Self adapting, decentralised assistance systems improve process capability and quality and are an important component in the smart factory, which is the focus of ENGEL's inject 4.0 programme. In the form of iQ clamp control, ENGEL presented a new software tool at Fakuma 2015 that automatically determines and adapts the optimum clamping force for each individual application based on mould breathing.
While the clamping force is being built up, the mould height and the volume of the cavity are slightly reduced (picture middle). Part of this compression is compensated for by the opening pressure exerted by the melt during injection (picture below). The resulting change in the mould height is referred to as mould breathing. iQ clamp control determines the extent of the mould breathing and automatically adopts the optimal clamping force.
At Fakuma 2015, a new member was joining the ENGEL iQ family of products. The prefix "iQ" stands for "intelligent quality"; this means that expert knowledge is integrated into the injection moulding machine's control unit. The goal is to sustainably improve the quality of the production process and thus of the finished products. While the iQ weight control software introduced at Fakuma 2012 optimises the injection process, the focus in developing iQ clamp control was on the injection moulding machine's clamping unit. By continuously adapting the clamping force, the software keeps the mould breathing constant even under fluctuating process conditions.
Eliminate subjective influences
During the injection process, the inflowing melt exerts pressure that pushes the two halves of the mould apart by a couple of thousandths or hundredths of a millimetre. This process is known as mould breathing. If the mould breathing is too great or to small, this can cause rejects due to flashes or burn marks (diesel effect). If the clamping force is too high, the mould is also subject to excessive stress and clamping force build-up unnecessarily consumes more energy.
In order to optimise the clamping force manually, the mould breathing can be determined with the help of a gauge. This is however a subjective and imprecise approach. The measurement results are heavily dependent on the position of the gauge. In addition, it takes much experience to interpret them. Many injection moulders therefore work with the maximum clamping force available instead of adapting it to the respective process.
In order to keep efficiency potential that is relevant for competitiveness from being wasted, ENGEL has developed the iQ clamp control software that automatically determines and adopts the optimal clamping force on an objective basis. Thus the CC300 control unit for ENGEL injection moulding machines is the first machine control unit worldwide that is capable of autonomously determining a process-relevant target value.
New process signal without additional hardware
Because mould breathing is caused by the pressure acting in the cavity, its curve is very similar to the curve of average cavity pressure calculated for the projected surface of the moulded part. The advantage over measuring the cavity pressure in the mould is the fact that there is no need to add extra sensors or expensive hardware. Development engineers at ENGEL have discovered a method for using the existing sensor system on the injection moulding machine to compute mould breathing during the ongoing process. To this end, the clamping system including the mould is conceived of as a spring, and the stiffness of the spring is determined during clamping force build-up. During injection, the tension in the spring increases slightly due to mould breathing so that the clamping force increases minimally compared with the set value. In order to determine this increase very precisely, dry cycles are performed at the start of production and the changes in clamping force are stored as reference curves.
In this way, iQ clamp control significantly reduces the risk of quality deficiencies, ensures optimal mould ventilation, protects the mould against overfilling and boosts energy efficiency.
In an initial step, the new software is being offered for ENGEL injection moulding machines with electrical clamping units up to clamping forces of 2200 kN.
