Sheet Metal Uncertainty

[Anonymous]

We are starting to use the IV9 sheet metal module and are having trouble
understanding the K-Factor values. I know a K-Factor is a number
between 0 and 1 that indicates the relative distance from the inside of
the bend to the neutral axis of the bend. IV9 sets a default K-factor
of 0.44.

How does this equate with the Machinery's Handbook bending allowance
formulas for 90 degree bends stating:

Soft Brass/Soft Copper
L=(0.55 x T)+ (1.57 x R)
Half Hard Copper/Brass/Aluminum
L=(0.64 x T)+ (1.57 x R)
Bronze/Cold Rolled Steel
L=(0.71 x T)+ (1.57 x R)

I did multiple tests and the first variable in the formula DOES NOT
equate to the K-Factor in IV9.

Also, we have determined that changing the material via iProp has ZERO
affect on unfolded flat patterns, that is, the total length is identical
regardless of material. (Which is not the case in the real world.)

Can anyone shed some light on what K-Factor settings (other settings as
well ???) to make for different materials??

Thanks,
Jim Lacey
Cornell University

[Anonymous]

Not sure if this explanation will help.
K Factor definition: K-factor is a ratio that represents the location of the
neutral line with respect to the thickness of the sheet metal part. The
location of the neutral line varies depending on the material itself, the
radius of the bend, the ambient temperature, direction of material grain,
and the method by which it is being bent, etc. The location of this line is
often referred as the K factor. (Olaf Diegel)

For more information and bend calculator by Olaf Diegel visit:

http://www.massey.ac.nz/~odiegel/bendworks/

Wolfe



"James Lacey" wrote in message
news:4857883@discussion.autodesk.com...
We are starting to use the IV9 sheet metal module and are having trouble
understanding the K-Factor values. I know a K-Factor is a number
between 0 and 1 that indicates the relative distance from the inside of
the bend to the neutral axis of the bend. IV9 sets a default K-factor
of 0.44.

How does this equate with the Machinery's Handbook bending allowance
formulas for 90 degree bends stating:

Soft Brass/Soft Copper
L=(0.55 x T)+ (1.57 x R)
Half Hard Copper/Brass/Aluminum
L=(0.64 x T)+ (1.57 x R)
Bronze/Cold Rolled Steel
L=(0.71 x T)+ (1.57 x R)

I did multiple tests and the first variable in the formula DOES NOT
equate to the K-Factor in IV9.

Also, we have determined that changing the material via iProp has ZERO
affect on unfolded flat patterns, that is, the total length is identical
regardless of material. (Which is not the case in the real world.)

Can anyone shed some light on what K-Factor settings (other settings as
well ???) to make for different materials??

Thanks,
Jim Lacey
Cornell University

[Anonymous]

Each material should have its own sheet metal style and corresponding
k-factor. The k-factors I use are:

Soft Brass/Soft Copper = 0.3501
Half Hard Copper/Brass/Aluminum = 0.4074
Bronze/Cold Rolled Steel = 0.4520

The constants (0.55, 0.64, 0.71) that are in the Machinery's Handbook are
Y-Factors. To find the K-Factor use the formula: Y-Factor * 2 / Pi.

Allen




"James Lacey" wrote in message
news:4857883@discussion.autodesk.com...
We are starting to use the IV9 sheet metal module and are having trouble
understanding the K-Factor values. I know a K-Factor is a number
between 0 and 1 that indicates the relative distance from the inside of
the bend to the neutral axis of the bend. IV9 sets a default K-factor
of 0.44.

How does this equate with the Machinery's Handbook bending allowance
formulas for 90 degree bends stating:

Soft Brass/Soft Copper
L=(0.55 x T)+ (1.57 x R)
Half Hard Copper/Brass/Aluminum
L=(0.64 x T)+ (1.57 x R)
Bronze/Cold Rolled Steel
L=(0.71 x T)+ (1.57 x R)

I did multiple tests and the first variable in the formula DOES NOT
equate to the K-Factor in IV9.

Also, we have determined that changing the material via iProp has ZERO
affect on unfolded flat patterns, that is, the total length is identical
regardless of material. (Which is not the case in the real world.)

Can anyone shed some light on what K-Factor settings (other settings as
well ???) to make for different materials??

Thanks,
Jim Lacey
Cornell University

[Anonymous]

This is EXACTLY the info I was hoping to get, thank you!

Allen Hart wrote:

> Each material should have its own sheet metal style and corresponding
> k-factor. The k-factors I use are:
>
> Soft Brass/Soft Copper = 0.3501
> Half Hard Copper/Brass/Aluminum = 0.4074
> Bronze/Cold Rolled Steel = 0.4520
>
> The constants (0.55, 0.64, 0.71) that are in the Machinery's Handbook are
> Y-Factors. To find the K-Factor use the formula: Y-Factor * 2 / Pi.
>
> Allen
>
>
>
>
> "James Lacey" wrote in message
> news:4857883@discussion.autodesk.com...
> We are starting to use the IV9 sheet metal module and are having trouble
> understanding the K-Factor values. I know a K-Factor is a number
> between 0 and 1 that indicates the relative distance from the inside of
> the bend to the neutral axis of the bend. IV9 sets a default K-factor
> of 0.44.
>
> How does this equate with the Machinery's Handbook bending allowance
> formulas for 90 degree bends stating:
>
> Soft Brass/Soft Copper
> L=(0.55 x T)+ (1.57 x R)
> Half Hard Copper/Brass/Aluminum
> L=(0.64 x T)+ (1.57 x R)
> Bronze/Cold Rolled Steel
> L=(0.71 x T)+ (1.57 x R)
>
> I did multiple tests and the first variable in the formula DOES NOT
> equate to the K-Factor in IV9.
>
> Also, we have determined that changing the material via iProp has ZERO
> affect on unfolded flat patterns, that is, the total length is identical
> regardless of material. (Which is not the case in the real world.)
>
> Can anyone shed some light on what K-Factor settings (other settings as
> well ???) to make for different materials??
>
> Thanks,
> Jim Lacey
> Cornell University

[Anonymous]

Can you shed some light on the differences between K-Factor & Y-Factor??

Are the values you use an industry standard or have you determined them
via trial and error?

Thanks for the help.

Tim O'Connell
Cornell University

Allen Hart wrote:
>
> Each material should have its own sheet metal style and corresponding
> k-factor. The k-factors I use are:
>
> Soft Brass/Soft Copper = 0.3501
> Half Hard Copper/Brass/Aluminum = 0.4074
> Bronze/Cold Rolled Steel = 0.4520
>
> The constants (0.55, 0.64, 0.71) that are in the Machinery's Handbook are
> Y-Factors. To find the K-Factor use the formula: Y-Factor * 2 / Pi.
>
> Allen
>
> "James Lacey" wrote in message
> news:4857883@discussion.autodesk.com...
> We are starting to use the IV9 sheet metal module and are having trouble
> understanding the K-Factor values. I know a K-Factor is a number
> between 0 and 1 that indicates the relative distance from the inside of
> the bend to the neutral axis of the bend. IV9 sets a default K-factor
> of 0.44.
>
> How does this equate with the Machinery's Handbook bending allowance
> formulas for 90 degree bends stating:
>
> Soft Brass/Soft Copper
> L=(0.55 x T)+ (1.57 x R)
> Half Hard Copper/Brass/Aluminum
> L=(0.64 x T)+ (1.57 x R)
> Bronze/Cold Rolled Steel
> L=(0.71 x T)+ (1.57 x R)
>
> I did multiple tests and the first variable in the formula DOES NOT
> equate to the K-Factor in IV9.
>
> Also, we have determined that changing the material via iProp has ZERO
> affect on unfolded flat patterns, that is, the total length is identical
> regardless of material. (Which is not the case in the real world.)
>
> Can anyone shed some light on what K-Factor settings (other settings as
> well ???) to make for different materials??
>
> Thanks,
> Jim Lacey
> Cornell University

[Ray_P]

We have been using Inventor since r 4. All of our parts (flat Patterns) are saved as a DXF's for CNC punch processing (THE REAL WORLD). We could not work with the K-FACTOR. We use a bend table instead that is derived from our bend allowances for each material & die combination there is a different BA for each. Non 90 deg bends require changing ID bend radius per flange/bend. I suggest using bend tables.

[mcgyvr]

k factors are also different depending on the press brake and the pressure/die type.
what works on our press brake will not work on others with the same material and same bend radius.
I once found a GREAT excel formula for calculating the k factor for each press brake but cant seem to locate it again.

but here is the kfactor that we use for .125 copper with a .032 bend radius kfactor=.340
press brake is a guifil (essay int.) just for anyones info

[Anonymous]

I've got a "paper", somewhere, from several years ago that explains how this
was all developed. I'll have to find it. It is based on the formulas in
the Machinery's Handbook. So I guess it is an industry standard.
These three basic k-factors have worked very well for our CNC and brake
press work. The finished parts are usually dead-on, or at least well within
tolerance (+/- .016). (We make architectural metal panels & trim.)

When I find the info I'll post it.

Allen



"Timothy O'Connell" wrote in message
news:4857963@discussion.autodesk.com...
Can you shed some light on the differences between K-Factor & Y-Factor??

Are the values you use an industry standard or have you determined them
via trial and error?

Thanks for the help.

Tim O'Connell
Cornell University

Allen Hart wrote:
>
> Each material should have its own sheet metal style and corresponding
> k-factor. The k-factors I use are:
>
> Soft Brass/Soft Copper = 0.3501
> Half Hard Copper/Brass/Aluminum = 0.4074
> Bronze/Cold Rolled Steel = 0.4520
>
> The constants (0.55, 0.64, 0.71) that are in the Machinery's Handbook are
> Y-Factors. To find the K-Factor use the formula: Y-Factor * 2 / Pi.
>
> Allen
>
> "James Lacey" wrote in message
> news:4857883@discussion.autodesk.com...
> We are starting to use the IV9 sheet metal module and are having trouble
> understanding the K-Factor values. I know a K-Factor is a number
> between 0 and 1 that indicates the relative distance from the inside of
> the bend to the neutral axis of the bend. IV9 sets a default K-factor
> of 0.44.
>
> How does this equate with the Machinery's Handbook bending allowance
> formulas for 90 degree bends stating:
>
> Soft Brass/Soft Copper
> L=(0.55 x T)+ (1.57 x R)
> Half Hard Copper/Brass/Aluminum
> L=(0.64 x T)+ (1.57 x R)
> Bronze/Cold Rolled Steel
> L=(0.71 x T)+ (1.57 x R)
>
> I did multiple tests and the first variable in the formula DOES NOT
> equate to the K-Factor in IV9.
>
> Also, we have determined that changing the material via iProp has ZERO
> affect on unfolded flat patterns, that is, the total length is identical
> regardless of material. (Which is not the case in the real world.)
>
> Can anyone shed some light on what K-Factor settings (other settings as
> well ???) to make for different materials??
>
> Thanks,
> Jim Lacey
> Cornell University

[Anonymous]

I think what it really comes down to is that the Machinery handbook has
resolved the equations for bend allowance to their simplest form so instead
of an equation that has k*2/pi you have this "Y" value. That's all, it's a
convenience value. "K" factor is used because it has a direct, physical
relationship with the bend geometry.

Patrick

[Anonymous]

I have attached an Excel Spreadsheet that I created and use where I work.
We do mostly air-bending, with a variety of press brakes, as you can see from our website.
We have been using these values for 30+years, holding +/- .005 on forms when necessary.

As mcgyvr stated, what works for some, will not work for everyone.
There are too many variables involved.

I have yet to receive any models from customers that use the same values as we do,
and even between different customers, the values vary.

Ken

[Anonymous]

Well, I've lost my paper - been years since I've seen it anyway. It's
probably in some ancient backup set on 5-1/4 inch floppys collectiong dust
somewhere.
Anyway, the Length equation in the Machinery's Handbook says

> Half Hard Copper/Brass/Aluminum
> L=(0.64 x T)+ (1.57 x R)

which is shorthand for
L= (0.64 x T) + (Pi/2 x R)

and if K-Factor = 0.64 x 2/Pi

then, L=2 x K x (R + T)

To figure the Length of a bend of any angle
L = 2K(R+T)(A/90)

That's it in a nutshell.

Allen