What Are Bend Allowance, Bend Deduction and K-Factor? to review the most important sheet metal design terminology — Bend Allowance. In sheet metal, there is a powerful bend constant known as the K-Factor. It ultimately allows you to estimate the amount of stretch without. In my previous post I talked about K-Factor, Bend Allowance and Bend Deduction and what they mean in sheet metal design. Now let's see.


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These are all distinct methods of forming, and each is calculated differently because of how the radius is produced in the workpiece.

Analyzing the k-factor in sheet metal bending - The Fabricator

Have no fear; I will bring the K-factor into the discussion soon. Until then, bear with me.

There are four types of bends: Try forming a radius smaller than the minimum, and you crease the center of the radius, giving you a sharp bend. If your radius is percent of the material thickness or more, you have a radius bend. Even if you are producing a sharp bend, the smallest radius you can use for your bend calculations is sheet metal k factor minimum bend radius, if you want your numbers to work out in practice.

Note also that air forming a sharp bend usually is very detrimental to consistency. The crease in the center of the bend tends to amplify any angular variations caused by changes in sheet metal k factor grain direction, hardness, thickness, and tensile strength.

About Y Factor and K Factor

The sharper and sheet metal k factor the crease, the greater the effect. Your punch nose radius comes into play here too. If the bend turns sharp at an inside radius of 0. As the punch nose radius gets smaller in relation to material thickness, the more significant the total amount of angle variation you will experience.

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Figure 2 You can run test pieces to calculate a specific K-factor, or you can refer to a chart such as this one. The Forming Methods And yes, there is a difference between bottom bending and coining.

Sheet metal k factor forces the punch nose into the material, penetrating the neutral axis. Advantages of bottoming include greater accuracy and less springback. A disadvantage is that a different tool set is needed for each bend angle, sheet thickness, and material.

Sheet metal k factor general, air bending is the preferred technique.

There is little, if any, spring back. Coining can produce an inside radius as low as 0.

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While coining can attain high precision, higher costs mean that it is not often used. Three-point bending[ edit ] Three-point bending is a newer process that uses a die with an adjustable-height bottom tool, moved by a servo motor.

Analyzing the k-factor in sheet metal bending

The height can be set within 0. Adjustments between the ram and the upper tool are made using a hydraulic cushion, which accommodates deviations in sheet thickness.

Three-point bending can achieve bend angles sheet metal k factor 0. While three-point bending permits high flexibility and precision, it also entails high costs and there are fewer tools readily available. They involve other ingredients that spice up our k-factor gumbo, including ductility.

One measure of ductility is the reduction of area, also known as the tensile reduction of area. So, if your 0. Note that this is just a rule of thumb that gives you a ballpark figure.


Sheet metal k factor the correct minimum bend radius for steel or aluminum plate requires a little research and should include data from your material supplier and another critical ingredient in your k-factor gumbo: Grain Direction The grain direction, created in the direction the sheet is rolled at the mill, runs the length of the full sheet.

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