Re: [CAD_CAM_EDM_DRO] Rolled vs. Ground ballscrews

>1 - there can be no tighter bearing than flat metal to
>metal
>
>

True. However you cannot have a true metal-metal contact on both flanks
of the screw without the whole thing binding up. You have to have
clearance for the screw to turn. Acme screws also wear fast. You will
soon have backlash in the nut. After a while you will also get wear on
the screw itself so you will not be able to compensate by tightening up
the nut.

>2- as soon as you introduce additional elements, like
>rollers, you are dealing with multiplied tolerances of
>all the parts (read as ERRORS of all the parts)
>
>

True. That is why screws are manufactured to very close tolerances.
Balls can be manufactured to extremely tight tolerances. In fact Newall
use balls packed into a tube as the measuring element for a DRO system.

>3- ball screws/nuts immediately reduce native
>resolution cuz they can not have as many tpi as a fine
>thread screw.
>
>

Who cares what the native resolution of the screw is. You can soon
change it with suitable gearing or encoders on the motors.

>4- they are expensive, sound hella sexy in a
>specsmanship pissing contest.
>
>

Yup they are expensive. What you get for your money is _consistent_ very
low backlash.

Les