Modular Machining Line Design and Reconfiguration: Some Optimization Methods

Automated flow-oriented machining lines are typically encountered in the mechanical industry (Groover, 1987; Hitomi, 1996; Dashchenko, 2003). They are also called transfer (or paced) lines, being preferred mainly for the mass production, as they increase the production rate and minimize the cost of machining parts (Hutchinson, 1976). They consist of a linear sequence of multi-spindle machines (workstations), without buffers in between, arranged along a conveyor belt (transfer system). Each workstation is equipped with several spindle heads, each of these latter being composed of several tools. Each tool executes one or several (for the case of a combined cutting tool) operations. A block of operations is defined by the set of the operations executed simultaneously by one spindle head. When all blocks of a workstation have been accomplished, the workstation cycle time is terminated. The cycle time of the line is the longest workstation cycle time; its inverse is the line’s production rate. A machining line designed to produce a single product type is called dedicated line; its optimal structure, once found and implemented, is intended for a long exploitation time and needs high investments. The main drawback of such a system is its rigid structure which does not permit any conversion in case of change in product type. Thus, to react to changes effectively an alternative is to design the system from the outset for all the product types intended to be produced. Research has been conducted to an integrated approach of transfer lines design in the context of flexibility (Zhang et al., 2002). This is the most important aspect which characterizes the potential of a system for reconfiguration (Koren et al., 1999). The chapter deals with the designing of modular reconfigurable transfer lines, where a set of standard spindle heads are used to