Lean Manufacturing is a manufacturing philosophy that shortens the lead time between the receipt of a customer order and the shipment
of that order to the customer by eliminating waste. Anytime that an order is delayed, the cost of one or more of the Seven Types of
Wastes - overproduction, performance of non-standardized work, queue time, transportation (or material handling) time, inventory
(raw material, WIP and finished goods), unnecessary motions and travel, defective products and underutilized (workforce) skills - gets
added to the cost of producing the order and prevents on-time delivery of the order to the customer. Empirical evidence suggests that,
in any manufacturing facility, typically 95% of the production lead time of an order is comprised of two of the Seven Types of Wastes:
Queuing at each workcenter and Transportation between workcenters. These dominant wastes, which reduce the velocity of material flows and
inventory turns in a facility, result from an incorrect and inefficient facility layout.
For decades, textbooks on Facilities Planning have listed the following principles of Design For Flow for design of any facility layout:
- Principle #1: Minimize production flows,
- Principle #2: Maximize directed paths for production flows,
- Principle #3: Minimize the cost of production flows.
For example, the Toyota Production System (TPS) is a classic example of how the above principles apply to an assembly facility.
Principle #1 is embodied in flattened product Bills Of Materials that have minimum number of components and product Bills of Routings
that contain manufacturing routings with the least number of operations on different machines. Principle #2 is embodied in POUS
(Point-Of-Use-Storage) focused factories and assembly line-type material flow routes. Principle #3 is embodied in U-shaped cells with one-piece
flow, kanban-based WIP control and Pull-based production scheduling.
Jobshops are complex high-variety low-volume manufacturing facilities where the changes in product mix, volume, customer base, workforce
skills, process technology, etc. are significant. A complete reorganization of a typical jobshop into a Cellular Layout may be ill-advised
due to the inherent inflexibility of manufacturing cells to adapt to changes in their product mix, demand volumes and capacity requirements
(machine and labor) to meet production schedules. Hybrid Cellular Layouts, unlike the traditional network of manufacturing cells in a Cellular
Layout, provide an effective foundation for jobshops to configure their shopfloors differently from the typical assembly facility. These
layouts integrate the flexibility of a Process Layout with the order flow tracking and control of a Cellular Layout. They are designed based
on the principles of Design For Flow to achieve waste-free, and therefore high-velocity, flows of orders in a Make-To-Order (MTO) realm without
necessitating repeated shopfloor reconfiguration.
This book is based on work done for the Flexible Forge Shop Design project(
http://fdmc.aticorp.org/) funded by the Defense Logistics Agency and the Forging Defense Manufacturing Consortium (FDMC) managed by the Advanced Technology Institute.
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