Types of CNC Machines

CNC machining has become one of the most popular methods of cutting and producing parts and components in the manufacturing industry, as processes with computer numerical control can perform quickly and accurately while offering significant cost savings compared to traditional machining processes. With computer numerical control, automated CNC machines eliminate human errors and ensure faster output.

However, many different types of CNC machines exist, including CNC milling machines, CNC drilling machines, CNC grinding machines, CNC routing machines, and CNC turning machines. Some are also based on the types of cutting methods used, such as CNC machine tools, CNC laser cutters, CNC plasma cutters, CNC waterjet cutters, and CNC electrical discharge machines. It can be challenging for shop owners and fabricators to know which CNC machine type they should use for their specific industry.

In this article, we explain the applications and limitations of the types of CNC machines to help you decide which will best fit your CNC machining operations.

CNC machines can be divided into two main categories: 3-axis CNC milling machines and multi-axis machines.

A 3-axis CNC machine type can be used for either milling or turning. In contrast, multi-axis CNC equipment has three different classifications:

Indexed CNC machining 3+2 axis
Continuous 5-axis CNC machine
Mill-turning

3-Axis CNC Machines

These are the most common types of CNC machines found in workshops, with some having CNC laser cutters. These machines allow the automatic tool to move relative to the workpiece in three different directions: X, Y, and Z-axis.

The basic nomenclature of these axes is as follows:

X-axis: left-right
Y-axis: back-forth
Z-axis: up-down

There are two types of 3-axis CNC machines: milling machines and turning machines.

CNC Milling Machines

With a CNC milling machine, the workpiece is held stationary over the vice, and materials are removed using special cutting machine tools. These cutting tools are attached to a spindle that rotates at a very high speed along three linear axes: X, Y, and Z.

Benefits:

Relatively easy to program
Operates better than other configurations
Low-cost

Applications:

Good for producing standard geometries

Limitations:

Not suitable for applications where two or more combinations of the axes are required to produce the desired shape

CNC Turning Machines (CNC Lathes)

CNC turning machines can produce more volumes of work at a lesser cost per piece than the CNC milling machine. In this case, the workpiece is held stationary on a spindle while a cutting tool machines its external and internal perimeter to attain the required shape. The CNC lathe machine can also drill holes in the center of the workpiece with center drills and internal cutting tools.

Benefits:

Low cost per unit
Excellent accuracy

Applications:

Useful for producing screw threads, plane surfaces, or three-dimensional, complex products

Limitation:

Can only produce parts in the cylindrical form

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5-Axis CNC Machine

A 5-axis CNC machine easily overcomes the limitations of a CNC turning machine, some even having CNC plasma cutters. As the name suggests, this CNC type rotates in five directions; X, Y, Z, A, and B. The A-axis is termed the fourth axis and denotes rotation around the bed or the X-axis. Similarly, the B-axis is the fifth axis and denotes rotation around the tool head or the Y-axis.

Benefits:

Easy to design complex geometries faster due to compound angle positioning
Lower cycle time to optimize CNC machining costs
Improved dimensional stability

Applications:

Parts involving complex shapes and minute clearances like impellers, turbines, intake ports, etc.

Limitations:

Requires a costly setup and expert operators

It is worth knowing that there are two types of 5-axis CNC machines: the indexed type and the continuous type. The continuous type allows simultaneous movement of all five axes, whereas the indexed type does not offer continuous contact around the A and B axes. It rotates around them, remains stationary during operation, and reorients again for the new cutting location.

Mill Turning CNC Center

Mill-turning CNC centers are equivalent to CNC-turning machines yet have milling capabilities. Thus, it becomes relatively easier to remove materials from the workpiece. The spindle holds the workpiece and can rotate like CNC lathe machines to achieve higher productivity. Mill-turning CNC centers can aim for complex geometrical flexibility like a 5-axis CNC milling machine.

Benefits:

Reduces clamping times
Lowers procurement costs
Saves tool changing time
Increases process efficiency

Applications:

These CNC lathes are useful for creating round parts requiring milling or drilling

Limitations:

Rotation around the z-axis is not possible

7-Axis CNC Machine

Sometimes, designing complex topographies for aerospace and military parts requires rotation around the workpiece or rotation of the tool head. These functions are not available in a 5-axis CNC machine. This is where a 7-axis CNC machine becomes imperative. In addition to all the axes of a 5-axis machine, they offer movement along the Z-axis and arm rotation to save time transferring the workpiece to another machine.

Benefits:

Rotation around the workpiece
Saves time on changing machines
Improves processing speed

Applications:

Used for designing complex aerospace and military components

Limitations:

More expensive than 5-axis machines

12-Axis CNC machines

Among all the different types of CNC machines available, a 12-axis CNC machine is the most advanced. These computer-controlled machine tools offer precision CNC machining autonomy without human intervention. They can perform milling, drilling, and cutting operations on light alloys such as aluminum. The best part is that these CNC machines come with two heads: a vertical machining center (VMC) and a horizontal machining center (HMC). Thus, they can achieve precision in 12 different angles, as shown in the figure below.

Benefits:

Unparalleled design flexibility
Quick setup changes

Applications:

Ideal for the most challenging machining process

Limitations:

Requires a highly sophisticated setup and expert operators

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What Are the Types of CNC Machines?