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What is a ballscrew drive and do I need one for a CNC Router?

A ballscrew drive is a mechanism employing recirculating ball bearings interposed between the leadscrew (termed a ballscrew) and the nut (termed a ballnut). In theory this provides a very high efficiency (>95%) drive mechanism since there is rolling friction rather than sliding friction as in the case of an ACME leadscrew.

The problem exists however in sealing the ball bearings in a wood dust environment. Even a little wood dust can cause the ballscrew/ballnut mechanism to freeze up (the ball bearings at that point are reduced to sliding friction). While a bellows seal can be used this adds to the already high cost of the ballscrew and cuts down on travel distance.

Additionally many ballscrews are produced as a rolled thread product that doesn't have a very high lead (ie the distance the nut traverses with each rotation of the leadscrew). Therfor the ballscrew must be spun at high RPM to maintain traversing speed. At high RPMs the ballscrew can vibrate quite a bit.

Acme leadscrews do not have the dust clogging problem associated with the the ballscrew/ballnut drive. They are essentially self-cleaning and can be manufactured with a high lead (ie the length the nut traverses per revolution) cutting down on leadscrew vibration problems.

If properly designed with a high lead and an anti-friction nut material they can be highly efficient (>80%) and are a very economical and practical alterntive to ballscrews.