In many vehicles air ducts are used to circulate cold and warm air. The essential requirements on these air ducts are thermal stability, weight, low noise of air flow and last but not least an often demanding 3D design.
All these demands can be realised by the twin sheet procedure. After the heating up process two materials are formed in two tool halves and are immediately welded with each other. Forming and punching in one tool guarantee high accuracy of positioning and repeatability at minimum punching mismatch, note this procedure is completely without frames.