Taiichi Ohno has described the ideal Lean workflow as one piece at a time, with continual movement through the process steps and minimal wait times. Continuous flow is a processing state in which a product moves through the stages of the process without stopping or moving backward for rework. The ideal workspace layout for continuous flow is a straight line or modified U shape.
Handoff is accomplished quickly and efficiently in a single-piece flow since much less information must be passed along. In contrast, batch processing is an older process that produces large amounts of product. Although this may seem practical, the build-up of inventory causes longer lead times, and the large batches need to be stored, moved, and monitored. These are all activities that are Lean "waste."
Batched processing produces longer wait times for the customer. Errors can remain undiscovered within large batches and progress uncorrected since it is much easier to identify and correct defects rapidly in a continuous, single-piece process workflow than when handling a large batch. One of the most significant challenges to adopting Lean processing methods in many existing workflows has been the acceptance and redesign of long-established batch processing methods and technology toward a more continuous and single-piece workflow.
