Last night we discussed the main tenets of TOC. Tonight we will introduce the Lean Pacemaker showing how it may not always be the constraint in our system. This, my friends, is where the TOC and Lean proponents often “bow up” and butt heads a bit.
In a Lean system we normally want to schedule production at one process. This process, called the pacemaker, is normally towards the end of the line (sometimes final assembly). The basic idea is that we schedule production at this pacemaker allowing it to then “pull” material to it. A key rule for selecting the pacemaker is that all processes after it must “flow” to the customer.
The debate over TOC Bottlenecks and Lean Pacemakers is best summarized by John Shook. I have never met John but have read much of his writing and can safely say he has likely forgotten more about Lean than I will ever know.
I came across an article on the LEI website awhile back where John explained some of the key differences between Lean and TOC. You can find the full article here. I will quote a portion of this article below as it summarizes the point I am trying to make perfectly.
Secondly, there is a fundamental difference between TOC “bottlenecks” and TPS “pacemakers,” though they are frequently misunderstood to be roughly analogous. What is analogous is that TPS, like TOC, strives to identify and “break” bottlenecks. But, TPS does not allow a bottleneck to set the pace of the value stream. After all, the bottleneck may exist for any number of problematic reasons – excessive downtime, poor quality, long changeover times, etc. Why would I choose to let an operation with such problems determine the way I flow my entire value stream? Of course, I have to deal with the problem operation (the bottleneck), and there are numerous techniques to do so, but I will not let it dictate the pace (takt) of my entire product flow!
Which Method is Right?
I personally believe in the end TOC and Lean practitioners are actually teaching very similar things. Let me explain.
Both Lean and TOC teach that bottlenecks must be broken. In a Lean system we know that if a process cycle time is greater than takt time we have an issue that must be resolved. This is roughly analogous to the TOC step of “elevate the constraint.”
Also, drum-buffer-rope is very similar to the Lean pull system. Sure there are some differences but the concepts are close. However, as Mr. Shook explained a Lean system will not allow a bottleneck to automatically be the pacemaker for the reasons he explained.
I must admit, I personally agree with Mr. Shook on this point. It makes little sense to me to allow the chubby kid to set the pace. As Jon Miller commented after last nights post, we should help Herbie lose weight!
And while they may not admit it, I really believe most TOC proponents believe the same thing. They just explain things a bit differently. I hope this helps explain some of the differences and similarities between TOC and Lean. Hot sports opinions are of course very welcome by clicking the “comments” link below.