Using In-Line Sensors to Optimize Reactive Injection Molding

Two family owned companies, NETZSCH and KISTLER, offer the most advanced process package for reactive injection molding. This targets zero waste production while ensuring maximum efficiency with an increased throughput.

For many decades, injection molding with thermoplastic materials has been underway. However, thermosets provide new avenues of high-performance with reference to mechanical strength. These come with their own set of production challenges.

Reliable production has been facilitated with the help of in-process sensors, which help the industry to guarantee a reliable production. With a view to advance production to a level that allows robust manufacturing, NETZSCH and KISTLER partnered together. This partnership also ensures a reduction in cycle time.

Good injection molders are responsible for combining fast manufacturing cycles with a high level of process stability. However, there are a number of influences that can create barriers to production:

  • Changes in the material behavior owing to different transportation environments until it arrives at customer’s site
  • The storage in the customer’s site
  • Machine failures like pressure loss
  • Temperature deviations inside the mold between the first and the last component of one batch or due to defects in the heating of the mold

To overcome these hurdles and to produce viable parts, the manufacturing process involves a substantial safety time. As a result, the full potential of manufacturing processes are often not fully exploited. It has become harder to compete in the market today, due to present commercial pressures on fast cure cycles for maximum throughput and zero waste production, combined with a high complexity of the processes themselves.

The NETZSCH- KISTLER partnership offers a sensor system solution that can monitor the in-mold pressure and the cure behavior during the entire injection molding process. With the help of this system, KISTLER pressure sensors record the in-mold pressure behavior to determine the success rate of the mold filling. Moreover, the sensors can observe if a leakage occurs or if the materials has bubbles inside.

Further, NETZSCH dielectric sensors monitor the cure behavior and can complete the real-time quality control as well as cycle time shortening, based on the state of material. The KISTLER ComoNeo system merges all sensor signals: pressure, curing and the temperature of the dielectric and the pressure sensors. The ComoNeo monitoring system can be combined with the ComoDataCenter, a browser-based storage system with equivalent functionalities of ComoNeo in terms of quality data analysis.

In-Mold Pressure and Cure Behavior at a Glance for a Complete Process Insight

A widespread process for electronics packaging in the automotive or aviation industry is reactive injection molding with epoxy molding compounds (EMC’s). In this process, one or more electric circuit boards are placed inside a closed mold and are encapsulated by the epoxy molding compound softened at elevated temperature, usually 140 – 180 °C.

A reduced number of rejects and shorter cycle times in the case of this mass-produced article make every cent saved increase the competitiveness of the product. The NETZSCH-KISTLER product is the package that distinguishes a highly efficient manufacturer from a standard producer.

Reference Curve under normal process conditions

Reference Cycle of an injection molding process for electronics packaging observed by NETZSCH and KISTLER sensors.

Figure 1: Reference Cycle of an injection molding process for electronics packaging observed by NETZSCH and KISTLER sensors.

As seen in Fig. 1, a reference cycle of an electronic packaging process is displayed. On the upper half of the graph, the cure signal of the NETZSCH sensors can be observed, while on the bottom, the pressure signal of the KISTLER sensors can be seen.

The red boxes indicate areas which – under normal conditions – must not be crossed by the cure signal or need to be crossed when a green entry and exit is given. The green entry shown with the pressure signal indicates the arrival of material inside the mold, under normal circumstances.

Process failure – no material available

No material arrival inside the mold.

Figure 2: No material arrival inside the mold.

Fig. 2 displays the abnormal conditions if no material arrived inside the mold. This can be due to the tank being empty or the snail not functioning properly. On the basis of the sensor response, the machine control system can be notified about the missing material, thereby stopping the current cycle.

Abnormal process – temperature is too low

Temperature loss inside the mold and deviating material behavior compared to the reference cycle.

Figure 3: Temperature loss inside the mold and deviating material behavior compared to the reference cycle.

Any temperature loss within the mold will inevitably lead to a slower curing of the resin, thus implying that the cycle time should be extended. Fig. 3 represents the sensor responses of the NETZSCH and KISTLER sensors of an abnormal cycle due to a temperature loss, in comparison to the reference cycle.

Since the pressure signal is not influenced by the temperature loss, the reference and abnormal shot display the same behavior. The NETZSCH sensor can detect the slower curing due to the temperature loss inside the mold. Thus, it can be used to adapt the process to avoid waste production.

Thus, as is evident, a combination of both – pressure and dielectric sensors – has the ability to  provide a complete insight into the manufacturing process, thus increasing process efficiency.

The combined package of NETZSCH and KISTLER provides the most powerful sensor package – with an ability to sort good and bad parts during manufacturing and beyond. This ensures an efficient process that avoids waste production and lowers cycle times.

This information has been sourced, reviewed and adapted from materials provided by NETZSCH-Gerätebau GmbH.

For more information on this source, please visit NETZSCH-Gerätebau GmbH.


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