The concepts of the Toyota Production System

The Toyota Production System (TPS) commonly referred to as lean production in America, has been a popular trend among American firms to remain competitive. Toyota learned how to do more with less by eliminating waste and has now become a world-wide manufacturing icon, especially in the auto industry. American manufacturing is now playing a game of catch up and has left the mass production, batch-and-queue era in an attempt to become more 'lean'. Lean manufacturing has become one of the more popular approaches to becoming more efficient in a global market (Badiru, 2006).

Lean manufacturing is the approach of applying the concepts of the Toyota Production System (TPS) (Shah & Ward, 2007).

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The name 'lean' was coined because of the idea of being capable of doing more with less (Womack & Jones, 2003). Toyota found this technique of doing more with less essential after World War II. Japan's economy was shattered after WWII and found the automobile industry to be of paramount importance to improving their economy (Shah ; Ward, 2007). Application/implementation of the lean principles alone identifies and/or reduces (sometimes eliminates) many forms of manufacturing waste.

Operations Startegy Overview

There are also many tools that are used within lean systems that help organizations to achieve or maintain lean operational status consistent with the aforementioned principles. These lean tools are also capable of eliminating waste within an organization (Abdulmalek ; Rajgopal 2007). Operations Startegy Overview Auto and bus assembly require getting large numbers of parts or components to production areas at the right time and of the right quantity.

Most automobile assembly plants make use of cellular manufacturing, or an assembly line (cells connected via a conveyor) (Chan and Jiang 1999).

This is done because there are many operations that need to be completed to completely assemble a finished automobile and breaking all the operations up into cells allows the system to operate more efficiently. Breaking all the operations up into cells also allows the vehicles to flow through the system. The automobile or bus will flow through the work cells and parts/components will be brought to the appropriate work cells, usually from a warehouse as storing all the parts on the assembly line would be nearly impossible due to space requirements.

An efficient system will bring these parts/components to the work cells Just-In-Time (JIT), especially if the system operates according to lean principles (Womack and Jones, 2003). Getting parts from the warehouse to production is a concern of any assembly plant. This concern is of greater emphasis within automobile (or automobile related) assembly simply due to the vast amount of parts/components that need to get to the assembly line on time as to not hinder production schedules. Factor in a large production volume with the vast amount of parts required in a complete automobile assembly and the problem becomes even larger.

With the increased global competition this is one area among many that can be improved to remain competitive in a global automotive market (Badiru, 2006). A common method of physically getting the warehoused parts to the assembly line is by means of a kit cart. The kit cart is loaded with the required parts in the warehouse and is then taken to the assembly line. The kit cart is then unloaded at the assembly line and taken back to the warehouse where the kitting cycle continues. When using a kit cart method for internal operations one must take into consideration the storage, cost, and method of kitting the kit carts (Hopp and Spearman 2001).

A proper methodology of kitting

A proper methodology of kitting the kit carts reduces the number of kit carts required which then reduces the principle cost (purchasing kit carts) of the kit carts and required storage area. With the last statement in mind, one may conclude that it would be beneficial to just load up every kit cart with as many kits as possible which then minimizes the total number of kit carts necessary and thus reduces storage requirements and the principle cost of purchasing kit carts (Chan and Jiang 1999).

This maximum loading scheme will indeed reduce the number of kit carts required, but results in decreased production schedule flexibility and increased work-in-progress (WIP). Production schedule flexibility is lost due to the fact that certain assemblies now must be completed in the order that they are kitted on the kit carts (Womack and Jones, 2003). If for example, a kit cart can hold five assembly kits at a certain workstation then that workstation must be scheduled for those five subsequent assemblies that are already kitted on the kit cart.

The second side effect of maximum kit cart kitting is obvious, increased WIP at every workstation. So it becomes obvious that just loading the kit carts with the maximum number of kits is not always the best solution depending on the system. Therefore, selecting a proper kitting methodology is unique to the system that is being studied and is not a simple, straight-forward task as one may first think (Womack and Jones 2003).

Scheduling techniques or Operations Research

Scheduling techniques or Operations Research techniques are often used for cases of trying to optimally schedule jobs or find minimal resource requirements respectively. In the case of trying to find kit cart requirements for an assembly operation it would be very difficult to try to apply these techniques as most internal operations systems are complex. There are often many rules or guidelines within the internal operations system that would require simplification in order to be optimally scheduled or to use operations research techniques (Badiru 2006).