Machining
Machining
What is Machining?is any of various processes in which a piece
of raw material is cut into a desired final shape and size by a
controlled material-removal process.
Machining ProcessesDrillingIt is used to create a round hole. It
is accomplished by a rotating tool that typically has two or four
helical cutting edges. The tool is fed in a direction parallel to
its axis of rotation into the work piece to form the round hole.A
cuttingprocess that uses adrill bitto cut or enlarge a hole of
circularcross-sectionin solid materials. The drill bit is a rotary
cutting tool, often multipoint.
Advantages and DisadvantagesA variety of materials can be
chosenShort lead timeLarge scrap wastageTurninga cutting tool with
a single cutting edge is used to remove material from a rotating
work piece to generate a cylindrical shape. The primary motion is
provided by rotating the work piece, and the feed motion is
achieved by moving the cutting tool slowly in a direction parallel
to the axis of rotation of the work piece.
Advantages and DisadvantagesShort lead timesVery good
tolerancesCompatibilityLimited to rotational partsMay require
several operations and machinesHigh equipment costLarge amount of
scrapSignificant tool wearMillingA rotating tool with multiple
cutting edges is moved slowly relative to the material to generate
a plane or straight surface. The direction of the feed motion is
perpendicular to the tool's axis of rotation. The speed motion is
provided by the rotating milling cutter.
Two basic forms: Peripheral milling and Face milling
Advantages and DisadvantagesCompatible with all
materialsFlexible useShort lead times
Inaccuracy in surface dimensionsSurface roughness
Grindingis anabrasive machiningprocess that uses a grinding
wheel as the cutting tool.
Advantages and DisadvantagesCompatibilityShort lead timeGood
surface finishLarge scrap wastageTool wear is quite highChip
FormationIs a phenomenon at the point where the tool meets the
work.
Chip Classifications1.) Continuous Chip - are formed by the
continuous plastic deformation of metal without fracture in front
of the cutting edge of the tool and is formed by the smooth flow of
the chipup the tool face. Formation conditions:Ductile materialHigh
cutting speedSmall chip thicknessLarge rack angleMinimum chip
frictionBest metals to use: mild steel and copper2.) Discontinuous
Chip is formed by a series of rupture occurring approximately
perpendicular to the tool place face.Formation conditions:Brittle
materialLarge chip thicknessLow cutting speedSmall rack angle3.)
Continuous Chip with built up edge similar to a continuous chip but
it has a built up edge adjacent to tool face and also it is not so
smooth. It is obtained bymachining on ductile material, in this
condition of high local temperature and extreme pressure in the
cutting and high friction in the tool chip interference, may cause
the work material to adhere or weld to the cutting edge of the
tool.
