The milling machines are the building blocks of manufacturing industries. Whether you own a woodwork shop or a metalwork store, you should have milling machines in your manufacturing gear.
As per recent reports, the global milling machine industry has shown a tremendous uplift of 5.3% annual growth rate with an estimated revenue of $8.5 billion by 2026.
But how do these machines help reshape metal, wood, and other solid materials? In this article, you will learn how the manufacturing industry works through milling machines and how to operate them for efficient working.
Definition of Milling
Milling is one of the machining processes that use different rotating tools to simply cut or shape the workpieces at a preset speed. The material is removed from the surface when the cutting tool comes in contact with the workpiece clamped on the table. Several operations are used for manufacturing the parts by milling process.
What is a Milling Machine and its Major Types
Milling machines, also known as multitasking machines, are a perfect tool to remove any redundant material from your metal object. By just utilizing a rotary cutter, they can drill all kinds of engineering, mechanical, or architectural materials in no time. Thus, you can trust milling machines for your metal work.
However, most milling machines feature three movement axes, i.e., X, Y, and Z. The X axis is obtained when using hand wheels for moving the table side-to-side, while the saddle is responsible for the y direction, and the z direction is due to the spindle that holds and rotates the cutting tool along the z-axis.
Moreover, milling machines are categorized into several types. Let’s talk about all of the major types one by one.
1. Column and Knee Type Milling Machine
The knee and column type milling machine deal with two parts of the machine, i.e., knee and saddle. The vertical column holds various gear devices and plays a role in the rotation of the knee and saddle. The machine offers you the vertical movement of the material located at the base of the machine. However, the saddle moves in the transverse direction. It is ideally used for small materials.
The following are the subtypes of the column and knee-type milling machines:
a) Horizontal Milling Machine
The type of milling machine in which the spindle is parallel to the working table is called a horizontal milling machine. It possesses shorter and thicker cutting tools as compared to vertical mills. Thus, it provides deeper and heavier cuts.
Using various horizontal mill cutting tools, you may process bevels, planes, slots, and planes.
b) Vertical Milling Machine
In vertical milling machines, the spindle axis is arranged vertically and offers rotation at the same axis. You may move the head up and down or in other directions. Generally, it allows you to perform different operations, like grooves, slots, flat surfaces, etc.
The two types of vertical mill are:
- Turret milling machines
- Bed milling machines
➔ Turret Milling Machine
You may move the spindle plus table perpendicular and parallel to the axis in the turret mill. They are well-known for their versatility.
➔ Bed Milling Machine
However, in the case of bed milling, only the table is allowed to move perpendicular to the axis. This is because the table is located directly on the huge bed of the machine, so it can’t move transversely.
c) Universal Milling Machine
Universal milling machines are able to perform a wide range of milling operations. It consists of a fitted table and a dividing head featuring several gears. You can make this table rotate at any angle on both sides from its normal position up to 45 degrees. Unlike a horizontal milling machine that moves in only three directions, a universal mill can move in all four directions.
On top of that, you may install additional attachments to ensure the increasing capacity of the machine. The attachments include slotting, vertical milling, index head, or rotary attachment. It also allows you to perform helical milling operations.
2. Ram-Type Milling Machine
The milling machine in which a spindle is organized upon a movable housing on the column allowing the milling cutter to slide forward and backward, is called a ram-type milling machine. This milling machine is further classified into universal and swivel cutter head mills.
3. Gantry Type Milling Machine
The body of the gantry-type milling machine is arranged horizontally, while the columns and connecting beams are present on both sides of the machine. Moreover, the milling head is located on the beam and column.
The multiple cutters of the gantry-type mill offer high machining precision and parts production efficiency. This milling machine is commonly used in aerospace and power generation industries.
4. Planer Type Milling Machine
Planer-type milling machines are somehow similar to bed-type mills. It features spindle heads that can be adjusted in both vertical and transverse directions. Further, the cross rails benefit in lowering and raising the cutters.
Planer-type milling machines are ideal for workpieces having broad surfaces.
5. Desktop Milling Machine
Desktop milling machines are mini machines that can be easily placed on working tables. Normally, they are used for manufacturing small parts, such as meters and instruments.
6. Cantilever Milling Machine
The cantilever milling machine contains a head mounted on the cantilever. Whereby the bed is arranged in a horizontal position. The cantilever is able to move vertically along the column guide rail. On the other hand, the milling head moves along the cantilever guide rail.
7. CNC Milling Machine
CNC milling machines are the most popular ones for their computerized control functions. The operators only need to give commands to the machine; the rest process is completed automatically. They use rotating cylindrical cutters to create holes and slots and produce variously shaped parts.
CNC milling machines operate on multiple axes in order to ensure the manufacturing of highly precise parts at a faster rate. In addition to metals, it also deals with plastics, ceramics, and many other materials.
How Do Milling Machines Work
The working principle of milling machines is somewhat similar to drilling. In the case of milling, the first step to follow is an appropriate adjustment of all the components of a milling machine. Then clamp the workpiece on the table with the help of clamping screws. Here the game begins!
Once the machine starts, the rotating spindle leads to the spinning of the cutting tool. While the cutting tool is whirling at high speed, the workpiece is moved by changing the positions of different machine parts, i.e., knee, table, and saddle. You may feed the workpiece in a longitudinal, vertical, or cross-direction. As a result, the tool’s cutting edges shape the material according to your requirements at a pretty fast rate.
What are the Parts of the Milling Machine
The following parts of milling machines play a crucial role in the working of the machines:
● Base
A base is the most crucial part and acts as the foundation on which all other parts rest. Typically, it is the fundamental unit on which the weight of the machine depends and is mostly made of cast iron.
● Column
Along with the base, the column provides strength to all machine parts. The column is mounted at one end of the base. It has an oil reservoir that acts as a cooling agent during the machining operations.
● Knee
Another component that rides vertically on the column of a milling machine is a knee. Based on the position of the knee, the milling machine may be of two types:
- Vertical Milling machine
- Horizontal Milling machines
● Saddle
The movement of the machine is under the control of the saddle. A saddle is responsible for the X-axis and Y-axis rotation of the machine during operation. In this way, it supports the table both from side to side and in and out positions.
● Table
The standard part of any milling machine is a table, also known as a milling table or swivel table. It functions as an adjusting tool that assists in maintaining the position of the lever during the manufacturing or cutting process. It is the place where you set a workpiece for further operation.
● Over-arm
Just parallel to the spindle portion of the milling machine, an over-arm is present, which is a horizontal beam on the column. This overhanging arm moves forward and helps stabilize the long arbors.
● Spindle
A spindle is a tool that holds the material when you are performing the cutting or drilling of a workpiece. It is positioned on the bearings and runs with the help of an electric motor during the manufacturing process.
Operations of Milling Machine
As milling involves the removal of unwanted objects from a workpiece, it follows some operations for smooth working. Below are some milling operations used in milling industries.
● Face milling
The most common among all milling operations is face milling. Most flat-surfaced or plain objects are being cut with this type of milling, and the ends are trimmed instead of the sides.
● Side milling
A side milling operation is the only suitable cutting method if you want to cut a metal piece from its sides. It uses a side milling cutter that rotates the table and helps in the perfect grinding of peripheral parts.
● Plain milling
In cutoff operations, plain milling is generally involved. It is also known as slab milling or surface milling and cuts the axis of the surface with the help of a milling cutter.
● Angular milling
During angular milling, the object is cut down from its angles perpendicular to the axis. The angle may be single or double, depending on the type of angular groove present in the material.
● Straddle milling
Unlike other machining operations, straddle milling uses two separate cutters that cut the workpiece’s parallel vertical surfaces under construction. The cutters may be of different forms. Some factories use plain and side face cutters, while others use spacers or washers to trim the material effectively.
● Gang milling
For those who want multiple workpieces in a limited amount of time, a gang milling operation is the best milling method for them. Multiple cutters with the same or different diameters are used in this CNC milling operation which is placed on the arbor of the machine.
● Gear milling
Out of all the CNC milling operations discussed above, gear milling is the most common. This manufacturing process includes different processes like:
- Casting
- Forging
- Extruding
Besides, the gears used in this milling process may be of metal, wood, or plastic.
Conclusion
Finally, you have clearly understood how milling machines can help you manufacture and cut large or rough-shaped materials. The process is simple and involves a few cutting tools so you can quickly get your desired shape of the workpiece as per your demands. Moreover, the above-discussed parts and operations are highly beneficial in getting a clear idea of how you can trim your objects precisely.
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