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1 Machining Process Intro

Oct 24, 2014

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Machining Processes

Machining Processes

Chapter ITheory of Metal Machining

Overview of machining TechnologyTheory of chip formation in metal machiningThe orthogonal cutting modelActual chip formationForce relationships and the Merchant EquationForces in metal cuttingThe Merchant EquationPower and Energy relationships in machiningCutting TemperatureAnalytical methods to compute cutting temperaturesMeasurement of cutting temperature

Before beginning

Material Removal Processes

Conventional Machining

Abrasive Processes

Nontraditional machining and thermal cutting processes

Turning and related operations

Drilling and related operations

Milling

Other machining processes

Grinding

Other abrasive processes

Electro- discharge machining

Electrochemical machining

Thermal energy processes

Chemical machining

Some basic definitions

Material removal processesA family of shaping operations in which excess material is removed from a starting workpart so that what remains is the desired final geometry.Conventional machining processesProcesses in which a sharp cutting tool is used to mechanically cut the material to achieve the desired geometry. Abrasive processesProcesses in which material is mechanically removed by the action of hard, abrasive particlesNontraditional processesProcesses that used various energy forms other than sharp cutting tool or abrasive particles to remove material

Machining

A manufacturing process in which a sharp cutting tool is used to cut away material to leave the desire part shape.

The predominant cutting action in machining involves shear deformation of the work material to form a chip; as the chip is removed, a new surface is exposed.

Advantages and DisadvangesWhy is it so important?

Variety of work materialsVariety of part shapes and geometric featuresDimensional accuracyGood surface finishes

Wasteful of materialTime consuming

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Overview of Machining Technology

To perform a machining operation, relative motion is required between the tool and work. This relative motion is achieved in most machining operations by means of a primary motion, called the CUTTING SPEED, and a secondary motion, called the FEED.

The shape of the tool and its penetration into the work surface, combined with these motions, produces the desired geometry of the resulting work surface

Tipos de procesos de mecanizado

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The Cutting Tool

A cutting tool has one or more sharp cutting edges and is made of a material that is harder than the work material. Single-point cutting tool (turning)

Multiple-cutting-edge tools (milling and drilling)

There are two angles of interest in a single-point cutting toolRake angle Relief angle

Cutting Conditions

Cutting speed (m/s) v meters of chip per secondFeed (mm/rev) fDepth of cut (mm) - d

Cutting Conditions

Material removal rate (mm3/s)

Machining operations Rough cutting: removal of big quantities of material with the highest speedFeed = 0.4 to 1.25 mm/revDepth = 2.5 to 20 mmFinishing cutting: lower cutting speed and depth of cut in order to finish the work piece. Tolerances and surface finishing. Feed = 0.125 to 0.4 mm/revDepth = 0.75 to 2 mm

Cutting Conditions

Cutting fluids: usually applied to cool or lubricate the cutting tool

Cutting Conditions

The term is applied to those machines that perform machining operations. However the term is also applied to those machines that perform bulk deformation processes: rolling, die forging, etc.

Theory ofChip Formation in Metal Machining

THE ORTHOGONAL CUTTING MODEL

Theory ofChip Formation in Metal Machining

THE ORTHOGONAL CUTTING MODEL

Lo = Length of shear planeto = chip thickness before cuttingtc = chip thickness after cutting = shear angleDefine chip thickness ratio r = to/tc2. Define interest triangles 3. Obtain formula for

Theory ofChip Formation in Metal Machining

THE ORTHOGONAL CUTTING MODEL

Theory of Chip Formation in Metal Machining

THE ORTHOGONAL CUTTING MODEL Chip straining in parallel shear plates theory

Homework 1!!

Finish the derivation of the formulas presented in classes for the shearing angle and for the shear strain

DUE DATE: October 22nd. (Via Sidweb)

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