| 摘要 |
<p>Methods and apparatus of forming stiffening structures in a material are disclosed. In an example method, a first inner bend line (708a,708b) is formed in the material (102) and a portion of the material is drawn toward the first inner bend line (708a,708b) to form an intermediate stiffening structure (706a,706b). A second outer bend line (714a,714b) is then formed adjacent and parallel to the first inner bend line (708a,708b) so that the intermediate stiffening structure (706a,706b) is located between the first inner (708a,708b) and second outer bend lines (714a,714b). A plurality of stiffening structures (204b,204c) is then formed in the intermediate stiffening structure (706a,706b) without substantially stretching the material.</p> |
