Formal analysis of product variability and the effects on assembly operations

A challenge for highly configurable products, like vehicles, is that the product system has to support all possible variants that can be configured by a customer. The production system is often highly automated with software in robots, machines and programmable logic controllers that need to be prepared to handle all possible variants. The link between the product and the assembly system can be expressed through operations where each operation models how a part in the bill-of-material is assembled to the product to be built. Typically the operations have precedence constraints that express that certain parts have to be assembled before other parts might be assembled. Given only the precedence constraints a product can generally be assembled in many different ways and through line balancing the operations are assigned to different stations, machines, and/or assembly workers. For configurable products the bill-of-material might be different for each variant, consequently the necessary operations will be different. However, since the operations have precedence constraints we have to make sure that all possible variants can be successfully assembled while still satisfying all precedence constraints. The contribution in this paper is a fully automated novel method that can determine if all possible product variants can be successfully assembled while still satisfying precedence constraints between operations.