Understanding CNC Machines: What They Are and How They Work





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What are CNC Machines?

CNC, or Computer Numerical Control, is a manufacturing technology that utilizes a computer program and specialized, automated tools in subtractive manufacturing processes. The term “computer numerical control” refers to the methodology used to carry out the manufacturing process rather than the specific function performed by the CNC system.

Unlike a 3D printer, which adds material on top of the material to create a “printed” item, subtractive manufacturing removes material from a blank or workpiece. 

Various factors must be considered to program the complex cuts and produce a usable and consistent product, such as the type of material used, the optimal cutting techniques, the required speed, and other relevant parameters. Elemet, a leading fabrication company, employs advanced machinery capable of operating on a broad range of axes to achieve optimal results in milling and other manufacturing processes.

The only limit to what our machines can do is your imagination. The uses of CNC machines are in fabrication, biomedical, food service, prototype creation, small business manufacturing, and large-scale industry. CNC machines can fabricate difficult-to-find mechanical parts and millstones and produce finished products for consumer use.

Computer Numerical Control

CNC machines

CNC machines use a programming language that understands the function of the various machine tools, the machined materials, and their composition and compiles them to complete the job. G-Code is the most common programming language, and machinists input each function that needs to be done as a line of code. 

The machine carries out each step as directed with extremely low margins of error and variation. Since computers can function perfectly, CNC coding is used for assembly line work, where multiple products can be nearly identical throughout the project.  


CNC machining can be performed on a broad selection of metals, including both ferrous and non-ferrous materials. Some of the most commonly used metals in CNC machining include: 

  • aluminum, 
  • brass, 
  • copper, 
  • stainless steel, 
  • titanium, and various types of steel, such as mild steel and tool steel. 

Additionally, specialty alloys like Inconel and Monel may be used for specific applications. The selection of a specific metal will depend on the required properties of the finished product, such as strength, weight, corrosion resistance, and thermal conductivity, among other factors.

Types of CNC Machine Tools

Computer numerical controlled printer, 3D milling machine and other thematic symbols.

Subtractive manufacturing involves using various cutting tools to remove material from a raw workpiece or blank. The blank is secured within the CNC machine. A series of control arms, laser guidance systems, and pre-programmed cuts and angles are used to shape the material according to the desired specifications. 

The computer controls the movement of the cutting tools to ensure precise and accurate results. By carefully removing material from the workpiece, complex shapes and intricate designs can be achieved with exceptional precision and accuracy. The selection of the specific cutting tools and parameters will depend on the type of material being machined and the required specifications of the finished product.

Here are the most common CNC machine tools.

  • Mills: Milling involves using precision routers, drills, and other cutting tools to remove material from a workpiece according to a pre-programmed course. By rotating the workpiece on an axis, the cutting arms of the mill can operate on a grid pattern, allowing for 3D subtractive fabrication.
  • Lathes: Lathes are machines that rotate blanks at high speeds while using indexing bits to remove material and shape it relative to the die and required cut. This process, also known as turning, can produce prototypes and finished products with low degrees of tolerance on various materials, including aluminum, steel, copper, bronze, brass, titanium, zinc, and wood.
  • Plasma cutters: Electrical arcs and pressurized cutting gas vaporize blank stock with precise cuts. The CNC program factors the workpiece’s metallurgical properties, speed, and dimensions to make cuts requiring minimal finishing. Plasma cutters operate at temperatures higher than the sun’s surface, and using different types of cutting gas can direct the plasma with high precision. Not ideal for temperature-sensitive materials.
  • Waterjet cutters: A precision tool, waterjet cutters use highly pressurized water jets focused through a jewel orifice, usually made of ruby or diamond. The water speed travels twice the speed of sound, and sometimes a garnet abrasive is used to affect the size and depth of the kerf or cut. The erosive properties of the water jet can cut through metal without affecting the temper or causing thermal zones, unlike plasma cutting tools. Waterjet cutters can cut plastic without melting it and glass without shattering it. Also, use waterjets to cut stones such as granite, quartz, and marble, and you can configure them to be used in commercial kitchens to cut food with high precision.
  • Lasers: A very versatile machine tool that uses focused light and cutting gasses to control kerf size and reactivity. Pulse laser cutting minimizes heat and can make cuts with minimal depth, not much larger than the beam size. Lasers cut various materials, including metal, wood, and plastics. 

Milling Machine Operation

CNC machines rely on a programming language to determine the fabrication process based on the selected tool and its operation. Skilled CNC milling operators are trained to create programs in the required programming language, which may only sometimes be G-Code, to execute the machining operations accurately. The quality of the program and operator proficiency are critical factors in determining the final product’s quality.

When performing CNC milling, various factors must be considered in determining the appropriate machining process, such as the size of the blank, required cuts, materials used, the time required to make the cuts, and the milling speed.  

CNC machines can operate with extremely high precision and low degrees of tolerance, making them suitable for a broad array of industries, including aerospace, automotive, defense, electronics, medical, and telecommunications. By ensuring that each cut is consistent, CNC machines can be utilized in both mass production and prototype building, producing high-quality and precise finished products.

Manufacturers utilizing CNC machines offer customers numerous advantages, including precision, speed, and consistency. CNC machines enable manufacturers to produce high-quality products efficiently, reducing waste and overhead costs associated with traditional manufacturing methods that require multiple machines and machinists to accomplish the same tasks.

Additionally, CNC machines offer unparalleled versatility, allowing manufacturers to perform a broad range of machining tasks with a single tool. This, in turn, results in faster turnaround times, improved quality control, and, ultimately, increased customer satisfaction.

Elemet Manufacturing offers a wide range of CNC milling machines equipped with cutting-edge technology to efficiently and effectively mill a variety of materials, resulting in high-quality finished products for our customers. For more information, or if you have questions about how to get started, visit our website and contact us today to step into the future of fabrication with CNC machines.

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