Concept of milling machine working principle and types

milling machine working principle and types – Friends, milling machine has an important role in the engineering field, without which every tool made with the help of engineering is incomplete.

Eli Whitney is believed to have built the first milling machine in 1818, to aid in the manufacture of interchangeable gun parts.

In the field of machine tool application, the milling machine occupies a place opposite to lathe. Lathe is very useful for producing cylindrical surfaces, but milling machine is very useful for producing plane surfaces. Both these machines are very versatile (capable of performing a variety of jobs).

Some milling machine producers claim that their machine is more versatile than lathe, but we must admit that it is easier to do milling on lathe than it is to turn on the milling machine.

So in today’s article, we will know what is a milling machine and and  working principle of milling machine as well as types of  milling machine.

What is the milling meaning?

A machine process in which metal is removed by a revolving multiple tooth cutter to produce flat or profiled surfaces, grooves or slots is known as milling.

What is milling machine?

A machine tool which is used for producing flat or profiled surfaces, grooves or slots with the help of a revolving (mostly) multiple tooth cutter is known as a milling machine.

milling machine working principle

milling machine working principle

The work is held rigidly on the table of milling machine while the cutter is mounted on a spindle or arbor. The chips are cut off by the rotating milling cutter. The cutting edges ( teeth) of which are arranged in a circular way. To enable the cutting-edges of the milling cutter to penetrate into the material, the cutting edges are made wedge-shaped (like a turning tool).

The circular motion of the cutter is called cutting motion. To form the chip thickness, the work is given feed motion in a straight line against the rotating cutter. During the cutting operation, each cutting edge (tooth) takes part in cutting only for a part of each revolution of the cutter. For rest of the revolution it runs idle and can cool off. Therefore, the stress on the cutting edge is not so heavy as that of a turning tool, the cutting edge of which is constantly remaining in the cut.

types of milling machine

Milling machines are being made of numerous types and sizes. According to general. Design, they are, classified in the following types

  1. Column and Knee Type Milling Machines.
  2. Planner Type Milling Machines.
  3. Fixed Bed Milling Machines.
  4. Special Purpose Milling Machines.

1. Column and Knee Type Milling Machines

These are low production machines. They derive their name from the fact that the work-table is supported on a knee-like casting which can slide in a vertical direction along a vertical column. The table can travel longitudinally and cross-wise. It can also be moved up and down.

These machines can further be sub-divided in three types as follows.

(i) Plain Milling Machine or Horizontal Milling Machine: The cutter revolves about the horizontal axis of the machine spindle and the work table can have movement in longitudinal, cross and vertical directions, manually or by automatic feeding. Work-table cannot be swiveled in a horizontal plane.

(ii) Vertical Milling Machine: The cutter revolves about the vertical axis of the machine spindle. The work can be moved in longitudinal, cross and vertical directions. Work-table cannot be swiveled. In some modern vertical milling machines, the spindle head (or milling head) can be swiveled in a vertical plane.

(iii ) Universal Milling Machine – this machine very much resembles with a plain milling machine but its table can also be swiveled in horizontal plane.

2.Planner Type Milling Machines.

This is a high production machine for heavy jobs. It is very much similar to a double housing planer. In this machine, spindle carriers are mounted in place of planer tool-posts which are operated by individual motors. In addition, two vertical milling heads are fitted on a cross rail and can travel along it.

3. Fixed Bed Milling Machine

These are high production milling machines. In these machines, the work table is mounted on a fixed bed and it has a longitudinal travel only. It cannot be moved up, down or crosswise, The adjustable spindle or spindle head (carrier) attached to a vertical column can move along vertical ways on the column to adjust tool to the work.

These machines can further be sub-divided in three types as follows.

(i) Simplex Milling Machine : It has single adjustable, horizontal spindle head.

(ii) Duplex Milling Machine : It has two adjustable, horizontal spindle heads, each attached to a separate vertical column, one on each side of the fixed bed.

(iii) Triplex Milling Machine : It has two adjustable horizontal spindle heads like a duplex machine attached to two different vertical columns, and one vertical spindle head on a cross-rail.

4. Special Types of Milling Machines

There are special purpose machines. Some of these are as follows :-

(i) Rotary Table Milling Machine : It is a mass production machine with a heavy, rotating, circular work-table mounted on the base of the machine.

(ii) Drum Milling Machine : It is a production type machine, It has a drum fixture upon whose periphery Fork pieces are mounted. The drum fixture rotates slowly carrying work against rotating cutters. The operation s continuous since work pieces are removed and new ones added as soon as some of the work pieces have completed their cycle.

(iii) Planetary Milling Machine : Contrary to the normal practice, the work is held stationary and cutter performs machining operation by revolving about its own axis as well as around the work (like a planet).

(iv) Off-set Milling Machine : In this machine, the cutter is mounted on a vertical spindle which extends into a fixture. The fixture is mounted eccentrically with cutter, so that, as in revolves, the work is- milled as it passes by.

(v) Stationary Long Table Milling Machine : This machine has a long stationary’ table 10 to 30 metres long. All cutters are contained and operated within a carriage. This carriage is mounted on and travels along the length of the bed. This machine was developed for contour milling on main parts, channel beams etc. used in the construction of modern aeroplanes.

(vi) Duplicator or Profiling Machine : In this machine, the cutter movement is guided by the path of a tracer which travels along the outside surface on a template, thus reproducing the same profile on the work as is that of the template.

(vii) Pantograph Milling Machine : This machine makes use of the pantograph linkage to guide the direction of the feed of the cutter to reproduce form of a template at either an enlarged or a reducing scale. 2.5. PLAIN MILLING MACHINE.


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