Thermal Aspects of Metal Machining

Thermal aspects of metal machining

Presented by : Lav Kumar 106073 Vishal Chaturani 114089

Machining or metal cutting

Objective of metal cutting:• Removing unwanted material• Cutting/chipping/machining/metal

cutting• To get desired

o Shapeo Sizeo Surface finish

Essentials of MetalCutting Operation1.Machine Tool 3.Method2.Cutting Tool 4. Operator

Mechanism of MetalCutting

Tool & Workpiece interaction: given a depth of cut and relative of motion between tool and workpiece results in chipping.

Thermal Aspect Of Machining

• The power consumed in machining is largely converted into heat near the cutting edge of the tool.

• This causes the temperature of the tool, chip and workpiece to rise.

• This can influence the properties of the work material being machined, as well as the effective life of the cutting tool.

Distribution of Heat Plastic deformation by shearing in the primary shear

zone Plastic deformation by shearing and � friction on the

cutting face � Friction between chip and tool on the tool flank

PRIMARY ZONE• Also known as shear zone.• Maximum heat is generated due to plastic

deformaion of metal.• Since the process is continuous and rapid

process,80-85% heat is generated from this zone.

SECONDARY ZONE• It is also called a friction zone.• As the chip moves along the tool face under great

pressure being resisted by the friction• Heat is generated due to friction between moving

chip on rake face of tool.• 15-20% heat is generated in this zone.

Tertiary zone• It is the work tool contact zone.• Burnishing action is the cause of heat

generation.• Rarely present , if present then 1-3% of

heat generation occurs and occurs due to built up edge formations.

Disadvantages of heat generation

• Affects the wear of the cutting tool.• Can induce thermal damage to the

machined surface• Causes dimensional errors in the

machined surface

Heat dissipation

The temperature in metal cutting can be reduced by:

Application of cutting fluids .Application of coolants. Change in the cutting conditions by reduction

of cutting speed and/or feed; Selection of proper cutting tool geometry

(positive tool orthogonal rake angle).

Simplest way of temperature reduction

simplest way to reduce the cutting temperature is to reduce the cutting speed and/or feed.

Cutting temperature T as a function of cutting speed V, feed f, and depth of cut d

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