SERVO & STEPPER MOTORS IN CNC MACHINES

Computer Numeric Control (CNC) machines convert instructions into actions for controlling operating tools. Movement is triggered when alphanumerical codes are entered in a CNC machine, and they have several attached tools: laser cutters, routers, and cutting tips. Component design is automated using computer-aided design and computer-aided manufacturing programs. CNC machines use either servo or stepper motors, each having its own unique dis- and advantages.

Servo Motors

Servo motors transfer information to the CNC machine using closed-loop circuitry. A regular (DC or AC) motor is connected to an encoder with a fixed sensor: this encoder is why servo motors have high accuracy and resolution. The servo amp powers the motor and counts the steps made as well. The servo motor’s impressive torque-to-inertia ratio permits rapid load acceleration and, with light loads, efficiency may be as high as ninety percent.

The downside to using servo motors in CNC machines is they are more complicated to operate and typically more expensive than stepper motors. Servo motors are also more susceptible to damage from overheating and -loading because their ventilation system is easily contaminated at high speed. What’s more they require servicing once the brush has reached its two thousand-hour lifespan.

Stepper Motors

The stepper in stepper motor comes from the steps the motor makes, which are triggered by each signal pulse. Stepper motors are easy to operate, generally cost less than servo motors, and have a higher reported accuracy. Several loads can be driven without gearing due to stepper motors’ low-speed torque, allowing use of a timing belt and pulley reduction. Steppers usually use fifty to a hundred-pole brushless motors, whereas servo motors have only four to twelve poles. Steppers don’t require encoders.

Stepper control systems are optimal for applications requiring low-to-medium acceleration, high-holding torque, and the flexibility of open- or closed-loop operation.

Stepper motors are normally less efficient than servo motors. Smooth movement often necessitates microstepping because steppers are resonance prone. Their low torque-to-inertia ratio causes loads to accelerate less quickly. Steppers are louder than servo motors and, like servo motors, are prone to overheating at high performance. Lastly, stepper motors have a lower overall power output relative to their weight and size.