1. How to choose between stepper and servo motors ?
It mainly depends on the specific application. Simply put, you need to determine: the nature of the load (e.g., horizontal or vertical load), torque, inertia, speed, accuracy, acceleration/deceleration requirements, higher-level control requirements (e.g., port interface and communication requirements), and the primary control method (position, torque, or speed control). Also, determine whether the power supply is DC, AC, or battery-powered, and the voltage range. Based on this, determine the model of the motor and the corresponding driver or controller.
2. Should I choose a stepper motor or a servo motor system?
In fact, the choice of motor should be based on the specific application, as each type has its own characteristics.
3. How to use a stepper motor driver?
Choose a driver with a current greater than or equal to that of the motor. For applications requiring low vibration or high precision, a microstepping driver can be used. For high-torque motors, use a high-voltage driver whenever possible to achieve good high-speed performance.
4. What are the differences between 2-phase and 5-phase stepper motors, and how do you choose between them?
Two-phase motors are inexpensive, but they vibrate more at low speeds and their torque drops rapidly at high speeds. Five-phase motors, on the other hand, vibrate less, have better high-speed performance, and are 30-50% faster than two-phase motors, making them a viable alternative to servo motors in some applications.
5. When should a DC servo system be selected, and what are the differences between it and an AC servo system?
DC servo motors are divided into brushed and brushless motors. Brushed motors are low-cost, simple in structure, have high starting torque, wide speed range, and are easy to control. They require maintenance, but maintenance is convenient (replacing carbon brushes). They generate electromagnetic interference and are subject to environmental requirements. Therefore, they are suitable for cost-sensitive general industrial and civilian applications. Brushless motors are small in size, light in weight, have high output, fast response, high speed, low inertia, smooth rotation, and stable torque. Control is complex but easily achieved through intelligent systems. Their electronic commutation is flexible, allowing for square wave or sine wave commutation. These motors are maintenance-free, highly efficient, operate at low temperatures, have minimal electromagnetic radiation, and have a long lifespan, making them suitable for various environments. AC servo motors are also brushless motors, divided into synchronous and asynchronous motors. Currently, synchronous motors are generally used in motion control due to their wide power range, allowing for very high power outputs. They have high inertia, a low maximum speed that decreases rapidly with increasing power, and are therefore suitable for low-speed, stable operation applications.
6. What precautions should be taken when using a motor?
Before powering on, perform the following checks: 1) Ensure the power supply voltage is appropriate (overvoltage may damage the drive module); the +/- polarity of the DC input must be correct; check the motor model or current setting on the drive controller for suitability (do not set it too high initially); 2) Ensure the control signal lines are securely connected; in industrial environments, shielding should be considered (e.g., using twisted-pair cables); 3) Do not connect all necessary wires at the beginning; only connect the most basic system. After it runs smoothly, gradually connect the others. 4) Be sure to understand the grounding method, whether to use a floating ground or no grounding. 5) Closely observe the motor's status for the first half hour of operation, such as whether the movement is normal, the sound, and the temperature rise. If any problems are found, stop the machine immediately for adjustment.
7. When the stepper motor starts running, sometimes it moves briefly and then stops, or it moves back and forth in place. Sometimes it also loses steps during operation. What is the problem?
The following aspects should generally be considered during inspection: 1) Whether the motor torque is large enough to drive the load. Therefore, we generally recommend that users select a motor with a torque 50% to 100% greater than the actual requirement, because stepper motors cannot be overloaded, even momentarily, which will cause loss of steps, and in severe cases, stop or irregularly move repeatedly in place. 2) Whether the current of the input step pulse from the upper controller is large enough (generally >10mA) to ensure stable conduction of the optocoupler. Whether the input frequency is too high, resulting in no reception. If the output circuit of the upper controller is a CMOS circuit, a CMOS input type driver should also be selected. 3) Whether the starting frequency is too high. Whether an acceleration process is set in the starting program. It is best to accelerate from the motor's specified starting frequency to the set frequency, even if the acceleration time is very short, otherwise it may be unstable or even in an idle state. 4) This situation sometimes occurs when the motor is not properly fixed, which is normal. This is because it actually causes strong resonance in the motor, leading to loss of steps. The motor must be properly fixed. 5) For 5-phase motors, if the phases are connected incorrectly, the motor will not work.
8. I want to control the servo motor directly via communication. Is that possible?
Yes, it's possible and relatively convenient, but there's a speed issue. It's suitable for applications where response speed isn't critical. If rapid response to control parameters is required, a servo motion control card is best. These cards typically have a DSP and high-speed logic processing circuitry to achieve high-speed, high-precision motion control, such as S-curve acceleration and multi-axis interpolation.
9. Is it good to use a switching power supply to power stepper and DC motor systems?
Generally, it's best to avoid this, especially for high-torque motors, unless a switching power supply with more than twice the required power is used. This is because motors operate as large inductive loads, creating instantaneous high voltage at the power supply terminals. Switching power supplies have poor overload performance and will shut down under protection, and their precise voltage regulation is unnecessary, potentially damaging both the power supply and the driver. A conventional DC power supply with a toroidal or R-type transformer can be used instead.
10. I want to use ±10V or 4~20mA DC voltage to control the stepper motor, is that possible?
Yes, but an additional conversion module is required.
11. I have a servo motor with encoder feedback. Can it be controlled by a servo driver with only a tachometer port?
Yes, but you'll need an encoder-to-tachometer signal module.
12. Can the encoder part of the servo motor be disassembled?
Do not disassemble, as the quartz plates inside the code disk are easily broken, and once dust gets inside, the lifespan and accuracy will not be guaranteed, requiring professional inspection.
13. Can stepper and servo motors be disassembled for inspection or modification?
No, it's best to have the manufacturer do it. Without specialized equipment, it's very difficult to reassemble it after disassembly, and the clearance between the motor's rotor and stator cannot be guaranteed. The performance of the magnets will be damaged, potentially causing demagnetization, and the motor torque will decrease significantly.
14. Can the servo controller sense changes in external load?
If you encounter set resistance, stop, return, or maintain a certain amount of thrust to continue.
15. Can domestically produced drives or motors be used in conjunction with high-quality foreign motors or drives?
In principle, it's possible, but you must understand the motor's technical parameters before using it. Otherwise, it will greatly reduce the expected performance and may even affect long-term operation and lifespan. It's best to consult with the supplier before making a decision.
16. Is it safe to drive a motor using a DC power supply voltage greater than the rated voltage?
Normally this isn't a problem, as long as the motor operates within its set speed and current limits. Because motor speed is proportional to its line voltage, choosing a specific power supply voltage won't cause overspeed, but it might lead to driver malfunctions.
Furthermore, it is essential to ensure that the motor meets the minimum inductance requirements of the driver, and that the set current limit is less than or equal to the motor's rated current. In fact, if you can run the motor at a relatively slow speed (below the rated voltage) in your designed device, this is beneficial. Operating at a lower voltage (and therefore a lower speed) results in less brush bounce, less brush/commutator wear, lower current consumption, and a longer motor lifespan. On the other hand, if the motor size and performance requirements necessitate additional torque and speed, overdriving the motor is possible, but this will sacrifice product lifespan.
17. How do I choose the appropriate power supply for my application?
It is recommended to choose a power supply voltage 10%-50% higher than the maximum required voltage. This percentage varies depending on Kt, Ke, and the voltage drop within the system. The driver's current should be sufficient to deliver the energy required by the application. Remember that the driver's output voltage differs from the supply voltage, therefore the driver's output current also differs from the input current. To determine the appropriate supply current, calculate all the power requirements of the application, then add 5%. The required current can be calculated using the formula I=P/V.
18. What operating mode can I choose for a servo drive?
Different modes are not all present in all drive models.
19. How are the driver and system grounded?
a . Do not connect the non-isolated port of the DC bus or the ground of non-isolated signals to earth if there is no isolation between the AC power supply and the DC bus of the driver (such as a transformer). This may result in equipment damage and personal injury. Because the AC common voltage is not grounded, there may be a very high voltage between the DC bus ground and earth.
b . In most servo systems, all common ground and earth ground are connected together at the signal end. Ground loops created by multiple earth ground connection methods are easily affected by noise and can generate current at different reference points.
c . To maintain a constant command reference voltage, the driver's signal ground should be connected to the controller's signal ground. It should also be connected to the ground of an external power supply, which will affect the operation of both the controller and the driver (e.g., the encoder's 5V power supply).
d . Grounding the shielding layer is relatively difficult and there are several methods. The correct grounding point for the shielding is at a reference potential point inside its circuitry. This point depends on whether the noise source and receiver are grounded simultaneously or floating. It is essential to ensure that the shielding layer is grounded at the same point so that ground current does not flow through the shielding layer.
20. Why can't the reducer be matched with the motor at the standard torque point?
If we consider the maximum continuous torque generated by the motor after passing through the reducer, many reduction ratios will far exceed the torque rating of the reducer. If we were to design each reducer to match full torque, there would be too many combinations of internal gears (larger size, more material). This would increase the product price and violate the principle of "high performance, small size".
21. How do I choose between using a planetary gear reducer or a spur gear reducer?
Planetary gear reducers are generally used when high torque is required in a limited space, i.e., small size and high torque, and their reliability and lifespan are better than spur gear reducers. Spur gear reducers are used for applications with lower current consumption, lower noise, and higher efficiency at lower cost.
22. What is duty cycle?
Duty cycle refers to the ratio of the working time of a motor to (working time + non-working time) within each duty cycle. A low duty cycle allows the motor to operate at three times the continuous current for a short period, thus generating more power than when running at its rated continuous operating speed.
23. Can the drive circuit of a standard rotary motor be used for a linear motor?
Generally, yes, that's fine. You can think of a linear motor as a rotary motor, such as a linear stepper motor, brushed, brushless, and AC linear motor. Please consult your supplier for specific details.
24. Can a linear motor be installed vertically to make up-down movements?
Yes. Depending on the user's requirements, we can add a mover slider balancing device or a guide rail brake for vertical installation.
25. Can multiple actuators be installed on the same platform?
Yes, it's possible. As long as the movers don't interfere with each other.
26. Is it possible to install the mover coils of multiple brushless motors on the same magnetic track?
Yes, it's possible. As long as the movers don't interfere with each other.
27. What are the advantages of using a linear motor over a ball screw linear motor?
Because there is no mechanical connection between the stator and the mover, backlash, wear, and jamming problems are eliminated, resulting in smoother motion. This leads to higher precision, higher speed, higher acceleration, faster response, smoother motion, higher control accuracy, better reliability, compact size, low profile, long lifespan, and maintenance-free operation.
Another suggestion for users is that, unless absolutely necessary, avoid simultaneously demanding high levels of the three main parameters: push-pull force or load capacity, speed, and positioning accuracy. This is because an actuator is a high-precision, high-tech mechatronic product. During design and manufacturing, we need to consider various aspects such as mechanical structure, electrical performance, material properties, materials, and processing methods, and select appropriate component motors, drive controllers, feedback devices, as well as guide rails, lead screws, support bases, and other mechanical systems of different precision levels to achieve the required overall motion parameters. It's a product where a single change affects the entire system. Of course, if you have high-requirement products, we can still meet your needs, but the cost will increase accordingly.
