DESMA PRESSURESENSE | valve gate refinement in molds and CRBs
DESMA offers several technologies to reduce waste and improve part quality during the rubber molding process.
One such technology is our FlowControl valve gate system that can be incorporated into our solid-cold runner block (CRB) design. With FlowControl, DESMA replaces basic open-nozzle technology with selectable valve-gates inside the CRB. FlowControl accurately doses material by closing each valve gate independently of each other, relying on the position of the injection piston and or the injection pressure.
A technology refinement to FlowControl is called PressureSense. PressureSense will automatically close each valve gate based on actual cavity pressure. Cavity pressure is measured by piezoelectric sensors located within the mold or CRB. This valve gate closure represents a significant improvement in process control, as it monitors actual cavity pressure at or near the molded article itself, as opposed to monitoring methods such as injection pressure or injection piston location. PressureSense is highly effective in reducing manufacturing defects and helps mitigate the impact of raw material batch-to-batch variation. PressureSense can also compensate for mold wear to ensure proper filling of the mold cavity.
PressureSense enables the machine controller to interface with an amplifier connected to each sensor. When the voltage changes or pulsation is measured, this signal is “interpreted” by the DESMA DRC 2030 controller, which in turn closes the FlowControl valve.
Sample Molded Parts produced in different lengths representing different volumemetric shot requirements in a mold is shown in the image on the left. In this application of PressureSense technology, four different size articles are produced in a four cavity mold. The individual length (or volumetric size) of each different molded part requires a different valve gate closing sequence. FlowControl PressureSense does not rely on position or injection pressure of the injection unit – rather relying on cavity pressure in the mold cavity monitored by the sensor (as show in the image above).
Above image shows four blue molded articles of various different geometric lengths molded simultaneously using FlowControl PressureSense for optimal cavity filling.
PressureSense piezoelectric sensors generate an electrical charge when subjected to mechanical stress, such as cavity pressure or pulsations that occur during injection. The piezoelectric effect is not new, but its applications in the field of rubber injection molding are relatively uncommon. To develop PressureSense, DESMA R&D created unique software and electrical components that detect voltage changes at the sensors that are amplified and “interpreted” for optimal valve-gate closing.
Mold cavity half showing PressureSense piezoelectric sensor relative to the cavity geometry. Also shown is the gate location of the FlowControl (inside circle).
Top half of mold showing all four cavities with different volumetric lengths. The electrical manifold on the side of the tool connects to the amplifier for FlowControl PressureSense functionality.
Contact a DESMA Sales Engineer for more information on FlowControl PressureSense.
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