Plastics Technology

AUG 2016

Plastics Technology - Dedicated to improving Plastics Processing.

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A new wave of valve- gating technologies has emerged. Making the right choice can help molders boost their bottom line by increasing the profitability of the job for the life of the tool. Know Your Options in Valve-Gated Hot Runners Valve-gated hot-runner systems have been used for almost 50 years as a way to efficiently mold large parts. At first they were considered an expensive and complicated alternative to thermal gates and were only used when absolutely necessary. Over time they have become more and more common, to the point where in many markets they are the norm, not the exception. Valve gates allow molders to elimi- nate gate vestige, decrease cycle times, and manipulate the filling of various gates during the injection cycle. As with any technology, advances have been made over time. In fact, recent years have resulted in some of the most significant technology gains. Valve-gate actuators began as simple pistons connected to a valve pin, allowing molders to open and close the hot-runner gates at a time of their choosing. The actuators used to drive the pins have become much more advanced, providing the molder and tool-shop personnel with a variety of abilities and benefits they did not have previously. Actuators fall into two categories with respect to how they mount in the tool: in-plate and bolt-on. In-plate actuators fit into pockets machined in the top clamp plate, while bolt-on actuators bolt directly to the hot-runner manifold. In-plate actuators are typi- cally installed into the top clamp plate by the tool maker after the remainder of the "A" half of the mold has been assembled. By Bill Rousseau, Synventive Molding Solutions WHAT YOU WILL LEARN 1. VALVE-GATE BENEFITS: They eliminate gate vestige, cut cycle times, and control filling of various gates. 2. OPTIONS: Hydraulic, pneumatic, or electric. 3. PASSIVE COOLING: These devices transfer heat out of the actuator and into the top clamp plate. 4. POSITION SENSORS: Good for diagnostics & more. Water-cooled isolation plate between the actuator and the hot manifold protects actuator from the heat of the manifold. @plastechmag 49 Plastics Technology V A LV E - G AT E D H O T R U N N E R S

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