This document discusses sheet metal parameters and bend allowances. It explains that sheet metal parameters must be set to invoke sheet metal tools. These parameters include the standard, bend radius, and K-factor. It then describes how to modify bend extremities such as adding square or round reliefs. The document also discusses how bending works using press brakes and die sets. It explains that the neutral axis is neither compressed nor stretched during bending. Finally, it provides the formula for calculating bend allowance based on factors like K-factor, bend radius, thickness, and bend angle.

1.  Prepared By: Anubhav Singh

2. 1. Editing the Sheet and Tool Parameters:-
This tool used to set the different sheet metal parameters
needed to create your first feature. Without setting the sheet metal
parameters you can’t invoke the sheet metal tools.
The Standard field displays the Standard to use with the part, if
implemented. The name of this standard file is defined in a Design
Table.
The Bend radius defines the minimum internal radius allowing
the creation of a bend. You can set the value to 0 to create bend
with no radius.
Parameters can be defined in a Design Table. To do so, press
the Sheet Standards Files button to access to the company-defined
standards.

3. 2. Modifying the Bend Extremities
This section explains how to change the bend extremities, i.e. how to
change axial relimitations for a straight bend.
Choose a bend extremity, either from the drop-down list or using the
graphical button underneath.
(1) Minimum with no relief (default option):-
The bend corresponds to the common area of the
supporting walls along the bend axis, and shows no relief.
(2) Square relief:-
The bend corresponds to the common area of the supporting
walls along the bend axis, and a square relief is added
to the bend extremity. The L1 and L2 parameters can be modified if
needed.

4. (3) Round relief:- The bend corresponds to the common area of the
supporting walls along the bend axis, and a round relief is added to
the bend extremity. The L1 and L2 parameters can be modified if
needed.
(4) Linear:- The unfolded bend is split by two planes going through
the corresponding limit points (obtained by projection of the bend
axis onto the edges of the supporting walls).
(5) Tangent:- The edges of the bend are tangent to the edges of the
supporting walls.

6. A
B
C
E
D
Rm
t
B
A C
D
E
P Rm/2 P Rm/2
t

7. Bending is a flexible process by which a variety of different shapes
can be produced through the use of standard die sets or bend brakes.
The material is placed on the die, and positioned in place with
stops and/or gages. the upper part of the press, the ram with the
approximately shaped punch descends and forms the v-shaped bend.
Bending is done with Press brakes. Programmable back gages, and
multiple die sets currently available can make bending a very
economical process

8. When Sheet metal is bent, the inside surface of the bend is
compressed and the outer surface of the bend is stretched. Some
where within the thickness of the metal lies its Neutral Axis, which
is the line in the metal that is neither compressed nor stretched.
What this means in
practical terms is that if we want a
work piece with a 90 degree bend
in which one leg measures A and
another leg measures B then the
total length of the flat piece is not
A+B as one might assume at first
assume.
To work out what the length of flat
piece of metal needs to be, We
need to calculate the Bend
Allowance or Bend Deduction that
tells me how much we need to add
or subtract to our leg lengths to get
exactly what we want.

9. The location of the neutral line varies depending on:
The material itself
The radius of the bend
The ambient temperature
Direction of material grain
The method by which it is being bent,etc.
The location of this line is often referred to as the K-factor.
K-factor is a ratio that represents the location of the neutral
sheet with respect to the thickness of the sheet metal part.

10. Computing the Bend Allowance
The bend allowance corresponds to the unfolded bend width.
L is the total unfolded length
A and B the dimensioning lengths as defined on the
above figure.
•K Factor
Physically, the neutral fiber represents the
limit between the material compressed
area inside the bend and the extended
area outside the bend. Ideally, it is
represented by an arc located inside the
thickness and centered on the bend axis.

11. 1) L is the total unfolded length.
2) A and B the dimensioning lengths as defined on the above figure.
3) K factor defines the neutral fiber position.
4) W is the bend allowance.
5) R is the inner bend radius.
6) T is the sheet metal thickness.
7) α is the inner bend angle in radians.
8) β is the opening bend angle in degrees
K Factor:- Physically, the neutral fiber represents the limit
between the material compressed area inside the bend and the
extended area outside the bend. Ideally, it is represented by an arc
located inside the thickness and centered on the bend axis.

12. When you define the sheet metal parameters, a literal feature
defines the default K Factor and a formula is applied to implement
the DIN standard. This standard is defined for thin steel parts.
Therefore the K Factor value ranges between 0 and 0.5.
This formula can be deactivated or modified by right-clicking in
the K factor field and choosing an option from the contextual menu.
It can be re-activated by clicking the Apply DIN button. Moreover,
the limit values can also be modified.

13. THANKS