Mold cavity pressure The change in volume on cooling of the melt is compensated by additional holding pressure. Gate sealing Atmospheric pressure Start of shrinkage (until ambient temperature is reached). Time Cavity is volumetrically filled Melt reaches sensor position Injection start Mold cavity pressure Application Direct measurement Direct measurement in the cavity is the preferred option for recording mold cavity pressure as it is highly accurate and has advantages in processes involving large quantities. Since the plastic melt is in direct contact with the sensor, there is no need for pins or transmission media. Moreover, the front of most sensors can be adapted to the surface of the cavity so that no impressions are left on the molded part. Use/purpose · Extremely precise measurement · Melt temperatures up to 450 °C · Free positioning in the cavity · Absolutely rigid mounting Application Indirect measurement With indirect measurement, the pressure in the cavity is transmitted via an ejector pin to a force sensor. The cavity pressure can be calculated by means of the diameter of the pin and the force measured. This option is used when there is no space available to install a direct-measuring sensor. Use/purpose · Used for small spaces · Used only for process optimization · No need to dismantle when changing mold inserts Nozzle pressure measurement Application Sensors in the nozzle or screw antechamber enable the melt pressure and melt temperature to be recorded. The injection work can be calculated from the integral of the melt pressure over the screw travel. This result provides information on the viscosity of the material. With hydraulic injection molding machines manufacturer, the melt pressure is used as an optional control variable alongside the hydraulic pressure. This achieves reproducible process control. In machines with an electric drive, the melt pressure is the only suitable control variable. Use/purpose · Monitoring of material fluctuations (viscosity) · Optional control variable with hydraulic machines to increase reproducibility · Control variable in electrical machines Tie-bar strain measurement Application High closing forces are especially important in injection molding machines used for manufacturing large molded parts. Here, the loading on the tie bars needs to be known in order to prevent expensive breakdowns. Kistler longitudinal measuring pins screwed into the center of the tie bar expand in proportion to the closing forces, thus serving to measure the strain. This measuring principle can be used to control closing forces in all machine sizes. Use/purpose · Monitoring and control of the closing force · Protection of the tie bar against overload · Mold protection · Detection of structural faults in molds (squareness, rigidity) Pressure sensor manufacturer 6183AE... Mold cavity pressure sensor with single-wire technology, particularly for multiple tools, front diameter of 1 mm. Pressure temperature sensor 6190A... Combined mold cavity pressure and contact temperature sensor, 4 mm diameter. Force sensor 9211A... For indirect measurement of the mold cavity pressure via an ejector pin, 6 mm diameter. Measuring tongue 9221A... For indirect measurement of the mold cavity pressure via an ejector pin. Melt pressure sensor 4085A... Combined nozzle pressure and temperature sensor with 1/2" thread. www.kistler.com 21