Pull Systems Need Push Systems

It’s a collaborative synergy

Published: Thursday, January 20, 2011 - 06:00

The concept of “pull” gained ever more ground with the publication of Womack and Jones’ Lean Thinking: Banish Waste and Create Wealthin Your Corporation.  (Simon & Schuster, 1996). All this sounds terrific in theory and can be taught relatively easily through simple simulation exercises. Even one-piece flow systems can be demonstrated fairly simply. However, achieving this for most organizations is a different practical matter. In fact, companies that are leading their industries are moving beyond the folklore approach of push vs. pull and one-piece flow to achieve bottom-line results by focusing on the practical science behind manufacturing supply-chain management.

In implementing these practices organizations realize that whether it’s called push systems or pull systems, the intent is to reduce unproductive effort, not to become a slave to subjective definitions. The intent is to reduce work-in-process (WIP) inventory and cycle time while increasing throughput. Too low a WIP or too high a WIP can both be disastrous.

In order for these systems to work, organizations need to push employees to perform certain tasks. This obviously flies in the face of pull systems. However, it becomes imperative that employees consistently follow a system of procedures or standard work. For example, if an organization sets up a kanban system, it will fail if employees do not follow the process (e.g., move the cards, build to the instructions given on the kanban).

One example of how organizations are dealing with this dilemma of pushing employees is by using software systems where employees must enter certain data into fields before they can move to the next step. Well-designed software systems do not allow employees to enter incorrect data in an incorrect sequence; they push them to perform the correct tasks. This is something we have all experienced even when entering information on the web: one cannot proceed to the checkout unless an e-mail address (or state or zip code) has been entered correctly.

Another example are those organizations operating in a make-to-stock vs. make-to-order environment. Recently, while visiting a medical devices organization, I noticed that each medical device was manufactured and assembled individually to forecast. However, because of the high demand for these devices that replace heart valves and systems, potentially eliminating open-heart surgery, this is an ideal application for pull systems—manufacturing to demand, rather than forecast.

The organization met the challenge by implementing a number of initiatives:

• The skill and expertise required to assemble this product was accomplished by providing eight weeks of intensive training to every employee before he was allowed on the assembly floor to work on the product.
• Process controls were implemented to ensure that required procedures were followed.
• Products were built to demand, using a supermarket strategy, to ensure the least amount of WIP and a reasonable amount of finished inventory was available to meet unexpected demand.
• Collaborative effort was led not only by medical experts but also manufacturing and quality professionals

This is a well thought-out implementation strategy: putting in push systems to ensure success of pull systems.

Although the concept of pull systems sounds simple, its success requires strategic thinking and a firm grasp on the science behind the operations.

As Edward Pound and Mark Spearman state in Factory Physics (McGraw-Hill/Irwin, 2007), “Telling employees that they should ‘pull to demand’ or ‘pull work only as needed’ has a nice, intuitive ring to it.” 

Making it work requires strategic thinking and a combination of push and pull; they do not work in a vacuum.

About The Author

Akhilesh Gulati

Akhilesh Gulati has 25 years of experience in operational excellence, process redesign, lean, Six Sigma, strategic planning, and TRIZ (structured innovation) training and consulting in a variety of industries. Gulati is the Principal consultant at PIVOT Management Consultants and the CEO of the analytics firm Pivot Adapt Inc. in S. California. Akhilesh holds an MS from the University of Michigan, Ann Arbor, and MBA from UCLA, is a Six Sigma Master Black Belt and a Balanced Scorecard Professional.