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When discussing CNC machines, we often mention stepper motors and servo motors and sometimes even explain their differences briefly. However, in this article, we will delve into the topic thoroughly. We’ll explore what each type entails, the differences between them, and why certain equipment uses one type over the other. Read on below!
Stepper motors
What is it?
A stepper motor is a synchronous brushless mechanism that converts control signals from a control system into physical movements of the shaft to a specific position, with subsequent fixation in that position.
It transforms electrical energy into mechanical energy, to put it another way. These motors are used in laser and router equipment.
Functioning principle
Typically, a stepper motor is made up of the following parts:
- Stator. This has several windings or coils that are powered by current in order to produce a magnetic field.
- Rotor: This device spins due to the force of applied energy and contains magnets that move the shaft at a predetermined angle.
- Shaft: The portion of the mechanism that the motor is attached to is driven by the shaft’s rotation, which ultimately transforms electrical energy into mechanical energy.
- Stepper motor driver: The motor’s functioning is managed by this part.
However, depending on the type of stepper motor, the composition and principle may differ somewhat. Variable reluctance, permanent magnet, and hybrid are the three varieties. Let us examine their distinctions.
In Wattsan CNC machines, hybrid stepper motors are utilized to guarantee long-term and dependable equipment performance for clients.
Servo motors
What are they?
This motor is synchronous and has feedback. The primary distinction between these two kinds of motors in this situation is as follows: Angular position sensors are found in servo motors. This is a feedback control system, meaning that the controller provides a signal to rectify even the smallest variations in position or speed.
What does that mean?
Functioning principle
It is important to note that mistakes happen when motors are operating. Although these inaccuracies are very small and measured in millimeters, they might become apparent over time. Both servo motors and stepper motors experience this. The feedback mechanism is used in this situation.
For example, after some time, the difference between the position of the motor on the left side of the gantry and the other one on the right might be 2 millimeters. This can affect the result of cutting or milling. However, with servo motors, there is constant monitoring, and if the controller detects deviations, it sends a signal to correct them. The motors then align with each other, returning to a parallel state and eliminating the error. This ensures the proper operation of the equipment.
These motors are necessary for big machinery and applications where accuracy is critical. Wattsan installs them on metal cutters because of this.
Principal differences
What then are the primary distinctions between a servo motor and a stepper motor?
- Accuracy of motion
Servo motors can attain up to 0.002 micrometers of accuracy, but stepper motors can only accomplish up to 0.01 mm. Angular position sensors allow a servo motor to maintain its accuracy even under heavier loads.
- Movement and acceleration speeds
Servo motors are a preferable option if the CNC machine runs at high speeds and decreasing acceleration time is crucial. This is another reason they are installed on metal cutters. For medium speeds, stepper motors work just fine.
Speaking of acceleration, stepper motors can reach 120 rpm, whereas servo motors can go up to 1000 rpm. As a result, the portal can move at speeds of 25 m/min or 60 m/min, respectively.
- Cost
You might wonder — if servo motors are so good, why don’t we use them everywhere? The answer is cost. Following the principle of adequacy, we install servo motors where they are truly needed, so the equipment’s cost isn’t excessively high. Stepper motors are a more affordable yet reliable option for low or medium speeds, which is why they are commonly used in CO2 machines and router CNC machines.
Additionally, it’s worth noting that stepper motors handle emergency stops better than servo motors, which require additional protection in such cases.
Conclusion
A servo motor or stepper motor should be selected based on the equipment’s intended use, cost, and technological viability. Stepper motors are appropriate for CNC machines that handle soft materials and for applications like CO2 machines and some router machines where extreme accuracy is not needed. Servo motors are required for high-precision operations with hard materials, such in metal-cutting machines.
