Manufacturing Breakthrough Blog
Friday August 21, 2015
In my last several postings we have been discussing the Conflict Resolution Diagram (CRD) which is one of TOC’s Thinking Process tools. As the name implies, the CRD is a tool used to resolve conflicts. In my last posting we developed our CRD as is displayed in the figure below.
I also explained that the CRD’s purpose was to articulate the key elements of a conflict and then suggest ways to resolve it resulting in a win-win solution. The CRD uses necessity based logic which uses the syntax, “In order to have “x” I must have “y”…… because….” The CRD includes the common objective, necessary, requirements that lead to it, and the prerequisites needed to satisfy the requirements. Let’s continue our discussion on the key elements of the CRD.
To refresh your memory, the figure below is the CRT we developed in my last post.
The Conflict Resolution Diagram
One side of our conflict is stated as, “In order to have Throughput Rates High, we must have limited WIP inventory because excess WIP extends cycle times and causes late deliveries. The other side of our conflict is stated as, “In order to have Throughput Rates High, we must increase production starts because more WIP results in higher levels of production. Remember, the “because” statements are the assumptions used to justify each side’s reasoning. Let’s now look at the relationship between each side’s requirement and the corresponding prerequisite.
On one side of our conflict we state that in order to limit our WIP inventory, we must use a constraint based “pull” schedule because new starts don’t begin until something exits the constraints. On the other side of our conflict we state that in order to increase production starts, we must use a “push” system to schedule production because idle time by resources results in lower production. Obviously both a pull and a push system can’t operate simultaneously, so herein lies our conflict. That is, the two prerequisites are calling for two completely different production scheduling methods.
As with all of the Thinking Process logic trees, the presence of an arrow indicates the existence of underlying assumptions about the relationship between the entities of the CRD and it is these assumptions that are the key to solving the conflict. So the real key to solving the conflict is to invalidate the assumptions. It’s important to remember that they may never have been valid in the first place. Doing so usually involves finding a substitute for the entity in question. This substitute is referred to as an injection. In our example, I have only listed one assumption between each of the requirements and prerequisites, but there could be multiple assumptions.
Injections are specific actions to be taken that would invalidate one or more of the assumptions. Bill Dettmer  refers to single injections that “kill the conflict” as “silver bullets.” Dettmer also tells us that it is unlikely that a single injection will resolve our conflict and that “thinking outside the box” is necessary. The way I would approach our example conflict is to try to understand the logic behind why one side wants a push system to schedule production. If, for example, the reasoning behind why one side wants a push system is their belief that the performance metric efficiency should be high in order to gain higher throughput, then we might be able to demonstrate why this thinking isn’t sound. So think about how we might convince this side that their thinking is flawed?
What if this side has never been exposed to the Theory of Constraint’s accounting method called Throughput Accounting (TA)? You will recall that TA believes that performance metrics like manpower efficiency and/or equipment utilization are both sound metrics as long as they are limited to measuring the performance of the constraint. The key to improving throughput is to maximize the output of the constraint without creating excessive amounts of WIP in front of the constraint which causes the cycle times of in-process parts to be extended and that result in a deterioration of throughput and on-time delivery. To quote Dettmer , “In complex conflict situations, injections are likely to be conditions you want to create, rather than actions you expect to perform. Many separate actions may be necessary to achieve these conditions.”
So think about the impact of only measuring efficiency within the constraint. The figure above is our Current Reality Tree (CRT) that we developed earlier. If we only measure efficiency within the constraint operation, operators in non-constraints will stop over-producing which would lead to minimum levels of WIP which in-turn would lead to shorter cycle times and ultimately would lead to significantly improved throughput. In an earlier post, I explained that we are always after solutions that create only win-win results for both sides of our conflict. By implementing this one simple change, our common objective should be achieved.
Before completing this post, I want everyone to understand that there may be other injections that can be developed to break any conflict, but for brevity sake, I wanted to keep it simple for you.
In my next posting we’ll move on to the next Thinking Process tree, the Future Reality Tree. As always, if you have any questions or comments about any of my posts, leave me a message and I will respond.
Until next time.
 The Logical Thinking Process – H. William Dettmer, Quality Press, 2007