Milling machine-Working principle, types and related terms
History of Milling machine
A milling machine is a machine tool which widely used in industries to manufacture a high precision product. The first milling machine is introduced in about 1770 and it was French origin. In 1782 Jacques de Naucanson developed the first milling cutter. In 1818 Eli Whitney designed the first successful plain milling machine and in 1861 Joseph R Brown a member of Brown and Shape shop company invented the first universal milling machine.
What is a Milling Machine?
Milling is a machining process in which a cutter rotates in an axial direction of the workpiece to remove the material. The basic difference between the lathe machine and milling machine is that in the lathe machine the workpiece rotates and the tool remains constant. Whereas, in milling machine tool rotate and workpiece remain constant.
Parts of a Milling Machine
1. Face milling cutter
2. Spindle
3. Spindle head
4. Column
5. Table
6. Saddle
7. Knee
8. Base
9. Spindle switch
10. Spindle speed gear lever
11. Spindle speed control lever
12. Oil tank
13. Table manual wheel
14. Table lock bar
15. Saddle automatic moving bar
16. Saddle automatic moving control dial
17. Saddle manual wheel
18. Knee manual wheel
- Base
The base of the milling machine is manufactured by grey cast iron. And other parts of the machine are rested upon the base of the machine. It contains a coolant reservoir and a pump which is used to pump the coolant during the machining operation.
2. Column
The column is mounted vertically on the one end of the base. It houses all driving mechanism for spindle and table feed. It also contains an oil reservoir and a pump for lubricating the spindle.
3. Knee
The knee is manufactured by grey cast iron. It slides up and down in vertical direction of the column face. Elevating screw mounted on the base and also supports the knee for adjustment of the height of the table. It houses the feed table and different controls of the machine.
4. Table
The table is a rectangular shaped and manufactured from grey cast iron. And mounted on the saddle in such a way that travel longitudinally. It contains T-slots which providing for clamping the work and work holding device. There is leadscrew under the table Which engages the nut on the saddle to move the table in a horizontal direction by manually or power.
5. Overhanging arm
The overhanging arm is a horizontal beam which is mounted on the top of the column and it extended beyond the face of the column which satisfies its name. There is an Arbor support at the one end of the arm. The arm can be adjusted so that Arbor support may be provided nearest to the cutter.
6. Front brace.
The front brace is fitted between the knee and Arbor. It gives extra support to the arbor. It allows the adjustment of the height because it is slotted.
7. Spindle
The spindle is located in the upper part of the column. It receives power from the motor and transmits it to the arbor.
8. Arbor
Arbor receives power from the spindle. It also considered as the extension of the spindle. The one end of the arbor is connected to spindle and another end is supported by Arbor support. The cutter is mounted on the arbor.
Working principle of milling machine
In a Milling machine, the workpiece is held in the fixture which is clamped in the T-slots of the table. The movement of the table controls the feed of workpiece against the rotating cutter. The cutter is mounted on the arbor and rotates at high speed. At high-speed cutter is feed into the workpiece and cutter teeth remove the material from the surface of the workpiece.
Operations performed on the milling machine.
Follow are the various operations which are performed on the milling machine.
● Plain milling operation
● Face milling operation
● Side milling operation
● Straddle milling operation
● Angular milling operation
● Gang milling operation
● Form milling operation
● Profile milling operation
● End milling operation
● Sawmilling operation
● Slot milling operation
● Gear cutting operation
● Helical milling operation
● Cam milling operation
● Thread milling operation Type of Milling machine.
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Types of Milling machine.
1. Column and knee type
● Hand milling machine
● Plain or horizontal milling machine
● Vertical milling machine
● Universal milling machine
● Omniversal milling machine
2. Manufacturing type or fixed bed type
● Simplex milling machine
● Duplex milling machine
● Triplex milling machine
● Planer type milling machine
3. Planer type milling machine
4. Special Type
● Rotary table milling machine
● Drum milling machine
● Profile milling machine
● Planetary milling machine
● Tracer controlled milling machine
● Pantograph milling machine
Terms related to a milling machine
- Cutting speed.
Speed of milling cutter resulting from rotation. Cutting speed of milling cutter is expressed in term of m/min.
The formula for cutting speed of milling cutter.
v = πdn/1000 m/min
Where, v = cutting speed in m/min
d = diameter of the cutter in m
n = cutter speed in r.p.m.
2. Feed.
The feed of the milling machine is defined as the rate or speed of the cutter with which is fed to the workpiece.
Feed per tooth (sz )
It is defined as the distance of the work completed in the time between the two successive teeth. It is expressed in term of mm per teeth of cutter.
Feed per cutter revolution (srev )
It is defined as the distance of the work completed in the time when the cutter one complete revolution. It is expressed in term of mm per revolution of the cutter
Feed per minute (sm )
It is defined as the work completed in one minute. It is expressed in term of mm/min
The formula for feed rate of milling machine
sm = n×srev = sz×Z×n
Where Z=number of teeth in the cutter
n=the cutter speed in r.p.m.
3. Depth of cut.
Depth of cut is measured by the thickness of material removed in one pass of the cutter in a workpiece. It a difference between the original and final surface of the workpiece. It expressed in terms of mm.
That’s an overview of the Milling machine. If you like this post or have any suggestions do let us know in the comments we would love to hear from you.
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