Re: [CAD_CAM_EDM_DRO] Re: Ball screws for CNC plasma cutters

Joe,

My CNC plasma has the servos, gear reducer are mounted on a spring loaded plate. The spring removes the backlash between the rack
and pinion. The encoder feedback is tied to the output shaft of the gear reducer so the gear box backlash is not an issue. The
machine will hold about .015, which is better than the plasma torch can cut. The spring loaded pinion also allows it to be
disengaged from the rack so the axis can be moved manually. This is a big help when zeroing in a plate.

Racks can be used on machines of unlimited length. They also help to keep the weight of the drive system down. Low inertia means
smaller drives.

Jay

Helen Fahy wrote:

> Hi Jay,
>
> I am considering using a rack & pinion system for my machine due to the
> 16'-20' x axis dimension. Did you use any of the zero backlash hardware,
> split pinions, harmonic gear drives,.. in your design? What kind of
> tolerance and repeatability does your system maintain?
>
> Thanks for any guidance,
>
> Joe Fahy
>
> ----- Original Message -----
> From: "Jay Hayes" <xmas4lites@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Monday, February 12, 2001 7:38 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Ball screws for CNC plasma cutters
>
> >
> > If you've seen a plasma cutter then you have also seen all the particulate
> slag and grit that is generated. This grit can play havoc
> > with any type of screw. A better solution is a rack and pinion drive. If
> the teeth on the rack are positioned vertically or upside
> > down the grit problem is minimized. Racks can also be of unlimited length.
> Screws on the other hand suffer from whip lash at longer
> > lengths. My 72 x 126 inch CNC plasma, with rack and pinion drive, holds
> the same tolerances it did when it was new fifteen years
> > ago.
> >
> > Jay Hayes
> >
> > Smoke wrote:
> >
> > > I'm just wondering...I've seen plasma cutters in use. It appears to me
> any
> > > attempts to hold
> > > REALLY CLOSE tolerances seems to be a lot of overkill. I've never seen
> a
> > > plasma cutting torch
> > > yet that will cut a really smooth edge, hence the lack of necessity for
> > > holding close tolerances.
> > >
> > > With this though in mind, i don't see why a person couldn't use threaded
> rod
> > > for the lead screw?
> > > Manufacturing an "antibacklash nut for this would be as simple as
> placing a
> > > heavy spring between
> > > a couple of hex nuts which are trapped to prevent rotation.
> > >
> > > I've even seen commercial nuts (used on acme screws) made this way.
> > >
> > > Smoke
> > >
> > > -----Original Message-----
> > > From: ozzietwo2001@... <ozzietwo2001@...>
> > > To: CAD_CAM_EDM_DRO@yahoogroups.com <CAD_CAM_EDM_DRO@yahoogroups.com>
> > > Date: Sunday, February 11, 2001 10:22 PM
> > > Subject: [CAD_CAM_EDM_DRO] Re: MillWizard + MaxNC-10, SuperCam &
> > > Millwizard...
> > >
> > > >Tracy,
> > > >I've found the website for Techno-isel and have found mountains of
> > > >interesting stuff, but it's daunting to try wading through it all.
> > > >Can you give us an idea of prices; for instance your 20" table, and
> > > >if you know, ball screw and nut prices.
> > > >
> > > >Thanks,
> > > >Jerry
> > > >
> > > >
> > > >
> > > >
> > > >One major "upgrade" I've
> > > >> made is using 20" X & Y tables from techno-isel to give me more
> > > >area
> > > >> to work with. It works great but really needs stronger stepper
> > > >motors
> > > >
> > > >
> > > >
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>
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