Mould Technology Turning heads with all-electric stack-turning technology

Editor: Eric Culp

Since the 1996 launch of its stack turning technology, Foboha says it has installed 400 of these production systems. Now the toolmaker has added an all-electric version.

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Cycle times in one application are at least 30% shorter than in injection processes using standard moulds thanks to stack-turning technology.
Cycle times in one application are at least 30% shorter than in injection processes using standard moulds thanks to stack-turning technology.
(Source: Foboha)

As all-electric injection moulding machines increasingly become the market standard, Foboha said its engineers have been searching for solutions on how to make stack-turning and cube moulds without hydraulic drives. One special challenge was figuring out how to integrate the necessary servo drives into the mould. The company said it has found a solution has been consistently applying it. All drives (axes) of the all-electric stack-turning mould – from the ejector to the reversing unit right though to the handling unit – are fitted with electric motors. The company said it planned to show a working model of the first such cube mould at Fakuma 2012 in Friedrichshafen, Germany, on 16 - 20 October.

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All-electric moulds are especially suitable in the food and the pharmaceutical industry, and also in medical engineering, the company explained, because they are much cleaner owing to the lack of hydraulic oil. Also, production without hydraulic drives is economically much more efficient, Foboha added.

A 4 x 8 + 8-fold mould for the production of a cap-sealing system for beverage bottles or bottles for food additives is to be on display at Fakuma, the company said, noting that the way this cap is used is also a novelty. The closure features a chamber for liquid additives in powder form. Photo-sensitive liquids can be stored and protected in this dark chamber until the date of consumption. Once the cap is opened for the first time, the separately stored liquid enters the bottle. Separating the flavouring substances before use not only improves the aroma, but also prolongs minimum shelf life, the company said.

The cap consists of two individual parts, manufactured using a cube mould, and a lid for subsequently resealing the powder chamber. Eight upper and eight lower parts each are injected in both the mould-parting lines of the cube mould. The slide bars necessary for demoulding the outer thread and the non-tamper seal are arranged on the nozzle side.

Once the injection process in both injection units is completed, the central block is turned by 90°. As soon as the next injection phase begins, the lower parts are connected to the upper parts on both exposed sides. This is done by a removal unit developed in-house, with the two handling units removing the eight upper parts, running these sideways to the lower part and screw-connecting them. The assembled parts are demoulded by means of a servo-driven novel ejector system. Overall, the mould system can produce 16 mounted sealing caps in each cycle.

Quicker cycle times with less space required

The cavity-assigned assembly of the individual parts guarantees an optimum degree of assembly precision and substantially enhances the quality of the assembly part, the toolmaker said. The cap-sealing system can also be made with greater economic efficiency. Owing to the cube engineering, the cycle time is at least 30% shorter than in injection processes using conventional moulds. The unit also requires a much smaller installation space as only one injection moulding machine and no separate automatic assembly unit is needed, the company reported.

Both the upper and the lower parts are made of polypropylene (PP). The cycle time including assembly of the 2 x 8 parts is said to be only 7.5 sec.