| 摘要 |
A patterned sheet having two long sides is wrapped around a mandrel. The mandrel is provided with at least one flat surface. The long sides of the sheet are secured adjacent to the flat surface of the mandrel and points along the long sides of the sheet are connected by laser welding or other connecting means. The laser beam is directed substantially perpendicular to the welding plane of the points to be welded, even if the weld points do not all lie on a single line parallel to the mandrel's longitudinal axis.
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