The Control Phase
The Control Phase is the fifth and final phase of the Six Sigma methodology. This is the phase where you will see if the improvements that you have implemented are working. This phase unfortunately is one of the most overlooked phases in the methodology. One of the main reasons for improvements not showing any sustainability is because this phase has been overlooked. One of the big reasons of why Six Sigma programs fail is also because people get so excited after the Improve Phase, that they do not pay much attention to the Control Phase - which leads to short-lived improvements.
Tasks performed in the Control Phase
This phase is where you make sure that the improvements that you have made stay in place and are tightly controlled. By the time you reach the control stage, you would have reached the end of your input filtering or funneling process. You should now be left with the main 3 or 4 extremely critical inputs that have a significant impact on the output.
Now that you know what the optimal settings for these input are, and you have also implemented these settings in the Improve Phase, you have to ensure that these inputs always remain at their optimal setting. After all, one of the main reasons for defects is variation…and if you do not control your inputs properly, there is a chance that their settings may change and cause variation in your process.
Why would the settings change you may ask? There could be multiple reasons. Most of the time the reason is humans. People make errors. There are also people who don't like to or don't know how to follow instructions. For example, if you know that the best setting for the temperature of the admin office is 25 degrees Celsius and you keep the thermostat at this level to get the best satisfaction out of the staff. How do you control someone who is feeling particularly hot on certain day to not change the temperature on the thermostat? One way could be to have a nice sign next to the thermostat knob saying "Please do not change the thermostat setting." This is a form of control, but you will have to monitor how effective the control is. A better control would probably be just to break the thermostat knob off while it is set at 25 degrees! This is a tight control. It would require a lot of skill and persistence for someone to change this setting.
We don't want to just pick on humans, as there are also other reasons that could cause settings to change. The environment, precision of machines, and inherent process variation are just some.
The steps you need to take to ensure control of the inputs can be outlined in a control plan. This will help you see which inputs require the most attention and the most stringent controls. It will also help you see how effective your controls are.
Another big task that is performed during the control phase is the monitoring of your NEW process. Now that you have changed the process, you need to monitor for a certain amount of time to see if it is giving the results that you had predicted back in the analyze and improve phases. You should also be able to see through this monitoring that your process has actually changed. SPC charts are one good way of looking at this.
There may be some improvements that have not worked, and you may need to go back to the improve phase to look at these and implement them in a better way. You may have to do a few loops between the improve and control phases before you can close out your project.
If your monitoring has shown that the improvements are working and that the new process is in control, you can give yourself a big pat on the back and consider your project finished.
It's time to throw a party and reap the benefits of your six sigma project!
Some of the tools used in the Control phase…
Control plan, FMEA, Control Charts, Error proofing
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