Milling Machine
Introduction
to milling machine:-
·
Milling is the
machining process in which the metal removal takes place due to the cutting
action of a revolving cutter when work piece is fed past it.
Milling is the
machining process in which the metal removal takes place due to the cutting
action of a revolving cutter when work piece is fed past it.
·
The revolving cutter is
held on a spindle or arbor and the work piece clamped on the machine table.
The revolving cutter is
held on a spindle or arbor and the work piece clamped on the machine table.
·
During the process, to
produce the desired shape, the cutter removes the metal in the form of chips
from the work piece surface’
During the process, to
produce the desired shape, the cutter removes the metal in the form of chips
from the work piece surface’
·
The machine tool on
which the milling operation is performed is called as milling machine.
The machine tool on
which the milling operation is performed is called as milling machine.
·
Also, the work piece
can be fed in a vertical, longitudinal or cross direction shows the working
principle of a milling machine.
Also, the work piece
can be fed in a vertical, longitudinal or cross direction shows the working
principle of a milling machine.
Fig: Working principle of milling
machine
machine
Types of Milling Machines:
A large variety of different types of milling machines
are available. Aclassification of these machines according to the general
design can be done as follows:
are available. Aclassification of these machines according to the general
design can be done as follows:
1. Column
and knee type milling machines :
a. Hand
milling machine
milling machine
b. Plain
or horizontal milling machine
or horizontal milling machine
c. Vertical
milling machine
milling machine
d. Universal
milling machine
milling machine
e. Omniversal
milling machine
milling machine
2. Fixed
bed or manufacturing type milling machines :
a. plain
type milling machine (having single horizontal
spindle)
type milling machine (having single horizontal
spindle)
b. Duplex
head milling machine (having double horizontal
spindles)
head milling machine (having double horizontal
spindles)
c. Triplex
head milling machine (having two horizontal and one vertical spindle)
head milling machine (having two horizontal and one vertical spindle)
d. Rise
and fall type milling machine (for profile milling)
and fall type milling machine (for profile milling)
3. Planer
type milling machines
4.
Production
milling machines:
a. Rotary
table or continuous type milling machine
table or continuous type milling machine
b. Drum
type milling machine
type milling machine
c. Tracer
controlled milling machine
controlled milling machine
5. Special
purpose milling machines :
a. Thread
milling machine
milling machine
b. Profile
milling machine
milling machine
c. Cam
milling machine
milling machine
d. Gear
milling or gear hobbing machine
milling or gear hobbing machine
e. Planetary
milling machine
milling machine
Column
and Knee Type Milling Machines
·
Column and knee type
milling machines are most commonly used in machine shops and tool rooms. These
machines are general purpose machines and have a single spindle only.The
worktable is supported on a knee-like casting. Which can slide in vertical
direction along a vertical column? Depending upon the spindle position and
table movements, they are further classified as follows:
Column and knee type
milling machines are most commonly used in machine shops and tool rooms. These
machines are general purpose machines and have a single spindle only.The
worktable is supported on a knee-like casting. Which can slide in vertical
direction along a vertical column? Depending upon the spindle position and
table movements, they are further classified as follows:
a. Hand
milling machine
milling machine
b. plain
or horizontal milling machine
or horizontal milling machine
c. Vertical
milling machine
milling machine
d. Universal
milling machine
milling machine
e. Omniversal
milling machine
milling machine
f.
Column and Knee type
milling machines
Column and Knee type
milling machines
Hand Milling Machine:
·
It is the simplest of
all the milling machines and smaller in size.
It is the simplest of
all the milling machines and smaller in size.
·
All the operations are
performed by hand except the rotation of an arbor.
All the operations are
performed by hand except the rotation of an arbor.
·
The table carrying the
work piece over it is moved by hand to feed the work piece.
The table carrying the
work piece over it is moved by hand to feed the work piece.
·
This machine is mostly
useful in producing small components such as hexagonal or
This machine is mostly
useful in producing small components such as hexagonal or
square headed bolts, cutting key
ways and slots on screw heads.
ways and slots on screw heads.
Plain or Horizontal Milling Machine:
·
Fig. shows block
diagram of a plain milling machine, in which the vertical column serves as
housing for electrical, main drive, bearings,
etc.
Fig. shows block
diagram of a plain milling machine, in which the vertical column serves as
housing for electrical, main drive, bearings,
etc.
 |
| Fig: Horizontal Milling Machine |
·
For supporting the
saddle, worktable and other accessories such as indexing head, knee is provided.
For supporting the
saddle, worktable and other accessories such as indexing head, knee is provided.
·
Overarm provides
support for the yoke which supports the free end of the arbor
Overarm provides
support for the yoke which supports the free end of the arbor
·
The arbor carrying the
cutter rotates about a horizontal axis.
The arbor carrying the
cutter rotates about a horizontal axis.
·
Except swiveling, the
table can be given motion in three different directions i.e.
Except swiveling, the
table can be given motion in three different directions i.e.
Ø Longitudinal direction
Ø Vertical direction
Ø Cross direction
·
For vertical movement
of the table, the knee along with whole unit over it slides up and down in the
guide ways provided on the column.
For vertical movement
of the table, the knee along with whole unit over it slides up and down in the
guide ways provided on the column.
For cross movement of
the table, the saddle is moved towards or away from the column along with the whole unit over it.
the table, the saddle is moved towards or away from the column along with the whole unit over it.
· To provide additional
support and rigidity to the arbor, a brace is
employed.
support and rigidity to the arbor, a brace is
employed.
vertical milling machine
·
In this type of machine
spindle position is vertical hence, called as vertical milling machine.
In this type of machine
spindle position is vertical hence, called as vertical milling machine.
·
This machine is
available in two types i.e. fixed bed type and column and knee type.
This machine is
available in two types i.e. fixed bed type and column and knee type.
·
Fig. shows the block diagram of vertical milling
machine with fixed head.
Fig. shows the block diagram of vertical milling
machine with fixed head.
·
It consists of a
vertical column on a heavy base and overarm is made integral with the column
and carrying housing at its front.
It consists of a
vertical column on a heavy base and overarm is made integral with the column
and carrying housing at its front.
·
This housing is called
as head which can be of fixed type or swivelling type. In fixed head type, the
spindle always remains vertical and can be adjusted up and down.
This housing is called
as head which can be of fixed type or swivelling type. In fixed head type, the
spindle always remains vertical and can be adjusted up and down.
·
Whereas, in swivelling
head type, the spindle can be swivelled to any required angle for machining
inclined surfaces. Refer Fig.
Whereas, in swivelling
head type, the spindle can be swivelled to any required angle for machining
inclined surfaces. Refer Fig.
·
Fig: Vertical
milling machine with fixed head
milling machine with fixed head
·
The knee carries a
screw jack with the help of which it is moved up and down along the guide ways
provided on the column.
The knee carries a
screw jack with the help of which it is moved up and down along the guide ways
provided on the column.
·
The saddle is mounted
on the knee which can be moved towards or away from the column, along the
horizontal guide ways provided on the knee.
The saddle is mounted
on the knee which can be moved towards or away from the column, along the
horizontal guide ways provided on the knee.
·
This enables the table
to move in cross direction.
This enables the table
to move in cross direction.
·
Similar to horizontal
milling machine, in vertical milling machine also there are three motions for
the table i.e. longitudinal, vertical and cross.
Similar to horizontal
milling machine, in vertical milling machine also there are three motions for
the table i.e. longitudinal, vertical and cross.
·
Hence, with the help of
knee the work piece gets vertical movement, by using cross movement; and
longitudinal movement by the table.
Hence, with the help of
knee the work piece gets vertical movement, by using cross movement; and
longitudinal movement by the table.
Universal Milling Machine:-
·
Universal milling
machines are most versatile of all the milling machines and most useful
because, they are capable of performing most of the machining operations.
Universal milling
machines are most versatile of all the milling machines and most useful
because, they are capable of performing most of the machining operations.
·
By using this machine,
large number of other machine tools can be
avoided.
By using this machine,
large number of other machine tools can be
avoided.
·
Universal milling shine
is similar to horizontal milling machine, except that the table can be given
one more additional movement. Refer Fig. Its table can be
swivelled in a horizontal plane and for this purpose circular guide way are
provided on the saddle.
Universal milling shine
is similar to horizontal milling machine, except that the table can be given
one more additional movement. Refer Fig. Its table can be
swivelled in a horizontal plane and for this purpose circular guide way are
provided on the saddle.
·
To read the angle of
swivelling, a graduated circular base is provided under the table with datum
mark on the saddle. Hence, Work piece can be set at an angle with the cutter
for milling helical and spiral flutes and grooves.
To read the angle of
swivelling, a graduated circular base is provided under the table with datum
mark on the saddle. Hence, Work piece can be set at an angle with the cutter
for milling helical and spiral flutes and grooves.
·
By using some attachments,
this machine can be worked as a vertical milling machine.
By using some attachments,
this machine can be worked as a vertical milling machine.
Omniversal Milling Machine:-
·
Omniversal milling
machine is a modified form of a plain milling
machine.
Omniversal milling
machine is a modified form of a plain milling
machine.
·
It is provided with two
spindles, out of which one is horizontal and other is carried by a universal
swivelling head. The latter can be fixed
in vertical position or can be set at any required angle up to 900 on
both the sides of vertical.
It is provided with two
spindles, out of which one is horizontal and other is carried by a universal
swivelling head. The latter can be fixed
in vertical position or can be set at any required angle up to 900 on
both the sides of vertical.
·
One more special
feature of this machine is that, it carries two more adjustments in addition to
all the adjustments provided in a universal machine. Its knee can be
swivelled about a horizontal axis to tilt the table and can be moved
horizontally also.
One more special
feature of this machine is that, it carries two more adjustments in addition to
all the adjustments provided in a universal machine. Its knee can be
swivelled about a horizontal axis to tilt the table and can be moved
horizontally also.
·
Hence, this machine is
very useful for tool room work.
Hence, this machine is
very useful for tool room work.
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