SolidWorks 2010 Bible

Chapter 29: Using SolidWorks Sheet Metal Tools

This Neutral Plane can be at various places across the thickness, depending on the material, tool-

ing, and process. The ratio of the distance from the inside bend surface, to the Neutral Plane, to

the thickness is identified as the K-Factor, where .5 means halfway, 0 means on the inside face,

and 1 means on the outside face. Typically, you can expect values between .5 and .3.

Bend Allowance and Bend Deduction

Bend Allowance and Bend Deduction are specific length values, not a ratio like the K-Factor. The

Bend Allowance is essentially the arclength of the Neutral Plane through the bend region. The

Bend Deduction is the length difference between a sharp corner and the radius corner, as

expressed by the formula in Figure 29.6.

The three values are related, as shown in Figure 29.6. The dark rectangle represents the bend area.

Material outside of the bend area really does not matter, although it is usually shown and used in

the generally accepted formulas about bend calculations for sheet metal.

FIGURE 29.6

Calculating the Bend Deduction from the Bend Allowance and K-Factor

K = t/T

BD = 2X - BA

You usually use a ratio t/T (the K-Factor) from a published table or by asking your sheet metal ven-

dor what values they typically use. The values from the tables have been developed experimentally

by bending a piece of metal of known length, and then measuring the arclength of the inside of the

bend and the arclength of the outside of the bend. By comparing these numbers to the original

linear length of the bent area, you can find the t value and thus the K value. From the K value, the

BA (Bend Allowance) value can be calculated and from that, the BD (Bend Deduction) value is easy

to find.