| Detecting and Correcting Manufacturing Problems |
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written by Drs. Robert & Marilyn Hart
In assembly line manufacturing operations, problems of poor quality are frequently transient in nature. For this reason, improvement can only be made by continuously monitoring the process and responding promptly by taking corrective action when the need arises. An effective mechanism for monitoring the process will be described below, but it must be kept in mind that the best monitoring methods become only an idle exercise unless corrective action is taken when needed.
A primary roadblock to process improvement is lack of timely information on manufacturing problems. All too often, management is totally unable to answer the questions:
- ON THE PRECEEDING SHIFT, WHAT WAS THE PERCENT DEFECTIVE (OR DEFECTS PER UNIT)?
- WHAT TYPES OF PROBLEMS WERE CAUSING THIS SCRAP AND/OR REWORK?
Read on... |
| How are You Using Control Charts? |
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There are many uses of the control chart and many benefits. Montgomery tells us:
- Control charts are a proven technique for improving productivity
- Control charts are effective in defect prevention
- Control charts prevent unnecessary process adjustment
- Control charts provide diagnostic information, and
- Control charts provide information about process capability.
Wheeler lists 5 uses for control charts:
- Report Card Charts
- Process Adjustment Charts
- Process Trial Charts
- Extended Monitoring Charts and
- Continual Improvement Charts
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| Using Pareto & Paynter Charts in a Quality Improvement Program |
Pareto charts and Pareto-derived Paynter charts are important statistical tools in quality improvement programs. Six Sigma and other methodologies rely upon Pareto analysis to define and focus continuous improvement efforts.
Although the term Pareto principle (or Pareto effect) has become a standard term in business and quality improvement jargon, it is often not clear when to use Pareto charts, or how to use them effectively.
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| Quality Q&A: Evaluating Process Improvements or Methods Using Cpk |
Q. We are interested in monitoring production over time and across shifts using the process capability index Cpk. How do we determine when a change in the Cpk is significant?
A. Process capability indices, particularly Cpk, are increasingly being used to evaluate the effectiveness of process improvement techniques. They are used to help reveal possible quality trends and to compare methods, work shifts, and even workers. However, Cpk by itself may not be the best tool to use for these purposes.
Read on... |
| Quality Link: SPC Press Reading Room |
Visit Dr. Don Wheeler's Reading Room, where you'll find dozens of articles and papers covering topics across the SPC spectrum. Topics include "Process Behavior Charts and Chaos Theory" and "Charts for Chunky Data."
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| Something You'd Like to See? |
Is there a topic you'd like us to discuss? Have a process improvement question? If so, submit a topic request and we'll see that your topic gets covered in an upcoming edition of the Statit Bulletin.
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