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learn more about injection molding
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FREQUENTLY ASKED QUESTIONS (FAQ) |
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Noble Plastics embraces the use of technologies that improve product quality, increase manufacturing efficiency, or expedite the development process. Although a comprehensive description of technologies defining "state of the art" in the injection molding industry is beyond the scope of this site, the following are presented as topics of frequent interest to our customers.
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Injection molding is the process of melting plastic resin, injection of the melted resin into a closed mold, the freezing or setting of the molten plastic, the opening of the mold, and finally the ejection of the molded part. These molds run anywhere from $5000 - $250000 for small to medium sized molds. The usual applications of Injection Molding are either large volume (minimum 1000 parts per run) or high cost parts with a need for precise dimensional repeatability. If you are not targeting annual production rates of 20,000 parts you would have a hard time recouping the costs of the molds. |
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Sometimes referred to as over-molding, this process is identical to the Injection Molding process with the exception that one or more "inserts" are loaded into the mold prior to the injection phase. Plastic is then injected around all or part of the insert. This process offers the ability to produce composite parts that would be difficult or impossible to assemble otherwise. Often the process is used to eliminate assembly steps thus reducing overall manufacturing costs. |
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A "Mold Flow" analysis is an injection molding process simulation that, at a minimum, includes the filling of the part cavity with a specific plastic material. Although any such simulation may be referred to as a "mold flow" analysis, the undisputed industry leader for simulation software is MoldFlow Corporation. MoldFlow produces several software packages of varying capability and cost. Noble Plastics uses the Mold Advisor package which allows the simulation of part and mold filling and cooling. Information that can be gained from such analyses includes:
All that is required for a basic analysis is a solid model and material spec. |
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It is a well known fact that many resins degrade or present cosmetic difficulties if processed with too high a moisture content. It is therefore surprising to find that many molding facilities do not directly test for moisture content but rely on "drying time" methods to achieve the appropriate moisture content. With some resins it is possible to over dry the resin, thus the window of acceptability is further narrowed. When one considers the significant effect that incoming material moisture content, changing environmental conditions, and variations in dryer efficiencies can have on drying time, one must accept the following possibilities when drying by time.
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A fancy name for a simple idea, Statistical Process Control, or SPC, involves the monitoring of manufacturing process variables for the purpose of defect solution and prevention. When implemented properly, SPC allows the elimination of mass inspection. For example, a variation in the amount of plastic injected would indicate a potential for an under filled part. Such parts would be diverted for later inspection. Thus, only a portion of the parts produced require inspection. One important aspect of SPC is the ability to detect process deviations that correlate to problems not directly observable by the typical human inspector. One example would be higher than normal plastic temperatures that would warn of potential plastic property degradation. |
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An injection mold is, or should be, a precision device engineered to endure thousands or millions of cycles while maintaining smooth and consistent mechanical operation as well as part geometry. Standards for mold construction have been established in the industry. Proper mold design, to include selection of core and cavity materials, can have the single most dramatic effect on part cost. |
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