Sheet Metal Fundamental

This article sheds light on the engineering aspect of Sheet Metal and Bend Allowance methods in SOLIDWORKS.

When a sheet is put through bending operations the metal around bend is deformed or stretched. As this occurs it gains a small amount of length that adds to the total length of the part. The compression or tension will affect the overall length however there is an axis or line which is not affected by this compression or tension. This line is known as neutral axis.

The location varies based on the material physical properties. This is where K-factor is used. K-factor is the ratio of position of neutral axis (t) to Thickness. Hence the K-factor is always less than 1.

K-Factor

Material physical properties and Bending operations are also considered while applying K-factor.

In SOLIDWORKS bend allowance can be applied using below methods:

• K-Factor
• Bend Allowance
• Bend Deduction
• Bend Calculation

Bend Allowance:  This relates to bend region value. The Flatten length = Sum of lengths + Bend allowance.

Bend Allowance

Bend Deduction: Here remove from the total length of the flanges in order to arrive at the flat pattern. Flatten Length = Total length (Out side setback) – Bend Deduction

Bend Deduction

Bend Calculation: Uses customize calculation table (excel). This is because there will be situations where a dynamic change in values is required. Like K-factor will be different for obtuse and acute angle. ‘Compensation factor’ is calculated and added to get the flatten length

Bend/Gauge table are the helpful to assign above bend allowances using excel sheet or a text file with extension (*.btl). Mostly excel is widely used, as it’s not required to be attached if the model is shared. Advantage:

• Manual process is prone to error
• Different tables created for different material
• Multiple thickness bend tables

Excel table (bend table) gets embedded in part file