CNC Machining: Definition & Types of CNC Machine

Computer Numerical Control (CNC) is an automated manufacturing process that controls and operates machinery—such as lathes, mills, drills, and more—by way of a computer.

It has evolved the manufacturing industry as we know it, streamlining the production process and allowing complex tasks to be done with precision and efficiency.

If you are looking to break into the field of manufacturing, CNC machining offers a cutting-edge career on the frontlines of innovation and technology. If you are looking to learn more about the manufacturing industry, read on.

First, let’s start with the basics of CNC and what it stands for.

What is CNC Machining?

CNC (Computer Numerical Control) machining is a subtractive manufacturing technology: parts are created by removing material from a solid block (called the blank or the workpiece) using a variety of cutting tools.

This is a fundamentally different way of manufacturing compared to additive (3D printing) or formative (Injection Molding) technologies. The material removal mechanisms have significant implications on the benefits, limitations and design restrictions of CNC. More on this below.

CNC machining is a digital manufacturing technology: it produces high-accuracy parts with excellent physical properties directly from a CAD file. Due to the high level of automation, CNC is price-competitive for both one-off custom parts and medium-volume productions.

Almost every material can be CNC machined. The most common examples include metals (aluminum and steel alloys, brass etc) and plastics (ABS, Delrin, Nylon etc). Foam, composites and wood can also be machined.

The basic CNC process can be broken down into 3 steps. The engineer first designs the CAD model of the part. The machinist then turns the CAD file into a CNC program (G-code) and sets up the machine. Finally, the CNC system executes all machining operations with little supervision, removing material and creating the part.

Related: What is the NC machine?

What is a CNC Machine?

CNC machines are machine tools that cut or move material as programmed on the controller, as described above.

The type of cutting can vary from plasma cutting to laser cutting, milling, routing, and lathes. CNC machines can even pick up and move items on an assembly line.

CNC machines are automated machines, which are operated by computers executing pre-programmed sequences of controlled commands.

CNC machines are essentially the opposite of “old-school” devices that are manually controlled by hand wheels or levers, or mechanically automated by cams alone.

Today’s modern CNC machines understand and function using CNC machining language – called G-code – which tells them precise measurements for production, like feed rate, speed, location, and coordination.

Today’s design and mechanical parts for CNC systems are highly automated – unlike the old, dangerous, factory machines you’d think of back in the day.

The parts’ mechanical dimensions are defined using computer-aided design (CAD) software and then translated into manufacturing directives by computer-aided manufacturing (CAM) software.

How do CNC Machines Work?

CNC machines usually feature a version of a CAD software program. A CAD program, or computer-aided design, is software that allows you to draw what you want to cut.

The drawing is either 2D or 3D and when completed it creates a code for the CNC machine to read.

CNC machines work by following coordinates along an axis. Basic machines move along one or two axis, but advanced machines, and those creating 3D items, will move along three axis. The machine’s tools follow thousands of coordinates, cutting and shaping as they move.

Before a CNC machine begins its first task, a trial run is conducted. This trial run is referred to as cutting air and is incredibly important as any mistakes could result in a damaged machine or part.

Types of CNC Machines

Following are the types of CNC Machines:

• CNC Milling Machine
• CNC Router
• CNC Plasma Cutting Machine
• CNC Lathe Machine
• CNC Laser Cutting Machine
• CNC Electrical Discharge Machine
• CNC Waterjet Cutting Machine
• CNC Grinder
• CNC Drilling Machine

In the next sections, I give a broad overview of each type of CNC machine.

#1. CNC Milling Machine.

One of the most common types of CNC machines, a CNC mill uses computer controls to cut various materials. Mills can translate specific programs from numbers and letters to move the spindle in different ways.

CNC milling machines are characterized by their ability to rotate cutting tools while holding the material workpiece/block stationary.

You can machine a wide range of shapes, including face-milled features and peripheral-milled features. Components manufactured on CNC milling machines are typically square or rectangular with a variety of features.

Many mills use something called G-code, which, as mentioned, is a standardized programming language recognized by most CNC machines. After inserting the workpiece into the milling machine, the computer takes over control.

The computer code guides and directs every movement and action of the spindle and tooling to cut the workpiece with high accuracy and convert it into a designed custom part.

A CNC mill can have a variety of functions, such as face milling, shoulder milling, tapping, drilling, and turning. Most CNC milling machines are available in three to six-axis configurations.

A CNC mill is very large compared to other tools and can be quite expensive. In general, CNC mills are used for machining hard metals and CNC routers are used for softer materials.

Related: What is Milling Machine?

#2. CNC Router.

A CNC router is a machine that is very similar to a CNC mill but is generally used for machining softer materials and is typically less precise compared to CNC mills.

CNC routers are significantly cheaper than CNC mills. This type of CNC machine can help cut steel, wood, aluminum, composites, plastic, and foam.

CNC routers are characterized by their ability to use computer numerical control to direct spindle and machine tool paths to cut and shape materials such as wood, steel, composites, aluminum, foam, and plastic into the desired design and shape.

CNC routers reduce waste and increase productivity by producing different items in much less time than other machines.

CNC routers generally consist of a mechanical base, a spindle, stepper motors, stepper drivers, controllers, and a power supply. CNC routers reduce waste, increase productivity and accuracy, and produce products faster.

Most routers can machine a given material in all three dimensions and are great for smaller projects and creating prototype models and complex designs. You can also find three-axis, four-axis, five-axis, and six-axis routers.

A quality CNC router can be purchased for less than $2,000, while even entry-level CNC Mills cost over $10,000. Also, you can buy a second-hand CNC machine, but before considering the old one, you should know how to assess the value of a CNC machine.

Most CNC router machines are capable of machining a workpiece in all three dimensions and excel at creating small projects and prototyping both simple and complex designs. Like CNC Mills, CNC routers are available in a variety of axes from three to six.

#3. CNC Plasma Cutting Machine.

CNC plasma cutting machines are similar to CNC milling machines in that they have the same function, which is cutting materials.

However, CNC plasma cutting machines use a plasma torch to cut through their materials, while a milling machine uses an end mill or milling cutter attached to a spindle.

The main requirement for CNC plasma cutting machines is that when plasma cutting, the material or workpiece to be cut must be electrically conductive. CNC plasma cutting machines are also used to cut materials.

However, they perform this process using a powerful plasma (electronically ionized gas) torch controlled by a computer.

Similar in function to a hand-held gas-powered torch for welding (up to 10,000 degrees Fahrenheit), plasma torches reach up to 50,000 degrees Fahrenheit. The plasma torch melts through the workpiece to create a cut in the material.

Whenever CNC plasma cutting is used, the material to be cut must be electrically conductive. Typical materials are steel, stainless steel, aluminum, brass, and copper.

Precision CNC machining offers a wide range of component production and finishing capabilities in the shop floor environment.

Depending on the deployment environment, materials needed, lead time, volume, budget, and required features, there is usually an optimal method to achieve the desired result.

Mainly used in heavy industries such as shipbuilding, automobile manufacturing, chemical manufacturing, and industrial steel construction sites.

Consequently, in CNC plasma cutting, the workpiece is generally large and heavy. An entry-level plasma-cutting CNC machine costs around $5,000, while the most expensive machines cost hundreds of thousands of dollars.

#4. CNC Lathe Machines.

A lathe is a CNC machine designed to cut workpieces while they are rotated. CNC lathes can quickly make precise cuts with a variety of tools. These CNC machines are very effective in the precision they offer compared to manual lathes.

They often have fewer axes than CNC milling machines and are therefore smaller and more compact.

CNC lathes have controls similar to CNC milling machines and can read G-code as well as other proprietary programming languages.

CNC lathes and turning machines are notable for their ability to rotate (turn) materials during the machining process.

The cutting tools for these machines are fed in a linear motion along with the rotating bar stock; Removing material around the perimeter until the desired diameter (and feature) is achieved.

CNC lathes and turning machines can create internal and external features on the part: drilled holes, bores, broaches, reamed holes, slots, threads, tapers, and tapping. Shafts, bolts, and screws are some of the components that are made on CNC lathes.

MORE: What is Lathe?

#5. CNC Laser Cutting Machine.

These types of machines are similar to CNC plasma machines, the only difference being that lasers are primarily used for cutting and are great for cutting metals, plastic, or hardwood.

Depending on the density and strength of the material, the intensity of the laser can be adjusted.

CNC laser machines have a pointed router with a highly focused laser beam that is used to precisely cut, cut, or engrave materials. The laser heats the material and melts or vaporizes it, creating a cut in the material.

Typically, the material is in sheet format and the laser beam moves back and forth across the material to create a precise cut.

This process can produce a wider variety of designs than traditional cutting machines such as lathes, turning centers, and milling cutters, and often produce cuts and/or edges that do not require additional finishing processes.

CNC laser engravers are commonly used for part marking machined components. For example, it can be difficult to incorporate a logo and company name into a CNC-turned or CNC-machined part.

Using laser engraving, however, can also be applied to the component after processing has been completed.

#6. CNC Electrical Discharge Machine.

A CNC electrical discharge machine (EDM) uses highly controlled electrical sparks to manipulate materials into the desired shape. It can also be referred to as spark erosion, die sinking, sparks erosion, or wire burning.

A component is placed under the electrode wire, and the machine is programmed to emit an electrical discharge from the wire that generates intense heat (up to 21,000 degrees Fahrenheit).

The material is melted or washed away with liquid to create the desired shape or property.

In this process, the material is removed from a specific workpiece by a series of repetitive electrical discharges between two electrodes. These electrodes are separated by a dielectric fluid, which often carries an electrical potential.

In this machine, the material is placed between two electrodes and the machine then calculates to see how much electrical discharge each electrode needs to create.

EDM is most commonly used to create precise micro-holes, slots, tapered or angled features, and a variety of other more intricate features in a component or workpiece.

It is typically used for very hard metals that would be difficult to machine into the desired shape or property. A good example of this is the typical gear.

MORE: What is an Electrical discharge machine (EDM)?

#7. CNC Waterjet Cutting Machine.

CNC Waterjet cutters, as the name suggests, use high-pressure jets of water to cut through materials.

Typically, CNC Water-jet Cutting is opted for when the material to be worked upon is sensitive to temperature and could melt at high temperatures, such as plastic and aluminum.

Although these machines can cut with just water, usually additional abrasive materials like garnet (a mineral) or aluminum oxide are added to the water for more efficient cutting.

A CNC Water-jet cutting machine costs more than a plasma cutter with similar specifications. But it costs less compared to a CNC Laser cutter with similar specifications.

One disadvantage of a CNC water-jet cutter is that it is typically slower than CNC plasma cutters and CNC laser cutters.

#8. CNC Grinder.

A CNC Grinder uses abrasive tools to smooth and finish a machined product. Grinders are typically used in applications requiring extremely high precision such as the machining of engine parts.

Generally, the product is first created with a rough surface using a CNC Mill or Lathe and then moved to the CNC Grinder for the final finishing. CNC Grinders come in various types such as surface grinders, roll grinders, and cylindrical grinders among others.

There is a lot of variety in the type of abrasive used for grinding as well, such as plated or vitrified CBN, Diamond grinding wheels, Aluminum Oxide, and Ceramic Blend Grinding Wheels among many others.

#9. CNC Drilling Machine.

The CNC drilling machine is typically applied for mass production. Drilling machines, however, often have a multi-function machining center that is occasionally mingled and sometimes twisted.

The greatest sink time for CNC drilling is with tool changes, so for speed, the variation of hole diameter must be reduced.

The fastest machine size for drilling holes consists of several spindles in the turret with drills of different diameters pre-mounted for drilling. This type of CNC machine can perform reaming, counterboring, and tapping holes.

These are the most common types of CNC machines that are in use today. The choice of machine depends on the type of job, the accuracy required job budget, and the time available to complete the job.

Types of CNC Machining Operations

In short, CNC machining is a metal fabrication method where written code controls the machinery in the manufacturing process.

The code determines everything from the movement of the cutting head and the part to spindle speed, RPMs, etc. CNC machining services use a subtractive fabrication method.

So, we now know how CNC machines work. But not all these machines are used for CNC machining.

We will take a closer look at all the different types of CNC machines that are available a little later. But in a traditional sense, CNC machining refers to only a few of these automated processes. Namely, milling, turning, grinding, routing, drilling, etc.

1. CNC Milling

It is an operation where the cutting tool rotates. When the milling tool comes into contact with the workpiece, it removes chips from it.

Milling operations include:

• End milling
• Chamfer milling
• Face milling
• Drilling, boring, tapping, etc.

It is a very universal manufacturing method with great accuracy and tolerances. Milling works on a wide variety of materials and is also very quick. The ability to make a wide range of complex parts is a huge asset.

The disadvantages include a large amount of waste, the need for a variety of tools, and high equipment costs.

2. CNC Drilling

Drilling is a machining process that uses multipoint drill bits to create cylindrical holes in the workpiece.

In CNC drilling, the CNC machine normally feeds the rotating drill bit perpendicular to the plane of the workpiece surface, creating vertically oriented holes with diameters that match the diameter of the drill bit used for the drilling process.

However, angular drilling operations can also be performed using special machine configurations and workpiece holding fixtures. The operational capabilities of the drilling process include counter-drilling, countersinking, reaming, and tapping.

3. CNC Turning

While the two are often just referred to as CNC machining, turning and milling have significant differences. Turning is pretty much the opposite of milling. This means that the workpiece rotates instead of the cutting tool.

CNC turning is commonly used to manufacture shafts, for example. The tool is brought against the rotating workpiece in order to cut off metal parts, known as chips or swarf. It is possible to achieve high accuracy for a suitable kind of limit values and adjustment systems.

Turning is possible on the outside of a cylinder or on the inside. The latter operation is called boring.

Machining Operation	Characteristics
Drilling	Employs rotating multi-point drill bits Drill bit fed perpendicular or angularly to workpiece Produces cylindrical holes in a workpiece
Milling	Employs rotating multipoint cutting tools Workpiece fed in the same direction as cutting tool rotation Removes material from workpiece Produces a broader range of shapes
Turning	Employs single-point cutting tools Rotates workpiece Cutting tool fed along the surface of the workpiece Removes material from the workpiece Produces round or cylindrical parts

4. CNC Grinding

CNC grinders use a rotating grinding wheel to remove material. The aim is to give a metal part a high-precision finish.

The surface quality that can be achieved is very high. Hence, it is used as a finishing operation rather than making the final piece from raw materials.

5. CNC Routing

CNC routers are seemingly similar to CNC milling machines. Again, the rotating piece is the cutting head. The main difference lies in the materials suitable for cutting.

Routers are perfect for cutting softer materials (not metals) that do not require very high accuracy. The reason for this is the lower output power.

At the same time, routers are faster. This allows you to manufacture the parts in less time.

CNC Machine Programming

In CNC manufacturing, machines are operated via numerical control, wherein a software program is designated to control an object.

The language behind CNC machining is alternately referred to as G-code, and it’s written to control the various behaviors of a corresponding machine, such as speed, feed rate, and coordination.

Basically, CNC machining makes it possible to pre-program the speed and position of machine tool functions and run them via software in repetitive, predictable cycles, all with little involvement from human operators.

In the CNC machining process, a 2D or 3D CAD drawing is conceived, which is then translated to computer code for the CNC system to execute. After the program is inputted, the operator gives it a trial run to ensure no mistakes are present in the coding.

Due to these capabilities, the process has been adopted across all corners of the manufacturing sector, and CNC manufacturing is especially vital in the areas of metal and plastic production.

Find out more about the types of machining systems used and how CNC machine programming fully automates CNC manufacturing below:

Open/Closed-Loop Machining Systems

During the CNC manufacturing process, position control is determined through an open-loop or closed-loop system. With the former, the signaling runs in a single direction between the CNC controller and motor.

With a closed-loop system, the controller is capable of receiving feedback, which makes error correction possible. Thus, a closed-loop system can rectify irregularities in velocity and position.

In CNC machining, movement is usually directed across X and Y axes. The tool, in turn, is positioned and guided via stepper or servo motors, which replicate exact movements as determined by the G-code.

If the force and speed are minimal, the process can be run via open-loop control. For everything else, closed-loop control is necessary to ensure the speed, consistency, and accuracy required for industrial applications, such as metalwork.

In CNC machining, movement is usually directed across X and Y axes. The tool, in turn, is positioned and guided via stepper or servo motors, which replicate exact movements as determined by the G-code.

If the force and speed are minimal, the process can be run via open-loop control. For everything else, closed-loop control is necessary to ensure the speed, consistency and accuracy required for industrial applications, such as metalwork.

CNC Machining Is Fully Automated

In today’s CNC protocols, the production of parts via pre-programmed software is mostly automated.

The dimensions for a given part are set into place with computer-aided design (CAD) software and then converted into an actual finished product with computer-aided manufacturing (CAM) software.

Any given workpiece could necessitate a variety of machine tools, such as drills and cutters. In order to accommodate these needs, many of today’s machines combine several different functions into one cell.

Alternately, an installation might consist of several machines and a set of robotic hands that transfer parts from one application to another, but with everything controlled by the same program.

Regardless of the setup, the CNC process allows for consistency in parts production that would be difficult, if not impossible, to replicate manually.

What Can CNC Machining Make?

Seemingly, CNC machining has no limitations. It is suitable for a wide range of materials, including different types of metal, plastics, foam, composites, and wood.

3-axis milling machines are able to produce most of the more basic geometric shapes. For more complex parts, multi-axis milling centers are available.

For example, a 5-axis CNC milling center can help out. While the more common 3-axis one has 3 linear axes of movement, 5-axis machines can also rotate the cutting head and the machine bed. This significantly improves flexibility but also increases the cost.

Even though CNC is a lot quicker, manual machining still has its place in the industry. Especially for low-volume rapid prototyping.

But CNC machining still prevails in the sector when high accuracy is necessary. This is the reason why so many industries take advantage of it, including:

• Aerospace
• Electrical
• Defense
• Mining
• Industrial machinery
• Food & beverage
• Clothing
• Automotive
• Product design, etc.

All in all, CNC machining has cemented its place in the manufacturing sector as a reliable and useful way of producing parts. At the same time, CNC machining costs may often be a little bit higher compared to other fabrication methods.

FAQs.