2013年3月1日星期五

The CNC Controller Components

The CNC controller is the brain of a CNC system. A controller completes the all important link between a computer system and the mechanical components of a CNC machine. The CNC controller components work together to interpret positioning signals created by a computer and NC software into precise motor control. This page will explain the function of each of the controller components and how they work together to make a controller system.

The Components
There are three primary CNC controller components that make up a CNC controller, the power supply unit, the circuitry protection system, and the motor driver.

The Power Supply Unit
When you plug a small flash drive up to your USB port, the computer powers the device through the port. When you plug a larger device, say a printer for example, you have to use an external power source because the computer is not capable of supplying sufficient power. This condition means that you have to plug that device into the computer as usual, but you also have to plug a second line to an auxiliary power source, such as the 110V outlet on your wall.
The same conditions are true for CNC devices. They require a low-voltage communication line, through which the computer tells the machine what to do, and a power source that provides the power for moving, cutting, and other such operations.
A power converter, usually referred to as the “power supply unit (PSU),” is often used to change the form of the supplied power from alternating current (AC) from the power grid, to direct current (DC) that is more easily used by the machine’s drive motors.
The power supply handles large voltages and currents that could be harmful to the NC circuitry. Therefore, the power source, motor drivers, and motors are often separated from the computer with a circuitry protection system that isolates surges in electrical power.
The Circuitry Protection System 
The circuitry protection system contains a breakout board to isolate signals from the computer, distribute the signals to the desired drivers, and also allows easy hook up of peripherals such as limit switches that feed information back to the computer. Fuses are also part of the circuitry protection system. Fuses could save the equipment in case of electrical spikes, shorts, or faulty wiring.
A low-voltage communication signal passes from the computer through the breakout board unchanged to the motor drivers. This isolated your computer from the CNC controller circuit but allows the signals to carry through to your motor drivers.

The motor drivers 
The motor drivers receives the communication signal and and then coordinates pulses of the desired current and voltage to elicit the movement in the drive motors. The motor drivers may communicate position information one way to the motor (open loop system), or send and receive position information(closed loop system), depending on the user’s choice of drive system. More on these systems may be found in the drivers sections.


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