Ask the Expert: Work Imbalance


We are converting some processes to lean. We have a high manual labor content in our processes and all work is done with pneumatic guns. We have combined the following three processes: one person on the first process (with work-in-process in between), two people on the second process (with WIP in between), and two people on the third process. The new process is as follows: Two people complete the first and second process on one table (with no inventory in between), and two people complete the third process.

The new process is somewhat imbalanced, and the output is down about 20 percent since the change to lean. We are discussing putting a small length of conveyor between the processes or moving work content around to balance the tables. Any suggestions?


The first step is to balance the work content. By adding a small conveyor, there will be WIP added back into the process. Standard work is a lean tool that will aid in balancing the work content. Standard work defines the interaction of people and their environment when processing a product or service. It details the motion of the operator and the sequence of action. Standard work also provides a routine for consistency of an operation and a basis for improvement. There are three central elements: takt time, standard work sequence and standard work-in-process.

Takt time is the frequency with which the customer wants a product or how frequently a sold unit must be produced. The number is derived by dividing the available production time in a shift by the customer demand for the shift. Work sequence is the specific order in which an operator performs the manual steps of the process. Standard WIP is the minimum amount of material or a given product that must be in process at any time to ensure proper flow of production.

Standard work provides a prescribed documented method or process that is sustainable, repeatable, and predictable.

Standard work is a tool to determine maximum performance with minimum waste through the best combination of operator and machine. Standard work helps eliminate variability from the process. It functions as a diagnostic device. Standard work also exposes problems and facilitates problem solving. It identifies waste and drives us to kaizen the process.

In a standardized work environment, production instruction is similar to continuous flow with verbal instructions, forecasting, and limited production locations. Product is manufactured to customer order with a defined WIP. The process is well defined to the work sequence for the operator. Machines are synchronized to approximately the same process speed. The lead-time for a product is predictable. Used as a tool, standard work establishes a routine for work and prevents backsliding. This makes managing schedules and resources easier. Relationships are also established between the operator, machine, and materials. Standard work provides a basis for making problems visual and obvious.

Elizabeth Cudney, Ph.D.