One of the most important Lean Workflow Measures is Workflow Factor. The Workflow Factor measures how Lean the work process is. By definition the best Lean Workflow Factor is 1 as given by the following ratio:
Workflow Factor = Total Process Workflow Time / Standard Process Time
The Total Process Workflow is normally a given Delivery Cycle Time from Start to Finish. That is, from the beginning of the first process to the end of the last process.
Normally, Workflow Factor is measured by:
Wf Factor = Total Workflow Cycle Time / Total Standard Process Cycle Time
Wf Factor = 12 Days X 24 hours / 120 hours = 2.4
In other words, for every standard hour of work, the actual workflow time taken is 2.4 hours.
Defining the hours for each day run is a necessary requirement for a proper understanding of the use of one day’s hours. One work day may be defined as:
12 hours; or
The time taken for each order completion in terms of days depends on the hours worked per day, the number of shifts and duration of each shift.
Batch Flow Workflow Factor:
For a given order size, a batch workflow will usually have a poorer Workflow Factor. This is because of Accumulated Cycle Time, Waiting Time, Delay Time, Logistics Time, QA Inspection and Approval Time, etc.
Continuous Flow-Workflow Factor:
For Continuous Flow in small quantity such as a basket size, container size, bundle size or even one-piece quantity, the Total Workflow Cycle Time for an average order size will be smaller. This is because of the overlapping cycle time of smaller quantity flow concurrently at the same time, resulting in a shorter Total Process Workflow Cycle Time.
One-Piece-Flow Workflow Factor:
Flow at one-piece at a time tends toward a Workflow Factor of 1, provided that the work process is short and well connected to subsequent processes with a balanced process cycle time. Achieving one-piece-flow does not necessarily attain a Workflow Factor of 1 if the production line is unusually long and the process cycle time is subject to occasional cycle time imbalance. Occasional Cycle Time Imbalance can result in a Line Loss of up to 30% capacity even in a one-piece-flow line.
The use of a Cell-Line of about 12 operators comprising not more than 12 different operations can provide better control to secure balanced production time for reduced loss due to waiting, imbalance, delay, transfer, handling, etc.
What then constitutes a Lean Workflow? As a guide, the following measures can be used to gauge how well your production line is doing with respect to lean implementation:
Above 1 and up to 1.5 = Good Lean Line
Above 1.5 and up to 2.5 = Standard Lean Line
Above 2.5 and up to 5.5 = Average Production Line
Above 5.5 and up to 10.5 = Fair Production Line
Above 10.5 = Bad Production Line
For more information on Workflow Factor and Line Design for One-Piece Flow,
contact the author, Mr. C. H. Wong (Email: firstname.lastname@example.org)