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Sensor-based efficiency gains for injection molders

Reliable and accurate sensors are the foundation for effective process monitoring in injection molding. Measuring where the process actually takes place is the key to maximum process transparency. That’s why it’s our philosophy to acquire the critical process values of pressure and temperature directly in the injection mold. Our monitoring systems immediately show any deviations from the ideal state in the relevant process curves, so users can reliably predict the quality of the molded part – shot by shot.

Benefits:  

  • Efficient and targeted setup phase for new molds
  • Minimum time and effort for tool startup
  • Reliable monitoring of the injection molding process
  • Highly informative individual documentation for each manufactured part

Unique sensors that can be integrated directly into the injection mold

We offer a wide range of sensors to match different applications and mold designs, and for special requirements such as high temperatures.

What you need to know about using our sensors in the injection mold

Learn about the points to watch when selecting and positioning our sensors.

Sensor selection

Kistler offers a wide range of sensors for monitoring injection molding processes.

Kistler offers a wide range of different sensors – but selection of the right sensor is simple, because it is essentially based on the installation conditions in the mold. Piezoelectric measurement technology has a key advantage: it provides a sufficiently good signal over the entire measurement range (usually 0–2,000 bar). The measuring chain will only need to be adapted in case of very low pressures (in foaming processes, for example). To make installation as simple as possible, select the sensor with the largest possible geometric dimensions.  The choice between a direct or indirect cavity pressure sensor depends on the basic design of the mold. For existing molds, a sensor behind an ejector is often the simpler option – but on the other hand, direct sensors offer more flexible positioning.

Sensor positioning

Sensor positioning is essential to properly monitor quality criteria.

Sensor positioning is essentially dependent on the quality criteria to be monitored, or on the overall quality monitoring strategy.

For characteristics that are significantly influenced by the filling of the cavity, a post-gate sensor position is recommended because this is the only way to visualize the mold filling. If a local quality criterion such as a weld line or complete filling is targeted, the sensor should be installed close to this critical position. When monitoring short shots, end-of-fill positioning offers significantly better resolution for failure detection.

Transfer based on cavity pressure

Sensors and systems based on cavity pressure determine whether or not a part is scrap at the earliest possible moment.

If the transfer to holding pressure is based on cavity pressure, a sensor position close to the sprue is recommended: at 1/3 of the flow path, for example. With this position, a clear switching point can usually be identified so a corresponding pressure threshold can be set. Cavity pressure-dependent switching offers higher process reproducibility as compared to other methods such as screw position-dependent transfer: this is because the actual flow behavior of the melt in the cavity is considered, rather than just a machine component. Influences from the nonreturn valve are compensated effectively. The same applies to overmolding of inserts with the higher tolerances that are well-known in this context.