# Learn How to Use Din 6935 Standard Pdf for Flat Steel Bending Projects

## What is Din 6935 Standard Pdf and How to Use It for Cold Bending of Flat Steel Products?

Din 6935 Standard Pdf is a document that provides guidelines and calculations for cold bending of flat steel products, such as sheets, strips, wide flat steels, etc. Cold bending is a process of forming metal parts by applying force without heating them. It is used for steel construction and general mechanical engineering applications.

## Din 6935 Standard Pdf

In this article, we will explain what Din 6935 Standard Pdf covers, how to calculate the stretched lengths and correction factors for bent workpieces, and what are the smallest allowable bending radius and bending angle for different materials and thicknesses.

## What Does Din 6935 Standard Pdf Cover?

Din 6935 Standard Pdf covers the following aspects of cold bending of flat steel products:

The rolling direction of the flat steel products, which should be considered for better suitability for bending. It is recommended to bend transverse to the rolling direction whenever possible.

The bending radius r, which is the distance from the center of curvature to the inner surface of the bent part. It should be chosen from a series of values given in Table 1 of the document. The bold values are preferred.

The bending angle a, which is the angle between the two legs of the bent part. It can be between 0Ã‚ and 180Ã‚.

The opening angle b, which is the angle between the two tangents to the curve at the ends of the bent part. It can be between 0Ã‚ and 180Ã‚.

The thickness s, which is reduced by about 20% in the rounding area due to cold bending.

The stretched length l, which is the sum of the leg lengths plus a compensation value u that depends on the value of the opening angle b. The compensation value u can be positive or negative and represents the deviation from the theoretical length due to elastic recovery of the material after bending.

The correction factor k, which indicates the deviation of the position of the neutral fiber s/2 from the theoretical position. It is used to determine the cutting lengths of bent workpieces.

## How to Calculate Stretched Lengths and Correction Factors?

To calculate the stretched length l of a bent workpiece, you need to add up the leg lengths a and b and then add or subtract a compensation value u according to the following formulas:

For opening angle b between 0Ã‚ and 90Ã‚:

u = -0.0025 * r * (b - 90)

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For opening angle b between 90Ã‚ and 165Ã‚:

u = -0.0025 * r * (b - 90) + (r - s/2) * (1 - cos(b))

For opening angle b between 165Ã‚ and 180Ã‚:

u = 0

The values for u are negligibly small and provide sufficient accuracy for practical purposes. Stretched lengths should be rounded to the nearest millimeter.

To calculate the correction factor k for determining the cutting lengths of bent workpieces, you need to use this formula:

k = (r + s/2) / (r + s)

This formula is valid for r/s Ã¢ 5. For r/s > 5, you need to set k = 1.

## What are the Smallest Allowable Bending Radius and Bending Angle?

The smallest allowable bending radius r depends on the sheet thickness s and the material type. Table 1 in Din 6935 Standard Pdf gives some values for different materials and thicknesses. The values apply for bending angle a Ã¢ 120Ã‚. For bending angle a > 120Ã‚, you need to use

the next higher table value.

For example, if you want to bend transverse to the rolling direction a sheet of QSt 42-2 (steel grade up to 390 N/mmÃ‚ tensile strength) with thickness s = 6 mm, then the smallest allowable bending radius r would be