VTube Overbend Calculations for Springback

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About Overbend Calculator

The Overbend Calculator is a built-in feature in VTube-STEP and VTube-LASER that can calculate the fixed and proportional springback values to be included in the Part Setup menu or the Springback Table.

These values have an effect the final bend angles when sending new data to the bender, and when making corrections to the bender.


Why Use Springback Compensation with Overbending?

The springback feature is for predicting the amount of overbend necessary to compensate for springback. ("Overbend" is a term that we created and use to describe what happens in the springback compensation process. To compensate for springback, you overbend each bend.) The goal is to make the first part after the initial bender setup closer to the nominal.

Traditional Fabrication

Traditionally customers just bent the first part without any springback compensation, then allowed VTube-LASER to correct the bender to bring the part close to the master data. For customers with inexpensive material and high-volume per-part production, this was not an issue. However, now more customers are starting to build up a database of springback information to drive the part more quickly to the master shape.

The Springback Compensation Method

The method is to measure the characteristics of springback for a given material and bender setup using a test piece, then store springback values that let VTube inject extra bend angle (and remove some straight distance between bends) to get to a part within the tolerance envelope more quickly. See the steps for calculating springback values below.

Justification for Using Springback Compensation

An increasing number of customers are asking if they should use springback compensation. Since there is a cost invested to bend and measure the test piece, each customer has a different trigger point for making springback compensation worth while.

For industries with very expensive material, the justification for springback compensation is very high. For example, in nuclear shipbuilding applications, material costs of $1000 per foot require that the first part be within tolerance every time.

To answer the question for your application, we recommend that you dedicate time to running time-studies to see at what point compensating for springback makes sense for your application.

Steps to Calculate Springback Values


Right click anywhere in the Part Setup menu and click on Overbend Calculator in the popup menu.

Vtube-step v2.2 partsetup popup overbendcalculator.png


Set the bender to bend a two bend part.

Typically the angles are 20 and 120 degrees. Enter the actual bend values used in the bender in this tab menu.

Vtube v2.2 overbend page1.png


The actual resulting bend angles are measured and entered into the Overbend Calculator.

If you're using VTube-LASER connected to a FARO measuring center, then you can create a part with the bend angles in the Bender Setup tab (the previous tab menu), then measure a test part, then copy the measured angles into the Overbend calculator.

Vtube v2.2 overbend page2.png


The proportional and fixed values are calculated and used in a springback formula to overcome springback at any angle by calculating the overbend angles.

Press the Calculate button to calculate the values.

After you calculate the values, you can choose one of these actions...

  • Save the values to Part Setup and close the window.

  • Add the values to the end of the Springback table and close the window.

  • Do both and close the window.

  • Or just Cancel and close the window.

Vtube v2.2 overbend page3.png

Where the Values are Stored in VTube

Part Setup

The springback values are applied to the current project by storing the values in the Part Setup menu.

Vtube v2.2 partsetup springbackvalues.png

Springback Table

The springback values can also be stored in the Springback Table so that you can reuse the values in other projects.

Vtube v2.2 partsetup springbacktable popup.png

Vtube v2.2 springbacktable.png

Using Springback Values in VTube-STEP to Change the Bender Setup


These two calculated values will be used to automatically calculate overbend to overcome springback when sending data to the bender in the BEND OUTPUT Automated Supravision Link protocol menu in VTube-STEP.

Vtube-step v2.2 benderoutput SVnetwork.png


These two calculated values will be used to automatically calculate overbend to overcome springback when saving data to a bender file in the IMPORT/EXPORT menu.

Vtube-step v2.2 export menu.png

Using Springback Values in VTube-STEP Reports

These two calculated values can be used to report bender with springback compensation.

The springback values are used to adjust the length between bends and bend angles.

Vtube-step v2.2 springback report.png

Using Springback Values in VTube-LASER to Change the Bender Setup

The VTube-LASER license level uses the FARO measuring center to measure and qualify a tube shape, then correct tube benders.

The springback values can be used to automatically calculate overbend to overcome springback when sending setup data to the bender in the BEND SETUP page in VTube-LASER.

This image shows the AUTO SEND button inside the Bender Setup menu in VTube-LASER.


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