While air bending plate metals, the V-die slit sizes determine the inner bending radius. Metal sheet is formed at the radius according to the V-die slit. Punch tip radii do not have a significant impact. Does it suggest that the one-size punch nozzle radius works effectively in case of all applications. This is not the case.

## The least punch radius should be ≥ 63 percent of the sheet density.

On condition that punch nozzle 63 percent of the sheet density, it passes through the sheet face causing a quick deterioration near the punch nozzle because of the sheet folding about punch nozzle like a nutcracker. This fault is easily spotted because inspecting closely it becomes noticeable that punch nozzle radius seems to have got clamped. Punch nozzle radii must not be smaller than 63 percent of the sheet density.  So the possible least inner radii obtained through air bend process of plate metals should be 63 times as much as the sheet density.

## The utmost punch radius should be ≤ of bending one.

How does it happen that the punch nozzle radius appears excessively big?

While drafting a piece air bending, the most preferable way to develop blank sizes is using the natural inner bending radius for the calculation of bending deduction. Punch nozzle radii, that form bending must not exceed the naturally formed inner bending radius. Otherwise, bending corresponds to the punch nozzle radius bringing about bigger completed sizes. If punch nozzle radii exceeds the naturally formed inner bending radius, the bending inner radius falls under the control of punch nozzle radius rather than the V-die slit.

## Optimal punch radius is equal to the naturally formed bending radius.

If so, it is possible to gain compatible angles with the minimum degree of deterioration for the punch nozzle.

The possible prediction of the naturally formed inner radius of bending is as the following: the inner radius (IR) is gained through multiplying the V-die opening

(VO) by the sheet factor. Sheet factors: aluminum (AL) =14, cold-roll steels = 16, stainless styles (SS) = 21

Sample1: 059″ CRS formed in a 375″ VO

(CSR material factor) .16×375 = 060″ IR

Sample 2: 125″ SS shaped in a 875″ VO

(SS material factor) 21x 875 = 184″ IR

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