Optimizing Reactive Injection Molding with In-line Sensors

NETZSCH and KISTLER, two family owned companies, offer the most advanced process package for reactive injection molding targeting zero waste production while at the same time a maximum in efficiency with an increased throughput is enabled.

Injection Molding with thermoplastic materials is done since many decades. But thermosets open a new chapter of high-performance parts regarding mechanical strength with a lot of challenges in production! In-process sensors are helping the industry to guarantee a reliable production. NETZSCH and KISTLER partnered up to advance production to a level that is allows a robust manufacturing while at the same time a maximum in cycle time reduction will be enabled.
Good Injection Molders are in charge of combining fast manufacturing cycles with a high level of process stability. But there are a lot influences that can throw a production over the pile:
  • changes in the material behavior due to different transportation environments until it arrives at customer’s site,
  • the storage on 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 the hurdles and to produce good parts, there is a huge amount of safety time during manufacturing. As a result, the full potential of manufacturing processes can often not be fully exploited. Today’s commercial pressure on fast cure cycles for maximum throughput and zero waste production combined with a high complexity of the processes themselves makes it more difficult to compete on the market. The partnership of NETZSCH and KISTLER offers a sensor system solution that monitors the in-mold pressure and the cure behavior during the entire injection molding process. In this system, KISTLER pressure sensors record the in-mold pressure behavior to decide whether the mold filling was successful and can observe if a leakage occurs or if the materials has bubbles inside. NETZSCH dielectric sensors monitor the cure behavior and can take over the real-time quality control as well as cycle time shortening based on the state of material. All sensor signals are merged in the KISTLER ComoNeo system: the pressure, the curing and the temperature of the dielectric and the pressure sensors. The ComoNeo system is a monitoring system that can be combined with the ComoDataCenter, a browser-based storage system with the same functionalities of quality data analysis that are included in the ComoNeo.

In-mold pressure and cure behavior at a glance for a complete process insight

Reactive injection molding with epoxy molding compounds (EMC’s) is a widespread process for electronics packaging for the automotive or aviation industry. One or more electric circuit boards are put into a closed mold and are encapsulated by the epoxy molding compound softened at elevated temperature, usually 140 – 180 °C. For this mass-produced article, every cent saved increases the competitiveness due to reduced rejects and reduced cycle times. The NETZSCH and KISTLER package is the package that distinguishes a highly efficient manufacturer from a standard producer.

Reference Curve under normal process conditions

Fig. 1: Reference Cycle of an injection molding process for electronics packaging observed by NETZSCH and KISTLER sensors.
Fig. 1 shows a reference cycle of an electronic packaging process. On the upper half of the graph the cure signal of the NETZSCH sensors and on the bottom the pressure signal of the KISTLER sensors can be seen. The red boxes define areas which – under normal conditions – must not be crossed by the cure signal or have to be crossed when a green entry and exit is given. The green entry shown with the pressure signal indicates the normal arrival of material inside the mold.

Process failure – no material available

Fig. 2: No material arrival inside the mold.
Fig. 2 represents abnormal conditions if no material arrived inside the mold because the tank is empty or the snail is not working. Based on the sensor response the machine control system can be informed about the missing material and the current cycle will be stopped.

Abnormal process – temperature is too low

Fig. 3: Temperature loss inside the mold and deviating material behavior compared to the reference cycle.
A temperature loss inside the mold will lead to a slower curing of the resin, so the cycle time has to be extended. Fig. 3 shows the sensor responses of the NETZSCH and KISTLER sensors of an abnormal cycle due to a temperature loss compared to the reference cycle. The pressure signal is not influenced by the temperature loss, so the reference and abnormal shot show the same behavior. The NETZSCH sensor detects the slower curing due to the temperature loss inside the mold and can therefore be used to adapt the process to avoid waste production. This makes it obvious why just a combination of both – pressure and dielectric sensors – can provide a complete insight into the manufacturing process and thus be able to increase process efficiency. The combined package of NETZSCH and KISTLER provide the most powerful sensor package that is able to sort good and bad parts during manufacturing and beyond that to make your process more efficient with avoiding waste production and lowering cycle times.   You are interested to get more information? Please contact us!
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I’m very interested to know more about the Netzsch dielectric sensors for the curing process monitoring of epoxy resins.