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Process Measurement, Scrap Reduction, and Performance Reporting

Today's growing emphasis on higher quality at lower cost has caused manufacturers to look at creative ways to apply quality improvement technology. This was the case with one of MAP Quality Engineering's privately held clients facing excessive scrap costs. As the global leader in their market, MAP's client needed to increase productivity to meet a growing demand. But in a tight economic climate, they could not justify the capital expense for new production equipment. Instead, they had to make better use of the existing process and machinery.

Quality Improvement Objectives

The client identified two key project objectives. First, reduce scrap levels of the assembled product. Scrap amounts were running approximately 4000 square yards per assembly line per day. Second, enable production schedulers to schedule production based on real-time WIP inventory amounts.

Manufacturing Process

The client has a centralized manufacturing facility with several buildings housing different steps of the process. In the first step, spooled wire is coated with PVC in the coating process. After coating, the wire is drawn through an oven to cure the PVC and is wound onto spools. In the final step of the process, the spools are staged as WIP inventory for use in the assembly department.

Strategy Development

Variation in coated wire diameter causes the majority of scrap in the assembly stage. This fact drove MAP's strategic thinking. MAP's consulting engineers posited that if spools of coated wire could be segregated according to their average diameter and standard deviation, then the assembly department could pick spools that met the specifications for the product they were assembling. Measuring the diameter of the coated wire in real-time, as it was wound onto the spool, could enable the assignment of a quality disposition. Tracking the spools by disposition could also enable schedulers to monitor WIP and adjust production accordingly.

Strategy Implementation

A vision system that allowed the measurement of the diameter of 80 wires being wound at a rate > 60' per minute was identified and implemented. After fine-tuning the data collection by the vision system, MAP engineers implemented Wonderware® InTouch™ to crunch the data and to provide operators with a visual summary of each spool and a corresponding disposition label. Based on the disposition, assembly workers now pick spools that meet the quality requirements for the product in production.

InTouch was also used to manage the logging of actual and summary data to a Microsoft® SQL Server® database.

In addition to reporting current quantities on hand, production schedulers wanted the ability to analyze the data and to create statistical charts, in an ad hoc manner, from remote locations. Therefore, NWA Quality Analyst Web Server^® was chosen to facilitate WIP reporting. Production schedulers are now able to schedule specific products based on the actual coated wire inventory levels and production trends.

Production managers also used Quality Analyst Web Server to access manufacturing performance metrics such as scrap rates and throughput. Client engineers are now able to identify when substandard production has occurred, and they have immediate access to data that help uncover assignable causes.

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Quality Improvement Results

In total, the project required an investment of approximately $250,000 U.S. dollars. While the necessary investment was substantial, the results were fantastic! As explained by the client's project manager, "Over the first three months, we observed a reduction in assembly scrap from approximately 4000 square yards per assembly line per day to an average of 250 square yards per assembly line per day." This calculates to a 94% reduction in scrap.

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The reduced scrap, in turn, reduced the amount of "rescheduled production." This effect resulted in a throughput gain calculated at 5% " …which is a significant amount of product when you consider the total volume produced each day!"

The projected annual savings, with the new system deployed to the other manufacturing lines, are estimated at ~$1.6 million U.S. dollars.

About MAP Engineering:

MAP is a consulting firm specializing in the integration and utilization of statistical tools for process improvement. To contact MAP, please visit www.mapqe.com or call 1-877-SPC by MAP.

About NWA:

NWA is a leading provider of analytical software for statistical analysis. NWA's tools for on-line SPC and off-line SQC are HMI/SCADA independent. To contact NWA, call 1-888-692-7638.

About Wonderware:

Wonderware is the world’s leading provider of HMI software. To contact Wonderware, please visit www.wonderware.com or call your local Wonderware Distributor.