This website covers topics on knowledge management, personal effectiveness, theory of constraints, amongst other topics. Opinions expressed here are strictly those of the owner, Jack Vinson, and those of the commenters.

Push me Pull you

In general, operations management circles have grown to understand the hazards of push systems and the benefits of pull systems when managing work on the shop floor or the engineering department or the supply chain. 

Push systems operate under the assumptions that starting work sooner will ensure that it finishes sooner and that work centers need to be kept busy, so the obvious solution is to give them work: push.  Pull systems arose out of the realization that pushing more into the system doesn't actually get the desired results: more coming out the other end.  You usually end up with success by extrusion* instead of management environments.  Pull suggests limiting the release until the system signals for new work.

There are a number of mechanisms to implement a pull system with the biggest names being Just-in-Time / Kanban and Drum-Buffer-Rope.  They each use somewhat different mechanisms, and they are all generally successful at reducing the amount of work-in-process, which helps improve flexibility and responsiveness, which leads to shorter lead times.

In reading Essays on Theory of Constraints (just reviewed), I came across an interesting comment: that the Kanban system is not the pull system it is touted to be.  Specifically, while the ideal behind Kanban is single-item bins (which often means drastically lower inventories, and batch-of-one), this still means that there is plenty of extra work push into the system in order to keep those bins full, even if the item(s) in the bins might not be needed for a long time relative to the manufacturing lead time. 

Question: Did I read that correctly?  Is this the right interpretation of the Kanban version of Just-in-Time?  Or was the analysis in the book not quite right?

If Kanban isn't pull, how do you design a pull system that operates more closely to the ideal?  I think the goal is still the same: creating getting more product / service sales (in other words, more throughput).

*Extrusion: I heard this from a client talking about their project management environment, but it applies to the manufacturing shop floor just as easily.  Jam enough into one end of the pipe, and something is bound to come out, right?

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Woeppel doing a CCPM webinar