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Part shrinkage anomilies from stereolithography injection mould tooling

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journal contribution
posted on 14.05.2009, 08:31 by Russell Harris, H.A. Newlyn, Richard J.M. Hague, Phill M. Dickens
The use of stereolithography (SL) tooling allows plastic parts to be produced by injection moulding in a very short time due to the speed of mould production. One of the supposed advantages of the process is that it provides a low volume of parts that are the same as parts that would be produced by the conventional hard tooling in a fraction of the time and cost. However, this work demonstrates different rates of polymer shrinkage are developed by parts produced by SL and conventional tooling methods. These revelations may counter the greatest advantages of the SL injection moulding tooling process as the parts do not replicate those that would be produced by conventional hard tooling. This work identifies the different shrinkage that occurs in mouldings produced by an SL mould as compared to those produced from an aluminium mould. The experiments utilise two very different types of polymers and two mould geometries, which are 2 processed in the same manner so that the heat transfer characteristics of the moulds are isolated as the only experimental variable. The work demonstrates how the two mould materials exhibit very different rates of expansion due to the temperature profiles experienced during moulding. This expansion must be compensated for to establish the total amount of shrinkage incurred by moulded parts. The compensation is derived by a mathematical approach and by modelling using finite element analysis. Both techniques depend upon knowledge of the thermal conditions during moulding. Knowledge of these thermal conditions are obtained by real-time data acquisition and simulated by FEA modeling. The application of the findings provide knowledge of the complete shrinkage values relating to the mould material and polymer used which would enable the production of geometrically accurate parts.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Citation

HARRIS, R.A....et al., 2003. Part shrinkage anomilies from stereolithography injection mould tooling . International Journal of Machine Tools and Manufacture, 43(9), pp. 879-887.

Publisher

© Elsevier

Version

VoR (Version of Record)

Publication date

2003

Notes

This article has been published in the journal, International Journal of Machine Tools and Manufacture [© Elsevier] and is available at: http://dx.doi.org/10.1016/S0890-6955(03)00080-4

ISSN

0890-6955

Language

en