Re: [CAD_CAM_EDM_DRO] Re: Re: Re: Rack and pinion

In a message dated 12/6/03 5:34:12 PM Eastern Standard Time,
imserv@... writes:

> >All interesting stuff about the pros &cons of rack &pinion drive, I can
> >indeed
> >vouch for the accuracy and speed of the big Bystronic laser machines - and
> >seeing them run
> >is unreal !! However, could one of the many learned members of the group
> >either
> >point me to a site or in simple terms explain the concept of 'Preloaded'
> >with respect to
> >rack &pinions - I see this term in many posts and am not fully aware of
> >what it means ?
> >
>
> Dave, One of the least complicated implementations of preload of a rack and
> pinion
> drive has the drive pinion motor mounted on a hinge that lets the gear and
> motor rotate into
> and out of the rack teeth. This device is then preloaded with a strong
> spring that holds
> the gear tightly against the rack, thus eliminating backlash. If you can
> get a close
> up shot of a Shopbottools.com, (the X axis assembly), their full size CNC
> router
> uses this principle. It allows for dust and crud buildup that will stop
> other drive systems
> dead in their tracks and still holds close enough tolerances for
> woodworking.
>
> Fred Smith - IMService
>
>

Fred:

DITTO, the woodworking industry has been using that principle on several
different designs for years due to it's simplicity and reliability. From
pre-loading the actual drive pinions into the rack gears to pre-loading the pinion
gears on a rotary encoder into the same rack gears. I will add that the
accuracy is maintained using this method and allows for much longer travel and faster
speeds over the longer distance than does using ballscrews as the longer they
get the bigger in diameter so as to reduce "whipping" and that increases the
cost almost exponentially.

Randy Abernathy
4626 Old Stilesboro Road
Acworth, GA 30101-4066
Ph/Fax: 770-974-5295
Cell: 678-772-4113
E-mail: cnc002@...

I furnish technical support, repair, and other related services for your
industrial woodworking machinery. My background as Senior Service Engineer for the
SCMI Group for nearly fifteen years with factory training, combines with my
extensive background in electronics, mechanics, pneumatics, electrical and CNC
machinery to offer you needed support for your machinery.


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