Efforts in Estimating the Resin Viscosity Model

Efforts in Estimating the Resin Viscosity Model

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In injection molding, especially during the prototype stage of molds, resin flow analysis based on 3D CAD models is performed to examine moldability and address molding defects. During this process, the resin flow analysis software references material property values such as viscosity and heat capacity for each type of plastic stored in its material database.

Recently, environmentally friendly materials, such as recycled plastics and bioplastics, have gained attention, leading to an increase in their use. However, compared to traditional virgin plastics, these materials exhibit greater variability in properties, posing challenges in maintaining quality with conventional molding methods.



One solution to address this issue is to verify the quality of molding before manufacturing the mold through resin flow analysis. However, existing resin flow analysis software databases do not include data for recycled plastics and bioplastics, necessitating the need for new measurements of their properties. Meanwhile, the equipment used to measure the properties of plastics is expensive, making it a challenge to measure these properties. Consequently, there is a demand for tools that can simplify the measurement of plastic properties necessary for resin flow analysis.


To meet this challenge, we have initiated the development of an algorithm and a mold that can estimate resin viscosity without the need for expensive measuring equipment. This development is a joint project with Futaba Electronic Industrial Co., Ltd. The mold is equipped with resin pressure sensors and resin temperature sensors. By utilizing the data obtained from these sensors, it is possible to estimate the resin viscosity after it passes through the nozzle of the injection molding machine. This technology allows for a relatively low-cost estimation of the resin viscosity model.

Figure 1. Image of Resin Viscosity Estimation


Resin flow analysis involves calculating the numerical solution of the motion equations of molten resin. The smaller the discrepancy between the numerical solutions obtained from this analysis and the actual measurements taken by the resin pressure and temperature sensors during molding, the more accurately the real phenomena are captured, indicating a high-precision resin flow analysis. In resin flow analysis, a formula representing resin viscosity, dependent on pressure, temperature, and velocity, known as the resin viscosity model, is used. Parameters of this model are estimated based on experimental data. Therefore, the accuracy of resin flow analysis is significantly influenced by the precision of the resin viscosity estimation. For this project, viscosity estimation will be conducted using the Cross-WLF model.


Figure 2. Cross-WLF Model

Additionally, due to the significant variability in experimental data for recycled plastics and bioplastics, there is a need to develop a robust algorithm for

estimating the parameters of the resin viscosity model that can handle disturbances and other variations. In this joint development, Futaba Electronic Industrial Co., Ltd. will provide high-precision sensors, and MAZIN Co., Ltd. will build the algorithm based on their expertise in analyzing data from mold internal pressure. The goal is to develop a mold capable of high-precision resin viscosity estimation.