As competitive pressures and globalization continue to put a squeeze on plastics processors, it is becoming ever more important for manufacturers to explore ways to optimize production across the entire process flow. Seeking faster cycle times, lower energy consumption and a more economic use of raw materials, manufacturers are also looking at existing technologies that can offer benefits in these areas.
Gas injection molding (GIM) is a tried and tested technology that is used to mold hollow components with minimal internal stresses, reduced warpage and no sinkage — at lower machine clamp pressures. Common applications include handles for cars and appliances, automotive panels and similar parts with thicker cross-sections.
GIM involves injecting pressurized gas into the polymer melt. As gas flows through, it pushes molten resin against the wall of the mold cavity to create a hollow core. Typically, nitrogen is the pressure fluid used.
Over the past decade, water injection molding (WIM) has also grown in popularity as an alternative to GIM, especially for fluid pipes, due to its cooling performance. However, despite its high heat removal capacity and good pressurizing performance, water has various handling drawbacks, including the need for drying and the risk of water leakage, which can result in production stoppages, high scrap rates and even mold surface damage. Furthermore, WIM requires complex and expensive equipment.