A servo motor is a conventional motor fitted with an additional control sensor acting as a feedback device. A stepper motor is a brushless motor operated in tandem with an on-board driver.As mentioned above, a servo motor is an ordinary motor equipped with an extra control sensor for feedback purposes. During operation, the controller maintains the motor at a set position. This interconnection principle enables the equipment to achieve speed and precision down to less than 1 micrometer.To lock motion at a position and prevent reverse movement, the controller must continuously switch the motor current to the opposite direction until the next command is received. This method eliminates step loss, as the encoder constantly monitors shaft deviation and corrects errors by reversing the motor direction each time.Disadvantages of Servo MotorsCostly maintenanceHigh upfront costA stepper motor is a brushless motor operated together with an on-board driver. Typically, stepper motors feature multiple phases (windings), which are energized alternately by the driver. The motor rotates when short pulses are applied to one of the stator windings, causing the magnetic rotor to shift position.Stepper motors generally deliver low power and are not suitable for high-speed and continuous rotation.Depending on rotor design, the motor’s physical step angle ranges from 90 degrees to 0.9 degrees. Software algorithms can be utilized to subdivide step angles, reduce driver noise, and improve precision by increasing the number of steps per revolution. Precision can reach 20 micrometers.Despite the high precision of stepper motors, they have a notable drawback: since there is no feedback sent from the motor to the controller, step loss occurs under higher loads, and the controller cannot track the stepper motor’s operating status without an angular sensor.Disadvantages of Stepper MotorsStep loss under high acceleration and heavy loadsDifficult maintenanceEncoder-equipped stepper motors are identical to conventional stepper motors except for the additional wiring for the angular encoder. This solves the problem of step loss but adds substantial cost. Furthermore, a dedicated controller with step error correction functionality is mandatory.Notwithstanding these drawbacks, stepper motors are widely adopted in large-scale industrial and consumer applications:Heavy-duty, high-precision machinery (metal processing, laser cutting)Light-duty CNC equipment (consumer 3D printers, engraving machines)Robotics (robots with complex kinematics)Toys (model cars, model aircraft)Frequently Asked QuestionsWhat similarities exist between stepper motors and servo motors?Stepper motors are used in 3D printers and other equipment requiring precise motion control. Servo motors are deployed in devices that demand smooth motion.The key similarity between stepper motors and servo motors is that both employ electromagnets to generate motion.What advantages do servo motors have over stepper motors?Servo motors can deliver high torque at high speeds. They are also easy to control and can be programmed to execute complex tasks, such as moving robotic arms in three-dimensional space. Servo controllers are less expensive than stepper controllers and have lower power requirements, making them ideal for mobile robots used in automobile manufacturing or warehouse automation.Why choose a stepper motor instead of a servo motor?The primary distinction between stepper motors and servo motors is that stepper motors are usually cheaper. Stepper motors also do not require load feedback to determine the amount of power to be applied to the motor shaft.Which is more powerful: a stepper motor or a servo motor?Stepper motors are less powerful than servo motors due to limited versatility. Servo motors can rotate continuously in any direction, while stepper motors only rotate in discrete steps.Stepper motors have a more intricate internal design yet cost less to manufacture and operate. Servo motors carry a higher price tag and require greater operating power, but they offer superior precision and controllability.
The model number of a stepper motor consists of four segments, representing frame size, motor type (BYG stands for hybrid type, BC for variable-reluctance type), phase number, and rotor tooth quantity respectively.1. Frame SizeAlso known as motor outer diameter. Standard specifications include 28, 42, 57, 86, 110 and 130.2. Motor TypeVariable-Reluctance Stepper MotorThe stator is equipped with windings, and the rotor is made of soft magnetic materials. It features a simple structure and low cost with a small step angle down to 1.2°. However, it suffers from poor dynamic performance, low efficiency, severe heat generation, and insufficient reliability.Permanent Magnet Stepper MotorThe rotor of a permanent magnet stepper motor is made of permanent magnetic materials, and the number of rotor poles equals that of stator poles. It delivers favorable dynamic performance and high output torque, yet has low accuracy and a large step angle (typically 7.5° or 15°).Hybrid Stepper MotorHybrid stepper motors combine the advantages of variable-reluctance and permanent magnet types. The stator carries multi-phase windings, while the rotor adopts permanent magnet materials. Numerous fine teeth are fabricated on both stator and rotor to improve step accuracy. Such motors provide high output torque, excellent dynamic performance and small step angles, but come with a complicated structure and relatively higher cost.3. Phase NumberIt refers to the number of excitation coil pairs that generate alternating N and S magnetic poles, generally denoted by the symbol m.Changzhou Hetai Motor & Electric Appliance Co., Ltd. mainly manufactures hybrid stepper motors and drivers. Feel free to contact us for inquiries.
There are five primary reasons why stepper motors are rarely adopted in industrial robots:Stepper motors operate at low rotational speeds with limited torque, restricting the maximum rated payload at the robot end effector.Stepper motors offer low positioning accuracy and are prone to step loss. The serial-link structure of industrial robots inherently generates cumulative errors. Using stepper motors further degrades absolute accuracy to a level inadequate for most industrial applications.Speed regulation of stepper motors relies on pulse frequency. They exhibit poor low-speed response and are susceptible to stall.High operational noise.Stepper motors cannot implement closed-loop position sensing. The controller lacks real-time position feedback for each robot joint, which means homing calibration is mandatory every time the system powers on.Nevertheless, stepper motors have their merit: low cost. The total cost can be further reduced when reducers are not required. Therefore, they are well suited for applications with relaxed requirements on accuracy, payload and noise.
Planetary gearboxes are widely used speed reduction devices. Featuring high precision, they are primarily adopted to reduce rotational speed, boost torque and lower the load-to-motor inertia ratio while ensuring precision power transmission. Planetary gearboxes are also known as servo reducers or servo planetary gearboxes.A planetary reducer serves as a power transmission mechanism. It utilizes gear speed conversion to reduce the motor rotational speed to the target value while generating higher torque. The small gear with fewer teeth on the drive shaft meshes with the large gear on the output shaft to achieve speed reduction. Conventional reducers also employ several pairs of gears working on the same meshing principle to obtain ideal reduction effects. The gear ratio equals the tooth count ratio of the large and small gears.Planetary gearboxes adopt involute planetary gear transmission, which makes rational use of internal and external meshing as well as power split. The housing is made of ductile iron, greatly enhancing housing rigidity and shock resistance. All gears undergo carburizing and quenching to form hard, wear-resistant surfaces. Every gear is precision ground after heat treatment to lower noise and improve overall efficiency and service life. Two-stage and three-stage planetary transmission configurations are the most commonly adopted types.The main transmission components of a planetary gearbox include planetary gears, sun gear, ring gear, driving motor and transmission shaft.Visually, a planetary gearbox can be divided into three sections: input section, reduction section and output section.Input Section: The end connected to the motor, consisting of input bore and input flange.Reduction Section: The core part of the reducer. It appears as a housing from the outside, while internally housing key components such as planetary gears, sun gear and ring gear.Output Section: The end connected to equipment, comprising output shaft and output flange.Advantages of Planetary Gearbox TransmissionThey feature compact size, light weight, high load capacity, long service life, stable operation, low noise, large output torque, wide speed ratio range, high efficiency and reliable performance. They possess unique characteristics of power split and multi-tooth meshing. The transmission efficiency of planetary gearboxes is generally above 90%, and can reach over 95%, supporting extensive application scenarios.Applications of Planetary GearboxesPlanetary gearboxes are widely used in spring machinery, manipulators, textile machinery, machine tools, precision processing machine tools, aerospace industry, smart home equipment, automobile manufacturing, shipbuilding industry, semiconductor equipment, printing machinery, food packaging equipment, automation industry, industrial robots, medical inspection equipment, precision testing instruments and other high-precision automated mechatronic industries.Visit Holtek Motor planetary gearbox catalog >> Planetary Gearbox
Brushed DC MotorsAdvantages: Low cost, simple control, low noise.Disadvantages: Relatively short service life; brushes require regular replacement. Performance is greatly affected by variations in load and supply voltage, resulting in poor transmission stability. Slow startup speed; incapable of rapid, successive start-stop operations. Unstable low-speed operation accompanied by creep.Brushless DC Motors (BLDC)Advantages: Brushless construction delivers substantially longer service life than brushed motors; low noise and constant torque output.Disadvantages: Dedicated control circuitry is required for driving. Operation is sensitive to fluctuations in load and supply voltage. Closed-loop control can be implemented, yet overall stability remains limited. Unstable low-speed performance with creep phenomenon.AC MotorsAdvantages: Low cost, low noise, long service life.Disadvantages: Low starting torque; difficult speed regulation. Operation is heavily influenced by load and supply voltage variations. Unstable low-speed running and creep occur.Stepper MotorsAdvantages: Speed is regulated by pulse signals, maintaining outstanding stability at both low and high speeds, unaffected by voltage and load fluctuations. Long service life and high positioning accuracy.Disadvantages: Higher noise level compared with other motor types. Resonance occurs at specific speeds depending on motor characteristics. A dedicated drive circuit is necessary. Low energy efficiency; under equal power rating, it produces lower torque at high speeds than other motors.
Advantages of Linear Stepper Motors (Compared with Conventional Rotary Stepper Motors)(1) Fast Dynamic ResponseGenerally speaking, the dynamic response time of mechanical transmission components is several orders of magnitude longer than that of electrical components. By eliminating mechanical transmission parts with large time constants such as lead screws in the system, the dynamic response performance of the entire closed-loop control system is greatly improved, delivering extremely sensitive and rapid reaction.(2) High PrecisionThe removal of mechanical transmission mechanisms including lead screws reduces tracking errors caused by transmission system hysteresis during interpolation. Closed-loop control via linear position detection feedback can significantly enhance the positioning accuracy of machine tools.(3) High Transmission Stiffness and Stable ThrustDirect drive technology improves transmission stiffness. Meanwhile, the layout of linear stepper motors can be arranged according to the surface structure of machine tool guideways and the stress conditions of worktables during motion. Symmetric uniform arrangement is commonly adopted to achieve steady driving thrust.(4) High Speed and Short Acceleration / Deceleration CyclesLinear stepper motors were firstly applied to maglev trains (with a top speed of 500 km/h). When deployed for machine tool feed drives, they easily satisfy the maximum feed speed requirements for ultra-high-speed cutting (60～100 m/min or higher). Benefiting from the fast response of zero-transmission architecture, acceleration and deceleration phases are drastically shortened. The motor can instantly reach high speed upon startup and come to an accurate halt rapidly during high-speed operation. Its acceleration can normally reach 2～10 g (g=9.8 m/s²).(5) Unlimited Travel StrokeThe travel range of the mover can be extended infinitely by connecting multiple stators of linear stepper motors in series on the guide rails.(6) Low Operating NoiseMechanical friction from transmission components such as lead screws is eliminated. Furthermore, rolling guideways or magnetic levitation guideways (non-contact structure) can be adopted for the guideway pairs, which substantially reduces operating noise.(7) High EfficiencyWithout intermediate transmission links, energy loss generated by mechanical friction is eliminated.In-depth Analysis: Operating Principle of Linear Stepper MotorsApplication Fields of Linear Stepper MotorsLinear stepper motors are widely adopted in numerous fields demanding high precision, including manufacturing, precision calibration, precision fluid measurement, accurate position displacement and other scenarios.
Nowadays, stepper motors are being adopted in an increasingly wide range of fields and are commonly used in machinery, electronics, textile and other industries. A brief introduction is given as follows:Stepper motors are mainly applied in scenarios requiring positioning control.Examples include worktable driving for wire electrical discharge machining (WEDM), worktables of flocking machines (pore positioning), and packaging machines (fixed-length feeding). They can be utilized in basically all applications involving positioning.They are widely used in ATMs, inkjet plotters, engraving machines, photo printers, spraying equipment, medical instruments and devices, computer peripherals and mass storage equipment, precision instruments, industrial control systems, office automation equipment, robots and other fields.They are especially suitable for applications that demand smooth operation, low noise, fast response, long service life and high output torque.Stepper motors enjoy extensive utilization in textile machinery such as computerized embroidery machines. Stepper motors for such equipment feature low holding torque, rapid response during frequent startup, low operating noise, stable running, favorable control performance and low overall equipment cost.At present, most stepper motors deployed in computerized embroidery machines are 5-phase hybrid stepper motors. Adopting high-phase-count stepper motors aims to reduce the step angle and enhance control accuracy. Nevertheless, the performance improvement achieved through this method is limited, accompanied by relatively high costs. The adoption of microstepping drive technology can greatly optimize the operating performance of stepper motors, reduce torque ripple, suppress oscillation, lower noise and improve step resolution. If reactive stepper motors are adopted, the product cost can be substantially cut while achieving remarkable performance enhancement.
As a digital actuator, stepper motors are widely adopted in motion control systems. Many users notice considerable heat generation during stepper motor operation and wonder whether such phenomenon is normal. In fact, heating is common for stepper motors. However, what temperature range is regarded as acceptable, and how can heat generation be minimized?First, let us analyze the causes of heat generation in stepper motors.All types of stepper motors consist of iron cores and winding coils. Windings possess resistance and produce power loss when energized. The loss is proportional to resistance and the square of current, commonly known as copper loss. If the current waveform is not standard DC or sine wave, harmonic loss will also occur. The iron core generates loss due to hysteresis and eddy current effects under alternating magnetic fields. Such loss, termed iron loss, is related to material properties, current, frequency and voltage. Both copper loss and iron loss manifest in the form of heat and reduce motor efficiency. Stepper motors are generally designed for positioning accuracy and torque output, resulting in relatively low efficiency, high operating current and abundant harmonic components. In addition, the alternating frequency of current varies with rotational speed. Consequently, stepper motors routinely generate significant heat, more severely than ordinary AC motors.Second, controlling stepper motor temperature within a reasonable range.The permissible operating temperature mainly depends on the motor’s internal insulation class. Internal insulation will degrade only at temperatures above 130°C. Therefore, the motor will not suffer damage as long as its internal temperature stays below 130°C, corresponding to a surface temperature lower than 90°C. In practice, a surface temperature of 70–80°C is normal for stepper motors.Temperature can be measured with a point thermometer, or roughly judged by touch:If the surface can be touched by hand for 1–2 seconds or longer, the temperature is below 60°C;If only momentary contact is tolerable, the temperature is approximately 70–80°C;If water droplets vaporize instantly upon contact, the temperature exceeds 90°C.A thermal gun can also be used for accurate measurement.Third, variation of heat generation with rotational speed.When constant-current driving technology is applied, the current remains relatively constant at standstill and low speeds to maintain constant torque output. Once the speed rises above a certain threshold, the back EMF inside the motor increases, causing gradual reduction of current and torque. Hence, heat generated from copper loss varies with speed: heat is normally higher at standstill and low speeds, and lower at high speeds. Nevertheless, the variation of iron loss (which accounts for a smaller proportion) follows a different trend. Since total heat generation equals the sum of copper loss and iron loss, the above rule only serves as a general reference.Fourth, impacts of motor heating.Moderate heating generally does not shorten motor service life and can be ignored for most applications. Nevertheless, excessive heating may trigger adverse effects. Different thermal expansion coefficients of internal components lead to changes in structural stress and tiny variations of internal air gap, which degrade dynamic response and easily cause step loss at high speeds. Furthermore, some applications prohibit excessive motor heating, such as medical equipment and high-precision testing instruments. Thus, necessary measures should be taken to control motor temperature.Finally, methods to reduce motor heat generation.Reducing heat generation means lowering copper loss and iron loss.There are two approaches to cut copper loss: reducing resistance and operating current. During motor selection, preference should be given to motors with low resistance and low rated current. For two-phase stepper motors, series connection is preferred over parallel connection where applicable. However, this often conflicts with torque and high-speed performance requirements.For already selected motors, users should make full use of the driver’s automatic half-current control function and de-energization function. The former automatically reduces current when the motor is stationary, while the latter completely cuts off winding current. Moreover, microstep drivers produce less motor heat because their current waveform approximates a sine wave with fewer harmonics.Few solutions are available to reduce iron loss, which is related to drive voltage level. Although high-voltage driving improves high-speed performance, it also increases heat generation. Accordingly, an appropriate drive voltage grade shall be selected to balance high-speed performance, running smoothness, heat generation, noise and other indicators.
Stepper motors have undemanding power supply requirements and do not require voltage regulation. A transformer with a similar voltage rating, after rectification and filtering, is sufficient as long as the current requirement can be met.Switching power supplies are not recommended for stepper motors. This is because switching power supplies feature peak current protection, while stepper drives frequently generate peak currents. In addition, power supply solutions consisting of a transformer plus rectifier circuitry offer higher reliability than switching power supplies.Components of the Stepper Motor Driver Control SystemTypically, a stepper motor drive system consists of three parts: control circuit, drive circuit and stepper motor. Their main functions are described as follows:① Control Circuit: Generates pulses to control the speed and rotation direction of the motor.② Drive Circuit: This is the research subject of this paper. It comprises pulse signal distribution circuitry and power drive circuitry as shown in Figure 1. In accordance with pulse and direction signals input from the controller, it supplies power to each winding of the stepper motor in the correct sequence, and provides the high voltage and large current required by the motor. Meanwhile, it implements multiple protection functions including overcurrent protection and overheating protection.③ Stepper Motor: Driven by control signals amplified by the driver, the stepper motor drives the connected load.
Servo motors are generally categorized into stepper motors, brushed DC servo motors, brushless DC servo motors, and AC servo motors. With continuous technological advances, many special servo motors have emerged, such as piezoelectric ceramic motors, linear motors and voice coil motors. This article mainly discusses the selection of servo motors in the conventional sense.The choice of servo motor largely depends on the physical characteristics of the load, load operating characteristics, system requirements and working environment. Once the system requirements are confirmed, regardless of the type of servo motor selected, the first consideration is to determine the appropriate motor size, which mainly relies on the physical properties of the load including load torque and inertia. For servo motors, size is usually measured by torque or force. Therefore, motor selection starts with calculating the load torque or force reflected to the motor shaft. A safety margin must be reserved after torque calculation; generally, the continuous torque of the selected motor shall be no less than 1.3 times the load torque to ensure reliable motor operation. In addition, the load inertia reflected to the shaft must be calculated. As a general guideline, the ratio of load inertia to motor rotor inertia should be less than 5:1 to guarantee fast response of the servo system. If inertia and torque mismatch exists between the motor and the load, the only solution is to sacrifice speed and install a reducer between the motor and load, which requires comprehensive trade-offs.After determining the required motor torque, it is necessary to analyze the load operating characteristics and working environment. Load operating characteristics cover operating speed (high or low), required acceleration, demand for frequent start-stop cycles, cycling frequency, system motion accuracy and other parameters. There are no fixed rules for servo motor selection at this stage. The core principle is that the selected motor must satisfy the motion requirements of the load.For instance, stepper motors serve as an ideal option for systems with low precision requirements, operating speeds ranging from several revolutions up to 500 rpm (higher than 1 rpm), and no demand for frequent start-stop operations. This is because stepper motors adopt open-loop control with limited positioning accuracy. Their torque drops drastically at excessively high speeds, resulting in insufficient driving capacity for loads, while low speeds may trigger discontinuous rotational crawling. Furthermore, stepper motors feature slow response and are unsuitable for applications requiring frequent start-ups.DC or AC servo motors are preferred for applications with speeds from several revolutions to under 3000 rpm and relatively high control accuracy. In most cases, AC servo motors exhibit inferior low-speed performance compared with DC servo motors. For loads running at low speeds, DC servo motors are recommended. Nevertheless, brushed DC motors generate commutating sparks via brush commutation, making them inapplicable in vacuum, explosion-proof, underwater and similar environments. Moreover, such sparks cause thermal expansion of the motor shaft and connected components, disqualifying brushed DC motors from high-precision systems.Permanent magnet synchronous AC servo motors are widely adopted in industrial applications. Thanks to their constant-torque characteristic below rated speed, they are extensively used in scenarios with constant or slightly fluctuating load torque, such as machine tool feed systems. Motor selection is relative: either AC or DC servo motors can be viable for the same application, and the final decision sometimes hinges on environmental conditions. For certain robotics projects where AC power supply is difficult to access, DC servo motors become the only feasible solution.Conventional servo motors struggle to meet the demands of many special working conditions. For example, ultra-low-speed stable operation (in some cases as low as several revolutions per year) cannot be achieved by standard servo motors, and torque motors are required instead. For applications demanding frequent start-stops, rapid response and high acceleration, ordinary servo motors are inadequate. The frequent start-stop frequency of loaded standard AC servo motors generally does not exceed 5 Hz, whereas linear motors deliver superior performance, capable of achieving acceleration up to 30G and start-stop frequencies reaching 20 Hz.The fundamental rule of motor selection is to fully understand load characteristics, working environment and motor performance attributes — only in this way can a suitable servo motor be chosen.
Functional Module DesignThis module consists of the following three parts:Single-chip microcomputer system: Controls the stepper motor;Peripheral circuit: Interface circuit between the PIC single-chip microcomputer and the stepper motor;PIC program: Develops the interface program for the single-chip microcomputer to control the stepper motor and realizes the output of triangular wave signals.(1) Interface between Stepper Motor and Single-chip MicrocomputerThe single-chip microcomputer is a high-performance control processor. When controlling a stepper motor, the interface device must fulfill the following functions:① Voltage isolationThe single-chip microcomputer operates at 5 V, while the stepper motor works at several tens of volts or even higher. If high voltage from the stepper motor leaks into the single-chip microcomputer, the chip will be damaged. In addition, signals from the stepper motor may interfere with the single-chip microcomputer and cause system malfunctions. Therefore, the interface device must provide isolation.② Signal transmissionThe interface device shall transmit control commands from the single-chip microcomputer to the stepper motor circuit and generate required control signals. Corresponding control waveforms shall be produced for different operation modes.③ Generation of variable frequenciesTo drive the stepper motor at different speeds for various application requirements, the interface device needs to generate working signals of different frequencies.(2) Voltage Isolation InterfaceThe voltage isolation interface is specially used to isolate the low-voltage single-chip microcomputer section and the high-voltage stepper motor drive circuit to ensure stable operation of both sides.Pulse transformers or optocouplers can be adopted for voltage isolation, and optocouplers are the mainstream choice at present. Output signals from the single-chip microcomputer can pass through TTL gates or be directly sent to the base of transistors, which then drive the light-emitting diodes inside optocouplers.Light emitted by the light-emitting diode irradiates the photosensitive transistor inside the optocoupler and is converted into an electrical signal to drive the power amplification circuit of the stepper motor. The current amplification interface serves as the preamplifier of the stepper motor power amplifier circuit. It amplifies the output current of the optocoupler to supply sufficient driving current for the power amplifier circuit.(3) Operation Mode Interface and Frequency GeneratorWhen a single-chip microcomputer is used to control a stepper motor, three I/O lines on the input and output interface are required. In this scheme, RA0, RA1 and RA2 of the microcontroller I/O port control the three phases of the stepper motor.Stepper motor control is generally divided into open-loop control and closed-loop control. Among them, open-loop control is the simplest scheme. Under open-loop control, the input of control pulses for the stepper motor is independent of the rotor position; pulses are generated according to fixed rules, and the stepper motor runs relying on this set of predetermined pulses. Thanks to the inherent characteristics of stepper motors, this control method is widely applicable.Its prominent features include simple control logic, easy implementation and low cost. One key characteristic of open-loop control is that no feedback of load position is sent back to the control circuit.Consequently, the stepper motor must respond accurately to every excitation change. If the excitation frequency is excessively high and the motor fails to move to the target position, a position error between the actual load position and the target position will occur. When the load remains relatively constant, generating control pulse sequences is straightforward. However, under conditions with large load variations, it is difficult to optimize the pulse sequence, which may lead to step loss. With the widespread application of microcomputers, microcontrollers can generate relatively complex control pulse sequences for stepper motors.
Failures of the stepper motor itself are generally manifested as burnout of one or multiple phase windings (coil short circuit or open circuit). This type of fault can be diagnosed by measuring the DC resistance of the motor coils with a multimeter and comparing the readings with those of intact coils. (In most cases, not all motor coils burn out simultaneously; at least one or several groups remain functional.)For motors assembled with screws, the housing can be disassembled directly using screwdrivers and pliers. If the housing is welded, carefully take it apart with a file or hacksaw. Avoid prying forcibly to prevent deformation.After disassembly, the internal structure of the motor can be inspected. If one or two phase coils are burnt out but the coil bobbin remains undeformed, new windings can be wound manually according to the original wire gauge and turns.(When removing burnt coils, count the number of turns accurately and measure the wire diameter of the removed enameled wire with a micrometer. Since the insulation coating thickness differs between imported and domestic enameled wires, burn off the insulating varnish with a gas lighter before measurement. The same measuring method applies to replacement wires.)If the bobbin is deformed, it must be replaced. If a matching bobbin cannot be obtained, a similar bobbin can be modified. Alternatively, a new bobbin can be fabricated from high-temperature resistant flame-retardant insulating materials and bonded to replicate the original shape.After winding, reassemble the components carefully. Rotate the motor shaft by hand; the assembly qualifies if there is no obvious jamming.It should be noted that if a stepper motor fails, the corresponding stepper motor drive circuit must also be inspected for damage before replacing the motor.
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