CNC stands for Computer Numerical Control. In very simple terms, we can think of a CNC machine being one where a computer commands a machine to make predetermined movements. There are two main methods for the computer to position the machine. Positioning control systems having no feedback are called open loop systems and those with feedback are called closed loop systems.(6)
Information travels one-way in an open loop system. Commands sent from the machine controller go to the various motors and drives, but no information is fed back to the controller. With no feedback, the controller cannot verify machine performance (feed speed, position, etc). Open loops are less sophisticated than closed loop systems because there is no verification system. (6)
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Information in a closed loop travels in both directions: from the controller to the machine and back to the controller. It uses a system of electronic devices to verify that the machine is moving as the controller intends it to. Machines with closed loop systems can be considered more intelligent in this manner. If the information loop detects that the machine is not in the right place, then the system will compensate for this by making the necessary adjustments.(6)
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