How Does a CNC Machine Work?

CNC milling closeup

CNC machines simplify and automate the manufacturing process by delivering precise cuts that are pre-programmed by a computer. Used in a variety of industries and a wide range of applications, CNC machines improve productivity while reducing errors. 

If you’re considering using CNC machines in your operations, it’s important to understand how they work and the types of machines available.

How Does a CNC Machine Work?

A CNC machine is designed to make precision cuts, which are programmed into its software. Essentially, the software tells the machine which tools and machinery to use carry out the programmed cuts. 

Position is directed through an open- or closed-loop system:

  • Open-loop: Signaling moves in a single direction between the machine’s controller and motor. With this type of system, there is little room for error.
  • Closed-loop: With this type of system, the controller can receive feedback, and errors in position or velocity can be corrected.

With a CNC machine, movements run along X and Y axes. The positioning and movement are guided by either stepper or servo motors, which rely on coding to direct their movements.

In most cases, a closed-loop system is preferred because it allows greater control over speed, accuracy and consistency.

Because CNC machines rely on pre-programmed software, production is primarily automated. Computer-aided design, or CAD, software is used to set the dimensions of the item, and that information is used to bring the design to life using computer-aided manufacturing, or CAM, software.

How Does a CNC Lathe Machine Work?

CNC lathe machines cut in a circular direction with precision and using high velocity. They’re used to create intricate and complex cuts that would otherwise be impossible with manual machines.

Like with other CNC machines, the lathe variation can be controlled via G-code or a special code created by a manufacturer. Typically, CNC lathes run along two axes: X and Z.

There are two main types of CNC lathes:

  • Horizontal: The most common type of CNC lathes used in workshops. These machines rotate workpieces cylindrically, and they tend to have larger footprints. Typically, horizontal lathes are used for lighter materials.
  • Vertical: The workpiece is rotated in a vertical (upright) position. This allows cuts to be made in hard-to-reach positions and angles. These machines are often used to work on heavy materials.

CNC lathes are used in a wide range of industries, including electronics, automotive, firearms, and aerospace.

Lathes can be used for a variety of applications, including grooving, turning, sanding and cutting. Some common operations include:

  • Tapering: An operation that narrows the metal object to create a cone shape.
  • Facing: One of the simplest operations. The metal is sheared at the end, so it can fit into the right angle of the axis and remove marks.
  • Parallel Turning: Uses a rotational axis that is parallel to the workpiece. This operation decreases the metal’s diameter.

How Does a CNC Milling Machine Work?

A CNC mill machine uses special cutters to shape parts or workpieces. Like other types of CNC machines, mills use pre-programmed software to control the machine’s movements. This allows for high precision, increased productivity and superior accuracy compared to the manual milling process.

A CNC milling machine is controlled by a program that uses letter- and number-based prompts. These prompts are what guide the machine’s movements.

The programming for mill machines can be based on G-code or a special language developed by a manufacturer. 

A basic CNC mill runs on three axes: X, Y and Z. Newer and more advanced models can accommodate three more axes. 

The most common types of milling operations include:

  • Plain milling: Also known as slab milling. With this process, the axis of rotation is parallel to the workpiece. Both narrow and wide cutters can be used, depending on the design’s specifications.
  • Face milling: Primarily used for creating contours and flat surfaces on finished pieces. Face milling cutters have two sets of teeth. One is used for cutting, and the other for finishing. The cutter’s axis or rotation is perpendicular to the workpiece surface.
  • Form milling: Used to create intricate designs and complex parts, such as beads or semi-circular cavities. Fly or formed milling cutters are used.
  • Angular milling: As the name suggests, the cutting tool’s axis of rotation is placed at an angle to the workpiece. The angle is, of course, based on the design’s specification and is used to create angular features, such as grooves, serrations and chamfers.

Production follows the same basic process that all CNC machines follow:

  • A design is created using CAD software.
  • The CAD design is converted to a CNC program using CAM software.
  • The CNC mill is prepared and carries out the work.

Due to its versatility and high level of accuracy, CNC mills can be used in a wide range of industries.

How Does a CNC Router Work?

A CNC router is very similar to a CNC mill. Older, industrial-level machines take up quite a bit of space, while newer, smaller desktop models are much more compact. However, desktop models aren’t quite as powerful as their industrial counterparts.

CNC routers are commonly used to manipulate wood for furniture-making or other woodworking applications. The computerized aspect of this machine makes it easy to cut wood at precise angles. 

Carpenters and woodworkers may use a CNC router to cut dadoes, edges, rabbets and intricate details. These machines can run and cut along three axes: X, Y and Z.

CNC routers are easy to use and offer an intuitive design that allows hobbyists to use them.

How Does a CNC Plasma Cutter Work?

A CNC plasma cutter uses a plasma torch to cut materials. While these machines are used primarily to cut metal, they may also be used with other types of materials. Electrical arcs and compressed air gas are used to create the level of heat needed to cut the material. 

Once the nozzle reaches the right temperature, the machine is ready to slice through the metal or material.

A plasma cutter is unique among CNC machines because it uses a torch and requires extreme heat to make cuts. They come in a wide range of sizes and prices, but they all offer a high level of accuracy and cutting speeds of up to 500 inches per minute.

Plasma cutters take up more space in a workshop because they require a gas or compressor in addition to the computer system.

There are two types of tables used with CNC plasma cutters:

  • Downdraft: These have built-in ventilation. They are designed to pull debris and fumes away from the metal workpiece. Specialized exhaust systems or other ventilation systems will be required for this type of table. 
  • Water: The workpiece and the plasma torch are submerged in water and resurfaced to remove debris while keeping parts cool. Standard workshop ventilation will work fine for this type of table.

CNC plasma cutters are used in a variety of industries, including auto repair and restoration, welding, fabrication, salvage operations and more. They can be used by large-scale manufacturing facilities, or small-scale hobbyists.

These are the most common types of CNC machines used in manufacturing and other applications. Each offers its own benefits and uses, which need to be considered carefully if you plan to add them to your operations.

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