INNOVATION | CAPS AND CLOSURES
Right: Caps are becoming lighter, causing increasingly tough
challenges for injection moulding machine technology, says Engel
tion moulding machines. “This is why the continuous further development of E-cap now is being integrated into a next generation machine. Continuous part weight reduc- tions play a central role. For still water, caps with a weight of significantly less than 1g are produced today. As a result, the cooling and cycle times have continued to drop. Where the cycle times ten years ago were still 2.5s, today’s cap machines need to be able to produce at 2s intervals and faster.”
When developing the new generation of machines, Engel says that the main focus was therefore both on performance and stability. The new E-cap achieves faster mould opening and closing movements and is designed with a more stable machine bed for more frequent load cycles. The company has demonstrated an E-cap 2440/380 producing 29/25 caps in a 96-cavity mould from Plastisud. The shot weight is 1.3g per cavity with a cycle time of less than 2s. An HDPE from Borealis/Borouge is processed. The system is equipped with camera-supported 100% quality inspection by IMDvista and a dry air system by Eisbär. Further system partners are Piovan, PackSys Global and PSG. The reinforced frame and mould mounting
Below: With extremely short cycle times of less than 2s, Engel’s new E-cap machine ensures high precision and repeatability
platens on the new E-cap ensure good stability of the machine movements even with extremely short cycles and small shot volumes. The company says that the result is outstanding reproduction of surface detail and a maximum number of good parts. The fast dry cycle times of 1.3s with the E-cap 380, for example, and the parallel movements included in the standard right from the outset make an important contribution to achieving cycle times of less than 2s. Ejection occurs parallel to the mould opening.
What is new is that the ejectors can be amplified by a switchable hydraulic booster on demand. This ensures that the machine operates with the best
possible efficiency both during produc- tion and start-up after a production interruption. While the caps are not yet completely cooled and easy to demould during ejection in ongo- ing production, the ejectors have to apply more force in stop situations to remove caps that have already cooled down in the mould. Since production interrup- tions are rare, it is more efficient to use servo-hydraulic drive amplification than to
generally equip the machine with more powerful ejector drives. The new E-cap generation is offered with two different ejector drive technologies. The machine works with hydraulic ejectors as standard. Servo-electric drives are available as an option, which require around 10% less energy. In addition, the plasticising unit has been
redesigned, because the properties of the materi- als to be processed have also changed. Raw material manufacturers have adapted their products to lower cap weights. For CSD (carbon- ated soft drink) caps, the melt flow index (MFI) of current HDPE grades is 0.8-1.4g/10 min. Very short cycle times require particularly high plasticising rates. Engel has increased the torque of the plasticising drive accordingly and developed both a new plasticising screw and a new highly wear- resistant sliding ring non-return valve specifically for cap manufacture. Both products are part of the standard scope of supply of the new E-cap machines. With its new design, the barrier screw processes high viscosity HDPE in a particularly gentle way, even given high throughput levels, while ensuring a good melting rate and homoge- neity of the melt. This further contributes to the high process stability and repeatability of E-cap machines.
Engel adds that an encapsulated toggle lever
and a clean linear guide of the moving platen, result in E-cap machines reliably meeting the requirements of strictly regulated production standards of the food industry. The machine’s all-electric drive technology makes a major contribution to good energy efficiency. In addition, braking energy is recuperated, reliably prevent- ing the need for expensive peak power. Due to the high efficiency of the drives used, E-cap machines also only require a minimum of coolant. The E-cap 380, for example, operates at high speed with a specific energy consumption of 0.37 kWh per kg of pellets processed. The new E-cap is available in the sizes 220, 280, 380 and
32 INJECTION WORLD | April 2020
www.injectionworld.com
IMAGE: ENGEL
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