CNC machining technologies rapidly grew as technological capability only accelerated in the late 20th century – which brings us to how modern CNC machines work.
Machining is a way to transform a stock piece of material such as aluminum, steel, or titanium into a finished product or part. CNC machines rely on digital instructions, specifically referred to as G-code. Before modern computer aided manufacturing (CAM) and computer-aided design (CAD) programs such as Autodesk’s Fusion 360 were around, machinists would manually write the G-code to control these machines. CAM programs today allow you to take a 3D model and automatically generate G-code that will drive the machine with little input required.
When you compare the capabilities of automated CNC machining to the manual alternative like lathes and other machining techniques, you can see the benefits. CNC machines simply run faster at higher precision and accuracy while simultaneously allowing the transformation of a digital design into a physical part.
CNC machines are precise and are measured in thousands of an inch, Standard machining can provide tolerances on parts around ±0.005″, fine machining can produce tolerances of ±0.001″, and specialized processes like polishing can offer up repeatable tolerances as tight as ±0.00005″. For reference, a human hair is .00069 inches thick.
Many designs or specific machining processes require the use of multiple tools to make cuts. One tool doesn’t function universally. For this, machinists will often build digital tool libraries that interface with the physical CNC machine. These machines, often costing hundreds of thousands of dollars, can automatically switch tooling when directed by their digital instructions allowing for them to become manufacturing workhorses.
Basic CNC machines will move in one or two axes, referred to as the x-axis and y-axis, followed by third, z-axis, which you’ll hear the term 2.5 axis, meaning only two axes move together, rather than all 3. You’ll often hear the terms 2.5, 3-axis and 5-axis CNC machines, which simply refer to the degrees of freedom a machine can make cuts in. A three-axis machine can move in the x, y, and z-axis, whereas a 5-axis machine can move in these 3 axes along with 2 rotational axis.
