Page 68 - Design for Six Sigma a Roadmap for Product Development

Six Sigma and Lean Fundamentals 45

Restaurant operation is a perfect example of pull-based production—
the customer places the order, and then the kitchen produces exactly
that, based on what the customer ordered.
In general, the key feature for the pull-based production is that the
information flow direction is opposite to the material flow. The infor-
mation flow means the production control order. In the restaurant
case, the production control is the order for the kitchen to cook, and
this order direction is clearly from customer to kitchen. On the other
hand, the direction of material flow is the flow of food in the restau-
rant case; clearly, it will take the direction from the kitchen to the
customer. Clearly, the information flow direction and material flow
direction in a restaurant kitchen are opposite to each other.
The opposite of pull-based production is push-based production. The
key feature for the push-based production is that the direction of
information flow is the same as that of material flow. In push-based
production, each work stop will send the work downstream of the oper-
ation, that is, push the work downstream, without considering
whether the downstream can make use of it. Typically, activities are
planned centrally but do not reflect actual conditions in terms of idle
time, inventory, and queues.
Agricultural production is a typical push-based production. Because
the production cycle is very long, there is no way that farmers can pro-
duce only the amount of food purely based on real-time demand. The
production plan is purely based on market forecast, and sometimes it
is just based on last year’s production. The production command will
flow in the same direction as the workflow. It is well known that
agricultural production often suffers from oversupply and market fluc-
tuations. Clearly, pull-based production, whenever possible, will create
much less overproduction so the waste caused by overproduction can
be reduced.

2.6 Process Mapping, Value Stream
Mapping, and Process Management
2.6.1 Process mapping
A process map is a schematic model for a process. “A process map is
considered to be a visual aid for picturing work processes which show
how inputs, outputs, and tasks are linked” (Anjard 1998). Soliman
(1998) also describes the process mapping as the “most important
and fundamental element of business process re-engineering.” Many
business processes are poorly defined or totally lacking in descrip-
tion. Many procedures are simply described by word of mouth or may
reside in documents that are obsolete. In process management, often