Monday, November 29, 2010

Unfolding Shell Models

For designing design sheet metal models, some designers use solid modeling commands rather than sheet metal commands. Such models are made initially using solid modeling commands and then shell command is used to get uniform wall thickness and finally the model is converted into a sheet metal model. Such models when received by manufacturing vendors are often not suitable for unfolding. There are two reasons for this (i) unripped edges and (ii) sharp bends. To handle such cases, Sheet Metal Feature Recognition library (SMFR) provides options like (i) ripping and (ii) insert bends.
Model with an Unripped Edge and Sharp bends

For example consider the model shown in the figure above. Faces A and B are connected together, whereas to unfold the model, both these faces need to be unconnected. The unripped edge shown in the figure needs to be ripped. Sheet Metal Feature Recognition library provides an option to rip such edges in imported solid models. The edges to be ripped and the rip gap are to be provided for ripping. The imported model after ripping is shown below.

Model after Ripping

The model has two sharp bends with inner radius and outer radius as zero. For accurate unfolding and sheet metal bending, inner radius has to be specified. Sheet Metal Feature Recognition library provides an option to automatically convert such sharp bends into cylindrical bends. The sharp bend and the inner radius are to be specified for automatic conversion. SMFR can also detect sharp bends automatically for such conversion. The imported model after conversion of sharp bends into cylindrical bends and flat pattern obtained using SMFR are shown below.
Model after Conversion of Sharp Bends into Cylindrical BendsFlat Pattern

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