Driving your nuts

What do you do with the ball screw? Despite the fact that it’s the preferred method for motion control in machine tool applications due to its efficiency, precision and stiffness, it does have one significant disadvantage over linear systems – speed.

To counter that challenge, designers at Thomson IBL in Barnstable have taken another look at the ball screw and come up with a significant redesign, increasing traverse speeds up to 200 metres per minute, double that of existing designs.

According to Technical Manager Kelvin Kollond, there are two factors that limit the transfer speed of conventional shaft driven ball screws. They are the vibration caused by the shaft running at its critical speed, and the ability of a ball transfer system to efficiently handle the necessary flow rate of ball bearings over an acceptable life.

These limitations have been overcome in the new RN series by allowing the shaft to remain fixed and driving the nut instead. This means that there are no rotational critical speeds to limit traverse rates. The new design also incorporates a hollow shaft, further reducing vibration and noise. The RN series comprises a standard diameter and standard lead screws around a flange type precision housing that enables a timing belt to drive the nut and contains the preloaded rotating ball nut assembly.