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OLIVEIRA, R. R. ; HOPKINSON, N. ; RIBEIRO JUNIOR, A. S. . In: IV CONEM - Congresso Nacional de Engenharia Mecânica, 2006, Recife - Pe. Anais do IV CONEM - Congresso Nacional de Engenharia Mecânica, 2006.


Rapid tooling technologies have helped multidisciplinary teams in the design of injected plastic parts, allowing for the consideration of aspects related to the moulding process along with the product features. Particularly, the use of stereolithography in the manufacture of injection moulding moulds has presented satisfactory results allied with relatively low costs. Stereolithography moulds (SL moulds) typically present very short life expectance. Research results reported in the literature showed that failure of this kind of tool was mainly due to the decrease of the mechanical properties of the mould material accompanying the temperature rise during operation. Owing to the typically low thermal conductivity of the materials used, in comparison to that of metals, SL moulds present a significant loss of efficiency in the injected part cooling stage. This makes the injection process slow and tedious and increases the risk of tool failure. Some authors suggest that the moulds be cooled between two consecutive injection cycles to prevent premature failure, since this would allow for the recovery of the material properties. However, the lack of prior knowledge of the stress acting on the mould makes it difficult to determine the necessary cooling time. In the present work, an evaluation is made of the usage of a computational code based on the finite elements method to determine the mould stress. The computational package ABAQUSä was used to implement a numerical model to determine the stress acting on a stereolithography mould during the injection process. A comparison of numerical and experimental results of the ejection force is presented and indicates that the proposed methodology can be used to provide guidance in the design of this kind of tools with extension of their life expectance.