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Development of a low cost process for the manufacture of storage and pressure vessels using novel composite thermoplastic materials (COMPOSITEFOAM)


Use of radiotelemetry to monitor and control the temperature of the concept tooling during the rotational moulding process cycle enables more accurate control of the process. The current state of the art in rotational moulding uses large hot air ovens to heat the tooling and forced cold air or cold-water spray to cool. This is only around 90 percent energy efficient, so increased control of the tooling temperature and use of the direct heating will improve energy utilisation. The use of radiotelemetry to monitor the tooling temperature is not possible when the ovens are used as the signal cannot pass through the steel walls, and the sender unit cannot withstand the temperatures in the oven. The novel concept tooling allows this technology to be used successfully.
Steel concept tooling was produced using Sprayform Technology (licensed from Ford) with conformal heating and cooling channels. The channels were manufactured using copper pipe work, shaped to the outer surface of the tooling, brazed in place to eliminate air gaps and then over sprayed with a thin layer of steel. The conformal channels were used in process trials to heat and cool the tooling directly using thermal oil and an external oil heater/cooler unit. The direct heating of the tooling has eliminated the requirement for a heating oven, which potentially dramatically reduces the energy requirements for the rotational moulding process. Future developments would include recycling the energy, from the cooling process and using it to assist in reheating the tooling during the process cycle. Direct heating and cooling when coupled with temperature measurement inside the tooling, will allow greater control of the moulding cycle, resulting in reduced energy wastage and reduced material scrap of reject product. The addition of conformal cooling channels to the Sprayform tooling could also be used in other polymer processing techniques and could potentially be used in other heat exchange situations.
Direct heating and cooling of the rotational moulding tool, using thermal oil allows greater control of the moulding process and greatly increases the energy efficiency of the process when compared to the current state of the art, where large air ovens are used for heating and forced air or cold water spray are used for cooling. The use of thermal oil could be developed to include energy recycling within the system, where the heat removed from the tooling during cooling is used to reheat the tool on the next cycle or heat another tool in an alternating system.