Besides load torque, acceleration torque, speed, and load inertia, failing to account for specific sizing parameters during the motor sizing process can significantly impact the performance and longevity of your machine.
A motor’s operational capabilities are primarily described by its torque-speed curve, indicating whether it can handle the required task. Meanwhile, the structural integrity of a motor is determined by its ability to withstand radial and axial loads, which define how long it can operate effectively. Radial and axial loads are influenced by the mechanical rigidity of the motor’s casing, flange brackets, output shaft, and bearings, especially those nearest to the load.
To better understand this, let’s examine the internal structure of an AC motor and its accompanying gearhead. The same principles apply to other types of motors as well.
| Internal Structure of an AC Motor and Gearhead |
|-----------------------------------------------|
| [Image of AC motor structure] |
| Description: The motor’s only moving part is the rotor and shaft, supported by ball bearings at both ends. Surrounding the rotor is the stator, followed by the motor case and flange bracket. All components work together to support the motor’s rated load. |
| Internal Structure of a Gearhead |
|---------------------------------------------|
| [Image of gearhead structure] |
| Description: In a gearhead connected to the motor’s pinion shaft, each gear and output shaft has its own bearing. The input shaft is still supported by the motor bearing. The largest bearing supports the gear shaft and the associated load. The gear flange and case complete the assembly.
Radial load, or overhung load, refers to the maximum force that can be applied to the shaft in a direction perpendicular to its axis. Axial load, or thrust load, is the force applied along the axis of the shaft. Both loads can act in various directions.
For instance, if a motor has a 100 N axial load specification, it means it can support a 100 N load (equivalent to approximately 10 kg) hanging from its shaft or bear the same weight pushing upward.
| Illustration of Radial and Axial Loads |
|-------------------------------------------|
| [Image of motor with radial and axial loads] |
| Caption: This diagram shows the forces acting on a motor shaft and gearhead.
Exceeding the permissible radial or axial load can lead to severe consequences, such as bending or breaking of the shaft or failure of the bearings. Such failures can result in costly downtime or reduced motor lifespan.
| Consequences of Excessive Radial/Axial Loads |
|----------------------------------------------|
| [Image of motor damage] |
| Caption: Excessive loads can cause damage to bearings or the output shaft, leading to system failure.
Here’s a simple tip to check for internal damage: Disassemble the motor or gearhead, disconnect the power, and manually rotate the shaft in both directions. If there’s uneven resistance, abnormal noise, or the shaft won’t turn, it indicates possible damage.
The lifespan of a motor is directly affected by how much these specifications are exceeded. For instance, if the permissible load is exceeded by 10%, the motor’s lifespan might decrease by around 1,000 hours. If you’re interested in a detailed service life estimation, our technical support team can assist you.
Manufacturers often present these specifications in tables, listing permissible radial and axial loads based on gearhead size and gear ratio. While the permissible axial load remains constant, the permissible radial load depends on the distance from the end of the gearhead output shaft.
| Example Table of Permissible Loads |
|--------------------------------------------|
| [Image of load table] |
| Caption: This table shows permissible radial and axial loads for common geared AC motors.
Understanding the "fulcrum effect" is essential for managing radial loads. As the load gets closer to the support bearing, more weight can be supported, similar to a seesaw.
| The Fulcrum Effect Explained |
|--------------------------------------------|
| [Image of seesaw] |
| Caption: The closer the load is to the support bearing, the greater the permissible load.
Static and dynamic loads must also be considered. Static loads include forces like belt tension at rest, while dynamic loads require calculations based on forces during operation. Similarly, static axial loads are straightforward, whereas dynamic axial loads are often less significant and can be ignored.
| Tip: Always Consider Belt Tension |
|--------------------------------------------|
| Remember to include belt tension as radial force. Neglecting this can lead to unnecessary motor issues.
To ensure proper handling of radial and axial loads, verify that:
- The static radial load is within limits.
- The dynamic radial load is within limits.
- The static axial load is within limits.
The formula for calculating dynamic radial load is:
\[ W = \frac{T}{y} \]
Where \( T \) is the torque (N·m) and \( y \) is the effective radius (m). Additional factors like load coefficients and service factors must also be considered.
Let’s walk through an example: Suppose you’re designing a conveyor system using a 2IK6 motor with a 360:1 gearhead. You need 10 N·m of torque on a 0.1 m diameter sprocket with an estimated chain tension of 10 N. The sprocket is mounted 10 mm from the end of the shaft.
First, check the permissible loads from the manufacturer’s table:
| Permissible Loads Table |
|---------------------------------------------|
| [Image of load table] |
- **Static Radial Load**: The belt tension is 10 N, which is below the permissible 200 N limit.
- **Dynamic Radial Load**: Using the formula:
\[ W = \frac{10 \times 1 \times 1}{0.1} = 100 \, \text{N} \]
This is also within the permissible limit of 200 N.
- **Static Axial Load**: Assuming no significant axial load, this condition is satisfied.
**Conclusion**: The 2IK6 motor with the 360:1 gearhead can handle the specified radial and axial loads.
Most motor-sizing software overlooks these considerations, so manual verification is essential. If you find the process overwhelming, our experts are here to help. Use our motor-sizing calculator to generate reports and consult with our engineers to ensure the right motor selection.
For more tips on motor selection and tools to simplify the process, stay tuned for future posts.
| Helpful Resources |
|--------------------------------------------|
| [Image of motor selection guide] |
| Caption: Simplify your motor selection journey with our tools.
Proper motor sizing starts with accurate information. Often, users oversize motors either due to lack of precise data or a desire to prolong motor life. Let us guide you through the process—contact us today for expert assistance!
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