Understanding CNC motors: Stepper vs. Servo Motors

Choosing the right CNC motor for your project

There are no universal solutions In engineering as every case requires the engineer or designer in order to identify as well as implement the most optimal solution for a specific project’s task, requirements, and budget.

Electrical motors are one such area; if the application needs a precise control, stepper and servo motors are typically the right components for that task. Both motors can perform the exact same general job, which is rotating the shaft a specific number of turns or degrees, but each of them does that differently.

In this article, we’ll discuss the difference between stepper motors and servo motors for CNC while providing you with all the necessary information you should know about.

What are Stepper Motors, and how do they work?

Stepper motors divide the full rotation of a motor into a couple of steps. They use the permanent magnet or an iron rotor to accomplish this as well as the series of electromagnets that surround it. All these components make up a motor’s stationary part, also called a stator.

A motor activates every electromagnet in a controlled sequence for advancing a rotor on step one by one. However, this kind of division isn’t universal. The motors are also able to attain the sub-step resolution by using the fractional stepping technique. During this technique, the motor activates several phases all at once, and the users are able to achieve greater control when they activate phases in the analog method known as ‘micro-stepping’.

What are Servo Motors, and how do they work?

Just like stepper motors, servo motors come in a vast range of sizes, price points, and shapes. Certain inexpensive hobby micro-servos usually feature the variable resistor, allowing them to move to the angular position as well as return there even if the external force moves them.

There are also more pricey industrial servos that feature position as well as speed feedback. Oftentimes users couple such motors with gearboxes in order to increase their torque. One commands servo motors by using external control hardware for traveling to a specific position and turning in a highly controlled manner in order to obey a command.

So which do you need, stepper or servo motors?

Which of the two you should choose depends on your requirements. The fundamental difference between the two that you should consider comes down to the following: 

  • Stepper motors don’t feature feedback. They can’t provide you with feedback on whether or not they have traveled their intended distance. In case there’s a glitch in a system or even physical impediment during spinning, they may �skip steps’ and then continue along like nothing’s wrong.
  • Servo motors feature feedback. When servo motors are commanded to get to a specific position, they will do their best just to get there.
  • Torque vs. speed. Another important factor worth mentioning is that stepper motors usually lose torque when the speed increases, meaning the servo motor can be a much better and optimal choice for higher speeds. However, steppers can exert great torque at low speeds.
  • Sensors. In case you are using a stepper, you will most likely require to have some way in order to “zero” a system to the known point before a system can accomplish its designated task. Stepper setups can use this zero sensor or others for verifying their processes. Adding the sensor may mean that using the servo motor can get more pricey or complicated in the long run, meaning that before choosing a motor, considering your needs is very important.

Need to order a stepper or servo motor for your CNC machine? Give us a call! We source parts for all models.   

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