ENGEL: thin-wall injection compression moulding for stack mould technology

Over the five days of the trade event, an e-speed 420/90 injection moulding machine with integrated in-mould labelling (IML) will be used to produce ready-to-use margarine tubs from polypropylene in a fully automated injection compression process. The containers, which have a wall thickness of 0.4 mm (including the label), will be removed from the 4+4-cavity stack mould via high-speed, side-entry automation and stacked on a discharge conveyor following camera-based quality control.

The continuing trend for reducing wall thickness is leading to ever more extreme flow path/wall thickness ratios that are often in the range of 1:400. From a ratio of 1:300 and above, consistently high component quality in many applications can only be achieved by means of injection compression moulding. Other advantages of injection compression moulding technology include the lower clamping forces and injection pressures required in comparison with conventional compact injection moulding, plus the fact that even high-viscosity materials can be processed in a repeatable manner. Overall, this means reduced energy consumption and competitive unit costs.

Despite this, injection compression moulding tends to be seen as ruling out the use of a stack mould; this is because for many injection moulding machines, the speed of the platen movements is insufficient for a stack mould. For the ENGEL e-speed injection moulding machine things are different. The electrically driven clamping unit and the toggle lever design facilitate very fast, short compression strokes – 4 mm in the case of the margarine tubs. The parallel movements can be controlled very exactly – the prerequisite for coordinating the compression stroke and injection profile to the necessary degree of precision.

With the new e-speed size 420, which offers 4,200 kN of clamping force, ENGEL continues to diversify its product range. The ENGEL e-speed injection moulding machines combine very short cycle times with maximum precision and very high injection speeds of up to 1,200 mm per second; they operate with extreme energy efficiency. An innovative energy recovery system absorbs braking energy from the platen movements and returns the stored energy to the motor.

The toggle lever is encapsulated to ensure particularly low oil consumption and maximum cleanliness. In this way, the machines of the e-speed series meet the strict requirements of the food industry as standard.

The labels of MCC Verstraete, which will be used for the production of the margarine tubs at Fakuma, are interactive. These labels are based on technology by Digimarc and, much like a QR code, Digimarc codes can be scanned with any smartphone camera. The main advantage of these is that they extend invisibly over the entire label surface. From production through retail and recycling, the interactive labels offer added value. Consumers can discover the details of the ingredients and manufacture for both the product and the packaging while shopping. And when the packaging has reached the end of its useful life, the label provides information on the recycling process.

The margarine tubs produced at the Fakuma event will be made of polypropylene, as will the labels. At the end of its service life, the monomaterial packaging can be shredded as is the case for production waste from the manufacturing process; the raw material thereby obtained is used in the processing of new products. At its stand, ENGEL will demonstrate these possibilities by processing waste label offcuts in the form of regrind. An ENGEL victory 460/80 will be used to produce Pöppelmann tapered closures from an 8-cavity mould. Like ENGEL, Germany-based Pöppelmann (at Fakuma in hall B5, stand 5107) is pioneering the establishment of a circular economy for the plastics industry. Protective elements in Pöppelmann’s KAPSTO product range are used in the logistical and construction fields, among others. The plastic in these products is 100% recycled material.