Feb 12, 2019

Multi-Stage Scheduling


In the automotive industry, the entire supply chain is driven by the assembly line sequence. Links within the chain are relied upon to produce and deliver parts on time to avoid shortages in subsequent links.

Whether scheduling multiple stages within one facility or across multiple facilities, the risk tolerance and the need to facilitate different production rules or constraints between the stages determine the work in progress to be carried out per part.


Stamping Press Line

Using the Stamping Press Line as an example of multi-stage scheduling, parts demand can be derived from various sources including the body line it feeds, service parts, or offsite facilities. The demand is exploded into their corresponding stamping parts (if required) and collated into a list of orders with their required due dates.

Inventory Simulation Constraint

Of the 23 Optessa constraints for modeling scheduling rules, the Inventory Simulation Constraint is often employed. As the name implies, this constraint type can be used to model the inventory of any number of raw materials, WIPs, finished goods, auxiliary resources like racks/stillages available for stamped parts, or even space constraints.

> Inventory Simulation Constraints also have a number of inventory modes' to match the inventory policy for the particular application. In the case of stamping, the Running Inventory Mode allows the user to define an acceptable part inventory range, as well as a safety stock. Based on the part's projected shipment and replenishments, the system dynamically determines the required target inventory level at the specified bin period. Rule Example: Always hold sufficient on-hand inventory of Floor Panels to satisfy (or cover for) the projected body line consumption requirement for the next 3 shifts.

> In addition to the Inventory Simulation Constraint, other production rules and considerations that can be modelled:

  • Assorted part cycle times
  • Automatic part assignment on multiple press lines
  • Multi Die set configurations – multi part variation, multi part per shot, multi line compatible
  • Maximum shot counts per shift, per press
  • Minimizing die changeovers
  • Maximizing part and or die set run length
  • Rack space availability

Holistic Optimization

Optimizing based on all constraints simultaneously, Optessa provides a dispatch list per machine that specifies when, what, and how much needs to be produced.

> The stamping press use case is can further utilize multi-stage scheduling to evaluate resource (manpower, storage space) availability, estimate coil size for re-ordering, and generating blanking and laser weld schedules.   

Multi-stage scheduling is complex. Optessa's versatility and optimization technology meets the complex requirements but also allows for leaner manufacturing as trade-offs between production efficiency and inventory levels are made visible.

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