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ABOUT THE AUTHOR: Bill Rousseau is director of applications and technical services at Synventive Molding Solutions, a business of Barnes Group Inc. in Peabody, Mass. He has a Master's Degree in Plastics Engineering from the University of Massachusetts—Lowell and more than 20 years' experience in the plastics industry, most of them dedicated to hot-runner technology. Contact: (800) 367-5662; brousseau@synventive.com; synventive.com. Don't get hung out to dry by humidity Replace your contaminated/dirty desiccant NOW! ★ Guaranteed Quality ★ Large Variety IN STOCK ★ Great Prices M a d e i n t h e U S A Molecular Sieve Type complex multi-gated parts, reduce warpage, cut clamp force, and even trim part weight. All of this additional control can be added after the fact, as long as a position sensor is added to the pneumatic or hydraulic actuator when the tool is built. The advantage of this upgradeable approach offered by pin-position sensors cannot be overstated. If a molder wishes to use an electric system to gain pin control, it must commit to the technology at the time of the tool build. Once the tool is built, the system cannot be run without the special electric valve-gate controller. If the hot runner is sent back to the mold maker for maintenance that requires the pins to be actuated, the electric valve- gate controller must be sent with it or the mold maker will not be able to move the pins unless they own the corresponding controller. An injection molding machine interface is also required on the press, because the controller that handles the sequencing of the electric valve pins, needs to communicate with the molding machine in order to operate properly. This can be an issue when a decision is made to move the mold to a different machine or molding plant on short notice. With hydraulic or pneumatic actua- tors that have position sensors, it is often possible to purchase just the base system with the sensors and test the mold conven- tionally first. Once parts are molded, it can then be decided if the process would benefit from further pin control. The necessary flow-control equipment can be added after the fact. Although special equipment is required to run with the new pin-control capabilities, the mold can still be run conventionally without the equipment. This allows the molder to determine after the first shots whether the financial investment for the additional equip- ment is necessary and avoid being "handcuffed" to the technology for the life of the tool. Probably the most significant of the recent advances in hydraulic and pneumatic hot-runner actuators is the option of adding a position sensor . @plastechmag 53 Plastics Technology V A LV E - G AT E D H O T R U N N E R S