Belt drive or lead screw? The answer is in the application
Engineering advancements in the field of linear motion have generated several options for driven actuator systems. Two of those types of drive systems that are essential to converting rotary motion into linear motion include the belt drive and lead screw. Both options have a unique role to play within actuator systems.
There are many important parameters to consider when choosing between a belt drive and a lead screw. Some of these core considerations include load, orientation, travel length, speed, precision, and environmental conditions. Precision can be further broken down into accuracy and repeatability. Accuracy is a measure of how close to a desired end point the assembly can move a load within a given tolerance. Repeatability, on the other hand, is a measure of how well a driven assembly can repeatedly move a load to the same position.
Cost is a factor as well, but can hinge on how the actuator is being used in an application. In other words, there may be more than just the up-front costs involved. For example, a drive system may require more long-term maintenance, or a harsh application may reduce the overall lifespan of the actuator. With these factors in mind, a proper evaluation of your application and its needs should be assessed in order to choose the most ideal actuator system.
Belt drives and their applications
A belt-driven actuator converts rotary motion into linear motion using a timing belt. The timing belt contains teeth that lock onto toothed pulleys, applying torque and preventing slippage. Often, the belt drive is enclosed within a protective case, and attached to a carriage. The driveshaft and motor are often situated perpendicular to either side of the actuator (horizontal motor mount), or perpendicular to the top of the actuator (vertical motor mount). The PROs and CONs for the use of belt drives, with respect to the application needs, includes:
- Long strokes. Typically up to 6 meters. Optimal for shuttle transport and material handling applications.
- High linear travel speed. Typically up to 3 - 5 m/sec for long travel distances.
- Higher efficiency. Typically 90-percent. Benefits high-speed and continuous power applications.
- Lower input RPM versus screw drives.
- Higher duty cycles. Continuous duty.
- Higher cost. Additional costs in vertical applications can be incurred due to gear reducer and motor fail-safe brake requirements, and the need for more input torque from motors.
- Lower accuracy and positional repeatability versus screw drives.
- Velocity ripple. Cogging effect inherent with belts and pulleys.