SPC Part5 EM8984 统计过程控制(5).pdfVIP

EM 8984-E •August 2009 PERFORMANCE EXCELLENCE IN THE WOOD PRODUCTS INDUSTRY Part 5: Cause-and-Effect Diagrams Scott Leavengood and James E. Reeb PERFORMANCE EXCELLENCE Our focus for the first four publications in this series has been on introducing IN THE WOOD PRODUCTS INDUSTRY you to Statistical Process Control (SPC)—what it is, how and why it works, and then discussing some hands-on tools for determining where to focus initial efforts to use SPC in your company. Experience has shown that SPC is most effective when focused on a few key areas as opposed to the shotgun approach of measuring anything and everything. With that in mind, we presented check sheets and Pareto charts (Part 3) in the context of project selection. These tools help reveal the most frequent and costly quality problems. Flowcharts (Part 4) help to build consensus on the actual steps involved in a process, which in turn helps define precisely where quality problems might be occurring and what quality characteristics to monitor to help solve the problems. In Part 5, we now turn our attention to cause-and-effect diagrams (CE diagrams). CE diagrams are designed to help quality improvement teams identify the root causes of problems. In Part 6, we will continue this concept of root cause analysis with a brief introduction to a more advanced set of statistical tools: Design of Ex- periments. It is important, however, that we do not lose sight of our primary goal: improving quality and in so doing, improving customer satisfaction and the profitability of the company. We’ve identified the problem; now how can we solve it? In previous publications in this series, we have identified the overarching qual- ity problem we need to focus on and developed a flowchart identifying the specific steps in the process where problems may occur. We now need to narrow our