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Specifying a Ball Screw? You May Need to Know the Equivalent Operating Load

Many engineers use the nominal operating load when calculating the life of a ball screw.

In relatively straightforward applications that works - but in extraordinary applications it is important to determine the equivalent operating load. Among other considerations, the equivalent operating load factors in significant loads and forces that result from impact, shock, extreme acceleration or deceleration and externally applied loads.  Miscalculations or incorrect selection of material can cause expensive retrofits or even worse catastrophic failures

Learn how to determine the equivalent operating load here - then read Selecting and Sizing Ball Screw Drives (Power Transmission Engineering, October 2012) to get the big picture on selecting the optimal ball screw for your application.

What might cause premature ball screw failure?

SOLUTION: Premature failure is most often caused by one of the following:

  • Misalignment – Misalignment of the ball nut to screw which results in side loading or eccentric loading. This may cause the bearing balls to split or get “flats” on them, and the bearing may even break out of the tube.
  • Debris - Metal chips or dirt in the ball nut will not allow the bearings free circulation, and the bearing balls may get flats on them because of skidding and spalling.
  • Lack of lubrication - Proper lubrication will help dissipate heat and reduce metal-to-metal component wear.
  • Excessive speed – Exceeding the ball nut critical speed can break pickup fingers off, causing the balls to come out of the nut. Exceeding the screw critical speed will cause the screw to whip or vibrate and cause misalignment. Shaft speeds resulting in screw surface speeds above 8,000 IPM will reduce rated life.


Linear Units 103: Applications and Selection via Decision Tree
March 27, 2013 11 am EDT/ 10 am CDT/ 8am PDT

Overwhelmed by all the variables that influence the selection of a linear motion system?  Not sure where to begin when trying to select the best linear unit for your application?  Get a step-by-step walk through of a unique decision-tree approach to selecting the right linear unit. 

Kyle Thompson, Product Line Manager - Systems Group, will break down the selection process into an easy-to-follow process that will simplify your selection of linear units.

REGISTER NOW! Spaces are limited.

Thomson WhisperTrak™ Electric Linear Actuators named a 2012 Golden Mousetrap Finalist!

Thomson WhisperTrak Electric Linear Actuators have been named a 2012 “Golden Mousetrap” finalist by Design News magazine!

Recognized for engineering innovation, Thomson WhisperTrak™ Electric Linear Actuators maximize design flexibility and improve performance and user comfort in personal mobility, rehabilitation, and medical equipment applications where reliability, small size and low noise are primary design considerations.

They also provide true maintenance-free operation throughout the entire life of the actuator, even with regular exposure to washdown, rain, dust or other particulates.

Learn How to Improve Productivity and Safety – and Reduce Costs – with Electric Linear Actuators

Are you a mobile off highway (MOH) machine builder who uses hydraulic and pneumatic systems?

Electric linear actuators from Thomson outperform hydraulics and pneumatics in many aspects that are significant to OEMs and their customers, including:

  • Lower cost of machine design, installation and operation
  • Greater mechanic and operator safety
  • Increased productivity from initial design to lifetime maintenance

If you’re looking to build a MOH machine with a clear competitive advantage, cost-effectively, visit our new dedicated microsite – - to learn more.

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