Factorial Design for Reduction of Variation on Plastic Parts Weight: Plastic Parts Weight and Injection Molding

Factorial Design for Reduction of Variation on Plastic Parts Weight: Plastic Parts Weight and Injection Molding

María B. Becerra (Instituto Tecnológico de San Juan del Río, Mexico), Arturo Hernández (Universidad Politécnica de Querétaro, Mexico), Ángel A. Franco (Instituto Tecnológico de San Juan del Río, Mexico), José M. Zea (Universidad Politécnica de Querétaro, Mexico) and Roberto Zitzumbo (CIATEC, Mexico)
DOI: 10.4018/978-1-5225-0130-5.ch013
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This research aims to find the causes of weight variation of plastic products that cause a high cost and rework. The importance of using statistical control on the weight of plastic parts is presented; describing the type of machinery used to manufacture, considering the properties and applications of material as Acetal and conditions for injection molding operation, where a 24 factorial experimental design was used to find the variables which influence the weight of the product to maintain a stable process. An efficient solution was developed considering the variables of pressure and injection time to be highly significant in the weight of the plastic parts. Finally an optimal arrangement is generated for the plastic injection process which ensures a stable production process and ensures the quality of the product, which implies a reduction of costs and compliance with design specifications.
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Through time, the man has known and made use of natural plastic materials such as horn, amber, and tortoiseshell because of their good properties. During the fifties and sixties the production and consumption of plastics grew enormously, being the time of greatest commercial heyday. Nowadays, almost all objects of daily life, even clothing, incorporate a percentage of plastic fibers. Most items around us on a daily basis are partially or completely made of plastic, such as: televisions, pens, calculators, disks, appliances, cars, airplanes, etc. So the technology has resorted to the use of plastics.

Some of the characteristics of the material used in this research are:

Acetal: Strong rigid plastic used in engineering, with exceptional dimensional stability, high creep resistance and vibration fatigue, low coefficient of friction, high resistance to abrasion and chemicals, low tendency to stress cracking.

Offering to the manufacturing engineer the initial data processing or initial operating conditions before setting up the plastic injection machine for a new product, can save time and money. To achieve high quality products as soon as possible, the regulation of the machine at the start of the stage of optimization of the injection process should be as close to the ideal processing conditions as possible.

Key Terms in this Chapter

Design of Experiments: Powerful statistical tool for testing and identifying the optimum operating points or quality of manufactured parts in the shortest time possible.

Processing: Sequence of operations to manufacture or transforming raw material into finished products.

Plastic: Synthetic polymer capable of melting at certain temperatures to be manageable and malleable. This kind of material can be recycled.

Scrap: Are the solid pieces after being manufactured and rejected by bad specifications or dimensions waste.

Optimization: Are the minimum resource utilization for the manufacture of any articles or manufacturing processes.

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