Process Control Reduces Scrap, Improves Injection Molding QualityProcess Control Reduces Scrap, Improves Injection Molding Quality
October 3, 2008
Originally Published MPMN October 2008
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Process Control Reduces Scrap, Improves Injection Molding Quality
The systematic/decoupled molding program optimizes injection molding by using process data.
Process control has enabled Atek Plastics (www.atekplastics.com), a division of Atek Companies (Minneapolis; www.atekcompanies.com), to reduce scrap, shorten start-up times and time to market, and improve quality at its injection molding plant in Kerrville, TX.
A standardized approach to developing, optimizing, and troubleshooting injection molding production processes, the systematic/decoupled molding program works on the principle that the more stable the process, the fewer defective parts will be produced. Developed by process control systems supplier RJG Inc. (Traverse City, MI; www.rjginc.com), the program focuses on optimizing injection molding by using process data—such as temperature, flow rate, pressure, cooling rate, and time—to identify and correct the viscosity variations that are the root cause of product defects.
Atek Plastics, a manufacturer of injection-molded products, began to implement systematic/decoupled molding techniques in 2004 and has since incorporated them across all departments to unify processing, tooling, and maintenance.
A key element of the program is the integration of data collection and analysis using a companywide real-time enterprise resource planning (ERP) system. The program helps ensure that the company’s products remain competitively priced in a volatile marketplace. Since it was implemented in 2005, the program has enabled the company to supply more than 144 million defect-free products per year while maintaining 100% on-time delivery.
“It’s one thing for monitoring equipment to communicate a higher-than-normal scrap rate or a below-standard condition. This method leaves the issue open for finger pointing and delay of root-cause analysis,” remarks Atek president Thomas Houdeshell. “However, using the systematic approach, team members are not only aware of the issue, but since everyone is speaking the same ‘language,’ the root-cause analysis and resolution are expedited.”
For example, team members can use cavity balance, gate-seal analysis, and pressure-loss studies to determine if the root cause of a defect is mold. To address materials issues, Atek processors run a relative viscosity curve, 30/30 melt temperature testing, and gate-seal analysis. For machine issues, they analyze check-ring repeatability, pressure response, and injection speed linearity. This combination of steps enables personnel to pinpoint and solve problems quickly, reducing product losses and downtime.
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