Measuring the shear viscosity of molten resin has been widely attempted. Although there are various methods of measurement, here we will introduce the capillary rheometer measurement, which is easy to measure in the flow rate range of injection molding CAE, especially with respect to in-mold flow.
The above is a conceptual diagram of the cross section of a capillary rheometer. The shear rate can be estimated by measuring the pressure difference between distances L and Q. By measuring while changing the flow rate Q, it is possible to measure the shear rate dependence of shear viscosity.
Although these are the contents of many books, it is assumed that a commercially available capillary rheometer is used for the actual measurement. At our company, we have developed a system to measure shear viscosity using an injection molding machine based on this concept. The shear viscosity is measured using this in-house developed system. By using the measurement results, it has been confirmed that the calculated and experimental results of the pressure in the mold in CAE are in good agreement.
By using such a method to measure shear viscosity, the in-house data (measured by this system) greatly improved the accuracy of pressure prediction compared to the resin data registered in the software with the same grade name. Only the measurement data of shear viscosity was changed, and the other resin physical property data was not changed, but it was greatly improved.
Measuring shear viscosity is considered to be important in predicting the pressure in the mold.
Preparation of the equipment is important, but the accuracy can also be improved by devising a measurement method.
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