HOT RUNNERS: Gate Crashers

Fact: Valve gating has become the preferred method of gating for precision molders, offering a  more stable injection process without stringing and drooling of the melt. And these are particularly interesting times for valves gates: two themes – electric drive and precise control – are dominating a lot of the new entries; hydraulic and pneumatic products are getting ever more sophisticated; and a very familiar distributor is launching its own product offering.  

THE ELECTRIC COMPANIES

From Husky Injection Molding Systems, the UltraSync-E electric technology is designed to offer shot-to-shot and part-to-part consistency through precise stem closing to help eliminate variability from the injection molding process – and by allowing for a minimum nozzle spacing of 18 mm, it’s particularly well-suited for high precision molding of small parts. “The unique plate actuation mechanism requires the lowest amount of maintenance of any product in its category, and wear is eliminated by the use of bearings for moving components,” said Martin Baumann, Husky’s business manager, hot runners. “Accessibility to perform routine maintenance tasks is simple and easy – stems on the UltraSync-E can be exchanged in the machine in less than five minutes.” In addition to the UltraSync-E, Baumann added, Husky offers its UltraSync hot runners in hydraulic, the UltraSync-H; and pneumatic, the UltraSync-P. “Electric, hydraulic and pneumatic options are available with Ultra 300, Ultra 500, and Ultra 750 valve gate hot runner nozzles,” Baumann said.

Synventive Molding Solutions recently introduced its new eGate high performance electric valve gate hot runner system, designed for injection molding applications that require multi-shot/multi-material applications, sequential/cascading molding, clean room environments, and premium cosmetic surfaces. According to Synventive, the eGate provides numerous advantages over traditional valve gates, including greater control, as processors can adjust the flow rate out of each nozzle gate at any time during the fill process; valve pin position that improves cosmetic gate quality; improved shot-to-shot and part-to-part consistency; and process monitoring that gathers and monitors data for real-time pin position. The eGate is said to be particularly effective when combined with the company’s eGate Shop software, which monitors the open and closed positions of the valve pins within 0.01 mm, as well as velocities and accelerations, resulting in improved gate quality and quicker closing of the valve pin.

The E-Drive electric valve gating system from Mold-Masters Ltd. is now available in larger sizes for automotive and large appliance parts. An example is the new EVH 110 (110 mm). The E-Drive is designed for multi-cavitation and precision molding applications in clean room and oil-free environments; its valve pin plate concept utilizes the full capabilities of servo technology, with the servo motor’s power transmitted to the valve pin plate by a timing belt and two ball screws, resulting in accurate linear motion to open and close the gates. And the E-Drive continues to help simplify the barrier process for food and medical packaging applications. At the recent NPE2012 show in Florida, for example, Mold-Masters included its E-Drive in a work cell for co-injection of three-layer HDPE caps with a three per cent to six per cent barrier layer of EVOH in the centre. This IRIS co-injection technology utilized Mold-Masters’ E-Multi secondary injection unit and an instrument from IMD Ltd. of Switzerland to test for the presence of the barrier layer.

Medical and electronics industry injection molders can attain a higher degree of process reliability for high-precision valve gate applications via an electric-drive system that’s now available with an optional position encoder from Ewikon Molding Technologies Inc. “The encoders provide real-time monitoring of valve pin position with an accuracy of 0.01 mm,” said company president David Boxall. Also new for the system is a second-generation touch-screen electric drive controller, which monitors the valve-pin position and corrects for any deviation. For instance, the controller will trigger an error message and alarm if the drive fails to reach its position, allowing it to detect gate blockages caused by resin contaminants. “The controller shows the current valve pin positions graphically and digitally and allows operators to select for synchronous or sequential control on all drives,” Boxall said. “The system can handle up to 32 drives, and slave units may be grouped together to control larger layouts. In addition to the normal functions, multiple valve-pin positions within one injection cycle are also possible in the standard unit. Various trigger signals can be used to open and close valves, and the signals may be digital from pressure or temperature systems or analog signals such as linear position devices for screw position. Data and settings can be saved on a compact flash card.”

NEW TWISTS AND NEW PLAYERS

Hydraulic and pneumatic valve gates are pretty standard by now – which isn’t always a bad thing. Hasco’s new Z2371 valve gates, available in hydraulic or pneumatic versions, are meant to offer a high degree of standardization for high-volume applications ranging from medical to auto parts.  “For hydraulic actuation there are two different types of housings in three sizes and two strokes each available,” said Klaus Kapp, hot runner sales manager with Hasco Hasenclever GmbH. “Pin diameters vary according to the sizes, and maximum pin strokes are 8 mm and 12 mm. For maintenance or repair work, the Z2371 it can be disconnected without disassembly of the complete unit; the hydraulic circuit won’t be touched, and there’s no contamination by hydraulic oil.” In the pneumatic actuation, the Z107910 is designed to be assembled into the back plate of the mold. “This version offers four sizes with different pin diameters and variable pin strokes,” Kapp said. “In addition, you have the possibility to lock the piston with the help of a snap ring. In case of trouble the corresponding pneumatic actuation unit can be locked – it’s an indispensable requirement from the industry in order not to stop the whole production due to a defect related to a single cavity.”

The new Zenith valve gate system from DME Company is the company’s first standard valve gate system of its own design, and is available in hydraulic or pneumatic versions and with nozzles two inches to 20 inches in length. Why bring out their first product now? “Materials in the industry are changing all the time and the valve gates have to change to handle them, and we didn’t want to be dependent on the vendor to make those changes for us,” said Craig Kovacic, the company’s hot runner business manager. Zenith valve gates maintain a perfectly flat thermal profile, Kovacic continued, with better heat profiles in the nozzle and tip – areas where uniform heat prevents drooling or stringing. “They’re designed for medical part molders – the pneumatic valve gates in particular – where a clean-room environment is necessary,” Kovacic said. “They use standard DME Flex manifold heaters and work with DME’s new hydraulic valve gate sequencer, which stores up to 32 recipes and 200 events.”