We will introduce the development of injection molding industry toward Industry 4.0 in a series. This article features the CAE simulation technology development, which is more relevant to process improvement. We will introduce production management automation in other subsequent articles.
“Information” is the main character in the journey to Industry 4.0. For injection molding process, the information contains process conditions, equipment, materials and product quality. Information is derived from “data”, and information can be analyzed into “knowledge”, which is the main power of technology progress. Thus, we can say Industry 4.0 is the process of continued integrating and enforcing information, data and knowledge. In the traditional plastic engineering industry, the process conditions, product and mold designs rely on experience transmission. Most of the information collected from factories come without comprehensive data base and could not be transformed into knowledge. In the Industry 4.0 era, the main goals of the plastics industry are to collect comprehensive data, automate information delivery and produce knowledge with the help of computer-aided calculations.
Then, how is data transferred from real physical environment (e. g. the data collected from sensors) into computable concepts? According to Dr. Jay Lee, Director of Intelligent Maintenance System Center, National Science Foundation as well as the consultant of Moldex3D’s manufacturing and service innovation, the concept of Cyber-Physical System is “to capture, save, build models of, analyze, mine, evaluate, predict, optimize and collaborate big data from the physical space, items, environment and activities, and integrate with the design, test, features and performance of the items for profound integration with physical space. Comprehensive smart industrial asset is then further promoted by self-perception, self-memorization, self-awareness and self-decision.”
The way to illustrate real processing environments through virtual models applied in injection molding process is “mold filling analysis”. It can transfer real space into virtual environment where we can solve problems with knowledge. In the process of building finite element analysis systems, the real items include mold, mold cavities, the boundary range built by mesh. The analysis of physical field is interpreted by fluid mechanics equations. The way to analyze the items and plastic materials is to transfer their thermal and fluid properties into material equations. The processing machine movement is transferred into the pressure, temperature and speed that are imposed on materials. All of the elements in injection molding mentioned above have been transferred into virtual systems, in which the product quality and production efficiency can be calculated for the production decision-making in the real world.
The technology evolution of integrating virtual and real world is from two aspects: the reality of model building and data analysis technology in virtual space. These are what the simulation software developers continue to strive for. As for the Moldex3D development, the improvement of material equations is always the core mission of Moldex3D Material Research Center. For example, material viscoelasticity characterization and the correspondent viscoelasticity coupling solver in Moldex3D software are the new technologies that improve the traditional viscosity equation to predict flow behaviors. Thus, we are now able to efficiently predict a variety of surface defects under unbalanced flow behaviors at earlier stages. If we expand the viscoelasticity prediction capability to warp analysis, we will be able to observe how the stress caused by in-mold shrinkage changes along with the length variation of cooling time. Therefore, the product warpage analysis will be more close to the real-world results under different processing conditions.
Another important progress in recent years is the model building of injection molding machine movement. In conventional simulation, the screw movement is transferred into the speed and pressure imposed on the melt. In this way, the melt flow behavior is oversimplified. Take a hydraulic press with closed loop circuit as an example, at the actual injection stage, the machine compares the measured speed and the injection speed input by the molders to decide the screw movement. The screw movement speed will be increased or decreased by the proportional valve which is adjusted by the controller. The reaction speed of this closed loop circuit is the key factor of the machine’s production stability. With poor product design or great injection pressure changes, it will take a longer time to stabilize the control of the closed loop circuit reaction. In the Industry 4.0 environment, production stability is the necessary condition of automation. Thus, the model building of machine movement in simulation is particularly important.
Next time, we will introduce injection machine suppliers’ different solutions in assisting customers to develop competitiveness in the journey to Industry 4.0.
Dr. Tober Sun