Chapter 1
MACHINE TOOLS
AND
MACHINING OPERATIONS
Prof. Dr. S. Engin KILIÇ
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
MACHINING IS THE REMOVAL
OF THE UNWANTED METAL FROM
A WORKPIECE IN THE FORM OF
CHIPS SO AS TO OBTAIN A
FINISHED PRODUCT OF DESIRED
SIZE, SHAPE, AND FINISH.
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History of Machining
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Before 18th century main material used was
wood.
Development of metal machining starts with
invention of steam engine (1776).
The production of cylinders of the engine was
a problem.
Wilkinson invented horizontal boring machine
to cope with this problem.
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Fundamentals of Machining
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The principle used in all machine tools is
generating the surface required by providing
suitable relative motions between cutting tool
and the work piece.
Metal removed is called chip.
Two types of relative motion must be provided
by a metal cutting machine tool: Primary and
feed motion.
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Fundamentals of Machining
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The primary motion is the main motion
provided by a machine tool or manually to
cause relative motion between the tool and the
work piece so that the face of the tool
approaches to the work piece material.
Usually the primary motion absorbs most of
the total power required to perform a
machining operation.
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Fundamentals of Machining
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The feed motion is a motion that may be
provided to the tool or work piece by a
machine tool which, when added to the
primary motion, leads to a repeated or
continuous chip removal.
This motion may proceed by steps or
continuously; in either case it usually absorbs
a small proportion of the total power required.
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Relative motion
between
tool and workpiece
Primary motion
Secondary motion
Cutting motion
Feed motion
Cutting speed
Feed speed
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Classification of the chip removing
methods according to relative motions
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Resultant cutting motion
in cylindrical turning
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
ISO Machine Tool Axis Definition
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AXIS
MACHINE TOOL WITH SPINDLE
Z
Axis of spindle, (+Z) as tool goes away from
work-piece
MACHINE
TOOL WITH
ROTATING
WORKPIECE
X
Y
Radial and
parallel to cross
slide, (+X) when
tool goes away
from the axis of
spindle
MACHINE TOOL
WITH NO
SPINDLE
Perpendicular to
the work holding
surface, (+Z) as
tool goes away
from work-piece
MACHINE TOOL WITH
ROTATING TOOL
HORIZONTAL
AXIS
Horizontal and
parallel to work
holding surface,
(+X) to the right
when viewed
from spindle
towards workpiece
VERTICAL
AXIS
Horizontal and
parallel to work
Parallel to and
holding surface,
positive in the
(+X) to the right
principle direction
when viewed
of cutting (primary
from spindle
motion)
towards
column.
Apply right hand rules
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RIGHT HAND RULE
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RIGHT HAND RULE
Vertical Machine
Horizontal Machine
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Types of cutting tools
CUTTING TOOL
SİNGLE POİNT
CUTTİNG TOOL
MULTI POİNT
CUTTİNG TOOL
ABRASIVE
TOOL
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Typical single-point cutting tool
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Machine tools using single-point
cutting tools
Lathes
Shapers
Planers
Boring M/C’s
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Machine tools using multiple-point
cutting tools
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Drilling M/C’s
Milling M/C’s
Broaching M/C’s
Hobbing M/C’s
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Machine tools using abrasive tools
Grinding M/C’s
Honing M/C’s

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Machine Tool Provides
work holding
tool holding
relative motion between tool and workpiece

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LATHES
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Components of a Lathe
Bed
Headstock Assembly
Tailstock Assembly
Carriage Assembly
Quick-change Gear Box
Lead Screw and Feed Rod.

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A typical turning machine
z
X
Y
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Engine Lathe
z
X
Y
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Types of Lathes
Engine lathe
Tool-room lathe
Turret lathe
CNC lathes
Automatic screw machines
Swiss-type automatic screw machines

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Cutting Tools
For cutting tools used in
lathes, geometry depends
mainly on the properties of
the tool material and the work
material.
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Tool geometry for a single point tool
Cutting part
Face
Tool axis
Minor cutting
edge
Shank
Base
Major cutting edge
Minor flank
Major flank
Corner
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Tool geometry for a single point tool
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Tool geometry for a single point tool
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Operations that can be performed
on a lathe
Turning
Boring
Facing
Parting (Cutoff)
Threading
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Typical Lathe Operations
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Typical Lathe Operations
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Turning
Turning is the machining
operation that produces
axisymmetrical parts
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Turning
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The process of
machining external
cylindrical surfaces
Usually performed
on a lathe
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Turning defined as the machining of
an external surface
with the work-piece rotating,
with a single-point cutting tool
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fed parallel to the axis of the work-piece
at a distance from the work axis to remove a
layer from the outer surface of the work.
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Turning process and adjustable parameters
Depth of cut
(back engagement)
Feed
Spindle speed
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Turning process
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Average cutting speed
Vave 
 .nw.(dw  dm)
2
nw:rotational frequency of workpiece
dw:diameter of workpiece
dm:diameter of machined surface
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Metal removal rate
Zw   .f.a p.nw.(dm  ap)
F :
ap :
nw :
dm:
Feed
back engagement (depth of cut)
rotational frequency of workpiece
diameter of machined surface
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Boring involves the enlarging of
an existing hole, which may have
been made by a drill or may be
the result of a core in a casting
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Typical boring operation
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Metal removal rate
Zw   .f.a p.nw.(dm  ap)
f : feed
ap : back engagement
nw : rotational frequency of
workpiece
dm: diameter of machined surface
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Facing is the process to
produce a flat surface normal
to work axis in turning
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Typical facing operation
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Maximum cutting speed
vmax   .nw.dm
nw: rotational frequency of workpiece
dm: diameter of machined surface
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Metal removal rate Zw,max
Zw, max   .f.a p.nw.dm
f
:feed
ap :back engagement
nw :rotational frequency of workpiece
dm :diameter of machined surface
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Parting is the operation by
which one section of a workpiece is severed from the
remainder by means of a cutoff
tool
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Typical parting operation
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In threading primary motion of tool is
combination of –C’ and –Z’ to
generate a helix on the workpiece by
setting the gears that drive the lead
screw to give the required pitch of
the machined threads.
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Typical threading operation
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Vertical Boring Machine

Similar to lathes but with a
vertical
axis
to
accommodate large and
heavy workpieces
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A typical Vertical Boring Machine
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Horizontal Boring Machine
They are very versatile and thus
particularly
useful
in
machining large parts
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Essential features of
Horizontal Boring Machine
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A rotating spindle that can be fed
horizontally.
A table that can be moved and fed in two
directions in a horizontal plane.
A headstock that can be moved vertically
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Horizontal Boring Machine
z
X
Y
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Shaping and Planing
Shaping is used to produce flat
surfaces only suitable for small
parts in low –batch quantities
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Shaping and Planing
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Among the oldest single-point machining
processes
Largely replaced by milling and broaching
In shaping, workpiece is fed at right angles to
the cutting motion between successive strokes
of the tool.
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Shaping and Planing
A shaper and a planer from 18th century
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Classification of shapers according to their
general design features

Horizontal
 Pull-cut
 Push-cut

Vertical
 Regular
 Keyseater

Special
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Horizontal Push-cut Shaper
z
X
Y
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A typical vertical shaper
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Vertical Shaper (Slotter)
Y
Z
X
•Vertical and inclined surfaces
•External and internal cylindrical surfaces
•Circular feeding of table between strokes
•Keyseater specially designed for mach.
keyways inside wheel and gear hubs
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Shaping and Planing
Planing is used to produce flat
surfaces on workpieces that are
too large to be accommodated
on shapers.
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Classification of Planers according to their
general design features
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Double-housing type planers
Edge planers
Open side planers
Pit planers
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Typical Planers
Z
X
Y
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Machines Using
Multipoint-Cutting Tools
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Drilling Machine
(Drill Press)
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Drilling
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Used to produce holes.
Constitutes about 25% of
all machining processes
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Parts of a Typical Drilling Machine
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Powerhead
Column
Spindle
Table
Base
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Various types of Drilling Machines
Gun (deep hole) drilling
Gang Drilling
Turret Drilling
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Typical operations performed
on drilling machines

Center Drilling

Reaming
Spot facing

Spot Facing
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Drilling, formulations
f
ac   sin r
2
ac :undeformed chip thickness
f :feed
Кr :Major cutting edge angle
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Machining time:
lw
tm 
f.n t
lw:lenght of specimen
f:feed
nt:rotational frequency of the tool
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Metal removal rate:
Zw 
 .f.d .nt
2
m
4
f:feed
nt:rotational frequency of the tool
dm:diameter of the machined surface
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Metal removal rate for hole enlargement:
Zw 
 .f.(d d ).nt
2
m
2
w
4
f:feed
nt:rotational frequency of the tool
dm:diameter of the machined surface
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MILLING
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Milling
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A process by which a surface is generated
by progressive chip removal.
Performed on a wide variety of milling
machines.
The cutting tool is used is known as milling
cutter.
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Major components of a milling machine
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Types of milling machines
Horizontal Milling Machines
Vertical Milling Machines

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Milling operation
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Milling operation with coolant
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Horizontal Milling Machines
In horizontal milling machines the
milling cutter is mounted on a
horizantal arbor driven by the
main spindle.
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A typical Horizontal Milling Machine
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Slab Milling Operation
Used to generate a horizantal surface
on the workpiece
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Slab milling formulations

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Maximum undeformed chip thickness:
ME 535 METAL CUTTING
85
Time for machining:
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Metal removal rate:
Zw= ae. ap.vf
ae :working Engagement
 ap :width of cut
Vf :feed speed of the workpiece

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Vertical milling machines
In vertical milling machines the milling
cutter is mounted on a vertical arbor
driven by the main spindle
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Vertical milling operations
End Milling
Face Milling
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A Vertical Milling Machine
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Face milling
Used to generate surface that is
at right angle to the cutter axis
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Various face and end milling operations
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In Face Milling feed is ;
V
f
f  nt



f:feed
Vf:Feed speed of the workpiece
nt:rotational frequency of the
cutter
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Maximum undeformed chip thickness:
ac, max
V
f

N.nt
Vf:Feed speed of the workpiece
nt:rotational frequency of the cutter
N:Number of teeth on the cutter
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Machining time if the path of the tool axis
passes over the workpiece:
lw :Lenght of the specimen
dt :Diameter of the tool
v f :Feed speed of the workpiece
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Milling time analysis
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Machining time if the path of the tool axis does not
pass over the workpiece:

lw  2 ae(dt - ae)
tm 
Vf

lw:Length of the specimen
ae:Working engagement
dt:Diameter of the tool
Vf:Feed speed of the workpiece
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Milling Operatios
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BROACHING
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Broaching is the machining of
metal by means of a tool which is
composed of a series of single
point cutting edges each slightly
larger than the previous one, made
on bar.
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Broaching
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Finishes an entire surface in a single pass.
Is used in production to finish holes, splines
and flat surfaces.
Is one of the most productive of the basic
machining processes.
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Vertical broaching
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The average metal-removal rate
(Zw) can be estimated by dividing
the total volume of metal removed
by the machining time.
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Machining time for broaching:
lt
tm 
v
lt:Lenght of the Broach
V:Cutting Speed
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Feed is the motion which an imaginary single cutting edge
would have to be given by the machine tool to produce the
same result as the array of cutting edges with which the
tool is actually provided. It is the height difference
between the two successive teeth. Uncut chip thickness:
a =af=f
 c
af:Feed engagement
f:Feed
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ABRASIVE MACHINING
PROCESSES
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Abrasive Machining
The basic process in which chips
are formed by very small cutting
edges that are integral parts of
abrassive particles
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Abrasive Machining
Two unique characteristics:


Cutting edge is very small, very fine
cuts are possible.
Cutting edges are actually extremely
hard abrasive particles therefore very
hard materials can be machined
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Abrasive machining: Grinding




A material removing process that involves the
interaction of abrasive grits with the work piece at
high speeds and shallow penetration depths.
Abrasive machining is the oldest machining
operation.
Cutting edges are very small and can cut
simultaneously.
Very fine and smooth surfaces can be obtained
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Types of grinding operations


Traverse Grinding: The primary feed motion is
the reciprocating traverse motion along the
length (or axis) of the part with an intermittent
infeed (cylindrical grinding)/cross feed (surface
grinding) at the end of each stroke.
Plunge Grinding: Intermittent feed motion is
normal to the work surface (infeed) at the end
of each stroke of the traverse motion (surface
grinding); infeed motion (normal to work
surface) without traverse motion (cylindrical
grinding).
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Types of grinding machines




Horizontal-Spindle Surface-grinding
Machine
Vertical-Spindle Surface-grinding
Machine
Cylindrical-grinding Machine
Internal-grinding Machine
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Horizontal-Spindle Surface-Grinding Machine

Has a horizontal spindle that
provides primary motion to the wheel.
The feed motion is the reciprocation
of the worktable on which the work is
mounted.
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Horizontal-spindle surface-grinding machine
Traverse grinding
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Metal removal rate for traverse grinding:
Z  f.a p.vtrav.
f:Feed
ap:Back Engagement
Vtrav.:Traverse Speed
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Machining time:
bw
tm 
2.f.n r
bw:Witdh of the workpiece
F:Feed
nr:Frequency of reciprocation
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Plunge grinding process with horizontal-spindle
surface-grinding machine
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Metal removal rate for plunge grinding:
Z  f.a p.vtrav.
f
:Feed
ap
:Back Engagement
Vtrav.:Traverse Speed
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Machining time:
at
tm 
 ts
2.f.n r
at :tool depth of workpiece
f :feed
nr :frequency of reciprocation
ts :sparking-out time
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Vertical-Spindle Surface-Grinding Machine

Employs a cup-shaped abressive wheel and
performs an operation similar to face milling
operation.
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Vertical-Spindle Surface-Grinding Machine
Metal removal rate:
Z  f.a p.vtrav.
f:Feed
ap:Back Engagement
Vtrav.:Traverse Speed
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Vertical-Spindle Surface-Grinding Machine
Machining time:
at
tm 
 ts
2.f.n w
at:tool depth of workpiece
f:Feed
nw:Frequency of reciprocation worktable
ts:Sparking-out time
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Cylindrical grinding
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Traverse grinding on a cylindrical grinder
Max. metal removal rate:
Zwmax   .f.d w.vtrav.
f
:feed per stroke of the machine table
dw
:diameter of the work surface
Vtrav.:traverse speed
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Traverse grinding on a cylindrical grinder
Machining time:
at
tm 
 ts
2.f.n r
at:tool depth of workpiece
f:Feed
nr:Frequency of reciprocation
ts:Sparking-out time
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Plunge grinding on a cylindrical grinder
Max. metal removal rate
Zwmax   .ap.dw.vf
ap:back engagement
dw:diameter of the work surface
Vf.:feed speed
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Plunge grinding on a cylindrical grinder
Machining time:
at
tm   ts
vf
at:tool depth of workpiece
vf:Feed speed
ts:Sparking-out time
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Internal-grinding machine

Commonly used for producing internal cylindrical
surfaces
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Traverse grinding on an internal grinder
Max.metal removal rate:
Zwmax   .f.d m.vtrav.
f
:feed per stroke of the machine table
dm :diameter of the machined surface
Vtrav.:traverse speed
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Traverse grinding on an internal grinder
The machining time:
at
tm 
 ts
2.f.n r
at:tool depth of workpiece
f:Feed
nr:Frequency of reciprocation
ts:Sparking-out time
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Plunge grinding on a internal grinder
Max.metal removal rate:
Zwmax   .ap.dm.vf
ap:back engagement
dm:diameter of the machined surface
Vf.:feed speed
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The machining time is;
t
m
s
f
a
t  t
v
at:tool depth of workpiece
vf:Feed speed
ts:Sparking-out time
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Abrasive machining: Honing



A stock removal process
that uses fine abrasive
stones to remove very
small amounts of metal.
Cutting speed is much
lower than that of grinding.
Used to size and finish
bored holes.
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Specific Cutting Energy
For a given work material machined under
given conditions, the energy required to
remove a unit volume of material (ρs) can be
measured. This mainly depends on the work
material.
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Machining power
Pm = ps Zw
Ps:Specific cutting energy
Zw:Metal removal rate
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Electrical motor power
Pe 
Pm

m
Pm: Power required to perform machining
ηm: Overall efficiency of the machine tool
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Unit for specific cutting enegy
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Specific Cutting Energy ps vs Uncut
Chip Thickness ac
a
a
a
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Selected Problems
1.1.
2000 bars 80 mm in diameter and 300 mm long must be turned down
to 65 mm diameter for 150 mm of their length. The surface finish and
accuracy requirements are such that a heavy roughing cut (removing
most of the material) followed by a light-finishing cut are needed. Both
the roughing and the light finishing cuts are to be taken at maximum
power. The light finishing cut is to be taken at a feed of 0.13 mm, a
cutting speed of 1.5 m/s.
Assume that the lathe has a 2 kW motor and an efficiency of 50 %,
specific cutting energy for the work material is 2.73 GJ/m3, the time
taken to return the tool to the beginning of the cut is 15 s, and the time
taken to load and unload a workpiece is 120s.
a) Calculate the total production time in kiloseconds (ks) for the batch of
work
b) Calculate the machining time of one part in the roughing cut
c) Calculate the machining time of one part in the light finishing cut
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Selected Problems
1.1. SOLUTION
Given:
Nb=2000
dw=80 mm
dm=65 mm
lm=150 mm
Psmax= 0.5x2= 1 kW = 1000 W
ps=2.73 GJ/m3
flf= 0.3mm
vlf = 1.5 m/s
tr=15 s
tl = 120 s
tpr= Nb(tl + tmr + tmlf + 2 tr )
only the machining times for the roughing
and the light finishing cuts are unknown
Machining time can be found by dividing the volume to be removed for a
given operation to the metal removal rate for the operation. Hence we
need to find the metal removal rate first.
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Selected Problems
1.1. SOLUTION (cont.’d)
Zw= Psmax /ps
Since for both the roughing and the light cutting operations maximum
available power at the spindle are to be utilized; the metal removal rate
for both of the operations wiil be the same.
Hence:
Zw= (1000 J/s)/(2.73 J/mm3) = 366 mm3/s
a) tmT= tmr+ tmlf = Vr/ Zw + Vlf / Zw =(Vr+ Vlf)/Zw =VT/ Zw
VT= (dw2 - 652).lw/4 = (802+ 652). 150/4 = 256236 mm3
tmT= 256236 /366.3≈ 700 s
tpr= 2000(120 + 2x15 +700) = 1700ks
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Selected Problems
1.1. SOLUTION (cont.’d)
b)
tmr= Vr/ Zw = 196985/366.3 ≈ 538 s
c)
tmlf = Vlf /Zw = 59251/366.3 = 162 s
Machining time for light finishing operation can also be found by
using the given cutting parameters, i.e. v=1.5 m/s and f= 0,13 mm
ap = Zw /(fv) = 366.3/(0.13x1500) = 1.88 mm
tmlf =  dlfave lm/vf
dlfave = dw+ ap= 65+ 1.88 = 66.88 mm
tmlf = ( x 66.88 x 150)/(1500 x 0.13) = 162 s
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