Milling Machine and Types of Milling Machine
In this article, we will explain about the milling machine and their types of milling machines. Milling is the machining process in which the removal of metal takes place due to the cutting action of a rotating cutter.
In this types of milling machine, the cutter is rotating due to this workpiece is fed against it. This can hold more than one tool at a time. The cutter rotates at a high speed and because of the many cutting edges, it removes metal at a very fast rate.
The machine can also hold one or number of cutters at a time. Thus, the milling machine is one of the most important machines in the workshop. In this machine, all the operations can perform with high accuracy.
The metal removal rate is high as compared to a lathe machine, planner machine, and shaper machine. It has good accuracy and better surface finish. This is why a milling machine finds wide application in production work.
Types of Milling Machines:
The types of milling machines are as follows according to their design.
- Column and knee type:
- Hand milling machine
- Plain or horizontal milling machine
- Vertical milling machine
- Universal milling machine
- Omniversal milling machine
- Manufacturing type or fixed bed type:
- Simplex milling machine
- Duplex milling machine
- Triplex milling machine
- Planer type milling machine
- Special Type:
- Rotary table milling machine
- Drum milling machine
- Profile milling machine
- Planetary milling machine
- Tracer controlled milling machine or Pantograph milling machine
- NC/CNC milling machine
1. Column and Knee Type:
For general shop work, the most used types of milling machines is the column and knee type machine. where the table is mounted on the knee-casting which in turn is mounted on the vertical slides of the main column.
The knee vertical adjustable on the column so that the table can be moved up and down to accommodate work of various heights.
The column and knee type milling machines are classified.
- According to the various methods of supplying power to the table.
- Different movements of the table. and
- The different axis of rotation of the main spindle.
1.1 Hand Milling Machine:
It simplest of all types of milling machines in which table feeding is controlled by hand. The cutter is mounted on a horizontal arbour and is rotated by power.
This type of milling machine is of small in size and suitable for light and simple milling operations. For Example, machining slots, grooves, and keyway.
1.2 Plain Milling Machine:
These are much stronger than hand millers. The table feeding is done either by hand or power. the plain milling machine having a horizontal spindle is also called as horizontal spindle milling machine. The table may be fed in a longitudinal, cross or vertical directions.
The feed is:
- Longitudinal – when the table is moved at right angles to the spindle.
- Cross – when the table is moved parallel to the spindle.
- Vertical – when the table is adjusted in the vertical plane.
1.3 Universal Milling Machine:
It can be adapted to a wide range of milling operations. Here the table can be swivelled to any angle up to 45-degrees on either side of the normal position.
In addition to 3 movements as mentioned earlier in a plain milling machine, the table may have the fourth movement when it is fed at an angle to the milling cutter. Helical milling operation can also be performed. The capacity of this type of machine is increased by using special attachments such as
- Dividing head or index head.
- Vertical milling attachment.
- Rotary attachment.
- Slotting attachment.
This a machine can produce spur, bevel, spiral, twist drill, reamer, milling cutter. All operations that are performed on a shaper can be done using a universal milling machine.
1.4 Ominversal Milling Machine:
Here the table also has four movements of the universal milling machine. It can also be tilted in a vertical plane by providing a swivel arrangement at the knee.
The additional swivelling arrangement of the table helps in machining spiral grooves in reamers and bevel gears.
1.5 Vertical Milling Machine:
Here the position of the spindle is vertical or perpendicular to the table. This type of machine is adapted for machining grooves, slots, and flat surfaces.
The machine may be of the plain or universal type and has all the movements of the table for a proper setting and feeding the work.
The spindle head is clamped to the vertical column which is swivelled at an angle. It allowing the milling cutter fixed on the spindle to work on angular surfaces. In some machines, the spindle can also be adjusted up or down relative to the work.
2. Manufacturing of Fixed Bed Type Milling Machine
These machines are large, heavy and rigid in construction. These machines are differ from column and knee type milling machines by the construction of its table mounting.
The table is mounted directly on the ways of a fixed bed. The table movement is restricted to reciprocating at a right angle to the spindle axis with no provisions for cross or vertical adjustment.
It is classified as simplex, duplex, triplex based on a machine provided with the single, double and triple spindle heads respectively.
- Simplex – single spindle head.
- Duplex – two spindle head.
- Triplex – three spindle head.
3. Planer Type Milling Machine
This types of milling machines are also called as “Plano-Miller”. It is a massive machine used for heavy-duty work having spindle heads adjustable in vertical and transverse direction.
It relates a planer and like a planing machine. This machine has a cross rail capable of being raised or lowered carrying the cutters. It has their heads, and the saddles, all supported by rigid uprights.
This arrangement of driving multiple cutter spindles enables a number of work surfaces to be machined. Thereby it obtains the great reduction in production time.
The essential difference between a planer and a Plano-miller lies in the table movement. In a planer, the table moves to give the cutting speed. But in a plano-milling machine, the table movement gives the feed.
4. Special Types of Milling Machines
Milling machines of non-conventional design have been developed to suit special purposes. This machine has a spindle for rotating the cutter and provision for moving the tool or the work in different directions. The following special types of machines of interest are described below:
4.1 Rotary Table Milling Machine:
Here the table is circular in nature and rotates about a vertical axis. Here cutters are set at different heights. Which results in one cutter roughing the workpiece and other one cutter finishing them.
The advantage of this machine is that continuous loading and unloading of workpieces can be done by the operator, while is in progress.
4.2 Drum Milling Machine:
It is like a rotary table milling machine. But its workpiece supporting table is called as “DRUM” and it rotates in the horizontal axis.
The face milling cutters mounted on three or four-spindle heads rotate in a horizontal axis and remove metal from workpieces supported on both the faces of the drum. The finished machined parts are removed after one complete turn of the drum, and then the new ones are clamped to it.
4.3 Planetary Milling Machine:
Here workpiece is held stationary while the revolving cutter. The cutter moves in a travelling path to finish a cylindrical surface on the workpiece either internally or externally. This machine is also adapted for milling internal and external threads.
4.4 Pantagraph Milling Machine:
A pantograph machine can duplicate a job by using a pantograph mechanism. It allows the size of the workpiece reproduced to be smaller than, equal to or greater than the size of a template. Also used for the different model for special purposes.
A pantograph is a mechanism that is generally constructed of four bars or links which are connected in the form of a parallelogram.
Pantograph machines are available in two dimensional and three-dimensional models. The two-dimensional pantograph is used for engraving letters or other designs. Whereas three-dimensional models are employed for copying any shape and contour of the workpiece.
4.5 Profiling Milling Machine:
A profiling machine duplicated the full size of the template attached to the machine. Here the spindle can be adjusted vertically and the cutter horizontally across the table.
A hardened guide pin regulates the movement of the cutter. The longitudinal movement of the table and crosswise movement of the cutter head follows the movement of the guide pin on the template.
4.6 Tracer Controlled Milling Machine:
The tracer controlled milling machine reproduces irregular or complex shapes of dies, moulds by synchronized (matched) movements of the cutter and tracing elements.
The movement of the stylus energized an oil relay system which in turn operates the main hydraulic system for the table. This arrangement is termed as a servomechanism.
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