Springback and inside radius calculator for sheet metal.


This Springback and Inside Radius Calculator estimates the amount of angular change and the relaxing of bend radius that occurs when metal is bent and released from pressure.  When the proportional limits of a specific material are reached or exceeded the material remains bent, figure one.

Stress-Strain Curve
Stress-Strain Curve

In the forming process, both sheet metal and plastic are bent to a specific bend angle. When the material is then released from the pressure of forming stresses within the bend (tension outside, the compression inside) causes the bend angle to open and the radius to open.

Both the angle and radius the material attempt to return to the flat position; relaxing as the pressure is released.  

The inside radius also relaxes getting larger which in turn affects the numbers for Bend Allowance (BA), OutSide SetBack (OSSB) and Bend Deduction (BD). This phenomenon is known as Springback when applied to angle change and as the Springback factor (Sf) applied to the radius.

Springback and forming method

Springback calculator
Bending and Bent Angles

Accurate numbers for Springback have been one of the more difficult values to predict due to a large number of variables involved: material type, inside bend radius and method of forming to name a few. With all of those variables, Springback can be calculated. Using the correct data points; the thickness, inside radius, modulus of elasticity and the K-factors, etc. it is possible to predict a reasonably accurate number.

Accurate numbers for Springback have been one of the more difficult values to predict due to a large number of variables involved: material type, inside bend radius and method of forming to name a few.

With all of those variables, Springback can be calculated. Using the correct data points; the thickness, inside radius, modulus of elasticity and the K-factors, etc. it is possible to predict a reasonably accurate number.


About the Calculator

All of that being said, please take note of the following instructions
especially the unit of measure for each data point and make sure to input that data correctly:

  1. Select the appropriate golden input box to enter data. Note the units of measure each required input, Inches, ksi, psi. etc.
  2. The degrees of bend angle are input as included angles.
  3. The appropriate K-factor will ll be calculated for you.
  4. For material, specifications look to Matweb.com.

Once there, enter your material type into the search bar (bottom right of the popup windowand transfer any appropriate data to the calculator, be sure the data is in the correct units of measure for this calculator.

For more details on the various inputs, please review the November 2017 edition of the Bending Basics column from the Fabricator magazine or under the Media Tab / Bending Basics from this site’s Menu Bar.


Springback Calculator

Again, pay close attention to your inputs “unit of measure!”

Revision date 11/7/19 to version 2.2.3


Note, predicting Springback will never perfect a perfect science

The material will change from bend to bend, grain direction for example.

The material will change from run to run, different batches of material.

Changes brought on by material coatings.

The material will not be constant throughout a given piece.

Material makeup will not constant throughout the sheet.

Try our Sharp Bend Radius Indicator and our Minimum Bend Radius Calculator


Please, leave us a comment about what you thought of the calculator, and how it might be improved upon.


Comments

Springback Calculator — 2 Comments

  1. Knowing how many degrees I might have to over-bend a part to achieve the final angle helps me choose the right die angle.
    Also I can see this tool being a big help in reducing the in-process trial and error to get the correct radius punch when forming profound radius bends.
    The calculator told me I need a .875″ radius punch to get a 1″ radius in .059 CRS at 90 degrees. I believe that’s about right.
    I like it! Thanks Steve!

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