BARIPADA : 7571

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SUB- MANUFACTURING TECHNOLOGY

TOPIC- Grinding Process

BRANCH- AUTOMOBILE ENGINEERING

SEMISTER- 4th,(SUMMER-2022)

SUBJECT- MANUFACTURING TECHNOLOGY

FACULTY- ER. A.K. JENA

Estd:.1994

CONTENTS

• TYPES OF GRINDING MACHINE
• SURFACE GRINDING MACHINE
• CYLINDRICAL GRINDING MACHINE
• INTERNAL GRINDING MACHINE
• CENTER LESS GRINDING MACHINE
• GRINDING WHEELS

Manufacturing Technology

Major advantages and applications of grinding

Advantages

• A grinding wheel requires two types of specification
• Dimensional accuracy
• Good surface finish
• Good form and locational accuracy applicable to both hardened and unhardened material

Applications

• Surface finishing
• Slitting and parting
• De-scaling , De-burring
• Stock removal (abrasive milling) finishing of flat as well as cylindrical surface
• Grinding of tools and cutters and re-sharpening of the same.

Manufacturing Technology

Grinding Machines

• Grinding Machines are also regarded as machine tools. A distinguishing feature of grinding machines is the rotating abrasive tool.
• Grinding machine is employed to obtain high accuracy along with very high class of surface finish on the work piece. However, advent of new generation of grinding wheels and grinding machines, characterized by their rigidity, power and speed enables one to go for high efficiency deep grinding (often called as abrasive milling) of not only hardened material but also ductile materials.
• Conventional grinding machines can be broadly classified as:
• Surface grinding machine
• Cylindrical grinding machine
• Center less grinding

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Manufacturing Technology

Surface grinding

• In surface grinding, the spindle position is either horizontal or vertical, and the relative motion of the work piece is achieved either by reciprocating the work piece past the wheel or by rotating it. The possible combinations of spindle orientations and work piece motions yield four types of surface grinding processes illustrated in the figure

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Manufacturing Technology

Surface grinding machine

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Schematic illustration surface grinding Machine

Manufacturing Technology

Surface grinding machine

• This machine may be similar to a milling machine used mainly to grind flat surface. However, some types of surface grinders are also capable of producing contour surface with formed grinding wheel.

A: rotation of grinding wheel B: reciprocation of worktable C: transverse feed D: down feed

Horizontal Grinding Machine

Vertical Grinding Machine

Manufacturing Technology

Cylindrical grinding

• In this operation, the external or internal cylindrical surface of a work piece are ground. In external cylindrical grinding (also center-type grinding) the work piece rotates and reciprocates along its axis, although for large and long work parts the grinding wheel reciprocates.
• In internal cylindrical grinding, a small wheel grinds the inside diameter of the part. The work piece is held in a rotating chuck in the headstock and the wheel rotates at very high rotational speed. In this operation, the work piece rotates and the grinding wheel reciprocates.

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Manufacturing Technology

Cylindrical grinding machine

• This machine is used to produce external cylindrical surface. The surfaces may be straight, tapered, steps or profiled.

A: rotation of grinding wheel B: work table rotation C: reciprocation of worktable D: infeed

Manufacturing Technology

Internal grinding machine

• This machine is used to produce internal cylindrical surface. The surface may be straight, tapered, grooved or profiled.

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Manufacturing Technology

Center less grinding

• Center less grinding is a process for continuously grinding cylindrical surfaces in which the work piece is supported not by centers or chucks but by a rest blade. The work piece is ground between two wheels. The larger grinding wheel does grinding, while the smaller regulating wheel, which is tilted at an angle i, regulates the velocity Vf of the axial movement of the work piece.
• Center less grinding can also be external or internal, traverse feed or plunge grinding. The most common type of center less grinding is the external traverse feed grinding.

Manufacturing Technology

Center less grinding Machine

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Manufacturing Technology

Grinding wheel

• Grinding wheel consists of hard abrasive grains called grits, which perform the cutting or material removal, held in the weak bonding matrix. A grinding wheel commonly identified by the type of the abrasive material used. The conventional wheels include aluminium oxide and silicon carbide wheels while diamond and CBN (cubic boron nitride) wheels fall in the category of super abrasive wheel.

Specification of grinding wheel

• A grinding wheel requires two types of specification
• Geometrical specification
• Compositional specification

Manufacturing Technology

Geometrical specification

• This is decided by the type of grinding machine and the grinding operation to be performed in the workpiece. This specification mainly includes wheel diameter, width and depth of rim and the bore diameter.

Compositional specifications

• Specification of a grinding wheel ordinarily means compositional specification. Conventional abrasive grinding wheels are specified encompassing the following parameters.
• The type of grit material
• The grit size
• The bond strength of the wheel, commonly known as wheel hardness
• The structure of the wheel denoting the porosity i.e. the amount of inter grit spacing
• The type of bond material
• other than these parameters, the wheel manufacturer may add their own identification code prefixing or suffixing (or both) the standard code.

Manufacturing Technology

Types

• Conventional abrasive grinding wheels

Manufacturing Technology

• Super abrasive grinding wheels

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The bonding materials for the super abrasives are (a), (d), and (e) resinoid, metal, or vitrified, (b) metal, (c) vitrified, and (f) resinoid.

Manufacturing Technology

Examples of Bonded Abrasives

• Conventional abrasives
• Al₂O₃
• SiC
• Super abrasives
• Cubic boron nitride (CBN)
• Diamond

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Manufacturing Technology

Selection of Cutting speed and Working speed is based on

• Material to be ground and its hardness.
• Amount of stock removal and finish required.
• Whether the grinding is done wet or dry.
• Wheel speed.
• Area of grinding contact.
• Severity of the grinding operation.

Manufacturing Technology

Truing and dressing of grinding wheel

Truing

• Truing is the act of regenerating the required geometry on the grinding wheel, whether the geometry is a special form or flat profile. Therefore, truing produces the macro-geometry of the grinding wheel.
• Truing is also required on a new conventional wheel to ensure concentricity with specific mounting system. In practice the effective macro-geometry of a grinding wheel is of vital importance and accuracy of the finished work piece is directly related to effective wheel geometry.

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