Defining-the-Bend-Allowance

By catia programmer

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This section explains the calculations related to folding/unfolding operations.
When a bend is unfolded, the sheet metal deformation is represented by the
bend allowance V defined by the formula:
L = A + B + V

where:
L is the total unfolded length
A and B the dimensioning lengths as defined on the figures below:

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Bend-Allowance (2)

By catia programmer

Another way to compute the sheet metal deformation is the neutral fiber
definition (K Factor):
W = a * (R + k * T)
where:
W is the flat bend width
R the inner bend radius
T the sheet metal thickness
a the inner bend angle in radians.
If b is the opening bend angle in degrees:
a = p * (180 - b) / 180
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. Therefore the K Factor always has a value between 0 and
0.5.

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Bend Allowance

By catia programmer

Continued....
When you define the sheet metal parameters, a literal feature defines the
default K Factor, according to the DIN standard:
K = (0.65 + log(R / T) / 2) / 2
This formula can be deactivated or modified using Knowledge Advisor
workbench.
When a bend is created, the bend K Factor and the bend allowance literals
are created.
Two cases may then occur:
If the Sheet Metal K Factor has an activated formula and uses the
default bend radius as input parameter, the same formula is activated
on the bend K Factor with the bend radius as input.
Else the bend K Factor is a formula equal to the Sheet Metal K Factor.
The bend allowance literal is equal to a formula representing the use of the
bend K Factor. This formula is fairly complex and it is strongly recommended
not to delete it.
V = a * (R + k * T) – 2 * (R + T) * tan ( min(p/2,a) / 2)
Though it is possible to deactivate the formula to enter a fixed value.
Finally, the bend flat width is computed from the bend allowance value.

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Specify A Working Plane

By catia programmer

The next step is to create a two-dimensional profile of the part. The Sketcher Work
Bench is a two-dimensional (planar) work area. To use the Sketcher Work Bench,
you must specify which Plane the profile is to be created on. Specifying the Plane
can be done several different ways.
3.1 Select (highlight) the desired Plane from the graphical representation in
the center of the screen as shown in Figure 1.5. Notice, as a particular
Plane is selected, the equivalent Plane in the Specification Tree is
highlighted. If the Specification Tree isn’t showing the branches with the
Plane, it will need to be expanded. To do this, select the Plus symbol
to the left of the Specification Tree or double click on the branch you
want expanded.
3.2 The step described above can be reversed. Select the Plane in the
Specification Tree and the coordinating plane in the center of the screen
will also be highlighted.
3.3 Other Planes, surfaces and/or other planner objects can also be selected to
define the Sketcher Plane. This option will be covered in more detail
later in the book.

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Start CATIA V5

By catia programmer

From the NT Desktop, double click on the CATIA V5R5 icon. Be patient, it may
take a few moments to bring up the CATIA V5 start logo and the actual CATIA V5
working window. Figure 1.3 shows what the screen should look like.
If you are not able to finish all of the steps in this lesson in one session, you can jump
to Step 23, which covers saving and exiting CATIA V5. This will allow you to save
your work for your next session

2 Select The Sketcher Work Bench.
Every time you start CATIA V5, the CATIA V5 screen will appear as it does in
Figure 1.3. The “Welcome to CATIA V5” pop-up window will prompt you to select
a work bench. The default work bench is Product Structure. For this lesson, you
will need to select the Sketcher Work Bench. Notice, as you select the Sketcher
Work Bench that the tool bars on the right hand of your screen change and the
“Welcome to CATIA V5” pop-up window disappears.

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Modifying the Bend Extremities

By catia programmer

This section explains how to change the bend extremities.
Click the Parameters icon .
The Sheet Metal Parameters dialog box is displayed.
The second tab concerns the bend extremities.
A combo box displays the six possible axial relimitations for the straight bend:
Minimum with no relief: the
bend corresponds to the
common area of the
supporting walls along the
bend axis.
Square relief: a square relief
is added to the bend
extremity. The L1 and L2
parameters can be modified
if need be.
Round relief: a round relief
is added to the bend
extremity. The L1 and L2
parameters can be modified
if need be.
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).
Tangent: the edges of the
bend are tangent to the
edges of the supporting
walls.
Maximum: the bend is
calculated between the
furthest opposite edges of
the supporting walls.

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Sheet Metal Parameters

By catia programmer

This task shows you how to configure the sheet metal parameters.
1. Click the Parameters icon .
The Sheet Metal Parameters dialog box is displayed.
2. Enter 1mm in the Thickness field.
3. Enter 5mm in the Bend Radius field.
4. Select the Bend Extremities tab.
5. Select Tangent in the Bend Extremities combo list.
An alternative is to select the bend type in the graphical combo list.
6. Click OK to validate the parameters and close the dialog box.
The Sheet Metal Parameters feature is added in the specification tree.

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Sheet Metal Design Function

By catia programmer

V5R18 CATIA - Sheet Metal Design offers the following main functions:
Associative and dedicated Sheet Metal feature based modeling
Concurrent engineering between the unfolded or folded part representation
Access to company defined standards tables
Dedicated drawing capability including unfolded view and specific settings.
All sheetmetal specifications can be re-used by the CATIA - Knowledge Advisor to
capture corporate knowledge and increase the quality of designs.
Natively integrated, CATIA - Sheet Metal Design offers the same ease of use and user
interface consistency as all CATIA V5 applications.

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Sheet Metal Design

By catia programmer

The V5 CATIA - Sheet Metal Design is a new generation product offering an
intuitive and flexible user interface. It provides an associative feature-based
modeling making it possible to design sheet metal parts in concurrent engineering
between the unfolded or folded part representation.
As a scalable product, CATIA Version 5 Sheet Metal Design can be used in
cooperation with other current or future companion products in the next CATIA
generation such as CATIA Version 5 Assembly Design and CATIA Version 5
Generative Drafting. The widest application portfolio in the industry is also
accessible through interoperability with CATIA Solutions Version 4 to enable
support of the full product development process from initial concept to product in
operation.

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