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News

Coolly calculated

Bayer MaterialScience AG : 19 October, 2004  (Company News)
Permanent quality improvement paired with concurrent cost reduction: these demands are frequently called for in the manufacture of refrigerator doors.
This is why Hennecke GmbH, one of the leading manufacturers of polyurethane processing machinery, is constantly engaged in the further development of their production lines to boost their customers‘ competitive position. The RotaMat lines‘ current degree of innovation serves as an example for this.

The mould carriers of this plant type for the production of refrigerator doors are fixed on a steel weldment and rotate about one common horizontal axis. Depending on the customer’s requirements, RotaMats are equipped with four to eight mould carriers. The usual cycle time is approximately 50 seconds.

RotaMats offer the benefit of decentralized units while in practice several production lines are often combined depending on the required production output. The basic model comes with one unit as a control and process station. Loading and unloading takes place manually, while the foam injection is implemented by a mixhead manipulator.

Electromotive drive
While conventional RotaMat lines are equipped with a hydraulic rotation system, Hennecke has now developed a new electromotive drive system based on ring and pinion gear. Hence, the mould’s closing time is reduced and the traversing time from one cycle position to the next more than halved. This prevents the mould from getting in the way of the already rising foam when closing, even in case of short cream times, and ensures a homogeneous foam structure without voids that is required for insulation purposes.

The electromotive drive has even more advantages such as
- the exact positioning of the mould carriers with an optimized acceleration and brake reaction during the starting and stopping stage of the rotational movement
- minimum maintenance requirements of drive components as well as
- a reduced number of machine elements resulting in a cost reduction.

Selectable parallel stroke
In practice, a distinction is made between open pouring and closed pouring. Foam injection into open moulds is particularly widespread in Europe and Asia as it offers good foam initial distribution results.

Closed pouring is most frequently used in North America owing to the application of the R-245 fa blowing agent with the well-known „froth effect“. In this region, doors that are extra large or thick, for instance with integrated icemaker, are also frequently manufactured.

Hennecke offers a parallel stroke solution for both variants. The parallel stroke ensures a plane-parallel closure of the moulds and prevents a displacement of the inserted door seal.

Hennecke makes use of mould carriers with special parallel guide units that are actuated by central units. Depending on requirements and design, the parallel stroke is between 30 and 40 mm.

For thicker doors, the parallel stroke is designed up to a length of approximately 300 mm and takes place, for instance, in the RotaMat’s lower horizontal cycle position.

Automatic change of model
The economic efficiency of the manufacturing process increases with a rising plant flexibility and a decreasing effort for the operating staff. This holds especially true of the mould change.

Hennecke’s delivery range includes an automatic mould change system both for RotaMats with open and closed pouring. In both variants, the mould packages to be exchanged are automatically coupled to or uncoupled from the mould carrier and then automatically fed to or withdrawn from the RotaMat by a pusher system through a horizontal stroke. This allows a complete model change within a minimum period of time.

In addition to this plant type, Hennecke also offers so-called paternoster production lines for the insulation of refrigerator doors. These lines are central units with strong points such as a rapid mould change.
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