Bend Deduction

Bend Deduction: The Ultimate Guide

Probably, you are wondering what bend deduction is and its importance in the sheet metal fabrication process. Well, this guide explores everything you need to know about bend deduction. Let’s dive right in.

What Is Bend Deduction?

It is the most accurate way to calculate the sum difference between the rim length of material and the beginning flat length. Bend deduction is calculated by knowing the bend angle, the K-Factor, your material thickness, and the Inside Radius. The deduction calculation helps to produce an accurate flattened model for manufacture.

Bend Deduction Vs. K-factor.

K-factor is the ratio between the inert axis and material thickness. Bend deduction is a way to calculate the sum difference between the rim length of material and the beginning flat length.

Bend deduction can be used to determine and give a great dimension to the bent part by calculating the flat length of sheet stock. K-factor is used to make a metal bending more precise without damaging the material. Bend deduction calculation helps to produce an accurate flattened model for manufacture while K-factor can be used to estimate the value of the bend allowance.

Bend Deduction Vs. K-factor.
Importance Of Bend Deduction In Sheet Metal Fabrication.

Importance Of Bend Deduction In Sheet Metal Fabrication.

The sheet metal part is always flat before any bends happen thus the length of the flat pattern is usually different from the best shape. This will depend on the material of the sheet metal part and its thickness.

  • Bend deduction can be used to determine and give a great dimension to the bent part by calculating the flat length of sheet stock.
  • The calculation helps to produce an accurate flattened model for manufacture.
  • It is a cost-effective shape process when used for low to medium-quality materials.
  • Additionally, it helps you to create an accurate size and dimensions required in the flat pattern.

How To Calculate Bend Deduction

How To Calculate Bend Deduction
How To Calculate Bend Deduction

Bend deduction is calculated by knowing the bend angle, the K-Factor, your material thickness and the Inside Radius.The calculation is determined by bending and the bending formation hence the methods can affect the mathematical values chosen for the calculation.

Before doing the bend calculation, you must change the bend angle to the complimentary angle of the part feature. That is, before doing the bend deduction and you can use decimal form for approximation. It is done when you insert the material thickness and the radius angle.

K-factor reflects how the material stretches when formed hence it is a product of the material that is bending.

Bend deduction=2*(tan(B</2) *(IR+MT)-22/7/180*B <*(IR+K*MT)

The formula can be long only if the bend allowance and the Out Side Set Back is calculated but it can be shorter when the Bend Allowance and the Out Side Set Back is already available.

Therefore, Bend deduction = 2* OSSB – BA

Bend Allowance Vs. Bend Deduction

Calculating Sheet Metal Rim Length
Calculating Sheet Metal Rim Length

Bend deduction is the most accurate way to calculate the sum difference between the rim length of a material and the beginning flat length.

Creating Flattened Model Vs. Size
Creating Flattened Model Vs. Size

Bend allowance helps to create a great flattened model for manufacture while the bend deduction helps to create accurate sizes needed in the flat pattern. Manufacturers use a chart with quality standards based on the material substratum and the thickness to find the values of the two measures.

Creating Metal With No Deformity
Creating Metal With No Deformity

Manufacturers depend on bend deduction to get bend allowance if they need metal with no deformity. They are two measures that relate the bent length of a piece of sheet metal to the flat length. Hence,  we use solid works and meta fab to figure out the bend deduction and bend allowance.

Prediction In Sheet Metal Bending
Prediction In Sheet Metal Bending

Bend allowance can also be used to predict the initial flat length of the sheet hence to get an accurate final product dimension. This will depend on how the final sheet dimensions are measured and on many variables like bend radius, sheet material and the material features.

Determining Bend Deduction Value
Determining Bend Deduction Value

Bend deduction is calculated by knowing the bend angle, the K-Factor, your material thickness and the Inside Radius. The two things that determines your bend deduction are the geometries of bending and the properties of your metal. Bend deduction can be used to determine and give a great dimension of the bend part by calculating the flat length of a sheet stock.

Bend Deduction
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