Motors and gearboxes: a comprehensive guide to selection and application (Ⅲ)

Motors provide power, while gearboxes adjust this power to suit specific application needs. In the first two articles, we introduced the field of gearbox. Understanding different types of gear transmission helps engineers to choose the best transmission mode suitable for their applications. This article introduces the importance of correctly choosing and applying motors and gearboxes for the performance and efficiency of equipment.

Motor Selection: The Key to Problem Solving

When choosing a motor, we need to consider the following aspects:

• Problem Identification: For example, if we are designing an industrial robot, we might need to choose a motor that can provide precise control and high torque. This is reverse design, i.e., having the physical object first, and the problem requirement is to innovate it again. Forward design is the process from concept to physical object.

• Motor Type: Brushless inner rotor, brushless outer rotor, and DC motors all have their own advantages and disadvantages. For example, brushless inner rotor motors usually have higher efficiency and smaller volume, while DC motors are cheaper and easier to control. If we are designing a drone, we might need to choose a lightweight, high-efficiency brushless inner rotor motor.

• Control Method: When we are designing a device that requires precise position control, we might need to choose a motor with a high-resolution absolute encoder. However, if the control method is chosen improperly, it may lead to insufficient control accuracy. Which control method to choose depends on how much precision we need and whether we need to know the exact position of the motor.

Gearbox Application: The Tool for Power Adjustment

When choosing a gearbox, we need to consider the following aspects:

• Gearbox Type: If we are designing a device that requires high efficiency and high torque output, we might need to choose a planetary gearbox.
• Gear Material: If we are designing a device that needs to run in a quiet environment, we might need to choose a gearbox with nylon teeth. POM: Advantages include good mechanical properties and rigidity, close to metal materials, excellent fatigue resistance and creep resistance, good wear resistance, self-lubrication and friction properties, high chemical stability, excellent electrical insulation properties. Disadvantages include low toughness, large notch sensitivity, poor heat resistance, poor weather resistance, large molding shrinkage rate.
• Alloy Steel: Advantages are high strength, high elongation rate, good plasticity, good wear resistance, low price3. Disadvantages are easy to rust, poor corrosion resistance.

• Output Shaft Bearing Form: Oil-containing bearings and ball bearings can both be used in gearboxes. Which output shaft bearing form to choose depends on where our equipment will be used and how much load capacity we need. Ball bearings cannot withstand larger overloads and are more common in light industrial machinery. Oil-containing bearings have low cost, can absorb vibration, low noise, do not need to add lubricating oil for a long time of work, especially suitable for not easy lubrication or not allowed oil dirty working environment.
• Backlash: In precision positioning applications, you may need to choose a gearbox with low backlash. But if the backlash is too large, it may lead to insufficient positioning accuracy.
• Confirm Modulus Gear: For example straight gears are simple in design and easy to manufacture with low cost and high efficiency. While helical gears have teeth inclined to the gear axis line. For the same width of helical rack, helical gear rack transmission is more efficient than straight rack transmission.