In my last posting, I told you I would expand upon the Interference Diagram and begin the process of linking it with another tool, the Intermediate Objectives map or what I call the Simplified Strategy.
The Interference Diagram (ID)
When the interference diagram was first being developed and drawn on whiteboards, it was done so, not with the intention of replacing or linking any of the current Systems Thinking Tools, but rather to fill the void of a necessity for completing the analyzes in less time. The ID is a thoughtful mind mapping tool that can quickly point a team, or individual, in essentially the right direction to solve a problem and not be required construct a Current Reality Tree (CRT). In essence, the Interference Diagram (ID) was able to answer the question: “What to change.” In this case, the “What to change” became a list of the many entities (Obstacles/Interferences) and not just a single entity (Core Problem).
The first uses of the ID came from Bob Fox2 at the TOC Center, New Haven, CT, circa 1995. Since then, the use and structure of the ID tool has not been well documented, published or transferred to the public at large, but rather used by a limited number of practitioners within the TOC network. The simplicity of the ID and the underlying robust concept to solve problems has been applauded by ID users. The global influence of the ID to solve problems is colossal. Unlike the other thinking tools the ID is not based on logic, but rather on intuition. The arrows in this diagram are just arrows without sufficiency or necessity. The applied thinking is not to develop or isolate a single answer, but rather to list the obstacles/interferences that block the achievement of the desired objective.
It has often been said that the biggest obstacle to solving a problem is to first be able to preciously define the problem. If you are not sure what problem you are trying to solve then, it is awfully difficult to determine the correct solution. In other words, if you don’t know where you are going, then any path you decide to take is sufficient to get you there – you’ll just never know when you get there. The ID structure and concepts are very simple and yet, very powerful in the results provided.
Interference Diagram (ID) Types
There are actually two different ways to apply an ID. The first application is using the ID as a thinking tool to exploit a known constraint. The second application involves using the ID in combination with the Intermediate Objectives (IO) map. The second application offers a fast and highly effective way to develop an overall strategy plan and implementation plan. We will discuss the second application later.
First, let’s consider the exploitation of a constraint within a system. When the system’s constraint is identified, then the exploitation question becomes – “How do I get more from the constraint?” What are the “interferences” that slow down or stop the constraint from doing more and or doing better? It is possible that there could be several interferences that block the enriched performance of the constraint. This list of “interferences” becomes the reasons “why” the constraint cannot do more. The interference list is best compiled from the resources that use the constraints. The constraint users can provide the subject matter expertise to define the interferences and are most familiar with the constraint and how it works, or doesn’t work. When constraint users are asked the question: “What stops (interferes with) you getting more from this operation?” - chances are good that the user resources will be brutally honest with their answers. What becomes important at this stage of information gathering is to filter the “emotional” response from the “logical” responses. You’ll need to determine is if the response is really a system problem, or strictly a personal annoyance or gripe. This analysis will provide better results if the emotional responses are removed up front before placing the statement on the interference list.
The entities on the list simply imply those “interferences” that stop the constraint from doing more - those interferences that “steal” time away from the constraint. In order to get more from the constraint, you must reduce the impact of the interferences, or remove them completely. Any interference that can be reduced or eliminated will free up additional time for the constraint to work more. As an example, let’s go through the building steps to construct an ID that is used to exploit a constraint in a production system. In our example let say that we have identified one particular machine in a production line as the constraint. We will refer to it as “Machine XYZ”. Let’s define the steps to construct.
Step 1 – Define the Goal/Objective
The goal/objective should be something that you really want, but something that doesn’t exist in your current reality. For our example, we will choose as the objective: “More parts from the XYZ machine.” This can be written on a whiteboard or in the center of a piece of paper.
Step 2 – Define the interferences
Step 2 is best accomplished using observation of the system and interviews with the operators. When observing the constraint look for those things that slow down or stop the constraint from working. What are the interferences that take time away from achieving more of the objective? If the identified constraint is truly a system constraint, then keeping it busy all the time and getting more output will be paramount to successfully gaining more system throughput. A possible list of obstacles/interferences might include:
1. Parts not available to work.
2. Operator on break/lunch.
3. Operator has to find his own parts.
4. Operator is looking for the Supervisor.
5. Operator is attending training.
6. Machine is broken.
The list could be extensive and varied. What is most important is to identify are those things that stop the constraint from doing more. Observation of the constraint might reveal others things that impact time at the machine, such as, having to do setups for a different product. All of the observation and interview items combined equal the list of obstacles/interferences that hinder achieving the objective “More parts from the XYZ machine.” There is not a set limit to the number of interferences that need to be gathered. Rather, you should list as many as you think necessary to fully describe “why” the machine stops working.
Step 3 – Quantify the Time Component for ALL interferences
Quantifying the time component associated with the interferences, becomes important to fully understand and appreciate the impact of the interference on the available time. The time component will help filter the important few from the trivial many and help express those items with the greatest impact. Knowing the impact of the time component will also be useful in determining the priority ranking for which interferences to reduce, or eliminate, first. Some of the interferences will be more important than others – they are not all equal. When you accurately quantify the time component for the interference, it also allows for excellent Pareto analysis. Pareto analysis will align the interference, based on time distribution, and determine which interference is most impactful, and the intrinsic order of improvement. Pareto allows the focus necessary to gain the most leverage from the action implemented. However, it is also not realistic to assume that ALL interferences can be reduced and/or eliminated. There will be some interferences that do not offer themselves as candidates for elimination, but rather as entities that can benefit from a reduced time impact. In other words, if an entity with a time impact of 45 minutes can subsequently be reduced to 15 minutes, then the benefit gained for the system is 30 minutes more timefor the constraint. In other cases, the interferences cannot be reduced or eliminated at all. In our example, the time for breaks and lunch cannot be removed. Employees are allowed lunch and break time. However, as an alternative you could gain some machine time by having an alternate person or crew to work the machine during lunch and breaks.
What you are really looking for in Step 3 is to quantify with time, those activities that are stealing time away from your constraint operation. If you can eliminate, reduce, or off-load some of these activities, then more time is available to get more parts through the constraint. If interferences are known, and corrected, then the end result should equate to more output from the machine and more throughput through the system.
Step 4 – Alternatives to the Interferences
The interference list defines all of the obstacles/interferences that stand in the way of having more of what you want. If these interferences/obstacles did not exist, then achieving the goal would be easier. With the interferences defined, you should be able to counter the seemingly negative effect of the obstacles/interferences with an Injection/Intermediate Objective (IO). This action can be accomplished by asking the question: “What must exist so that the interference no longer exists?” Whatever your answer might be is the Injection/Intermediate Objective to overcome the negative impact of the interference. Continue working your way down the list and create an Injection/Intermediate Objective for each Inference/Obstacles listed. The items on Injection/Intermediate Objectives list are the things that must be accomplished to reduce, or eliminate the negative effects of the inferences. If not, then consider revising your Injection/Intermediate Objective list until the answers are sufficient to remove the obstacles/interferences. With the addition of Injections/Intermediate Objectives the list should provide sufficient “ideas” to move you closer to the objective/goal you have established. With the list in place you have now preciously defined “What to change to.”
Obstacles/ Interferences Intermediate Objective/Injections
1. Parts not available to work . 1. Parts are kitted and ready for use.
2. Operator in on break/lunch. 2. Train an alternate crew or person.
3. Operator has to find his own parts. 3. Parts delivered to operator.
4. Operator is looking for the Supervisor. 4. Supervisor notification system.
5. Operator is looking for paperwork. 5. Paperwork follows job through the system.
6. Machine is broken. 6. Preventive maintenance (priority #1).
Figure 1 presents an example of what a completed Interference Diagram might look like for our example. The circle contains the objective and each of the interferences is listed around a circle. The direction of the arrows makes no difference because these arrows are based on the ID user’s intuition and not necessity or sufficiency logic.
Figure 1 – Completed Interference Diagram (ID)
Notice in the figure that the interference times have been added to each interference identified. This allows for a quick visual of the time impact.
When using the Pareto analysis you should base it on available machine time. This will succinctly show the impact of the interferences. If the available machine time for the XYZ machine is considered to be 8 hours, for one shift, then the available time is 480 minutes (60 min X 8 hours = 480 minutes) during an 8 hour period. When you use the 480 minutes as the baseline to measure the impact of the interferences, the results will show the conflict between the time available to work and the time the machine actually spends working. Figure 2 shows an example setup of the Excel input sheet to show the interference description, total minutes the interference consumes, and the percentage impact on the total minutes available. As you can see the leading time impact comes from not having parts available at the machine to work on. Fixing this interference alone could provide an additional 90 minutes of throughput time every day.
Figure 2 The Simple Excel Set-up
From this spreadsheet setup you can display two additional charts that help drive the point home for the impact of the interferences. With the interference percentage calculated you can create a pie-chart to visually display the breakout and “Interference Impact.” Figure 3 displays the Interference Impact for our example.
Figure 3. The “Interference Impact.”
Figure 3 shows that only 36% of the total time available is actually used to make parts on this machine. The other 64% of the time is consumed by the interferences. Figure 4 displays the interferences in a Pareto analysis to show the intrinsic (descending) order of improvement. Those interferences listed highest on the list should be reduced or eliminated first, if possible, to gain the most benefit.
Figure 4. Pareto distribution of Inferences
When the ID is used to analyze and exploit a constraint it can be a quick and effective tool to generate good ideas quickly. This method, when used in conjunction with Pareto analysis, can quickly provide the visual tool to determine the impactful interferences and provide the focus and leverage on those few important actions that will provide the highest levels of improvement.
In my next posting I will demonstrate how we can use the Interference Diagram for strategy development.
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