What does a CNC controller actually do?
It interprets the program, plans motion, drives the motors, watches sensors and stores offsets.
Start here
A CNC controller reads a program, works out the path each axis must follow, and sends timed commands to the motors so the tool moves along that path at the right speed.
Its main jobs
- Interpret. Parse each block of code and track active modes.
- Plan motion. Break lines and arcs into tiny steps, and look ahead to manage speed through corners.
- Drive. Send step or command signals to stepper or servo drives.
- Watch. Read limit switches, encoders, the emergency stop and spindle status.
- Remember. Store work offsets, tool lengths and machine settings.
Open loop and closed loop
Open-loop systems send steps and assume the motor followed. Closed-loop systems measure actual position with encoders and correct errors. Hobby machines are often open loop. Industrial machines are usually closed loop.
Why it matters to you
The controller decides which code dialect you write, how offsets are entered and how smoothly the machine handles complex paths. Two identical frames can feel very different with different controls.
Browse controller records in the index. Related: G-codes and M-codes.