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High Precision Digital Servo Control

In any laser engraver, motors are used to position the beam in the work area. It is important that the movement be smooth and accurate. There are generally two types of motors used - the older Stepper Motor, and the newer Servo Motor.

Older Stepper Motor Method:

To move a Stepper motor, a voltage pulse is applied to the motor. The motor moves a fractional degree. For each pulse applied to the motor, the motor advances. There is no feedback to the motor controller to monitor the current position. So, if a pulse is subjected to the motor, and the motor does not move the proper distance, the laser beam is not located where it is suppose to be. Since there is no feedback to the motor controller, the error goes undetected and the laser can end up cutting in the wrong location. This is referred to in the industry as an "open-loop" system. Also, since the stepper must always advance in discrete pre-determined steps, the movement can be dis-continuous and jerky.

Newer Servo Motor Technology:

To move a Servo motor, a voltage is again applied to the motor. The difference is, the Servo Motor has what is called an "optical encoder" that actually measures the distance it has moved and reports this back to the motor controller, which can then adjust the position. With a Servo Motor, the location of the laser beam is always precisely known. The continuous feedback to the motor controller is referred to as a "closed-loop" system. A closed loop Servo Motor provides very fast and precise movement with excellent acceleration and de-acceleration characteristics.

Bottom line, Servo Motors provide the precision, the speed and the continuous feedback essential to high-speed accurate laser cutting systems.