The ball-worm (BW) is a new type of mechanism created by adding a sequence of rolling balls between the worm and gear components of a worm mechanism. This eliminates the sliding friction between the components, which improves the performance of the mechanism. The advantages of the BW are similar to those of the well known ball-screw mechanism: low backlash, high precision, low friction, high efficiency, higher power transmission in a lower size, etc.

Backlash in a worm gear is reduced by adjusting the distance between the axes. In a classic worm there is a very fine limit between a loose and over tight adjustment, and this quickly deteriorates as the components wear through friction. With the balls, on the other hand, a tighter adjustment does not spike the friction allowing for adjusting the transmission for minimal backlash.

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Balls continuously roll between the two components. The balls coming out of the engagement region are then re-circulated through a helical path of the worm.

Ball-screws (BS) have been widely adapted for high-precision instrumentation, devices, and machinery but they only apply to linear motion. Until the BW, no mechanism equivalent with the BW existed for rotations. The BW opens a new area of applications for high-performance rotary motion. CNC machineries, for example, typically use BS for the linear axes while still relying on an ordinary worm gear to drive their rotary axes, such as rotary tables. The BW could provide a better performance alternative for rotary CNC actuation, with higher speeds and precision in a smaller package. Similar to the classic worm, the BW may also give high transmission rations allowing fine controlled motion.