Introduction to CNC: Page 3 of 4

->Increased speed at which parts are produced (productivity).

->Producing the same quality for all work parts.

->Better dimensional accuracy which gives exact and correct dimensions.

->Increased ability to produce difficult parts.

->Less scrap.

Open Loop System

Uses stepping motor to create movement. Motors rotate a fixed amount for each pulse received from the MCU. The motor sends a signal back indicating that the movement is completed. No feedback to check how close the actual machine movement comes to the exact movement programmed.

Closed Loop System

AC, DC, and hydraulic servo-motors are used. The speed of these motors are variable and controlled by the amount of current or fluid. The motors are connect to the spindle and the table. A position sensor continuously monitors the movement and sends back a single to Comparator to make adjustments.