Joint modelling of the order-dependent parts supply strategies sequencing, kitting and batch supply for assembly lines: insights from industrial practice
Parts can be supplied from warehouses to assembly lines via several production-order-independent and -dependent parts supply strategies. Order-dependent parts supply strategies sequencing, kitting and batch supply share enough similarities that allow joint modelling in picking order planning and execution, whereas line stocking, just-in-time, just-in-sequence and just-in-sequence kit supply require separate modelling. Joint modelling is the precondition for setting up a software system in industrial practice, covering multiple parts supply strategies efficiently. With similar input–output relations and process steps, joint algorithms can be used. This work presents insights from a software system for sequencing, kitting and batch supply implemented in the automotive industry. The main process steps modelled are order-dependent part requests determination, bundling of part requests to picking orders, scheduling and release, and picking and transportation execution. Given the prevalence of assembly lines, sharing knowledge about successful modelling of parts supply strategies is crucial both for practitioners and researchers.
Automotive works on its mojo
Top of the list here is reducing transportation costs. In fact, transportation is the largest single cost in the supply chain for automotive, says Matt Bush, vice president of engineering and innovation at KPI Solutions. The challenge, he says, is to increase the density of parts and components inside the trailer. But as Freeberg points out, LIB components can easily weigh out a truck faster than it can be cubed out. The other challenge is to maximize the return ratio of collapsed containers on their trip back to the manufacturing plant, wherever that might be, says Freeberg. The standard ratio today is 3:1, reducing the number of trucks needed to return sustainable containers by two for every three shipments.
As Bush of KPI explains, it’s a continuing battle for automakers to manage the flow and relative state of assembly completion of parts and components lineside, where space is at a premium. For instance, a key question continues to be: Is it better to send kits of parts to the line or stage all inventory there for on-the-spot assembly? “The kitting process takes space but reduces the number of steps people must take along the line,” adds Bush.