Inventor General Discussion

Inventor General Discussion

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*Allen, Albert
Post 1 of 13

Inventor vs SW for bend allowance

160 Views, 12 Replies
11-07-2002 02:08 AM
I did a simple bent up part in Inventor sheet metal by starting with a flat
plate,adding flanges and finally adding holes to each face. I then developed
the flat pattern and used this flat pattern in an idw with ordinate
dimensions for the holes from a set corner. I also used the flat to show the
bend centers and specified an inside radius for the bends. Ok simple Simon
stuff but when I sent it out to one of our vendors to be punched and bent
they called back and said the bend allowances and the flat pattern did not
jive with the drawing....what?! Turns out that when their engineer (who uses
SW) did a solid from my flat pattern and bent it on the lines I spec'd using
the same inside R that I used that things didn't work out. I have always
used the default K factor in Inventor sheet metal and everything has always
turned out exactly as the model when it's built in the shop, so what gives
here???? He did say that he uses K factors they load in from a spread sheet
into SW but there should not be more than a couple of thousands difference
should there?

Thanks,

Albert
*McLean, Stan
Post 2 of 13

Re: Inventor vs SW for bend allowance

11-07-2002 02:37 AM in reply to: *Allen, Albert
Albert,

Actually based on experience I had with SPI, Radan AutoSM and ProFold in
MDT, and now experience with Inventor there can be a significant difference
between parts that use different Kfactor or Bend allowances.

Many different people have their own variation on Kfactor and how it is
calculated. Inventor Kfactor is close to what I experienced in our own shop
but it doesn't take into account Sheetmetal material, and V-die sizes. It
is only based on 0.44(44%) offset of the neutral bend axis, which for most
situation is close but for others, can create a big difference (.010 - .05,
or more) per bend difference.

Stan McLean


"Albert Allen" wrote in message
news:66487808A1CE2C0C8F2870B46C4E70F2@in.WebX.maYIadrTaRb...
> I did a simple bent up part in Inventor sheet metal by starting with a
flat
> plate,adding flanges and finally adding holes to each face. I then
developed
> the flat pattern and used this flat pattern in an idw with ordinate
> dimensions for the holes from a set corner. I also used the flat to show
the
> bend centers and specified an inside radius for the bends. Ok simple Simon
> stuff but when I sent it out to one of our vendors to be punched and bent
> they called back and said the bend allowances and the flat pattern did not
> jive with the drawing....what?! Turns out that when their engineer (who
uses
> SW) did a solid from my flat pattern and bent it on the lines I spec'd
using
> the same inside R that I used that things didn't work out. I have always
> used the default K factor in Inventor sheet metal and everything has
always
> turned out exactly as the model when it's built in the shop, so what gives
> here???? He did say that he uses K factors they load in from a spread
sheet
> into SW but there should not be more than a couple of thousands difference
> should there?
>
> Thanks,
>
> Albert
>
>
*Bystry, Mark A.
Post 3 of 13

Re: Inventor vs SW for bend allowance

11-07-2002 03:03 AM in reply to: *Allen, Albert
welcome to sheet metal. i used to use pro/e's sheet metal package when i was
in the sheet metal field. i remember that they used some thing like R-FACTOR
or some thing like that. it was loosely based on the K-FACTOR. this default
setting didn't jive with our tried-and-true bend allowances out in the shop.
we used v-dies for all our breaking. we pretty much learned how to fudge our
models so the flat pattern would come our perfectly for our machines. pro/e
was just like SW and Inventor though. you were able to make a custom bend
allowance chart in xcel. we just never used that feature.

i'll tell you this though. bend factors are ALWAYS different for every shop.
i still regard K-FACTOR as reference only. let the shop guys tell you what
your bend allowances are. with that info and a little trial-and-error you'll
get it right every time.

--
Mark A. Bystry
Engineer
Ziggity Systems, Inc.
mbystry@ziggity.com
*Allen, Albert
Post 4 of 13

Re:

11-07-2002 03:06 AM in reply to: *Allen, Albert
Thanks Stan,

I guess the best way is to have each vendor send us their K factors for
their dies and use them, the only problem with that is we would have to make
different drawings of the same part for each vendor (purchasing loves to
bounce around for the cheapest price). As my old boss used to say "were
building tractors here not rocket ships"
so maybe it's just not that important
"Stan McLean" wrote in message
news:B33E90BBC1D49BCC2F288EF05E7FA479@in.WebX.maYIadrTaRb...
> Albert,
>
> Actually based on experience I had with SPI, Radan AutoSM and ProFold in
> MDT, and now experience with Inventor there can be a significant
difference
> between parts that use different Kfactor or Bend allowances.
>
> Many different people have their own variation on Kfactor and how it is
> calculated. Inventor Kfactor is close to what I experienced in our own
shop
> but it doesn't take into account Sheetmetal material, and V-die sizes. It
> is only based on 0.44(44%) offset of the neutral bend axis, which for most
> situation is close but for others, can create a big difference (.010 -
.05,
> or more) per bend difference.
>
> Stan McLean
>
>
> "Albert Allen" wrote in message
> news:66487808A1CE2C0C8F2870B46C4E70F2@in.WebX.maYIadrTaRb...
> > I did a simple bent up part in Inventor sheet metal by starting with a
> flat
> > plate,adding flanges and finally adding holes to each face. I then
> developed
> > the flat pattern and used this flat pattern in an idw with ordinate
> > dimensions for the holes from a set corner. I also used the flat to show
> the
> > bend centers and specified an inside radius for the bends. Ok simple
Simon
> > stuff but when I sent it out to one of our vendors to be punched and
bent
> > they called back and said the bend allowances and the flat pattern did
not
> > jive with the drawing....what?! Turns out that when their engineer (who
> uses
> > SW) did a solid from my flat pattern and bent it on the lines I spec'd
> using
> > the same inside R that I used that things didn't work out. I have always
> > used the default K factor in Inventor sheet metal and everything has
> always
> > turned out exactly as the model when it's built in the shop, so what
gives
> > here???? He did say that he uses K factors they load in from a spread
> sheet
> > into SW but there should not be more than a couple of thousands
difference
> > should there?
> >
> > Thanks,
> >
> > Albert
> >
> >
>
>
*Allen, Albert
Post 5 of 13

Re:

11-07-2002 03:27 AM in reply to: *Allen, Albert
The guy at the particular shop that had questions about our bend allowances
says they like to get the finished piece drawing (no flat pattern) and they
developed their own solid and do the flat. Is this normal operating
procedure for most sheet metal shops? If so it would be easier for me.
"Mark A. Bystry" wrote in message
news:smileyvery-happy:6CC3AEFE319C24C2AC238E8C1EC8344@in.WebX.maYIadrTaRb...
> welcome to sheet metal. i used to use pro/e's sheet metal package when i
was
> in the sheet metal field. i remember that they used some thing like
R-FACTOR
> or some thing like that. it was loosely based on the K-FACTOR. this
default
> setting didn't jive with our tried-and-true bend allowances out in the
shop.
> we used v-dies for all our breaking. we pretty much learned how to fudge
our
> models so the flat pattern would come our perfectly for our machines.
pro/e
> was just like SW and Inventor though. you were able to make a custom bend
> allowance chart in xcel. we just never used that feature.
>
> i'll tell you this though. bend factors are ALWAYS different for every
shop.
> i still regard K-FACTOR as reference only. let the shop guys tell you what
> your bend allowances are. with that info and a little trial-and-error
you'll
> get it right every time.
>
> --
> Mark A. Bystry
> Engineer
> Ziggity Systems, Inc.
> mbystry@ziggity.com
>
>
*Keller, Kent
Post 6 of 13

Re:

11-07-2002 03:51 AM in reply to: *Allen, Albert
It is what the shops I have dealt with prefer.

--
Kent
Member of the Autodesk Discussion Forum Moderator Program


"Albert Allen" wrote in message
news:72D87C6F56DA370D08C338D8034C80A9@in.WebX.maYIadrTaRb...
> The guy at the particular shop that had questions about our bend allowances
> says they like to get the finished piece drawing (no flat pattern) and they
> developed their own solid and do the flat. Is this normal operating
> procedure for most sheet metal shops? If so it would be easier for me.
Distinguished Contributor
387 Posts
0 Kudos
Registered: ‎12-10-2003
Post 7 of 13

Re:

11-07-2002 04:05 AM in reply to: *Allen, Albert
If you send itoutto be done let them find the flat they need don't supply it. If you do and it is wrong they put the blam on you if you send then what you want in finished dim and it is wrong its at there cost not your's
*Hintehoeller, Richard
Post 8 of 13

Re:

11-07-2002 04:13 AM in reply to: *Allen, Albert
That's the case for the few Sheet Metal fabricators I work with.

I won't flat pattern unless they really beg.

Richard
Distinguished Contributor
387 Posts
0 Kudos
Registered: ‎12-10-2003
Post 9 of 13

Re:

11-07-2002 04:30 AM in reply to: *Allen, Albert
If they realy want one tell them you want the bend deduction they use the radius and the bottom v dim. and have them check the flat before production.
*Dotson, Sean
Post 10 of 13

Re:

11-07-2002 05:55 AM in reply to: *Allen, Albert
As well as most of the ones I deal with. I prefer it this way as I want the
finished product. I could care less what the flat looks like...(of course
if you do sheetmetal in-house it's a different ballgame)

--
Sean Dotson, PE
http://www.sdotson.com
...sleep is for the weak..
-----------------------------------------
"Kent Keller" wrote in message
news:3B7DCA59ACEDC726DB1A8EAC5663869B@in.WebX.maYIadrTaRb...
> It is what the shops I have dealt with prefer.
>
> --
> Kent
> Member of the Autodesk Discussion Forum Moderator Program
>
>
> "Albert Allen" wrote in message
> news:72D87C6F56DA370D08C338D8034C80A9@in.WebX.maYIadrTaRb...
> > The guy at the particular shop that had questions about our bend
allowances
> > says they like to get the finished piece drawing (no flat pattern) and
they
> > developed their own solid and do the flat. Is this normal operating
> > procedure for most sheet metal shops? If so it would be easier for me.
>
>
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