This posting is the second and final piece on how I present the concept of the system constraint in my training material. You will recall in my last posting, we discussed a simple piping diagram with different diameter pipes and that the smallest diameter controlled the throughput of water through the system. In this posting we will expand that thinking to a simple 4-Step process used to make some kind of product. But for anyone new to this blog or the Theory of Constraints, here are Goldratt's 5 Focusing Steps:
1. Identify the system constraint
2. Decide how to exploit the system constraint
3. Subordinate everything else to the system constraint
4. If necessary, elevate the system constraint
5. Return to Step 1, but don't let inertia create a new system constraint
Because I want the class to get the connection from the piping system to the real world, my next slide is the aforementioned simple 4-step process with cycle times for each step listed. I ask the audience to tell me which step is constraining Throughput. It's been my experience that only about 40 % of the class makes the connection between the flow of water through the pipes and the flow of product through this process. What I have found to be very effective is to select someone who does understand the connection explain his or her reasoning. It's important that we don't move on until everyone understands this connection.
I use my next slide to reinforce what their fellow classmates or team members have just explained. I also relate Step 3 of this process to Section E of the piping diagram.
In my next slide, I have the class become consultants who are told that the company who owns this process needs more Throughput. I ask them what would they do and ask them to explain their answers. I usually break the class up into teams and let them discuss this question and that seems to work well.
After the team(s) have explained their plan to improve throughput, I then show them this next slide to reinforce each team's answer on what they would do to increase Throughput.
Because I want the class to understand the negative implications of running each step of this process at maximum capacity, I then ask the class what would happen to the WIP levels if they did.
In the next slide, I demonstrate the impact of trying to maximize the performance metric, efficiency, in each step in the process. The key point here is that the only place where maximizing efficiency makes sense, is in the system constraint. The excessive WIP build-up encumbers the process and extends the cycle time of the process.
I then ask the class, "How fast should each step in this process be running to prevent this excessive build-up of WIP?" This is intended to demonstrate Goldratt's 3rd step, subordination. That is, why it's so important to subordinate every other part of the process to the constraint. This next slide explains, in more detail, the concept of subordination. Steps 1 and 2 must be forced to not outpace the constraint, but must also assure that the constraint is never starved. This slide usually creates an epiphany of sorts for the team or class.
I have been using this simple method of teaching the concept of the constraint for quite a few years now and it has worked quite well for me. I strongly suggest that you try it yourself.