Increasing the life of ball screw assemblies is crucial in keeping equipment functioning properly and avoiding downtime. While the life span of a ball screw assembly will vary depending on the conditions of which it is operating, there are several key ways that engineers can help improve the life of their ball screw assemblies, regardless of the application.
How do you calculate the average ball screw life span?
In a typical application, a ball screw should last one million revolutions if operated at or below the dynamic capacity of the ball screw assembly. 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 ball screw 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:
- The screw diameter
- The thread pitch
- Ball bearing size
- Number of circuits
- Ball screw material
While this specification will give 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 ball screw life, 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
What can engineers do to increase the life span of their ball screw assemblies?
The easiest way to increase the life span of a ball screw assembly 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/grease schedule to ensure proper lubrication
Not implementing a proper maintenance schedule is the most common error out in the field that causes ball screws to fail prematurely.
How do you identify a failing ball screw?
How can you tell if your ball screw is failing prematurely? There are several key warning signs of ball screw failure:
- Loss of accuracy
- The need for additional torque when operating
- Excessive noise
While these warning signs are very easy to identify, often the damage is already done once they begin to appear. If you’re in this situation, it is a good idea to service the ball screw assembly immediately to correct the problem, or the ball screw assembly will need to be repaired or replaced.
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 was having problems with the ball screw assembly losing accuracy prematurely, causing the production line to fail.
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 life began to perform as expected.
Each ball screw application is unique, so PST looks at each situation individually, and identifies the problems to understand what the customer is looking to accomplish by increasing the life of a ball screw assembly.
Then, PST works with the client to recommend 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.