Stable injection moulding processes with iQ weight control

The production of plastic closures falls into the high-performance range. Characteristic of this are the very short cycle times and extremely high numbers of cavities.

Fluctuations in the environment and the raw material quickly result in rejects and thus unnecessarily increased costs. This is because the flow properties of the plastic melt change in such a case during injection. This means that a consistently high quality of the injection moulded parts cannot be guaranteed.

Intelligent assistance systems offer a great deal of potential in the high-performance sector, as ENGEL has demonstrated in tests with iQ weight control. They continuously analyse quality-relevant parameters during injection moulding that are essential for high quality and automatically readjust them.

The key to a stable process through iQ weight control is permanent analysis in every single cycle:

• During the injection phase, the pressure and screw position are checked in real time.
• The measured values are continuously compared with a reference cycle.
• On this basis, new process parameters are calculated and the current cycle is automatically readjusted.

The process control has a direct influence on the injection speed profile, the changeover point and the holding pressure during injection moulding. All these adjustments take place in parallel without extending the cycle time. Manual intervention is no longer necessary.

Any external influencing factors and fluctuations in the material are thus automatically compensated for. In this way, iQ weight control can guarantee consistently high product quality. Rejects are thus reduced to a minimum.

The performance of iQ weight control in high-performance applications was put to the test on an all-electric 380-tonne ENGEL e-cap injection moulding machine. Injection moulding tests were carried out for 29/25 plastic closures for still water from Plastisud:

• A 96-cavity tool was used.
• An HDPE type MB7541 from Borealis with an MFI of 12 was processed.
• The part weight was 1.25 g. The total shot weight thus corresponded to 120 g.
• The cycle time of this application is less than 2 seconds.
• The injection time is less than 0.3 seconds.

In order to better assess the performance of iQ weight control, deliberate changes were made to the process. For example, changing the raw material batch several times.

The result without iQ weight control was that the critical quality characteristics of the plastic closures were outside the tolerance range. The injected melt volume deviated from the reference value by up to 1.5 cm³.

With iQ weight control activated, however, all reference values are in the correct range. This means that no rejects were caused by the batch change. Good parts could be produced right from the first shot. In addition, the process stability was increased by 66 percent. With the same cycle time of less than 2 seconds.

Find out more about the e-cap injection moulding machine specially manufactured for the production of plastic closures : engelglobal.com/e-cap

Recyclates are often subject to greater batch fluctuations in material quality than virgin materials. This poses a major challenge for companies that want to work with recyclates.

However, the use of recyclates from different sources is becoming more and more important in the packaging industry. That's why we at ENGEL are always working to find an optimal solution for improved recycling management of plastics, also in terms of economic efficiency.

With the use of iQ weight control, profitability increases significantly when using recycled materials. This is because batch fluctuations are cushioned by the intelligent process assistance:

• Fluctuations in the raw material are detected.
• The injection profile is adjusted.
• The switchover point and holding pressure during injection moulding are adjusted to the current production conditions for each shot.