Scribd
Upload
160 views3 pages

Bend Allowance and K Factor

The document discusses the importance of using CAD software with a sheet metal environment for designing bent sheet metal parts, as it accounts for material specifications necessary for creating flat patterns. It explains the concept of the k factor, which is essential for calculating bend allowances and determining the position of the neutral axis during bending. Additionally, it provides formulas for calculating bend allowances based on bending angles and offers tips to avoid common mistakes in sheet metal design.

Uploaded by

nagaraju
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
160 views3 pages

Bend Allowance and K Factor

The document discusses the importance of using CAD software with a sheet metal environment for designing bent sheet metal parts, as it accounts for material specifications necessary for creating flat patterns. It explains the concept of the k factor, which is essential for calculating bend allowances and determining the position of the neutral axis during bending. Additionally, it provides formulas for calculating bend allowances based on bending angles and offers tips to avoid common mistakes in sheet metal design.

Uploaded by

nagaraju
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 3

Bend Allowance and K Factor

If you design your bent sheet metal parts in CAD software that has a special
sheet metal environment, use it. It exists for a reason. When making bends, it
takes material specifications into account. All this information is necessary when
making a flat pattern for laser cutting.
Unless you use our manufacturing service where CAD models are accepted for
production, you need to keep producing those flat pattern drawings.

The arc length of the neutral axis must be used for flat pattern
calculation
If you make your flat pattern drawings yourself, here’s something you need to
know. Bending elongates the material. This means that the neutral line or axis, as
we talked in the springback section, is not really in the middle of the material. But
the flat pattern must be formed according to the neutral line. And finding its
position requires k factor.
K factor is an empirical constant, meaning that its value was determined by
testing. It varies according to material, its thickness, bend radius and bending
method. Basically, the k factor offsets the neutral line to provide a flat pattern that
reflects reality. By using it, you get the bend allowance which is, in essence, the
length of the curved neutral axis.
K factor formula:

k – k factor, constant; ir – inside radius (mm); t – sheet thickness (mm)


Bend allowance formulas:
For bends between 0 and 90 degrees the formula is as follows:

ß – bending angle (°)


For bends between 90 and 165 degrees the formula is:

For bends over 165°, there is no need to calculate bend allowances, as the
neutral axis stays pretty much in the middle of the detail.
Calculating Bend Allowance
Let’s say you have a similar part to the one on the image above – it has a straight
leg of 20 mm and another of 70 mm. The bending angle is 90°, sheet thickness 5
mm and the inside radius is 6 mm. We want to know the final length of the detail.
First, we must start with the k factor:

Another way to determine the k factor is by following the “rule of thumb”. Just
select a k factor according to your material from the table below. This gives results
accurate enough for most cases.

Now we can move on to the bend allowance:


For the final length we just add the two leg lengths to the bend allowance:

Sheet Metal Design Tips for Bending


So, I talked to our experienced sales engineer who knows his bit about sheet
metal bending. He lit up and decided to make the fullest of the opportunity to
share his insights on sheet metal bending. Thus, he brought out a list of common
mistakes and the solutions to avoid them.

You might also like