Unfolding sheet metal parts: a graph-based approach

Yeh, Shuchieh; Kamran, Mehran; Nnaji, Bartholomew O.

doi:10.1080/00207549508930176

Cited by 4 publications

(1 citation statement)

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“…Manual determination of flat pattern is time-consuming and error-prone, especially for intricate parts. To shorten unfolding design cycle and eliminating errors, computer-aided flat pattern development systems have been developed either as prototypes or for commercial use (Yeh et al 1994, See Toh et al 1995, Shunmugam et al 2002, Prasa et al 2004.…”

Section: Strip Layout Designmentioning

confidence: 99%

Methodology for automatic operation sequencing for progressive die design

Chu¹

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Sheet metal components produced by progressive dies play an important role in modern day life. Progressive die design in most industries remains an art rather than a science. The job is mainly carried out manually, based on individual designer's skills and knowledge, which are accumulated primarily through work experience. Strip layout is the most critical task in progressive die design. The optimal die operation sequence enables both the precise part production and the manufacturing cost reduction. The aim of this research is to develop a novel, rigorous approach for strip layout design in progressive die design. The proposed approach incorporates rules and heuristics used by human process planning experts and synthesizes the reasoning process using graph theoretic algorithms. Two types of constraints between stamping operations are identified in this work: cluster and precedence constraints. Operations have cluster constraints should be performed simultaneously at the same station. While a precedence constraint implies that an operation or operation cluster must be performed before another operation or cluster. The proposed approach first generates the stamping features from the sheet metal features consisting of the CAD model of stamping part to-be-manufactured. In this process, the blank orientation is determined using nesting algorithm to obtain the optimal material utilization. The sheet metal features in the CAD part model are mapped to stamping features in a strip model. Auxiliary stamping features (pilot features and scrap features) are devised by the process planner. Then, stamping features are mapped to stamping operations, followed by generating the operation precedence and adjacency graphs. Next the operation precedence graph is verified to be acyclic using a colored DFS (depth-first search). Based on the operation xiii ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library precedence graph, a modified topological sort algorithm is applied to cluster the operations into partially ordered sets. Finally, a graph colouring algorithm is applied to the operation adjacency graph on the partially ordered operation sets. The approach has been implemented in a prototype system (AutoSOS-Automatic Stamping Operation Sequencing), which is written in C++ and is fully integrated with the SolidWorks CAD system. This system can be used in either of two ways: as an automated process planning system, i.e., a tool by someone who is not an expert but requires the use of expert knowledge; or as a checking system, i.e., an assistant to an expert in the field. If it is used as an automated process planning system, the result is a sequenced cluster of operations that meet the constraints of both graphs. It can output 2 numbers, the minimum number of stations based on topological sort (the ideal minimum) and the feasible number after colouring (the feasible minimum). The 3D strip layout is automatically generated. On the other hand, if it is used as a checking sys...

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Section: Strip Layout Designmentioning

confidence: 99%