By Pratyusha Nandy

INTRODUCTION

In future, it is to be seen whether hot runner systems will continue to use pneumatic or hydraulic actuation to operate valve gates or whether the more precise technology of electronics will take over. Companies are of the opinion that electrically actuated system will evolve to provide the best of both worlds, as it integrates the two very different technologies of hydraulics and pneumatics. While pneumatic and hydraulic actuated systems are useful for only a few applications, the new electrically actuated system is ideal for use in medical and other high-performance applications, and can be applied to virtually any application.

Currently, injection molding machines have become more complex in their design and build. Besides complexity, rising petroleum prices, increasing demand for thin-walled parts, and growing environmental regulations demanding clean and quiet factory floors lead to increased expenses for the molding machine manufacturers. This complexity in injection molding machines, along with increasing competition, require hot runner system manufacturers around the world to look for solutions that can add value to the injection molding machines. These trends promote the hot runners manufacturers to favor the use of an electrically actuated system, which will offer the injection molding industry a diverse set of benefits, such as, oil-free operations, more precise valve stem actuation, closer pitch spacing, higher quality gates, reduced maintenance and operating costs, and improved efficiency and lower noise levels than the existing hydraulic designs.

Pneumatics Actuated Systems – Limited Due to Reduced Stem Force

While the new electrically actuated valve systems offer a host of benefits, it does not mean that pneumatics will be completely superseded by them in future.

Pneumatics is currently the most widely accepted technology in the medical device industry, as it is considered to be a relatively clean technology that makes use of air. Pneumatics actuated systems can be easily integrated into the production system, to provide reliable actuation. In addition, maintenance of such systems are easy. However, they have limited performance, because air is typically available for up to only 100 psi to operate the gates. This limitation of pneumatics actuated systems may limit the available stem force, especially, in the case of small-pitch, individually-stem-driven systems with small piston diameters. To ensure proper operation, special attention must be paid when setting up the air supply hoses and solenoid valves. If they are improperly assembled, for instance, if the air supply hoses are too long or solenoid valves are mounted too far from the hot runner, valve stems can open and close causing slight delays between valve gate pistons; thereby, resulting in inconsistent cavity filling.

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