Flexflow Valve System Integrated in Moldflow
Filling Analysis Includes Valve-Pin Position
The Italian hot-runner specialist HRSflow, of San Polo di Piave, in cooperation with Autodesk, has developed a solution for simulating the staged opening and closing of its Flexflow shut-off nozzles with Autodesk Moldflow, and thereby predicting the pressure reduction and associated drop in clamping force. In addition, users have the possibility, with the Moldflow filling analysis, to determine the opening strokes (pin positions), the opening and closing times, and the opening and closing velocities of the shut-off nozzles. The data can be subsequently transmitted to the control unit as a first basic setting, making the initial sample test considerably easier.
The servomotor-operated Flexflow systems are especially suitable for manufacturing large-area parts with Class A surfaces, which are often produced by cascade injection molding. The electrically operated actuating cylinders of the shutoff nozzles permit stepwise, precisely controlled and individual opening and closing of the needle pins with preselected speeds. This permits a precise control of the melt flow and volume flow into the cavity. The result is all-round optimization of the filling process, avoiding the pressure drop, and resulting pressure-drop marks, which are a dreaded drawback of cascade injection molding.
HRSflow and Autodesk have investigated the staged mold-filling on a series-standard test mold for an actual spoiler. The mold is equipped with a 7-cavity hot-runner system and additional pressure transducers. The studies demonstrated that the holding pressure profile with the use of the Flexlow system is considerably more homogeneous and lower than with conventional cascade injection molding technology. That in turn has a positive effect on the part quality, since the moldings show considerably lower stress, and therefore reduced warpage tendency. In addition, the clamping force demand is reduced by up to 20 %.
Translated from Kunststoffe 4/2015, p. 13.
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