It is very similar to a horizontal milling machine in construction as it has the same parts of base, column, knee, saddle and table. The spindle of the machine is positioned vertically. The cutters are mounted on the spindle. The spindle is rotated by the power obtained from the mechanism placed inside the column. Angular surfaces are machined by swiveling the spindle head.
Types of Milling Machine
The milling machines are classified according to the general design of the machine.
- Column and Knee Type
- Plain of Horizontal Milling machine
- Universal Milling Machine
- Omniversal Milling Machine
- Vertical Milling Machine
- Hand Milling Machine
- Table Type Milling Machine (Manufacturing Type or Fixed Bed Type)
- Simplex Milling Machine
- Duplex Milling Machine
- Triplex Milling Machine
- Planer Type Milling Machine
- Special Type Milling Machine
- 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 Milling Machine
The column of a column and knee type milling machine is mounted vertically upon the base. Knee is mounted on the accurately machined guideways of the column. It is designed to move up and down accurately. Saddle and table are mounted on the knee.
There are different types of column and knee type machines.
1.1 Plain Milling Machine
It is rigid and sturdy. Heavy workpieces are mounted and machined on the machine. The work mounted on the table is moved vertically, longitudinally and crosswise against the rotating cutter. The table cannot be rotated. It is also called as horizontal milling machine because the cutter rotates in horizontal plane.
1.2 Universal Milling Machine
The table of a universal milling machine can be swiveled by 45º on either side and so helical milling works can be performed. It is named so because it can be adapted for a very vide range of milling operations.
Various milling attachments like index head, vertical milling head, slot milling head and rotary table can be mounted. It can machine drills, reamers, gears, milling cutters with a very high degree of accuracy and so it finds an important place in a workshop.
1.3 Omniversal Milling Machine
In addition to the table movements obtained in a universal milling machine, the knee can be tilted to a required angle. It is useful for machining helical grooves, reamer and bevel gears. It is mostly used in tool room work.
1.4 Vertical Milling Machine
A spindle of a vertical milling machine is positioned at right angles to the table. The cutter is moved vertically or at an angle by swiveling the vertical head of the machine.
The machine is adapted for machining slots and flat surfaces by moving the table. By mounting end mills and face milling cutters on the spindle, vertical milling and internal milling are preformed.
2. Table Type Milling Machine (Manufacturing Type or Fixed Bed Type)
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 Type Milling Machine
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 Pantograph 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.
4.7 NC/CNC Milling Machine
CNC milling, or computer numerical control milling, is a machining process which employs computerized controls and rotating multi-point cutting tools to progressively remove material from the workpiece and produce a custom-designed part or product. This process is suitable for machining a wide range of materials, such as metal, plastic, glass, and wood, and producing a variety of custom-designed parts and products.
Several capabilities are offered under the umbrella of precision CNC machining services, including mechanical, chemical, electrical, and thermal processes. CNC milling is a mechanical machining process along with drilling, turning, and a variety of other machining processes, meaning that material is removed from the workpiece via mechanical means, such as the actions of the mill machine’s cutting tools.