What may make your ball screw failure?

●Incorrect alignment 

The ball screw must be mounted in such a way as to ensure proper alignment with the guidance system to avoid bending moments and binding during travel.Ball screws are designed for axial loads only,so non-axial loads can create bending moments or radial loads on the ballnut,which can shorten service life and eventually jam the ball nut movement.Using accurate measuring equipment,alignment of the ballnut over the entire length of the ball screw can be confirmed.

●Insufficient lubrication 

Ball screw assembly designs rely on lubrication to minimize rolling resistance between ball bearings and ball threads,while reducing sliding friction between adjacent balls.When ball screws are not properly lubricated,grinding,metal-to-metal contact wear occurs.Operating temperature,duty cycle,environment,axial load and RPM/speed determine the required rate of lubrication application for each system.In applications where grease or oil is not an option,dry film lubrication is recommended,however,ball screws and ballnuts need to be coated with phosphate for the lubricant to work properly.Graphite-based lubricants should be avoided because they are abrasive and may clog the ball return circuit.

● Excessive heat

For applications with high temperature operating conditions,a high temperature rated lubricant that resists oxidation and evaporation is recommended.If the lubricant is not rated for high temperatures,it may oxidize,evaporate or be lost,keeping the ball bearing contact surfaces dry.

●Contaminant

Dirt or debris buildup can lead to clogged ball return circuits or worn contact surfaces.Chemical exposure can also contaminate ball screws by stripping the lubricant and eroding the contact surfaces,leading to oxidation or corrosion.When the operating environment is dusty or generates chips,the use of wipers or end seals is recommended to prevent debris from entering the ballnut.Bellows,way covers or other types of dust caps may also be required to prevent chip build-up on the ball screw and keep chips away from the ballnut.Regular cleaning of the ball screw and replacement of the lubricant is essential to avoid such failures.

●Insufficient ball recirculation

Short periods of back and forth stroking or shaking motion of the ball screw will concentrate the load on one area of the ball screw and the same ball bearing surface,resulting in premature surface wear,Brinell indentation and restricting lubrication from circulating in the ballnut.Eventually the ball bearing will deteriorate,resulting in increased friction and torque and an inability to roll properly,eventually jamming the ballnut motion.Therefore,it is recommended that long stroke strokes be performed periodically to fully recirculate the ball bearing and lubricant.

●Ball screw sizes

Overloading a ball screw will shorten the life of the ball screw,so it is imperative that the ball screw is properly sized or rated for the given application.Several factors can affect sizing,including the maximum load moved,its travel rate or speed,critical ball speed,column load,duty cycle,end fixity,and drive torque.Other factors may include operating environment,system installation,stroke length and load guidance.

●Excessive speed

The critical ball speed(DN value)defines the maximum speed at which the ball can pass through the ballnut without causing failure of the return assembly.In addition,operating a ball screw at or above the critical axis speed can produce resonant vibration,which can lead to excessive system vibration,control problems,loss of positioning accuracy,and premature failure of the end support bearing or drive system.Operating the ball screw assembly at or below the calculated maximum linear speed and critical ball speed will avoid these types of failures.

Click to select ALM high quality ball screw for your application:

https://www.autolinearmotion.com/ball-screws.html