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What are the application benefits of stepper motors?

time:2014/11/5 11:03:58 click:1486times

Stepper motors are digitally controlled and regulated drives. Their high level of acceptance and prevalence can be attributed to the technology transition from analog to digital technology, the current software solutions and the favorable prices with a very long service life and few control requirements.

a) PC+PLC-capable (directly controllable via PC, PLC and microprocessor).

Through the use of PCs even at the lowest, decentralized machine levels, Plug & Drive motors have achieved the highest levels of productivity growth. Nanotec was the first supplier worldwide to meet the demand for a compact, efficient and cost-effective drive system with an industrial-grade Plug & Drive motor. Not only did these motors drastically reduce the development, wiring and installation effort for a complete drive unit and increase EMC compatibility and machine availability, but they also greatly simplified setup, installation and servicing. Nanotec continuously develops additional features to meet customer-specific requirements. This results in the steady growth of new and close partnerships that ultimately bring forth better and more economical end products.

b) Speed stability

"No drop in speed when the load changes": Stepper motors fulfill this requirement like no other motor without any additional effort. Particularly for precise speed, synchronicity or ratio controls (e.g. in precision dosing pumps), the stepper motor can reach higher and finer resolutions thanks to digital processing. The improved control, process and surface quality is not just a theoretical advantage in this context.

c) Direct drive

Stepper motors have their maximum torque in the lower speed range and the Nanotec microstep drivers still achieve acceptable concentricity properties to approx. 2rpm. Other motors often need gears in order to fulfill the requested speed and force requirements. Direct drives reduce system costs while increasing operating safety and the life span. Naturally, if the space available is limited or the external inertia torques are high, gears will be essential to achieve the necessary power and force.

d) Avoiding injuries and damages to machines

The disadvantage of "falling out of step" when a motor is blocked, which is an issue that is sometimes brought up in connection with stepper motors, can actually be of an advantage in some cases in view of increasingly stringent safety requirements. Slip and overload couplings are not normally required in statutory safety requirements in conjunction with stepper motors.

e) Positioning accuracy

As a result of the small step angle, stepper motors also have, in addition to the lowest over run, the smallest transient response. Even without external linear encoders or angle sensors, stepper motors are excellent at fulfilling speed and positioning tasks. The microstep switching of the Nanotec final output stages can actually further increase precision and resolution at no extra cost. All Nanotec stepper motors are also available with competitively priced encoders for detecting step loss and blockages as well as for closed loop applications.

f) High stiffness without brake

Stepper motors have the highest holding torque when idle and thus offer a high degree of system rigidity. Because of this property, no external braking mechanism is necessary unless safety braking is required for the Z axis. Even for normal stopping, the stepper motor can be advantageous. For example, when a servo motor needs to be stationary, the closed loop control must still operate at full speed. The drive control oscillates around the selected null point with a slight back and forth movement. In most applications, this is of no consequence. However, when positioning a mirror for a metrological task that deflects a laser beam, for example, this oscillation can quickly become disruptive. A stepper motor, on the other hand, would simply move to the required position and remain still.

g) Highly dynamic

Primarily in conjunction with the new dynamic closed loop SMCI motor controller and the PD6 Plug & Drive motors up to a speed of approx. 2000rpm, stepper motors achieve higher dynamics and angular acceleration than servo motors due to the high number of poles, the low rotor mass and the small air gap. This primarily has a favorable effect wherever small distances and movements must be positioned or reserved very quickly while an extremely small settling time or transient response is exhibited, such as is required in semiconductor technology, optics and also in textile machinery and testing equipment.

h) Easy controllability

Drive solutions using stepper motors can be realized very easily and cost-effectively because they can be implemented in an open loop, i.e. without external encoders. In addition to the motor, the power electronics (driver) and an appropriate power supply are required. An external time base (PLC, PC or simple RC oscillator) can take on the speed or position. With a small additional board, the clock could even be specified via an analog input (0–10V, 0–5V or +/-10V) or potentiometer, and hence would be controllable similar to a BLDC motor.

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