Stepper motors enable precise positioning operations, and so they are used when high accuracy is required for demanding positioning tasks. They consist of a stationary stator and a rotor rotating inside it, which is driven by torque generated by differently aligned magnetic fields in the stator and rotor. The rotor always turns in such a way that the greatest possible magnetic flux is created. Stepper motors are primarily used in factory automation, but are also increasingly being used in machine and plant building.
Stepper motors are characterised by a very high torque at a low rotational speed. This enables the application to be both started quickly and – thanks to the high holding torque – to be stopped easily too. The direction of rotation can also be changed quickly and at any time. Other important advantages of stepper motors are the high accuracy they offer during operation and the easy monitoring of the rotor position. In addition, stepper motors do not have brushes, which contributes significantly to the high mechanical resistance of the application.
Basically, there are three different types of stepper motors: the reluctance stepper motor, the permanent magnet stepper motor and the hybrid stepper motor. The latter combines the properties of reluctance and permanent magnet stepper motors and is thus the most efficient of the three versions. Hybrid stepper motors have a stator with stator poles with multiple teeth and a rotor consisting of up to 200 teeth that can move at step angles of 1.8° each. Hybrid stepper motors have a high static and dynamic torque as well as a very high stepping speed and are therefore used in numerous applications, including PC drives and printers. The main application areas for hybrid stepper motors in industry are machine tools and handling machines.
Festo uses hybrid technology in the further development and production of stepper motors. The stepper motor EMMS-ST is part of our Core Range and is ideally suited for simple positioning applications. The EMMS-ST enables a small step width at high driving torques, has optimised connection technology and is available in four sizes with flange dimensions 28, 42, 57 and 87. It is also optionally available with a holding brake.
Stepper motors are very widely used in handling technology, for example in pick and place units, feed mechanisms and stop adjustments, point-to-point positioning over short distances and similar systems. Provided long distances and high speeds are not especially important, they are ideal positioning motors.
The attractive technical features are supplemented by the fact that stepper motors enable very cost-effective drive solutions to be set up. This is primarily due to the very easy commissioning – from the cabling to adjustment of the control parameters.
There are multiple stepper motors, but the three basic types of stepper motors, differing in their construction and function:
• the variable reluctance stepper motor,
• the permanent magnet stepper motor and
• the hybrid stepper motors.
This motor variant is the original principle for stepper motors. The word reluctance refers to "magnetic resistance", "permanent magnet rotor". The rotor consists only of a slotted or toothed soft iron cylinder. Soft iron is magnetically conductive and is thus involved in setting up magnetic fields, but is not a permanent magnet.
No windings are placed in the rotor. This means it has no magnetic field of its own and does not need commutators or collector rings. This makes practically maintenance-free and very cost-effective.
The fixed part is formed by the housing. The coil winding type results in six coils with an iron core, which form the poles or pole pairs (electromagnets). At least 3 pole pairs, i.e. 6 coils, must be installed. A unipolar motor has 6 connections.
The coil windings are parallel to the longitudinal axis along their entire length. The serrations and grooves of the stator correspond to the pitch, size and position of those of the rotor.
To make it rotate, certain coils (or pairs of) need to be alternately activated (voltage) and deactivated with transistors. This results in a stepped rotating magnetic field and it follows this movement. Specifying the rotation direction and speed control of the field determines the rotation direction and motor speed shaft.
These require at least two coil pairs. The rotor consists of a permanent magnet in which the two poles run parallel to the longitudinal axis of the motor shaft and is permantly connected to one side of the supply voltage. To enable high resolution, both are provided with a high number of poles;
The advantage over the reluctance motor lies in the higher torque, because in this case the rotor generates a separate and therefore additional magnetic field.
The hybrid stepper motor combines the advantages of reluctance and permanent magnet stepper motors. At least two coil pairs and permanent magnets, with pole alignment parallel to the motor shaft, and rotor directly opposite stator.
The poles are each fitted with cylinders of soft iron, toothed all around. The teeth of the cylinders at the magnetic poles are spaced half as far apart as the angular distance of the teeth. The front view of the motor thus shows both ring gears, the teeth for the south pole at the front and those for the north pole at the back.
Stepper motors are used:
- Control of positioning tasks in open and closed control loops,
- Tasks with holding torques,
- Precise positioning with medium dynamic response but optimum smooth rotation speed and high running consistency,
- Applications that are built very simply from a control point of view, including the private sphere and many more.
- They are load-independent. Within permissible torque limits, the driven stepper motor rotates at a very constant speed, even with changes in torque, unlike others.
- They can be used in an open control loop. Since the step width of the motor is precisely defined, the position of a drive can be determined by simply counting the steps, allowing one to operate it even without a displacement encoder. This enables economical drive solutions with only drivers.
- Stepper motors have a high holding torque even at rest but under voltage. Bipolar stepper motors are controlled by the rated current. Therefore, they have high holding torque even at rest and remain completely stationary. A product with a holding torque of 50 Ncm can move axes or robots with a load of 10 kg without step loss.
- They can be positioned very precisely. To increase the specified mechanical step resolution of the motor, so-called microstep activation is used. With this, numbers like 0.225° can be achieved and thus a large number of poles.
1. Discrete movement: Stepper motors move in discrete step pulses, rather than rotating continuously like a traditional DC motors. This allows for precise angle and control.
2. High precision: Stepper motors are capable of very precise movements, making them ideal for applications that require precise positioning or repeatability.
3. Easy control: Stepper motors are relatively easy to control, as they can be stopped and started at any position and can be easily reversed.
4. Low maintenance: Stepper motors have few moving parts, which means they require less maintenance than other types of motors.
5. Stepper motors can produce high torque at low speeds, making them suitable for applications that require a lot of power at low speeds.
6. Wide range of sizes: Stepper motors are available in a wide range of sizes, from small motors that can fit in the palm of your hand to larger motors that can power heavy machinery.
By selecting the right one from the various products and placing good stepper motors in the shopping cart, you will be shown price, delivery time and shipping costs to buy easily. Festo only sells to professional customers. Let us know the type of stepper motor you are looking for. Give us your needs: Low speed synchronous rotation, low speed torque, feedback mechanism or detent torque. Would you like a bipolar stepper motor or a unipolar stepper motor? do you also need stepper motor control? We are happy to help you.
Stepper motors EMMS-ST, is used for simple positioning applications with reduced requirements: the durable series of stepper motors work in two-phase hybrid technology
Small increments and high driving torques thanks to 2-phase hybrid technology
• Optimised connection technology
• Four sizes with flange sizes 28, 42, 57 and 87
• 28 types in stock
• With incremental encoder for closed-loop operation
• Degree of protection IP40 (motor shaft), IP54 (sizes 42, 27, 87: motor housing and plug connection), IP65 (size 28: motor housing and plug connection)
• Optionally with holding brake
A stepper motor controller is a device that is used to control the movement of a stepper motor. A stepper motor is a type of electric motor that moves in discrete steps, rather than rotating continuously like traditional DC motors. The controller sends digital input pulses to the motor, causing it to rotate a certain number of steps in a particular direction. Stepper motor controllers can be used in a wide variety of applications, including robotics, 3D printers, and other automated systems.