The milling machine is another important machine tool after the Lathe machine tool and drilling machine. In this machine, a multipoint cutter is rotating against the workpiece, and material is removed from the workpiece accordingly.
What is a Milling Machine?
The milling machine is defined as perhaps the most widely used in manufacturing industries after the lathe machine. However, In the case of lathe machine tools, the tools used their single-point cutting tools but In the case of this machine, the tool used multi-point cutting tools. The milling is a process of metal-removing by feeding the workpiece passes through the rotating multipoint cutter.
This machine can hold one or more cutters at a time and rotates at high speed to remove the metal at a faster rate. The metal removal rate is faster as compared to a lathe machine. This machine is used to make gears like Spur gears, and also drill the workpiece bore, and produce slots.
Parts of Milling Machine
A milling machine consists of the following parts:
It is the foundation part of a machine and all other parts are joined on it. The base carries the entire load so it should have high compressive strength and it is made up of cast iron.
The column is mounted vertically on the base. It supports the knee, table, etc., and works as housing for all the other driving members. The column is a hollow member which contains driving gears and sometimes a motor for the spindle and the table.
It is a casting that supports the saddle and table. All gearing mechanism is enclosed within the knee. It is fastened to the column by dovetail ways. The knee is supported and adjusted by a vertical positioning screw (elevating screw). The elevating screw is used to adjust the knee up and down by raising or lowering the lever either with the help of a hand or power feed.
This is placed between the table and the knee and works as an intermediate part between them. This can move transversally to the column face. This slides over the guideways provided situated on the knee which is perpendicular to the column face. The main function is to provide motion in a horizontal direction to the workpiece. This is also made of cast iron.
This is a rectangular casting that is present on the top of the saddle and is situated over the knee. It is part of a machine that holds the workpiece while machining. This is made of cast iron and has a T-slot cut over it. This provides vertical motion by moving the knee up and down. It provides horizontal motion by the feed screw. This provides a horizontal (transverse) motion by moving the saddle.
The overarm is used to fasten arbor support. It may consist of one or two cylindrical bars that slide through the holes in the column. It is made of cast iron.
The spindle is the main part of the machine which holds the tool in the right place. This spindle provides the drive for arbors, cutters, and attachments used on a machine.
This is a mechanical part, which is used as an extension part of the spindle in a horizontal mill machine. It is fitted on the spindle whenever it’s required. This holds the tool and moves it in the correct direction.
There are generally two types of arbor supports used in the mill machine. The first one has a small diameter bearing hole, 1-inch in maximum diameter, and the other one has a large diameter bearing hole, usually up to 23/4 inches. The arbor support has an oil reservoir that lubricates the bearing surfaces. It can be clamped anywhere on the overarm. The arbor support is used only in the horizontal types of milling machines.
It is the upper section of a vertical mill machine. It consists of a spindle, a driving motor, and other controlling mechanisms.
One end of the arm is attached to the column and the other ends to the milling head. The ram can be moved transversally ( in and out) on the column by a hand lever.
Main Types of Milling Machines
The main types of milling machines are as follows:
Column and knee-type milling machine
It is a very common machine type. In this machine, a vertical column is attached to the bed which consists of all gear drives which rotate the knee and saddle. A knee is situated on the base which provides vertical motion to the workpiece or which moves up and down. A saddle is attached to the upper section of the knee which can move in the transverse direction. The table is placed over the which can hold the workpiece by use of climbing bolts.
Vertical milling machine
The spindle of this machine is in a vertical position. No arbor is required in this machine. The cutter tool has a cylindrical shape and the cutting edges are situated at the circumference of the cylindrical face.
Horizontal milling machine
As the name implies, the spindle is situated horizontally. The spindle rotates horizontally. An arbor is attached to the machine which holds the cylindrical disk shape cutter which cuts the metal workpiece.
Universal milling machine
It is the same as the horizontal mill machine, except there is an arrangement of swings up the table to 45 degrees in either direction.
Fixed bed milling machine
In this type of machine, the bed of the machine is fixed to the machine. No arrangement of the knee and saddle can move vertically and transversally. The worktable is directly situated on the fixed bed. The spindle of this machine is mounted on a movable spindle head. It can move in the vertical and horizontal direction and perform the cutting operation.
Simplex milling machine
In the simplex machine, the spindle head or the spindle travels only in one direction. Mostly it travels in the vertical direction.
Duplex milling machine
In this machine, the spindle travels in both vertical and horizontal directions.
Triplex milling machine
In the triplex machine, the spindle can move in all three directions along the X, Y, and Z-axis.
Planer milling machine
The planer milling machine is mostly used for facing operations in mass production. These machines are similar to the bed-type mill machine, except they can be mounted with various cutters and spindle heads to the machine. These cutters in the machines can perform the facing operations simultaneously which is a great function.
Special milling machine
These machines are modern milling machines that are developed to ease milling operations according to the jobs.
Tracer milling machine
This machine performs all difficult operations like, die making job by synchronizing the tracing unit. This can develop any difficult shape. This is mostly used in the automobile and aerospace industries.
CNC milling machine
CNC is the most versatile milling machine which is controlled by a computer. It is an upgraded version of the bed-type mill machine, in which the spindle can move in all three directions and the table can rotate 360 degrees. These all movement is hydraulically controlled which is commanded by a computer. In this, any difficult geometry can make on it. A sketch of the workpiece is loaded onto the computer which is cut on the workpiece by the cutters automatically.
Operations of a Milling Machine
Following are the operations that can be performed in a milling machine:
Plain Milling Operation
It is the operation of producing a plain, flat, horizontal surface, parallel to the axis of rotation. This operation is also known as slab milling. This operation is very common and done in almost all jobs. This can be carried out on every mill machine.
Face milling Operation
This machining operation is done on the surfaces which are perpendicular to the axis of the cutter. The operation is performed by the face milling cutter mounted on the stub arbor of the machine.
End milling operation
It is the process of producing flat surfaces which may be horizontal, vertical, and at an angle taking worktable as a reference.
Form milling Operation
It is the process of machining a special contour (outline) composed of curves, straight lines, or entirely of curves, at a single cut. This operation is accomplished by using convex, concave, and corner rounding milling cutters.
T-slot milling Operation
It is the operation of producing the T-slots on the workpiece by using the T-slots milling cutter.
Side milling Operation
It is the operation of producing the flat vertical surface on the sides of the workpiece by using a side milling cutter. The cutter is having teeth on its face as well as its side.
Gear cutting Operation
It is the operation of producing gear tooth on the gear blank by using a form-relieved cutter in a milling machine. The cutter profile is exactly matched with the tooth space of the gear.
Straddle milling Operation
It is the operation of producing the flat vertical surface on both sides of the workpiece by using two side milling cutters mounted on the same arbor. The distance between the two cutters is adjusted by using a spacing collar. This is commonly used to produce a hexagonal or square surface.
Grooves milling Operation
It is the operation of producing the groove on the surface of the workpiece by using a saw-milling cutter or end-milling cutter. The workpiece is fixed firmly on a milling machine and fixing the end milling cutter on an arbor, by adjusting the depth of cut, the work is fed against the cutter to cut the groove on the work surface.
Gang milling Operation
It is the machining process in which two or more milling cutters are used together to perform different milling operations simultaneously. In gang milling, the cutters are mounted on the arbor.
advantages & Disadvantages of the Milling machine
- Suited for small batches.
- Complex shapes achievable.
- Cost can be modest.
- Costlier than alternatives.
- Special machines for mass production.
- High initial cost justifiable for precision and labor savings.
applications of Milling Machine
- This machines used to making gears.
- Usually used to a machined flat surface but can also produce irregular surfaces.
- Used to produce the groove or slot.
- Modern mill machine cut superalloys, titanium, tensile steel to closer tolerance, a greater accuracy, and faster rate.
- This machine is used to design of metal and other materials
Video on Milling machine
Milling Machine is a machine tool that performs rotary motion.
The tool used here is Multi-point cutting tool.
I hope you have understood everything about milling machines. If you still have any doubts or confusion, make sure to write in the comments.