Original Press Release
New Ball Screws with Rotating Nuts Solve Critical Speed Limitation
Press release date: January 10, 2003
Bedford, MA, January 10, 2003 -- Steinmeyer, Inc. announced a significant addition to its standard line of precision ball screws - Rotating Nuts. Automated machinery operates at high speed today - and increasingly higher speeds tomorrow. This places additional demands on critical linear drive components such as ball screws. Two speed - related factors must be considered when designing with ball screws. One is the rotational limit for the ball nut, referred to as its dN value. The second is the rotational limit for the screw, or its critical speed. Rotating a ball screw at or near its critical speed causes harmful vibration due to resonance. Holding the screw stationary and using the motor to directly rotate the ball nut can alleviate the critical speed limitation. Rotating the nut has the following advantages, compared to rotating the screw: o higher critical speed o higher rigidity o easier to cool the screw o easier to pretension the screw
"We are seeing significantly more applications for Rotating Nuts. As machines get larger and faster, ball screws get longer and designers constantly fight critical speed issues", observes George Jaffe, Executive Vice President. "One solution is to redesign the whole machine and switch to linear motors. But that adds considerable cost and complexity. And linear motors, though offering speed advantages, have their own disadvantages. An alternative solution is to rigidly fix the screw and reconfigure the ball nut to allow direct connection to the motor."
Steinmeyer offers several standard Rotating Nut designs in sizes 16 x 30, 32 x 40 and 65 x 80 (pitch x diameter). And, any Steinmeyer ball nut can be modified and converted into a rotating nut, by adding a precisely ground bearing seat on the outside diameter, together with lock nut threads (as shown on the attached photo). This allows assembling the nut support bearings directly to the nut body. Another alternative is to install a standard Steinmeyer ball nut into a sleeve. The sleeve is then configured to accept duplex bearings, locknut, drive pulley (to enable motor connection) and rotating union for lubrication.
For further information call 1-800 -297 -6403 or visit www.steinmeyer.com and click on Rotating Nuts!