Understanding 6 Essential Principles of Ball Screw Repair

Ball screw repair follows 6 essential principles which include lubrication, examination of the ball screw’s initial condition, extensive cleaning, rebuilding the ball screw assembly, extended testing, and refurbishing.

Ball screws are used in highly-specialized industries such as aircraft, missiles, machinery, precision assembly equipment and robotics industries. Because of the technical nature of these industries, ball screw components need to be regularly maintained and subjected to ball screw repair to ensure optimum performance and to troubleshoot failures. Although there might be varied causes of ball screw failures there are essential principles in repairing them. It is important to understand these principles to better know how ball screw repair is undertaken.

Lubrication

One of the most common factors that contribute to ball screw failure is routine wear or poor surface finish. This happens when the re-circulating ball screw surface is exposed to continuous contact with the hard surface of the ball screw shaft. Over time, the ball screw surface becomes eroded and worn down. The principle of lubrication is meant to provide a solution to this problem and helps maximize ball screw performance and service life. However, it is important to select the lubricant that best suits the component’s conditions. It is also crucial to avoid over-lubricating, as this can contribute to pressure on the ball nut return system and, consequently, cause the tube to burst from too much grease.

Examination of the ball screw’s initial condition

Before any changes are made to the ball screw, it is important to examine its initial condition. This principle includes checking the ball screw’s free running condition and its drag torque. The ball screw is also subjected to a health check focused on the main points that contribute to optimum ball screw performance. This principle is necessary to determine whether the ball screw is still in repairable condition.

Extensive cleaning

Before any subsequent repairs are conducted, the ball screw component has to be cleaned. The length of the ball screw track is first polished and, to remove accumulated grease and dirt, it is also subjected to ultrasonic cleaning and high pressure washing.

Rebuilding the ball screw assembly

Over-sized micron-graded precision ball bearings are rebuilt on the ball screw assembly. This is meant to achieve a satisfactory pre-load level that conforms to DIN specifications.

Extended testing

Ball screw units need to undergo extended testing. The running performance of ball screws are tested on motorized testing rigs. Extended testing helps determine whether a ball screw passes the necessary standards and criteria. When the ball screw completes the testing and passes, an extensive test report is compiled and logged. The report details the criteria employed, drag torque graphs and other important information.

Refurbishing

Bearing end journals are refurbished using methods like hard-chrome plating or metal spraying. After this, they undergo regrinding using a precision universal grinder. If it is necessary, fixing thread forms are also refurbished after comprehensive checking and cleaning. Components like fixing key ways, wiper seals and other smaller details may also be cleaned and refurbished if needed.

Proper ball screw repair and maintenance helps make sure that the machinery and operations that use ball screws are successful and efficient.