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Original Date: 07/21/2003
Revision Date: 01/18/2007
Best Practice : Elimination of Seams by Maximization of 360º Forming
Through its innovative design process, Electric Boat Corporation, Quonset Point Facility saved time and materials by forming closed loop structures using only one piece of material stock, making the final product more accurate.
Electric Boat Corporation, Quonset Point Facility (EBQP) developed new tooling and techniques to manufacture heavy-walled 360º cylinders from a single piece of material. In the past, these cylinders were formed by welding together two 180º segments. The process involved prepping segment edges, making four beveled edges, welding two seams, and then inspecting the seams. The use of two segments was more expensive than one piece because of the increased labor and excess material needed on all edges to allow for pre-bending. Aligning the segments was difficult and often created excessive root gaps and circular mismatch, which led to additional welding and liberal use of tolerances to make parts acceptable.
To manufacture a part from a single piece of material, EBQP uses the 360º forming process to minimize the number of welds. The process involves manufacturing special window dies so the material can be press-formed into a cylinder. As a result, only one weld is needed to complete the part. The 360º forming process is not limited to cylindrical structures, and can be used on any closed-loop structure for which a window die can be developed. The cost savings is at least 50% based on reducing the number of welds required in half. The new method produces less rework and scrap and saves time and materials. The increased quality of the product also produces cost savings in subsequent final assembly because improved tolerances are achieved.
By maximizing the 360º forming process, EBQP improved the dimensional quality of its cylinders (e.g., improved circularity, verticality, and girths). This approach also decreased costs by eliminating extra stock for pre-bends and reducing edge preparations, fit-ups, weld joints, and weld volume.
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