CNC Machining Basics

CNC Machining is a subtractive manufacturing process that involves using high speed, precision machines to remove plastic or metal from a block (“blank”) to create the design of a part. The machines use a variety of cutting tools, and are controlled by computers. The “CNC” in CNC machining stands for Computer Numerical Control. Machines commonly controlled in this manner include vertical milling machines, horizontal milling machines, lathes, routers and grinders.
The computers and control consoles used to control the machines make the CNC machining process unique. CAM (Computer Aided Manufacturing) programming instructions tell the machine how to move. The software works in conjunction with the CAD (Computer Aided Design) model of the part provided by the customer. The machines are programmed with CNC machining language (called G-code) that controls machine features like feed rate, coordination, location and speeds. With CNC machining, the computer controls the exact velocity and positioning of the tools.
The first step in the CNC machining process is that the CAD model for the part is loaded into the CAM software. Tool paths are generated based on the geometry of the part, and the software tells the machine how fast and where to move in a 3-, 4- or 5-axis coordinate system.
CNC machining has many advantages. It is a more precise process than manual machining, and it provides exact repeatability. Because the computer controls the machine movement, the machine tools can all move precisely and simultaneously on their axes to create complex, three-dimensional shapes that would be almost impossible with manual machining. These qualities make CNC machining a good manufacturing process for jobs that require a high level of precision or repetition.
CNC Machine
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