It would be great if all the components of your applications performed as expected forever. Unfortunately, that isn’t the case.
Ball screw life expectancy should always be considered when designing and developing a new application. Having an understanding of the expected life span of a screw can help you to plan for future maintenance and repair needs.
Calculating the Life Expectancy of Your Ball Screw
A ball screw’s life expectancy is calculated using the static and dynamic capacities applied within its specific application. This takes into account many factors, including:
- The diameter and lead of the screw
- The stroke length
- Circuitry of the ballnut
PST uses the DIN specification DIN-69051 to calculate the dynamic and static capacity. This is based off of a limit of one million revolutions of the ball screw.
If the ball screw is operated with a load equal to the dynamic capacity, the screw will have a life expectancy of one million revolutions. If your specific application requires more than one million revolutions, you may require a custom screw thread to meet your requirements.
Other factors, including screw wear and operating conditions, play a role in calculating the lifespan of your ball screws. If increasing ball screw life span is a concern, we’ve documented several methods that can help.
Planning for the Screw’s End of Life and Component Failure
When working on a new project, the life span of your screws may not be a primary concern. After all, the parts are new, so you should reasonably expect to get plenty of wear out of your screws prior to failure.
However, screw life span should be considered even when working on a brand new project. Having an understanding of the expected life span of the screws in your application allows you to accurately plan for future screw repair or replacement needs.
For existing applications, you may already know your ball screws are nearing the end of their lifespan. Once you are ready to take action, you have two primary options:
- Replace the assembly with all new components
- Repair the existing assembly
Each option has their own benefits and downsides to consider.
Replace the Ball Screw Assembly
If downtime is a concern, using a replacement ball screw assembly may be necessary. Using a replacement component allows you to swap out the failing component with the new ball screw assembly rather than waiting for the existing part to be repaired. Even if your ball screw is custom built and developed by a competitor, we can design, develop, manufacture and supply a replacement.
Repair the Ball Screw Assembly
You also have the option of sending in the ball screw assembly to replace and rebuild the components that have failed. This solution may be most cost effective, as there is no engineering time. However, it may result in additional downtime depending on the severity of the repair needs.
There are circumstances in which rebuilding the existing assembly is not possible. Depending on the demands of the environment and usage, the ball screw assembly may not be able to be repaired after completing its life cycle.
Reengineering a Solution
There are instances when a ball screw has not met the requirements of a particular application. PST can disassemble a damaged ball screw assembly and evaluate what failed within the assembly. Using specific applications, we can verify existing assemblies have the ability to meet any requirements. If the existing components don’t meet your needs, we can reengineer components so they do.
Custom Ball Screws
It is always important to consider the end of your ball screw’s life while crafting your application. The experts at PST can help you. Contact us today to get started.
Originally Published: March 29, 2017