ASQ CQA – 5. Quality Tools and Techniques Part 2

3. 5A2 Cause and Effect Diagrams

What we do in this tool is we list down all the causes which are creating that particular problem which we are studying. These causes are listed down based on the brainstorming or based on a group working. But why? We want to do this. We want to do this to list down all the possible causes which could create that particular problem. So once we list down all the causes, then we can study those causes, whether these are serious causes, whether we can do something about these causes. So that would be the second step. But the first step will be to list down all the causes.

And that’s what we do here in cause and effect diagram. Once we work on this tool as a group, then we reach a common understanding. So let’s say if we have an interdisciplinary group interdepartmental group which is working on a problem if all these four or five people sit down and create this particular diagram which has caused an effect diagram, then they will have a common understanding that what all could be causing this problem. Cause and effect diagram is an important tool for root cause analysis and the root cause analysis is another tool which we will be discussing here in this series of nine tools. We have talked about root cause analysis earlier as well when we were talking about the corrective action, when we said, that when Auditing gives you the corrective action, audit is expected to do the root cause analysis of the problem to see what is causing this problem and take action to remove that problem permanently.

So we have talked about root cause analysis earlier as well. But this particular tool, which is cause and effect diagram, helps us in doing that root cause analysis. There are a few other names also for this particular diagram, which is the cause and effect diagram. This is also called Ashikawa diagram because Quality Guru ishikawa was one who promoted this tool. So because of that this is also called as ishikawa diagram. And this is also called as fish bone diagram because the look of this tool is similar to fish bones. And let’s look at an example of that on the next slide, which is here. So here I have a problem. And this problem is a very general problem of poor. Quality.

Normally you will not be making fishbone diagram for poor quality. Normally you will be making fishbone diagram for problems such as the bolt was loose in the assembly, so lose bolts in the assembly. That will be the problem and for that you will be looking at number of causes what all could have caused that problem here what we do is we list down the main causes so in this particular example of poor quality the main causes. Listed down here are the methods, machine management and people. So these are main causes and then you list down the subcauses and sub causes. So main causes are something you can start with. So if you have any problem, you can start with some general main causes. So on the left I have written some typical top level causes which you can start with. These are man and when I say man, that means people, man or woman. And then machine material methods, measurement, mother nature or environment. So these are something which you can use for starting the discussion. But now we have a problem. Let’s look at the causes related to machine.

Now let’s look at causes related to the material. What could have caused then? Now let’s look at the measurement. So here, let’s say for example, machine is the main cause. And then in machine I have the subcause as the capability of the machine, subcause as the maintenance, subcause as the calibration. So these are sub causes for machine. And then you can look at sub causes. Let’s say the poor quality is because of machine maintenance. In machine maintenance the sub causes could be wear and tear or lack of tools and so on. So you can keep on discussing, keep on going into the lower level. So you start with the high level which is machine. Then you go to the next level, which is capacity, calibration, maintenance, then you go to the next level and so on. So this is how you represent all the causes related to a problem.

4. 5A3 Flowcharts

So what we have in flow chart is we have boxes which represent the process and we connect these boxes or processes with the help of arrow which tells the flow of the process. And we have decision boxes which tells that if something happens then you do this, if something else happens, then you do that. We will look at an example of this on the next slide. But let’s understand that while we need flowcharts to understand the process flow and to see the interrelationship between processes, so this basically helps you in visualizing the process. So what I do when I’m doing audit is that when auditing is explaining me the process in my notes, I keep on drawing the flowchart. That basically helps me in understanding how the process is working. So here on the right side is an example of a simple flowchart. So in a flowchart you have start and end boxes.

So this is my start box and this is my end box. So after starting we do process number one, then we do process number two. And then after process number two the item is inspected. So this is the decision box which is in the diamond shape. And then in the inspection when the item is accepted it goes to process three. If the item is rejected, it goes back to process two. And once process three is complete, then this whole process ends. So this is a very simple flow chart. So here what we have used is we have just used four symbols. The symbol for starting and ending, the symbol for process, the symbol for decision, and the connectors to connect all these. So here on the left side I have commonly used symbols in flowchart. We have talked about starting, ending, we have talked about process, we have talked about connectors which connect all these processes and we have talked about decision box. So basically these four are very common symbols in a flow chart.

But in addition to that you can have symbols such as symbol for data, where your data is your database is your document, where you document something, this is for preparation and this symbol is for delay. But in majority of your flow charts you will be just using these four common symbols which are start and process, connector and decision. So this is one example of a flow chart. Another type of flow chart is swim lane flowchart. This is also called as cross functional flowchart. So here what we have is in addition to the flow of processes, here we have different lanes for different functions. So let’s say here I have lane one, lane two, lane three, and this is a blank flow chart. And in lane one, let’s say I have sales. In lane two, let’s say I have design. In lane three I let’s say I have production. Lane four is a dispatch, lane five is after sales and so on. So what you can see on a swim lane flow chart is not just the flow of processes. But in addition to that, you can also see that who is responsible for this. So let’s say this particular process, which is process number one, is done by Sales. Then Sales gives some information to design. So this step number two is done by design. Then it comes back to sale, and then from here it goes back to the production.

And in production, there is a decision. If something happens, then you go this side. If something doesn’t happen, you go back and so on. So now, just by visually looking at this, you not only understand the process, but you also understand the responsibilities who are responsible for something. So on the previous slide, I have shown you a simple flow chart. Here I’m showing you swim lane flowchart. So if you want to make a flow chart, you can go to a site which is draw IO, and you can draw these flow charts online. So just in case, if you want to make nice presentable flowcharts, go to this website. And without any registration, without any login, you can just start drawing flowchart. And then you can save your flowchart files, which you can use later on.