Bend Table types and flat length calculation

The think3 application supports seven types of bend tables, corresponding to the different ways of computing the Bend allowance value:

• K-coeffient (default)
  Bend allowance — and thus development length — is computed based on the K-coefficient values, which are listed in the table.
   
• K-factor
  Bend allowance — and thus development length — is computed based on the K-factor values, which are listed in the table.
   
• Bend allowance
  Bend allowance values are listed directly in the bend table. For any angle a, Bend allowance is the product of Bend allowance for 90° bend angle and the a/90 ratio:
  
  BA = (BA for 90°) . a/90
   
• Bend deduction
  Bend allowance — and thus development length — is computed based on the Bend deduction values, which are listed in the table.
   
• Allowance internal
  Bend allowance — and thus development length — is computed based on the internal allowance values, which are listed in the table.
   
• Allowance external
  Bend allowance — and thus development length — is computed based on the external allowance values, which are listed in the table.
   
• Internal sharp edge
  Bend allowance — and thus development length — is computed based on the internal sharp edge allowance values, which are listed in the table.
   

The total flat length L is determined as shown in the following illustration:

L = L1 + BA + L2

where:

R	is the internal bending radius
T	is the thickness
t	is calculated based on the K-factor (in which case ) or on the bend table
a	is the bend angle
BA	is the Bend allowance that will be calculated using different formulas based on the type of bend table.

K-coeffient

The K-coefficient (K_C) is a deformation coefficient which can be positive or negative (and is different from the K-factor (K_F)). The default bend table in the think3 application is based on the K-coefficient.

There are two different formulas used to compute the developed length depending on the bend angle.

	If the bend angle is smaller than 90° (a < p/2): while the relation between the K-coefficient and the K-factor is:
	If the bend angle is greater than or equal to 90° (a ≥ p/2): while the relation between the K-coefficient and the K-factor is:

K-factor

The K-factor is the ratio of distance from the inside face to the neutral line (t) and thickness T:

The Bend allowance BA is the arc length measured along the neutral line (the one between the two red markers in the following illustration).



The following formula will be used to calculate the Bend allowance:


where:

Bend deduction

Bend deduction is the length to be subtracted from the developed edges when they are developed just by extending them to their intersection as displayed in the following illustration:



In this case the development length is:

L = D1 + D2 - B_D

where B_D is the Bend deduction value.

If the bend angle is 90° (a=90°), Bend allowance is:


Bend Table files of type Bend deduction support only an angle of 90°.

For any angle a, Bend allowance is the product of Bend allowance for 90° bend angle and the ratio:

Related Topics

• Bend Table
• Bend Table Parameters
• Bend Table Manager - Overview

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