Why are supported rack and pinion drives superior to ball screws on large tables?

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Accepted Answer

Supported rack and pinion drives are generally preferred over ball screws on any table axis longer than 24 inches. A ball screw is supported only at its two extreme ends; across a 4'x8' or 5'x10' bed, the center of an unsupported ball screw can flex and whip under rapid transport of a heavy gantry. This flex degrades positional accuracy, induces cut chatter, and wears out bearings prematurely. Supported rack and pinion gear tracks are bolted directly to the steel chassis along their entire length, eliminating that mechanical flex.

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