Incorrect Flat Pattern Size for Rolled Part

[dpeake1981]

Hi,  I hope someone can help. I have rolled a part but when I check the flat pattern size the size is unexpected

Obviously it's a setting but I'm not sure why

Radius is 350mm, Circumference should be 1/2 x 2.pi.r = 549.8mm but the flat pattern shows 542.7mm why is this?

[JDMather]

Search on the topics, Bend Allowance, k-factor, and Bend Deduction.

[johnsonshiue]

Hi! The default sheet metal flat pattern is computed using K-factor, 0.44. This means the neutral layer, where the sheet neither stretches nor contracts, is at 44% of the thickness from the inner side. If you want to get the measurement, you can create an offset surface based on inner side faces and set the distance to 0.44*Thickness.

Another way to check it is to change K-factor to 0. You will see the flat pattern length equals to the circumference of inner edges. On the other hand, setting it to 1 will get you the outer circumference measurement.

Many thanks!