There is another option—an electrically actuated valve gate system. This system combines the strengths of both pneumatic and hydraulic hot runner technologies. While both traditional systems are highly effective technologies in their own right, for some customers an electric system represents the best of both worlds.

This technology uses an electrical servo motor to open and close valve stems with precision. It is a timely development because over the past several years electrical servo motor technology has become more affordable. Full electric injection molding machines are another driver for this technology. The electrical synchronized valve gate actuation system satisfies a growing demand to electrify the entire molding cell by providing several unique solutions for the molding of medical and other high-performance applications.

Electrical Drive Creates a Cleanroom Environment
Electrically actuated valve gates for hot runner systems are the cleanest of all actuation methods. Pneumatic air systems can potentially carry dust or debris, while hydraulic systems use oil that can leak. In comparison, electric power, through servo motor, bearings and cams, is converted into mechanical movement. This process does not move any dust, debris or liquid that can potentially contaminate a medical part or product. As an added bonus—because of the elimination of seals and O-rings—there is a reduced need for maintenance, resulting in lower operating costs and increased up-time.

Synchronized Stems Offer a Repeatable and Recordable Process
The valve stems are synchronized by a plate that couples them together. This synchronized stem movement eliminates the lag that is sometimes seen in pneumatic valve gates by ensuring that all stems are exactly in the same position during filling and closing. The servo motor and stem movement is controlled and assembled through an Altanium temperature and process controller (that is designed to provide the most accurate temperature control possible using distributed control and active reasoning technology). An integrated module provides a convenient setup screen that is easy to use. Each shot can be consistently documented via its electrical signal. This integrated setup allows molders who need to monitor or document key injection parameters to easily add stem positioning to existing parameters, such as injection time or cavity pressure. Plus, the integrated option reduces clutter around the injection molding machine.

Accessible Serviceability in the Machine Produces Increased Up-Time
Electrical actuated valve systems are as easy to set up as traditional systems. The absence of air or hydraulic lines reduces hose requirements around the machine. The stem actuation unit can be easily separated from the hot runner. This allows access to the valve stems and cam action components with the mold remaining in the press for both stem removal and decoupling. In addition, they can be set in a service position that permits the removal of the actuation frame from the hot runner. The systems also use a maintenance-free servo motor and have only one easily accessible lubrication point within the machine.

Valve Stem Decoupling Provides Greater Efficiency
In the case of plate actuated valve stem movement—where multiple stems are mounted into one plate —there is a safety feature for the coupling of the valve stem to the plate. Self decoupling is designed to have a predetermined break with a predetermined force that results in the voluntary decoupling of the stem from the plate. For example, if a heater on a nozzle is lost or a foreign object blocks the gate, the stem automatically decouples from the plate avoiding damage to the gate or stem.

Servo Motors Offer Increased Consistency with Less Margin for Error
The use of servo motors allows for the ability to precisely open and close every stem at exactly the same time, with absolutely no difference in valve stem opening and closing. This precision increases the level of consistency for both shot-to-shot and cavity-to-cavity filling. In addition to consistency, the servo motor’s torque can be adjusted. This allows the stem’s closing force to be fine-tuned between 150 to 300 pounds. In some applications, this ability for fine-tuning provides additional protection from gate damage.