Powering a CNC - Stepper vs Servo Motors

When it comes to powering a CNC machine, the heart and soul of the machine relies in the motor. The CNC routers speed, accuracy, and precision all rely on the size and type of the motor. The two primary motor classes that are used with CNC machines are stepper motors and servo motors.

Both types of motor have several variances from size to power. This article shows some pros and cons of each motor, which will help choosing a CNC motor much easier. The following pros and cons of both stepper motors and servo motors are based on a comparison where both motors are of equal power. Both CNC motors are capable of delivering appropriate power when setup correctly.

• Cost- Both CNC motors are priced very well, however, stepper motors are usually priced lower. Even when servo motors and stepper motors share the same power rating a step motor will often be priced lower. Stepper motors are much easier to find, making them much more abundant.
• Versatility - Stepper motors are incredibly versatile, which makes them very popular among hobbyist and within industrial applications. Stepper motors can be found in thousands of products from personal computers to automobiles.
• Reliability - What makes a stepper motor more reliable, compared to the servo, is the fact step motors do not require an encoder. Servo motors are also very reliable, however they require an encoder which is known to fail.
• Life Span - A stepper motor is also considered a brushless motor, where a servo has brushes. Brushes must be replaced every 2,000 hours after operating, where the only parts that may wear on a stepper motor are the bearings.
• Frame Size - Although servo motors edge out stepper motors in this field, it is a very close comparison. Servo motors have a larger selection of frame sizes that range from small to large. Stepper motors also have a large selection, however not nearly the options of servo motors.
• Motor Design - Overall, the design of a servo motor is more complex because of their internal parts and the encoders. Stepper motors win the area of motor design since they are easy to use and understand how they operate.

Each CNC motor has their ups and downs, and both motors will work in different types of CNC machines. Stepper motors do have more advantages to servo motors, which often makes them the top pick. Since step motors are easy to use, and very common, they are the most widely used CNC motor.