How do numerical control systems use coded instructions to operate machine tools?

Numerical control (NC) systems operate machine tools by interpreting coded instructions that define the sequence and parameters of a machining operation. These instructions, derived from part drawings, are written as a program manuscript containing data such as coordinate dimensions, feed rates, spindle speeds, and tool selection.12

Historically, this coded information was punched into paper or plastic tape, which the NC system read to activate relays and electrical circuits. These circuits then drive the machine's servomechanisms to perform the programmed tasks automatically. Modern systems, known as computer numerical control (CNC), typically store these instructions in computer memory or receive them directly from a computer, often utilizing computer-aided design (CAD) data.123

The systems are generally classified into two types:
* Point-to-point: Controls motions between fixed starting and stopping points.3
* Continuous-path: Capable of contouring operations by maintaining awareness of previous actions to guide the tool along a specific path.13

In most setups, a position feedback control system verifies that the machine has correctly executed the coded instructions.2