23-08-2013, 04:12 PM
Fundamentals of cutting
Fundamentals of cutting.ppt (Size: 1.21 MB / Downloads: 45)
Introduction :
Cutting process : Remove material from the surface of the work piece by producing chips
Turning operation : the work piece is rotated an a cutting tool removes a layer of material as it moves to the left
Cutting off: Cutting tool moves radially inwards and separated the right piece from the back of the blank.
Slab-milling rotating cutting tool removes a layer of material from the surface of the work piece
End-milling rotating cutter travels along a certain depth in the work piece and produces a cavity
Mechanics of chip formation :
Orthogonal cutting
Rake angle – Alpha
Relief angle ( clearance angle)
Shear angle ( Pi)
Thickness of a chip – Tc
Depth of cut- T0
Cutting ratio r = To / Tc
= Sin Pi / Cos ( pi- Alpha )
Continuous chips
Continuous chips are usually formed at high rake angles and/or high cutting speeds.
A good surface finish is generally produced.
continuous chips are not always desirable, particularly in automated machine tools,
tend to get tangled around the tool
operation has to be stopped to clear away the chips.
Chip Breakers
Long continuous chip are undesirable
Chip breaker is a piece of metal clamped to the rake surface of the tool which bends the chip and breaks it
Chips can also be broken by changing the tool geometry,thereby controlling the chip flow
Forces acting in 2-Dimensional cutting
Cutting forces can be measured by using suitable dynamometers or force transducers mounted on the machine tool
They can also be calculated from the amount of power consumption,that occurs during cutting.