G&A Moulding
John Goff, of G&A Moulding Technology, writes for BP&R on the importance of utilising Computer-Aided Engineering flow analysis for part design, troubleshooting and material selection.
Computer Aided Engineering (CAE) flow analysis is well known and established as an excellent method of predicting how a mould will fill, as well as optimising part design, and it is also as an invaluable troubleshooting tool. It demonstrates the optimum point of melt entry (gate position), optimum wall sections, cooling capabilities, heat removal capabilities, identifies areas of possible gas entrapment, flow defects and the extent of shape change upon melt solidification, etc. It also demonstrates whether the part design is feasible for its end use and material selection.
G&A receives many enquiries where a company is experiencing issues when attempting to produce the same component but from a different thermoplastic material. Quite often poor quality or incomplete mouldings are produced when undertaking moulding trials using the same moulding equipment/mould tool, leading to the possibility that changes to the existing component geometry are necessary. CAD data of the original component, together with the cooling circuitry, feed design and geometry and hot runner etc of the mould tool, will enable a CAE flow analysis to be carried out that will provide an understanding of what can be achieved without going through a lot of trial, effort and expense.
Separate 3D flow simulation studies involving the use of different grades of material, melt and mould temperatures, filling times compared to the processing conditions used for the existing material and those used for the unsuccessful trial/s will further illustrate whether a fit for purpose component will be achieved and whether it is necessary to alter its geometry. Furthermore, by reviewing the results of using different material grades of various melt viscosities, the process window to be used will either increase or decrease, i.e. the degree of difficulty will be clearer. More importantly, the requirements of the processing equipment to manufacture the part may also need to be changed.
CAE therefore provides the information and confidence with which to carry out practical trials. More importantly, it highlights the reasons for a previous, unsuccessful trial.
What is very important, when using CAE simulations, is a true understanding and clear interpretation of the results of a full analysis. It will not provide a pass or fail tick box but information that needs to be fully interpreted with suitable recommendations made, i.e. it is a highly effective technical tool. Partial analysis provides a quick review.