Reconfigurable sheet metal fixtures are used to assemble sheet metal product families of similar locating layouts. These have to maintain locating and clamping layout fidelity for the entire range of a product family. Locating and clamping regions of a sheet metal part tend to dislocate and distort once subjected to nonequalized resistance spot welding guns. The resulted working regions are different in location and size from the original ones. In this article, Monte Carlo simulations are used by the authors to investigate the expected size and location of the working regions of parts in a sheet metal family subjected to random resistance spot welding forces. In the case study, proposed methodology is applied to an available automobile underbody floor panel family. Resulted working regions after the probabilistic deflection analysis are different from the initial ones both in size and location. The results show that by incorporating the random nonequalized clamping forces, the size of the working regions for fixturing elements is increased. Also, the possibility of designing a fixture that cannot assemble the full range of parts is reduced.

CNC press-brake forming is widely used to transform sheet-metal blanks into complex three-dimensional shapes in a low quantity high variety manufacturing environment. Sheet-metal bend sequence planning is a complex combinatorial problem. Process planning and tolerance reasoning for sheet-metal forming are critical to reduce manufacturing time and to address accuracy aspects. Handling time and accuracy of sheet-metal-formed components strongly depend upon the bending sequence. Process and material variations shrink the tolerance zones and therefore their effect must be incorporated in the overall sheet-metal process planning activity. Monte Carlo simulations are used in this article to evaluate the effect of process and material variations on bending accuracy. Branch-and-bound, traveling salesman problem (TSP)-based techniques are used to identify potential feasible bending sequences. Results from the Monte Carlo simulations are used as input for sheet-metal bend sequence planning. In the case study, proposed methodology is used for available industrial sheet-metal components. Resulted tolerance zones attenuated after the probabilistic deflection analysis. Expected error input from probabilistic deflection analysis produced bending sequences which resulted in formed components within designed accuracy limits. Possibility of forming out of tolerance components is also attenuated.

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Metal sheets have the ability to be formed into nonstandard sizes and sections. Displacement controlled CNC press brakes are used for 3D sheet metal forming. Though the subject of vendor neutral computer aided technologies (CAD, CAPP and CAM etc.) is widely researched for machined parts, research in the field of sheet metal parts is very sparse. Blank development from 3D CAD model depends upon the bending tools geometry and metal sheet properties. Furthermore generation and propagation of bending errors depend upon individual bend sequences. Bend sequence planning is carried out to minimize bending errors, keeping in view the available tooling geometry and the sheet material properties variation. Research reported in this paper attempts to develop a STEP-compliant, vendor neutral design and manufacturing framework for discrete sheet metal bend parts to provide a capability of bi-directional communication between design and manufacturing cycles. Proposed framework will facilitate the use of design information downstream at the manufacturing stage in the form of bending work plan, bending working steps and a feedback mechanism to the upstage product designer. In order to realize this vendor neutral framework STEP(ISO10303), AP203, AP207, AP219 along with STEP-NC(ISO14649) have been used to provide a basis of vendor neutral data modeling.