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 backwards for rework. The ideal workspace layout for continuous flow is a straight line or modified U shape.
Hand off is accomplished quickly and efficiently in a single piece flow since much less information is required to be passed along. In contrast, batch processing is an older process that produces large amounts of product. Although this may seem effective, the build up of inventory causes longer lead times and the large batches need to be stored, moved, and monitored. These are all activities which 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 any defects rapidly in a continuous, single piece process workflow than when handling a large batch. One of the greatest challenges to adoption of Lean processing methods in many existing workflows has been the acceptance and redesign of long-established batch processing methods and technology towards a more continuous and single piece workflow.