not make use of a spindle. The speed of the rotation of the wheels determines at what rate the material is removed.

Tool and Cutter grinder:

A tool and cutter grinder makes use of a CNC machine tool with up to 5 axes and multiple grinding machine wheels. These devices are used for sharpening and producing milling cutters such as drills, endmills, and step tools. It is also widely used for producing the tools needed in the wood working and metal cutting industries.

Component parts of grinding machine

1. Base: It is a cast iron casting rests on the floor and supports the other parts which are mounted on it. The base houses the table drive mechanism and on the top of the base accurately machined guideways are provided at right angles to the table to slide on it.

2. Table: There are two tables, a lower table, and the upper table. The lower table provides tranverse movement to the work by sliding over the guideways on the bed, which can be moved by hand or power. The upper table pivoted at its center over the sliding table and provided with headstock and tailstock and these can be positioned at any position along the table to hold the workpiece. The upper table can be swiveled and clamped for grinding straight or tapered surface.

3. Headstock: The headstock fixed over the bed and supports the workpiece by means of a dead center and drives it by means of a dog or it may hold the workpiece in a chuck and drives it.

4. Tailstock: The tailstock can be adjusted and fixed in any required position to accomodate different lengths of the workpiece.

5. Wheel Head: It consists of a grinding wheel and its driving motor. The wheel head is mounted on a slide at the rear end of the base and moves perpendicularly to the table ways by hand or power to feed the grinding wheel to the work.

6. Crossfeed: The grinding wheel can be fed to the work by engagement of the crossfeed control lever by hand or power.

Applications: It makes use of an abrasive wheel in the form of a cutting tool. The rough surface of the abrasive wheel shreds away small pieces of the workpiece as needed.

Milan Tomic

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Grinding Machine | operation | working principle | classification | types | component parts | application

Grinding