Project Description

The term scientific injection molding (SIM) is becoming a buzzword in the industry. How do you differentiate between true SIM and loosely used terminology? It comes down to data collection, machine performance, processes, material characteristics, and how they influence one another. SIM gives us the ability to identify flaws in the entire process of molding a part and allows us to solve the root cause rather than try to work around it. An important difference to realize is that scientific molding does not equal scientific processing. There are multiple key components in a well-developed SIM process including:

  • Mold Design
  • Part Design
  • Polymer Properties
  • Processing
  • Press Performance
  • Material and part validation through testing and analysis.

The goal of SIM is to move injection molding away from being an art founded in “tribal knowledge” to a data-driven, scientifically rigorous procedure.

So how do you establish SIM procedures?

Using advances in technology within the industry, New Berlin Plastics uses in-mold sensors along with well-defined procedures to collect extensive data on the behavior of polymer as its being molded. SIM focuses on polymer behavior rather than machine behavior with the goal of creating a robust repeatable process that reduces set-up times, scrap, and improves part quality and consistency. So what variables are observed and measured when developing a process like this?

In-mold sensors and other methods are used to collect a variety of data such as: polymer melt and mold temperature, fill/shear rate of the polymer, the pressure gradient within a part, and shrink/cooling rate. Each of these variables has an important effect on polymer behavior and the finished product. By understanding this behavior through data analysis, New Berlin Plastics is able to create processes that cater to particular materials and parts; providing a repeatable process that’s proven in the numbers. After molding, parts will undergo testing to see how the process affected the polymer. This ensures that none of the physical or chemical properties of the polymer were compromised, so not only does the part meet our customer’s specifications but the polymer characteristics they seek remain present.

New Berlin Plastics practices Decouple II and Decouple III style SIM. These are differentiated by the separation of the fill, pack, and hold stages of molding. Decouple II takes the velocity controlled fill phase and separates it from the pressure controlled packing and holding phase. This allows for better process control at faster fill rates, and during normal viscosity variation. When a higher level of control is needed a Decouple III process provides an even higher level of control, packing to a velocity until a desired cavity pressure is reached. In many cases this is the preferred method for extremely tolerance-critical parts. These two styles of SIM are based in controlling the velocity of the polymer, as well as understanding its viscosity and behavior. By employing the strenuous data collection and analysis, and tightly controlled molding techniques, New Berlin Plastics is able to produce data-driven dependable processes that create consistent and reliable parts.