Maximum Speed of Ball Screw

 

The maximum rotational speed of the ball screw assembly (RPM) depends on the diameter of the screw, the length of the screw and the configuration of the support housing. This is the point where the rotational speed of the ball screw creates excessive vibration within the assembly. The maximum speed should not be exceeded as it may cause immediate or premature failure of the ball screw assembly. Exceeding the posted speed rating can damage the assembly and should be avoided.

 

An example is provided below for illustrative purposes. The following application conditions are used.

 

Work plane: vertical

 

Load Weight: 200 pounds plus the 100-pound force required to pierce the material during the last 3 inches of the 32-inch down stroke.

 

Moving speed: 5 inches / second

 

Travel Length - 32 to 29 inches of travel is required to load the part.

 

System repeatability: 0.001 "(bi-directional)

 

Selected screw: RS075020

 

It is the mechanical limit that determines the maximum safe speed. If exceeded, it is defined as the highest speed that can cause excessive vibration, screw or support bearing damage.

 

To convert to inches / second in this example, multiply by the desired thread pitch.

 

5 inches / sec X rev /. 200 inches X 60 sec / min = 1500 RPM

 

Maximum travel length: 32 inches

 

Selected screw: RS075020

 

Repeatability: 0.001 inch (so pre-loaded nuts are required)

 

Length of preloaded nut: 6.080 inches

 

32 inches + 6.080 inches = 38 inches of required thread length

 

By deciding on a single fixed bracket configuration (simple-simple) from the maximum speed graph, you get 1640 RPM with 40 inches between the bracket housings. Because we want a margin of safety (if linear speed requirements increase), we opted for a more robust, simpler configuration that provides 40 inches of 2410 RPM of screw between the support housings.

 

Lintech also offers an online calculator to help you quickly determine the speed that matters.