How does Miraplast achieve consistent part quality in multi-cavity injection molding, and why is the non-return valve crucial?

Miraplast Kunststoffverarbeitung GmbH—a company established over 60 years ago with locations in Würmla (Austria) and Hungary—is one of the first companies worldwide to implement the latest product in the ENGEL inject AI portfolio in live production: iQ weight control plus.

• The first use of iQ weight control plus on an ENGEL victory 80 demonstrated exactly what production professionals strive for:

• significantly simplified sample testing

• improved and reproducible injection-molded part quality

• optimal balancing for multi-cavity molds

• efficient injection molding production despite a shortage of skilled workers

The results, expressed in numbers, surprised even experienced set-up technicians:

• Production-quality parts as early as the second parameter iteration – Simplified trial runs using only two injection molding process parameters, even without specialized personnel

• –10% reduction in energy consumption per cycle – achieved through pressure-optimized and material-friendly process control

• 50% reduction in the decompression stroke during the injection molding process—thanks to a non-return valve that closes reliably and reproducibly

Consistently high injection-molded part quality is crucial for the production of pipe clamp components using a 4-cavity mold. At the same time, process variations and the closing behavior of the non-return valve make it difficult to achieve reproducible injection molding production.

Typical challenges in day-to-day production:

• Surface defects and venting problems at corners and ribs

• Time-consuming sample inspection requiring significant skilled labor

• Gradual process fluctuations caused by temperature changes, batch changes, or masterbatch addition lead to process instability

• Unreliable closure of the non-return valve compromises the reproducibility of injection-molded part quality

The key question was: How can process fluctuations be minimized, the closing behavior of the non-return valve stabilized, and component quality ensured—all without increasing setup time?

Miraplast Kunststoffverarbeitung GmbH employs approximately 80 people at its main location in Würmla and operates 23 injection molding machines, including 17 ENGEL machines. With a deliberately diversified product portfolio, the company cushions the impact of market fluctuations, such as those in the automotive sector.

Using the software iQ weight control plus, the ENGEL victory 80 automatically adjusts the injection speed during injection molding in real time to match the current flow resistance. The system specifically leverages the physical characteristics of the process.

This results in an effect in the injection molding process that has received little attention to date but is nonetheless impressive: a significantly improved function of the non-return valve.

At the start of the injection phase—during the decompression stroke—there is virtually no flow resistance. iQ weight control plus uses this window of opportunity to achieve maximum screw acceleration (up to approx. 80 cm³/s). This makes optimal use of the inertia of the shut-off ring: the non-return valve closes faster and more reliably.

As a result, the decompression stroke was reduced by 50%, giving Miraplast significantly more flexibility with the injection molding unit.

After this rapid initial phase, the system reduces the screw speed and fills the cavities gently and with controlled pressure.

The results were fewer surface defects and cleaner molding of corners and ribs due to improved venting. This improvement in quality is already evident upon simple visual inspection.

1) Improved part quality in injection molding—visible without measuring instruments

• Reduced risk of surface defects

• Cleaner molding of corners and ribs due to improved venting

• Quality improvement already verifiable through visual inspection

2) Fast tooling approval—less reliance on skilled personnel

• Only 2 adjustment parameters for tuning the injection motion: injection pressure + switch-over point

• Production quality achieved after the 2nd iteration

• High tolerance for insufficient balancing in multi-cavity molds

• Pressure-controlled injection molding: A cavity failure does not immediately result in rejects in injection molding production

3) Sustainable process stability and energy efficiency

• –10% energy consumption per cycle thanks to a smoother, pressure-optimized operating mode

• Automatic compensation for gradual process fluctuations such as temperature, batch changes, or masterbatch thanks to integrated flow time control

• Long running times without manual readjustment

4) More reliable non-return valve function

• Faster and more reproducible closing of the non-return valve

• Decompression stroke reduced by 50%

• Greater flexibility and freedom of operation for the injection molding unit

• The test results at Miraplast impressively demonstrate the potential of iQ weight control plus in real-world production, right from the very first use.

Read more about iQ weight control plus in an interview with development engineer Matthias Hüttler: How can iQ weight control plus reduce scrap in injection molding?.