Measuring the shear viscosity of molten resins has been widely attempted. There are various measurement methods, but this section introduces capillary rheometer measurements, which are easy to measure in the flow rate range of injection moulding CAE, particularly with regard to in-mould flow.
Above is a conceptual diagram of the cross-section of a capillary rheometer. The shear rate can be estimated from the flow velocity Q by measuring the pressure difference between the distance L and the molten resin flowing in a cylindrical tube with a hole in it, and the shear rate dependence of shear viscosity can be measured by changing the flow velocity Q.
Although these are the contents introduced in many books, it is assumed that a commercially available capillary rheometer is used for the actual measurement. We have developed a system for measuring shear viscosity using an injection moulding machine based on this concept. The shear viscosity is measured using this in-house manufactured shear viscosity measuring system. By using the measurement results, it has been confirmed that the calculated and experimental results for the in-mould pressure in CAE are in good agreement.
By measuring shear viscosity using such a method, the in-house data (data measured with this system) greatly improved the accuracy of pressure prediction compared to the resin data registered in the software with the same grade name. Although only the measured data for shear viscosity was changed, and no other resin property data was changed, a significant improvement was achieved.
Measuring shear viscosity is considered important for predicting in-mould pressure.
While the preparation of the equipment is important, the accuracy can also be improved by devising the measurement method.
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