Process Control

Statistical Process Control (SPC)

Coi Rubber maintains its quality for manufacturing starting from inbound material checks, certifications, and quality governance audited by third parties.  Process controls are implemented from mixing to manufacturing, our ever passion for continuous improvements is driven by our team of experts and their dedication.

Mixing a batch or discrete process is conducted with Normal SPC charting for such process and employs X-bar and R charts.  This is the data for which are generated by testing small subgroup (2-6 test pieces or batches) adn averaging the resulting observations.  At least 30 observations are preferred for good charting to begin.  The ranges of all the averages for the initial observations are used to calculate an average range, known as R-bar.

Vulcanization

Controlling the vulcanization of thick molded rubber parts is an important industrial challenge. The vulcanization field of molded rubber parts, indeed, is dependent upon the temperature history undergone by any rubber points during molding process. The geometrical sophistication of many industrial parts causes inhomogeneity of heat transfers within the mold cavity during the molding cycle. Vulcanization field assessment requires to develop a heat transfer model, which would be coupled to the rubber chemical history within the mold. With this aim in view, a simulation tool is proposed here. In order to validate the model, a temperature-controlled molding device is developed and described in this paper. The accuracy of the thermal control and the supervision of heat transfers it allows is specially underlined. Mold temperature history checking is carried out using an original measuring device recording temperatures directly within the molded parts. The control of heat transfers achieved with the molding equipment presented here is verified with experimental measurements. These results also confirm the validity of the heat transfer model. Digital modelling here has made it possible to predict successfully the vulcanization front (dividing surface between unvulcanized and vulcanized materials) progress in various molding configurations.

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