# Bend Deduction

Bend Deduction Calculation

The V die opening is used to calculate the bend deduction, which is the reduction in size of the workpiece due to the bending process. This calculation involves the V die opening to ensure that the workpiece's size is reduced appropriately for the intended application.

[ BD = \frac{2 \times \tan(\frac{\theta}{2}) \times R \times T}{1 - \cos(\theta)} ]

Where:

    ( BD ) is the bend deduction.
    ( \theta ) is the bend angle in radians.
    ( R ) is the inside radius of the bend.
    ( T ) is the thickness of the material.

Calculating bend deduction involves several factors:

    Bend Angle (α): The angle at which the sheet metal is bent.
    Inside Radius (R): The radius of the bend where the material is not deformed.
    Material Thickness (T): The thickness of the sheet metal being bent.
    K-factor (K): A value representing the position of the neutral axis relative to the material thickness. It varies based on the material properties and the bending radius

The K-factor is used to calculate the bend allowance and is also relevant when calculating bend deduction. It helps determine the length of the metal plate stretched during the bending process and is a fundamental value for determining the bending allowance and bending deduction

Additionally, when calculating bend deduction, it's important to note that the neutral axis shifts towards the inside surface of the bend during the bending process. This shift, combined with the material's properties and the bending radius, affects the amount of elongation that occurs during bending, which is taken into account when calculating bend deduction

Bend deduction is a crucial concept in sheet metal fabrication, allowing for accurate prediction of the final size of a part after bending. It accounts for the material's stretch and compression during the bending process. The formula provided for calculating bend deduction is not standard and seems to be a misunderstanding. Instead, bend deduction is typically calculated using the bend allowance and the outside setback (OSSB). The correct approach involves understanding several key factors:

    Bend Angle (θθ): The angle to which the metal is bent.
    Inside Radius (R): The radius on the inside of the bend, where the material undergoes compression.
    Material Thickness (T): The thickness of the sheet metal being bent.
    K-Factor (K): A coefficient that represents the location of the neutral axis (the layer within the material that does not experience tension or compression during bending) relative to the thickness of the material. This factor varies based on material properties and bending operations.

The bend deduction (BD) can be calculated using the formula: BD=2×OSSB−BABD=2×OSSB−BA where:

    OSSB (Outside Setback) is calculated based on the material thickness, inside radius, and bend angle.
    Bend Allowance (BA) is the arc length of the bend along the neutral axis. It accounts for the material stretch in the bending area and is calculated using the formula that incorporates the K-factor, bend angle, inside radius, and material thickness.

The K-factor is instrumental in determining the bend allowance and, subsequently, the bend deduction. It influences how the neutral axis shifts during bending, affecting the material's elongation and the final dimensions of the bent part.