Re: Press brake auto back stops - DRO / Accuracy

We have an 'Acupress' 250T brake here at the shop. It is fully
programable and will calculate bend allowances and setback's if you
want it to, or you can just set your backgauge. If your talking
about a vertically acting top die and fixed bottom die brake, then
you'll not have issues w/ slippage. The mat'l will be pulled into
the bottom [female] die evenly from both sides of the die. I daily
program and design parts to be broke on it and we achieve less than
1/32" accuracy w/out really trying. If we need to up that a bit more
we can but for our type of work its not nesc. Typically the
project's that I'm involved w/ are laser cut to size w/ etch marks
on the mat'l that match the flat partern layout for the brake
operator. He imputs the backstop value's in decimal form and then
brakes the parts. It works and is repeatable every time. If the
parts aren't laser cut they are usually cut on our AcuShear which
also has a NC backgauge. The only time you get into issue's w/
slippage not being uniform is when your using too large a die set
for the lip sizes your breaking. ei; if you want to break a 1 1/2"
lip your gonna need a die smaller than 3" open at the top. If your
gonna brake a 1/2" lip the die must be less than 1" open at the top.
if not, then the mat'l may move in an unpredicatable manor because
when the top die comes down on the mat'l the mat'l isn't resting on
both sides of the bottom die and it will slide.. who knows where....

Anyway.. the short answer is it works and its repeatable.

Jarrett Johnson

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Andy Wander" <awander@...>
wrote:

>
> Darren:
>
> I have had only a bit of experience with a press brake, and it is

not a

> very good one at that(a Harbor Freight cheapy), but I will say

that it

> is a lot more difficult to figure out where the bend is going to
> actually happen on a press brake, as the material can(and must!)

move

> across the tops of the female V jaws during the bending process,

and

> this means that the actual center of the bend may not end up where

you

> expect it to be.
>
> 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
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of oneluckeboy
> Sent: Wednesday, April 05, 2006 11:54 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Press brake auto back stops - DRO /

Accuracy

>
> Anyone ever make an auto back stop for a press brake? Just

curious if

> anyone had and what construction method they had maybe used? I'm
> considering making a small press brake for bending metal as the

local

> shop takes ~FOREVER~ to do pieces for me. It'd sure beat

waiting.

> Looking at something with DRO and accurate movements.. ie backstop

move

> to 4.050" from 2.250" and back again or some such for bending

small

> brackets, gussets, etc every other bend. I would like to see

something

> w/ resolution - accuracy around .010" or less as long as it would

be

> repeatable?
> Darren Lucke
>
>
>
>
>
>
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