CONTROL PLANS
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Today, We'll discuss on control plans.
Lets start discussion on this topic. Hopefully, you'll understand this topic.
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Control plans are used to document and communicate the plan to monitor and control the process. The control plan summarizes information from a variety of sources into a single, handy document for quick reference on the production line.
"A control plan is a document that describes the procedures (measurement, inspection, quality check or monitoring of parameters) required at each stage of the process so that the process output conforms to the predetermined requirements."
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The control plan is the final link in a seamless chain that begins with the design FMEA. Potential failure modes that cannot be prevented through design are carried over to the process FMEA. Some failure modes in the process can be prevented through the use of poka-yokes or reduced to a very low frequency through the use of designed experiments to optimize the process. Other failure modes can be detected with high confidence. Despite our best efforts, some potential failures may still have unacceptable RPNs, so process controls should be added to monitor the process. The control plan should be checked to verify that all critical and significant characteristics identified during the design and process FMEAs are included.
At this point in the process, all nondestructive measurement systems listed on the control plan should have successfully passed the gauge repeatability and reproducibility (R&R) requirement. Keep in mind that sampling frequencies must often be high enough for the customer to be able to detect suspicious products prior to shipment. The quality engineer plays an important role in selecting the control method that best suits the specialty being monitored.
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Perhaps the most important aspect of the control planning method is the response planning. The response plan lists the steps to be taken by the operator when the control method indicates a problem.
For example, what should happen when Xchart gets out of control? Unfortunately, many references and training seminars do not adequately develop this concept. Examples simply stated "adjust and recheck" or "recheck and recheck". In addition, opportunities for permanent corrective actions will be missed.
Good reaction plans include four critical elements:-
- Containment
- Diagnosis
- Verification
- Disposition
Containment:
As soon as a problem is detected, quarantine and isolate all suspicious products. A good inventory management system that uses the first in, first out principle will simplify the task of containment whenever it is needed. Provide the operator with specific instructions on how to complete the control. It may also be wise to expedite the inspection until the problem is resolved.
Diagnosis:
Determine the root cause of the failure. It may be necessary to repeatedly ask, "Why?" For example, if the failure occurred because the operator was not adequately trained, ask, "Why was the operator not trained properly?" Repeat this process until a reasonable root cause is identified that can lead to permanent corrective action. Incorporate lessons learned from past failures. To facilitate the diagnosis process. Remember that common sense is not very common in the heat of war. Therefore, it is helpful to provide written guidance to the operator about possible causes of failure. In other words, specify the diagnostic steps and tests to be performed by the operator during the initial efforts to identify the root cause.
Verification:
Don't assume that corrective action solved the problem. Prove it! To verify that the problem has been fixed, collect additional samples after the corrective changes are applied. If possible, the response plan should specify how many additional samples are needed before normal operations can resume.
Disposition:
The obvious but still essential final step of the response plan is to determine an appropriate disposition for the material that was contained in the first phase of the response plan. Typical dispositions include scrap, resell, sort, use status quo, and return to seller. Written instructions for type or reworking are recommended.
Once an initial version of the control plan is released to production. Operations promoters must take ownership of the document and treat it as a living document.
You will understand this hopefully.
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