Validate Measurement SystemMaster :Now that the improved process is established, I'll show you how to keep it in place by following the steps of Control.
Master : Step one is validating the measurement system. To assure that the improved process continues working, you often have to measure it. As you may recall, the measurement system can potentially enter variation into your data, so you need to validate it first.
Master: Step two is determining process capability. Part of completing a project is documenting that the process has improved; to do this you need to re-calculate the process capability.
Master: And, step three is to implement a process control system and project closure. You need to make sure that the improved process stays in control, so you document the appropriate procedures for the process, including how to react if it goes out of control, and finalize a plan for checking the process control. Development of the process control system really gets started in step 1, but is implemented business-wide in step 3.
Master : Remember that an improvement is only valuable if it is consistently implemented. So, your job isn't over until a control system has been put in place!
Master : Linda, the control expert, will be helping you with this phase.
Master : So here is Linda to get you started.
Linda : Thanks Master. Before we jump into the Control steps, I want to tell you why I enjoy working with teams at this stage. I find it very rewarding to see improvement visions become reality in the work environment and to establish methods for keeping them in place.
Linda : Like almost everything in Six Sigma, a process control system generally includes taking some measurements to statistically verify your conclusions. And, making sure those measurements tell the truth about a process means first validating the measurement system. So our task in this step will be to perform another Measurement System Analysis.
Linda : Let's begin by discussing what you'll learn in this lesson. Before taking on the primary task for this step, I want you to understand where it fits in the control phase of the six sigma process.
Linda : So first you should be able to describe why and how a control system is established,
Linda : And also the role of a quality plan in the control process.
Linda : And finally, be able to apply the knowledge you gained to verify that you can take accurate measurements of those components.
Linda : Why is a process control system necessary?
Linda : Once the Improve phase is over, the chosen improvement has been shown to work, right? Unfortunately, processes have a tendency to degrade over time, particularly if it's assumed that they'll function in the real world just as they did in a pilot.
Linda : Also, at this stage, the process is generally moving beyond the hands of the Six Sigma team. Those who are responsible for continuing it need a clear understanding of how to implement it consistently and steps to take if it gets out of control.
Linda : Therefore, as part of the Process Control System the Six Sigma team needs to create an implementation plan that includes a strategy for controlling each improved sub-process.
Linda : And, the improved process needs to be communicated to all involved parties through documentation and training.
Linda : A data collection plan is also necessary to test the improved process and confirm that the solutions are indeed having positive impact.
Linda : For many processes GE already has in place what are called "quality plans" to ensure each product characteristic or sub-process stays in conformance with their overall process.
Linda : There are a couple of reasons that you should take into consideration any existing quality plans as part of establishing a process control system for your project. One, the plan may include process procedures and tolerances, as well as items to be monitored for control and response plans in the event of a process breakdown. These can inform your own control plan.
Linda : And two, your improved sub-process may have an impact on the quality plan, so you need to include changes to it as part of your documentation. For now that's enough background on process control, you'll learn more about general control strategies in Steps 2 and 3.
Linda : We currently know that the nut removal process at Rockledge can be improved by using a new nut type and torque setting, and we are getting ready to move into full-scale implementation of those solutions.
Linda : Another way of saying that is "based on our Design of Experiment we have determined the tolerances for the X's that will provide a positive impact on our project Y."
Linda : The overall goal of the control phase is to control the X's, so we must come up with a system to assure that the torque settings are being made correctly and the right nuts are being used. Step 1 is titled Validate Measurement System, and you may be wondering how that fits into the Control phase goal.
Linda : At this step, we haven't decided how to control our X's -- we will make that decision in step 3 -- for the moment, just be aware that because the torque setting is continuous data, it might involve taking ongoing measurements. As you now know, before using a measurement system, you have to validate it. So, that is one reason you perform this task in step 1.
Linda : A second reason is, whether or not we end up collecting data as part of our control system, before going any further, we must verify that the tolerances established in Step 9 were not influenced by any measurement system variation. This really should be done prior to conducting the DOE, but now is your absolute last chance.
Linda : That concludes your briefing. To validate the measurement system you should use the same process that you learned in Measure Step. The key difference is that in measure step the Y was measured, but in this Step it is the X that is being measured.
Linda : Remember the Measurement System Analysis Checklist you used back to guide your assessment? We'll walk through it again as we validate the torque setting measurement system.
Linda : The first couple of items look at the measurement procedure. Torque wrenches have a gauge that displays the torque that will be applied to a nut in foot- pounds. In this case, the measurement procedure would be for the operator to read the torque setting on the wrench, prior to installing each nut.
Linda : Items three, four, and five ask you to consider the three types of gauge error. In this case, the torque wrench has been well calibrated by the manufacturer. The setting is exact within plus or minus five percent. This is acceptable.
Linda : Looking at the last item, because the measurement procedure in this case is so straightforward and the manufacturer has guaranteed that the gage is accurate and precise, we will not be running a Gage R& R.
Linda : Before moving on to step 2, let's review what we have covered.
Linda : In step 1, you learned the importance of a process control system
Linda : and the role of a quality plan.
Linda : Finally, once you had that background knowledge, we validated the measurement system for one of the X's that are being improved by this project. In step two, you'll review how to evaluate if that improvement is having an effect.
Linda : And, that brings us to the end of this Step for the Rockledge case. By going through the Measurement System Analysis checklist, we now know that we have a valid measurement system for recording the torque applied to the nuts.
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