It
is a machine that is used to remove metals from the workpiece with the help of
a revolving cutter so-called milling cutter. It is used to machine the rough,
flat, and irregular surfaces and this is done by feeding the workpiece against
a revolving milling cutter.
Main Parts of Milling Machine
·
In a Milling
machine every individual part performs an important task.
·
Some important
parts of a Milling machine are as follows:
1.
Knee
It
is a casting that supports the table and saddle. All gearing mechanism is
surrounded inside the knee.
·
It is secure to
the column by dovetail ways.
·
The knee is
adjusted and supported by a vertical placing screw (elevating screw).
·
The elevating
screw is used to adjust the knee up and down by lowering or raising the lever
either with the help of a power feed or hand.
2.
Column & Base
The
column counting base is the main casting that supports all other parts of the
milling machine.
·
The column
contains an oil tank and a pump that lubricates the spindle.
·
The column rests
on the base and the base covers the coolant reservoir and a pump which is used
during machining operation that requires coolant.
3.
Power Feed Mechanism
It
is the knee that covered the power feed mechanism. It is used to control the
longitudinal (right and left), crosswise (in and out) and vertical (up and
down) feeds.
·
To get the desired
rate of feed on the machine, the feed selection lever is located as designated
on the feed selection plates.
·
On some universal
knee and column milling machines, the feed is obtained by turning the speed
selection handle until the wanted rate of feed is designated on the feed dial.
·
Most of the
milling machines have a speedy traverse lever which can be engaged when a
temporary increase in the speed of the longitudinal, transverse, or vertical
feeds is required. For example, this lever would be engaged when the operator
is aligning or positioning the work.
4. Arbor Support
It
is a casting with a bearing that supports the outer end of the arbor. It is
also helpful in aligning the outer end of the arbor with the spindle.
·
It prevents the
springing of the outer end of the arbor during cutting operations.
·
These are
generally two types of arbor supports to be used in the milling machine. The
first one has a small diameter bearing hole, 1-inch in maximum diameter. And
the other one has a large diameter bearing hole, usually up to 23/4 inches.
The
arbor supports have an oil reservoir that lubricates the bearing surface. It
can be fixed anywhere on the overarm. The arbor supports it,s used only in the
horizontal types of milling machine
5.
Ram
The
hanging arm in the vertical machine is called a ram. One end of the ram
straddling on the top of the column and on the other end milling head is
attached.
·
The ram can be
moved transversally (out and in) on the column by a hand lever.
6.
Over Arm / Overhanging Arm
It
is a horizontal beam current at the top face of the column. It may be a single
casting that slides on the dovetail ways present on the top face of the column.
·
The overarm is
used to fasten arbor support. It may contain one or two cylindrical bars which
slide through the holes in the column
Types
of Milling Machines
1. Horizontal
Milling Machine
2. Vertical
Milling Machine
3. Knee-Type
Milling Machine
4. Ram-Type
Milling Machine
5. Manufacturing
or Bed-Type Milling Machine
6. Planer-Type
Milling Machine
Basically,
the milling machines are divided into two types first is a vertical milling
machine and the second is a horizontal milling machine. They are further
categorized as ram-type, knee-type, manufacturing or planer-type, and bed-type
milling machines.
Most
of the milling machine categorized above has a self-electric driven motor,
power operated, coolant systems table feed, and variable spindle speeds.
1.
Horizontal Milling Machine
In
a horizontal milling machine, the axis of revolution of the spindle is
horizontal to the table. And due to the axis of the spindle being horizontal,
it is called a horizontal milling machine.
2.
Vertical Milling Machine
The
milling machine in which the spindle axis is vertical to the table is called a
vertical milling machine.
3.
Knee-Type Milling Machine
The milling machine which has a knee-like projection in the middle is called a knee-type milling machine. It is characterized by a vertically adjustable work table resting on a saddle supported by a knee.
4.
Ram-Type Milling Machine
A milling machine that has a ram on the top of the column is called ram type milling machine. Generally, ram is used in vertical milling machines. It can be moved on the column in the transverse direction (i.e. in and out when operated from the knee side).
5.
Planer-Type Milling Machine:
The
planner milling machine is generally used for facing operations in mass
production.
These
machines are similar to the bed-type mill machine, except they can be straddled
with various cutters and spindle heads the machine.
These cutters in the machines can complete the facing operations simultaneously which is a great function.
