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

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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