Increasing the life span of ball screw assemblies is crucial in keeping equipment functioning properly and avoiding downtime. While screw wear varies depending on the conditions of which it is operating, there are several ways that engineers can help improve the life span of their ball screw assemblies.
How do you calculate the average ball screw life span?
A ball screw should last one million revolutions if operated at or below the dynamic capacity of the assembly in a typical application. But there are many factors that can influence the actual life span of a ball screw.
At PST, we calculate the dynamic capacity using DIN 69051. The dynamic capacity calculates the rated load that a ball screw assembly can withstand for a life span of 1 million revolutions. It is crucial not to exceed this dynamic capacity during standard operation of the ball screw. This specification considers several factors, including:
- Screw Diameter
- Thread Pitch
- Ball Bearing Size
- Number of Circuits
- Ball Screw Material
While this specification provides a better idea of the ball screw life span based on the conditions in which it is operating, it does not consider the additional factors that impact screw wear, such as:
- Exceeding the static capacity of a ball screw
- Operating above the dynamic capacity for a number of cycles
- Improper care and maintenance
- Insufficient ball screw assembly lubrication
- Excessive heat
For a closer look at the process of calculating ball screw life span and addressing screw wear, we have a blog to get you started.
How can you increase the life span of ball screw assemblies?
The easiest way to increase the life span of ball screw assemblies is to perform maintenance regularly. Two regular ball screw maintenance procedures that make a big impact are:
- Regularly inspecting the wipers to ensure there is no foreign debris entering the ballnut
- A regular cleaning and grease schedule to ensure proper lubrication
Failing to implement a proper maintenance schedule is the most common error causing ball screws to fail prematurely. Maintenance is crucial in managing screw wear within your assemblies.
How do you identify ball screw failure?
There are several key warning signs of ball screw failure:
- Loss of accuracy
- The need for additional torque when operating
- Excessive noise
These warning signs are very easy to identify. However, the damage is often already done once they appear.
If you notice any of these warning signs, or are experiencing other ball screw problems within your assembly, it is a good idea to service the assembly immediately. This service will aim to either correct the problem or repair or replace the ball screw assembly.
How can PST help increase the life of your ball screw assemblies?
PST has worked with several businesses to identify failing ball screws and create solutions that will increase their life span. For example, a PST customer was using a ball screw assembly in an automotive production line environment but having problems with the ball screw assembly losing accuracy prematurely. The production line would then fail, causing downtime.
After reviewing the application and the loads required, PST determined that the customer incorrectly specified the necessary ball screw for their application. After working to identify a replacement ball screw assembly that could handle the loads required by the machine, the ball screw began to perform as expected.
Each ball screw application is unique, so PST looks at each situation individually. By identifying the problems within the application, we can understand what customer is looking to accomplish by increasing the life of a ball screw assembly.
After investigating the problem, PST recommends a plan of action to increase the life of the ball screw. This is often done by increasing the size of the ball screw or the ball bearing diameter, or by implementing a stricter maintenance schedule.
Would you like to increase the life of your ball screw assemblies? Contact the ball screw experts at PST today to learn what options are available to you.
