RE: [CAD_CAM_EDM_DRO] Press brake auto back stops - DRO / Accuracy

Yeah, the mechanical part I'm comfortable w/ designing
from looking at other actual units, using them, etc
and familiar w/ taking lash out as you described. A
lot of commercial stops have a stop the whole width of
press / dies which then sometimes have moveable stops
on it to facilitate narrow or wider pieces.

I was hoping there might be a way to do this w/o using
dedicated comp running mach or other and also how
would one have some kind of switch to actually
activate it to go to the next position other than
doing it manually. Sounds like John's idea would be
good but I do not know enough about it and I do not
know quite enough of electronics to design my own I'm
afraid. Perhaps one could buy a board to work for
this? I have gotten motors spinning through mach3 and
my plasma table is nearly complete but am starting to
gather info for the next project so am comfortable
enough working w/ power supplies, etc.

Darren Lucke

--- Andy Wander <awander@...> wrote:

> Well, I haven't built one, but my guess is a couple
> of threaded rods
> would be accurate enough to get the .01" accuracy
> you are looking for,
> along woth(as John suggested) a small stepper
> driving the 2 rods.
>
> I would actually figure out a way to mount 2 solid
> rods to the back of
> the brake, so that they can be the "rails" that the
> fence or back gage
> or back stop or whatever we are calling it slides
> along. Put these rods
> in place so that their top edge is at the same
> height as the top of the
> lower die in the brake, so that when you slide the
> sheet metal in, it
> will ride along the top of the rods, holding it
> level(this will only
> work if the sheet is wide enough, obviously, but if
> it is not that wide,
> support should not be an issue).
>
> Then I would figure out a way to mount 2 pieces of
> allthread(or 1 piece,
> centered, if you can get good bearings on the
> support rods, that will
> allow the fence to slide easily and stay
> perpendicular). These should be
> held at one end by a mounted bearing that will allow
> rotation but no
> longitudinal motion, like the leadscrews on a lathe
> or mill. The other
> end, if not too long, could be left floating after
> it passes through the
> nuts on the fence.
>
> If you go the allthread route, there will probably
> be a good amount of
> backlash, but you should be able to use the motor to
> always approach
> from the outside in(when you move out, you go
> further than you want to,
> and then come back in) so you can get rid of the
> backlash. You will want
> to have the threaded rod pushing the fence in
> anyway, so that pushing
> the sheet against it does not move it by whatever
> amount of backlash you
> have. Mounting a DRO to the fence should allow you
> to confirm the actual
> position.
>
> You could do all of this with mach3 and a linear
> encoder. I am sure
> there is other software that would do it as well.
>
> Just a few thoughts...
>
> ________________________________________
> Andy Wander |
>
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf
> Of Darren Lucke
> Sent: Wednesday, April 05, 2006 12:38 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] Press brake auto back
> stops - DRO /
> Accuracy
>
> The main thing I need is an accurate back stop so
> that
> the slippage, etc can be repeatable (and square w/
> ram
> - dies). I would make a pressbrake that would have
> a
> top ram movement in vertical rather than box and pan
> style. My parts would be quantity of this or that
> and
> would be nice to be able to repeat the length of the
> bend (adjust a few thousandths one way or the other
> in
> order to achieve length where I need).
> Darren Lucke
>
> --- Andy Wander <awander@...> wrote:
>
> > I am concerned that no matter how accurate your
> back
> > gage, the amount of
> > slippage of the metal may actually be the thing
> that
> > determines your
> > repeatability.
> >
> > What thickness of what type of metal do you need
> to
> > bend? And do you
> > need to make boxes, or simple bends only?
> >
> >
> >
> > ________________________________________
> > Andy Wander | Vice President, Engineering
>
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