Using of Milling Machine:
Milling is the cutting process used in various applications and is the most crucial process in industries. Milling machines are used for drilling, boring, and producing slots they are also used in the process of shaping metals and irregular surfaces. We should select a milling machine based on factors such as feed rates, cutting speed, the milling feed direction e.t.c
This can hold more than one tool or cutter at a time. The cutter rotates at a high speed, has many cutting edges, and removes metal quickly.
Types of milling machines:
Column and knee type:
The column and knee type milling machine is the most used type of milling machine for general workshops. In this machine, the table is mounted on the knee casting which in turn is mounted on the vertical slides of the main column the knee is vertical and adjustable on the column and the table can be moved up and down to accommodate work in various heights. Batch Reactor is here.
The column and knee type milling machine is divided into five types which are given below;
- Hand milling machine
The hand milling machine is the simplest type of all of the other milling machines. In this machine, the feeding is controlled by the hand. The cutter is mounted on a horizontal arbor and is rotated by power. This type of milling machine is small in size and is suitable for light and simple milling operations for example machining slots groups and keyways.
- Plain or horizontal milling machine
These are much stronger than hand millers. The table feeding is done by hand or power. The plain milling machine has a horizontal spindle also called a horizontal spindle milling machine. The table may be fed in longitudinal cross or vertical directions.
- Vertical milling machine
Here the position of the spindle is vertical or perpendicular to the table. This type of machine is adapted for machining groove slots and flat surfaces. The machine may be of the plane or universal type and has all the movements of the table for a proper setting and feeding the work. The spindle hand is clamped to the vertical column which is swiveled at an angle. It allows the milling cutter fixed on the spindle to work on angular surfaces
- Universal milling machine
It can be adapted to a wide range of milling operations. In this machine, the table can be swiveled to any angle up to 45 degrees on either side of the normal position. In the addition to three movements, the table may have the fourth movement when it is fed at an angle to the milling cutter. This machine can produce spur, bevel, spiral, twist drill, reamer, and milling cutter. All operations that are performed on a shaper can be done using a universal milling machine.
- Omniversal milling machine
In this machine, the table has four movements it can also be tilted in a vertical plane by providing a swivel arrangement at the knee. The additional swiveling arrangement of the table helps in machining spiral grooves in reamers and bevel gears.
Manufacturing type or fixed bed type milling machine:
These machines are large heavy and rigid in construction. These machines differ from the column and knee-type milling machines by the construction of their 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 into three types which are given below;
- Simple milling machine
- Duplex milling machine
- Triplex milling machine
Planer type milling machine:
This type of milling machine is also called a Plano miller. It is a massive machine used for heavy-duty work. These are having spindle heads adjustable in the vertical and transverse directions. This machine has a cross rail capable of being raised or lowered carrying the cutters. It has its heads and the saddles all supported by rigid uprights. This arrangement of driving multiple cutter spindles enables several work surfaces to be machined thereby it obtains a great reduction in production time in a planer the tables give the cutting speed but in a Plano milling machine, the table movement gives the feed.
Special type milling machine:
These machines have a spindle for rotating the cutter and provision for moving the tool or the work in different directions. This type of machine is further divided into these types which are given below;
- Rotary table milling machine
Here the table is circular in nature and rotates about a vertical axis and the cutter is set at different heights which results in one cutter roughing the workpiece and the other cutter finishing them. The advantage of this machine is the continuous loading and unloading of workpieces can be done by the operator while is in the progress.
- Drum milling machine
- Profiling milling machine
A profiling milling machine duplicates 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 the crosswise movement of the cutter head follows the movement of the guide pin on the template.
- Planetary milling machine
Here the workpiece is held stationary while the revolving cutter. The cutter moves in a traveling path to finish a cylindrical surface on the workpiece either internally or externally. This machine is also adapted for milling internal and external threads
- Tracer control milling machine
- 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. A pantograph is a mechanism that is generally constructed of four bars or links which are connected in the form of a parallelogram. These machines are available in two-dimensional and three-dimensional models.
- NC/CNC milling machine
Operations of milling machine:
- Plain milling operation:
This is the most common type of milling operation. Plane milling is performed a plain flat and horizontal surfaces. It is also known as slab milling. The work in the cutter is secured properly on the machine while performing the cut. The depth of cut is set by rotating the vertical feed screw of the table and the machine is started after selecting the right speed and feed.
- Face milling operation:
It is the simplest milling operation performed by the face milling cutter rotated about an axis perpendicular to the work surface and carried out in plane milling. The cutter is mounted on the arbor to design a flat surface. The depth of the cut is adjusted by rotating the cross feed screw of the table
- Side milling operation:
It is the operation of producing a flat vertical surface on the side of the workpiece by using a side milling cutter. The depth of the cut is set by rotating the vertical feed screw of the table.
- Straddle milling operation:
It is the operation of producing a flat vertical surface on both sides of a workpiece by using a two-side milling cutter mounted on the same arbor. Distance between the two cutters is adjusted by using suitable spacing collars. Straddle milling is commonly used to design square or hexagonal surfaces.
- Angular milling operation:
Angular milling is the operation used to produce an angular surface on a workpiece at right angle of the axis of the spindle. The angular groove may single or double angle and may be varying included angle to the type and contour of the angular cutter used. One simple example of an angular milling machine is the ‘production of the blocks’.
- Gang milling operation:
It is the operation of machining several surfaces of a workpiece simultaneously by feeding the table against a number of cutters having the same or different diameters mounted on the arbor of the machine. The method saves much of machining time and is widely used in repetitive work.
- Form milling operation:
It is the operation of producing the irregular contour by using form cutters. The irregular shape may be convex, concave, or of any other shape after machining the formed surfaces are inspected by a template gauge. The cutting rate for form milling is 20% to 30% less than that of plane milling.
- Profile milling operation:
It is the operation of reproduction outline of a template or complex shape of a master dies on a workpiece. Different cutters are used for profile milling an end mill is one of the widely used milling cutters in profile milling work.
The other milling machine operations are given below;
- End milling
- Gear milling
- Saw milling
- Keyways, grooves and slots
- Helical milling
- Cam milling
- Thread milling operations