K factor in sheet metal bending

How Does Sheet Metal Forming Work?

Sheet metal bending is a metal forming process in which a metal sheet is bent to the desired angle using a bending machine.

Sheet Metal Bending

Sheet metal Bending Cases

Technology Used In Sheet Metal Bend

When setting up sheet metal parts in software, some key dimensions to consider are the sheet metal thickness, the K-factor, and the bend radius.

  Key Terms and Concepts in Sheet Metal Fabrication

• Bend Line-The straight line on the surface of the sheet that marks the transition between the level flange and the start of the bend.
• Bend Radius-The distance from the bend axis to the inside surface of the material, measured between the bend lines. The outside bend radius equals the inside bend radius plus the sheet thickness.
• Bend Angle-The angle of the bend, measured between the bent flange and its original position, or as the included angle between perpendicular lines drawn from the bend lines. Sometimes specified as the inside bend radius.
• Neutral Axis-The line within the sheet metal that remains at a constant length during bending, as it is neither stretched nor compressed.
• K-Factor-The ratio of the distance from the neutral axis to the material thickness. The K-factor, which ranges between 0.25 and 0.50, is critical for calculating the flat pattern of a sheet metal part. It depends on material properties, bending operation, and bend angle. K-factor = T/t, where T is the distance to the neutral axis and t is the material thickness.
• Bend Allowance-The length of the neutral axis between the bend lines, or the arc length of the bend. The bend allowance added to the flange lengths equals the total flat length.

Importance of the K-Factor in Sheet Metal Design

The K-factor is essential for accurately calculating flat patterns in sheet metal design, as it relates to the material’s stretch during bending. An accurate K-factor ensures precision in CAD software and manufacturing. To determine the K-factor, measure bend allowance, bend angle, material thickness, and inner radius, and apply the formula:

Practical Application

To ensure accurate results, it’s advisable to calculate the K-factor using the average of three samples from bent parts. Here are some general guidelines for K-factor values based on different materials and bending operations.

Basic K-Factor Values (Guidelines)

• Mild Steel: 0.33
• Aluminum: 0.4
• Stainless Steel: 0.45

These values serve as starting points and should be adjusted based on specific material properties and bending conditions. Accurate K-factor values are crucial for achieving precise sheet metal components in the manufacturing process.

Some basic K-factor values are shown here. Use these as a guideline.