Digital Manufacturing Basics: CNC Machining
Computer numerical control (CNC) machining was invented more than 50 years ago, and since then, its high capacity for precision and automation has helped create countless products. Across industries — from defense, automotive, and aerospace, to medical, precision, and manufacturing — this sophisticated technology has become part of the world’s industrial DNA.
How did CNC machining come to be?
During World War II, the United States was quickly churning out ships, aircraft, and vehicles for the military. And even once the war ended, production kept up as the country experienced a post-war boom in home construction, infrastructure expansion, and transportation. Naturally, engineers and designers needed tools to help them efficiently meet the growing demand for industrial products.
Enter CNC machining. John T. Parsons, who worked in the production of helicopter rotor blades, was one of the first people to champion CNC machining. He and his colleagues at Wright-Patterson Air Force Base in Dayton, Ohio used interpolation curves, which could be applied to machining with computational methods, to achieve the complex tapers required for rotor blades. As Parsons’ company got called upon to make more and more complex aircraft parts, they turned to computational methods to achieve their desired shapes.
This was partly the genesis of CNC machining. Building off of Parsons’ innovations, MIT’s Servomechanisms Laboratory later developed a working machine able to use computational methods to fabricate precise machine parts. Their servo-mechanisms were able to use the Cartesian coordinates — the numerical control — to steer the machine and its moving parts, to fabricate with automated precision. Such automation only grew more sophisticated through the rest of the twentieth century and continues to develop today.
How does CNC machining differ from traditional machining?
In traditional machining, a skilled machinist operates a machine, removing or forming metal. This is done according to specifications provided by designers and engineers, usually through an engineering drawing or blueprint. They use turn wheels, dials, switches, chucks, vices, and a variety of cutting tools made of hardened steel, carbide, and industrial diamond then use measurement instruments to ensure all of the dimensions are correct.
CNC machining performs the same function as traditional machining — metal cutting, drilling, milling, boring, grinding, and other metal forming and removal functions — but it uses computer numerical control rather than manual control by a machinist. It is automated, driven by code and developed by programmers. It is about as precise the first time of cutting as the 500th. Widely used in digital manufacturing (and sometimes in low-volume production runs), it can be revised and altered for modifications and different materials.
This type of machining is much more precise and has largely superseded traditional machining (though not entirely) in manufacturing, fabrication, and industrial production. It uses mathematical coordinates and the power of computing to achieve the same end, with the greatest accuracy. Specifically, computer numerical control uses Cartesian coordinates. These are spatial coordinates — in several dimensions — using coordinates and axes. The automation of cutting tool machines controls its cutting, boring, drilling or other operation using the numerical control of a computer that reads the coordinates. These coordinates were designated by engineers in the product’s digital drawing and design.
What is the CNC machining process?
CNC machining uses subtractive processes, which means feedstock is machined to final form by subtracting and removing material. Holes are drilled, lots and pathways are bored, and metal stock is shaped into new material with varying tapers, diameters, and shapes.
For subtractive manufacturing, shapes are achieved by the subtraction of material. This contrasts with other types such as additive manufacturing — where materials are added, layered and deformed to a specified shape. It also contrasts with injection molding where material is injected in a different state of matter, using a mold, and formed to a specified shape.
CNC machining is versatile — and can be used with various materials, including metals, plastics, wood, glass, foam, and other composite materials. This versatility has helped make CNC machining a popular choice across industries, enabling designers and engineers to fabricate products with efficiency and precision.