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Gravity Blankholder to Expand Superplastic Forming Processes Disclosure Number: IPCOM000035588D
Publication Date: 2005-Jan-25
Document File: 1 page(s) / 28K

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The Prior Art Database

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Gravity Blankholder to Expand Superplastic Forming Processes

Superplastic forming (SPF) offers several advantages over conventional stamping techniques including increased forming strains, zero springback and low tooling costs. SPF of many parts is accomplished by blow-forming where a sheet is clamped in a die at elevated temperature and gas pressure is applied to one side. However, SPF is a rate-limited process and forming times are typically on the order of 10 to 30 minutes. To decrease forming time and expand the forming envelope of SPF, a new process is introduced here which incorporates elements of stamping and SPF into a single die system. In this process the sheet is first mechanically formed into a pre-form and then followed with SPF to finish the part. This process significantly reduces the cycle time by eliminating a large portion of the SPF while retaining the advantages of increased formability and zero springback. A schematic of this system is shown in Figure
1. The sheet is first mechanically stamped by lowering the upper die onto the lower with a protruding punch. A blankholder ring engages the sheet just prior to the moment the punch contacts the blank to restrain material flow into the die which prevents wrinkling of the blank as it enters the forming cavity. The force exerted on the sheet from the blankholder is generated by the weight of the blankholder. The blankholder is affixed such that it can slide with respect to the upper die. As the too...