Injection molding: Water molding: an alternative to gas-assist

Water injection technology is increasingly being applied as an alternative to internal and external gas injection technology in cases where the production of molded parts defies conventional processing methods. Battenfeld says its water injection technology (WIT), Aquamould, allows the production of very thick-walled parts such as pipes and handles in shorter cycle times.

Research at the Institute for Plastics Processing (IKV) at Aachen/Germany confirms that water injection technology produces more even wall-thickness and less residual wall-thickness than gas-injection molding. Moreover, the inner walls are smoother.

Another important aspect of the application of Aquamould is the significant cooling effect of water. Aside from the standard cooling of the mold, the injection of water has the effect of cooling the interior (“internal cooling”). The IKV discovered that the injection of water leads to a reduction in cooling times by up to 70% compared to gas. At the same time the markedly lower melt temperature allowed components produced with WIT to be demolded earlier.

However, there are special considerations for water injection technology. The water used in the process must be drained away. This can be achieved by an opening in the mold and the effect of gravitation, by using compressed air to blow the water out, or by using an outlet outside the mold. Water encapsulated in the produced component must be drained off, too. Hence, the component must be open at some point. At the same time, the sensitive mold needs to be protected from damage by squirting water.

Water injection technology involves a high water-injection pressure to ensure the required evenness in the wall-thickness distribution and smooth surfaces. Battenfeld has developed pressure control modules that are specially designed for the requirements of water injection technology.

The injection of water into the melt requires injection components with markedly wider diameters than those used for gas injection. The increase in diameter ensures that the water can penetrate the melt quickly.

Battenfeld Canada Ltd. 905-670-9384