6 January 2017

Types of Milling Machine

Types of Milling Machine :

According to the general design of the milling machine are :

1. Column and knee type
For general shopwork, the most commonly used is the column and knee type where the table is mounted on the knee casting which is turn in mounted on the vertical sides of the main column.
The knee is vertically 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 various methods of supplying power to the table, different movements of the table and the different axis of rotation of the main spindle. 
Column and knee type milling machine

  • Hand milling machine
The simplest of all type of milling machine is the hand milling in which the feeding movement of the table is supplied is the hand control.
The cutter is mounted on a horizontal arbour and is rotated by power. 
This machine is particularly suitable for light and simple milling operation such as machining slots, grooves and keyways.

  • Plain milling machine
The plain milling machine is much more rigid and sturdy than hand millers for accommodating heavy workpieces.
A plain milling machine having a horizontal spindle. In a plain 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.
The feed is cross when the table is moved parallel to the spindle. 
The feed is vertical when the table is adjusted in the vertical plane.

  • Universal milling machine
A universal milling machine is named because it may be adapted to be a very wide range of milling operation. A universal milling machine can be distinguished from a plain milling machine in that the table of a universal milling machine is mounted on a circular swivelling base which has degree graduations, and the tale can be swivelled to any angle up to 45 degrees on either side of normal position. In the universal milling machine, in addition to three movements as in plain milling machine, the table may have the fourth movement when it is fed at an angle to the milling cutter. this additional feature enables it to perform helical milling operation.
It may be also produced spur, spiral, bevel gears, twist drills, reamers, milling cutters including all conventional milling operation. so universal milling machine essentially a tool room machine designed to produce very accurate work.

  • Omniversal milling machine
In omniversal milling machine, the table besides having all the movement of the universal milling machine can be tilted in a vertical plane by providing a swivel arrangement at the knee.
The additional swivelling arrangement of the table enables it to machine taper spiral grooves in reamers, bevel gears etc.

  • Vertical milling machine
A vertical milling machine can be eminent from a horizontal milling machine by the position of its spindle which is vertical or perpendicular to the work table. The machine may be of plain or universal type and has all the movements of the table for proper setting and feeding the work.
The machine is adapted for machining grooves, slots and flat surfaces. 

Vertical milling machine

    2. Manufacturing of fixed bed type
    The fixed bed type milling machine is comparatively large, heavy and rigid and it different from column and knee type milling machine by the construction of its table mounting.
    The table is directly mounted directly on the ways of a fixed bed.
    The cutter mounted on the spindle head may be moved vertically on the column and spindle may be adjusted horizontally to provide cross adjustment. It can be classified below :
    • Simplex milling machine
    • Duplex milling machine
    • Triplex milling machine
    The name simplex, duplex and triplex indicate that the machine is provided with single, double and triple spindle heads respectively. 
    In the duplex machine, the spindle heads are arranged one on each side of the table.
    In the triplex machine, the third spindle head is mounted on a cross rail. 
    The feed cycle of the table includes the following : start, rapid approach, slow feed for cutting, rapid traverse to next work piece, quick return and stop.

      3. Planer type
      The planer type machine is built up for heavy-duty work, having spindle heads adjustable in vertical in transverse directions. It has a cross rail capable of being raised or lowered carrying the cutters their heads, and the saddles, all supported by rigid uprights.
      The use of the machine is limited to production work only and is considered ultimate in metal removing capacity.

      4. Special type

      • Rotary table milling machine
      This machine construction is a modification to a vertical milling machine.
      The face milling cutters are mounted on two or more vertical spindles and a number of workpieces are clamped on the horizontal surface of a circular table which rotates about vertical axis.
      The cutters may be set at different heights relative to the work so that when one of the cutter is roughing the pieces the other is finishing them.

      • Drum milling machine
      The drum milling machine is similar to a rotary table milling machine in that work-supporting table which is called drum and it rotates in a horizontal axis.
      The face milling cutters mounted on three or four spindle heads rotate in a horixontal axis and removal metal from workpieces supported on both the faces of drum.
      The finished machined parts are removed after on complete turn of the drum, and then the new ones are clamped to it.

      • Planetary milling machine
      In planetary milling machine, the work is held stationary while the revolving cutter or cutters moves in a planetary path to finish a cylindrical surface on the work either internally or externally or simultaneously. 
      This machine is adapted for milling internal or external threads of different pitches.

      • Pantograph, profiling & tracer controlled milling machine
      A pantograph machine can duplicate a job by using a pantograph mechanism which permits the size of the work piece reproduced to be smaller than, equal to or greater than the size of a template or model used for the purpose.
      A pantograph is a mechanism that is generally constructed of four bar which are joined in the form of pantograph. Pantograph machine are available in two dimensional or three dimensional models.

      Profiling machine duplicates the full size of the template attached to the machine. This is practically a vertical milling machine or bed type in which the spindle can be adjusted vertically and cutter head horizontally across the table.
      The movement of cutter regulated by a hardened guide pin.

      Tracer controlled milling machine reproduces irregular or complex shapes of dies, moulds etc.
      The feeding motion of the machine is controlled by means of a stylus that scans a profiled template or a contoured model which is to be reproduced.