Three New Mixing Heads
More Flexible and More Efficient
A prerequisite for a high product quality and maximum efficiency in PU processing is that the mixing heads adapt exactly to the requirements of the respective PU product. In this area, KraussMaffei Technologies GmbH, Munich, Germany, presents three new mixing head developments that make it possible to increase flexibility and shorten cycle time.
Linear Mixing Head for ColorForm
The linear mixing head MK 5-2+1K has been developed specially for the ColorForm process. During the ColorForm process the thermoplastic mold base body is flow-coated after the injection molding in the second cycle with polyurethane (PU) or polyurea (PUA) as a surface material. The use of the new mixing head allows for a very fast dye change – to do so, the dye module mounted to the mixing head needs only be replaced. This process is possible in few minutes. Dye carryover can be excluded due to the design of the mixing head because the dye circulates in a closed system in the dye module, and thus not through the mixing head. The dye nozzle opens only when material is discharged, and the dye is added directly in the mixing chamber.
The new ColorForm mixing head is lightweight and compact, which reduces the space requirements and facilitates the installation on molds. Furthermore, the new mixing head series is particularly well suited for reliable and uniform mixing of smaller PU quantities.
Transfer Mixing Head with Multiple Dye Dosing
In order to simplify the dye change during the production of semi-rigid foams or rigid, flexible foams, KraussMaffei has developed the transfer mixing head MK 10/15 ULP-2K+4 with multiple dye dosage. With this mixing head it is possible to feed up to four dyes directly and independently in the mixing chamber.
With the new transfer mixing head, it is now possible to change the dye in continuous production from shot to shot. To reach a higher mixing quality even in unfavorable mixing conditions, the mixing head works according to the principle of T-mixing, which means that the polyol component is split in two substreams and introduced through two nozzles to the mixing chambers. At the newly developed mixing head two different dyes can be added at both polyol nozzles respectively. The metering occurs at the same time between polyol nozzle and mixing chamber, so that no dye carryover into the polyol component takes place. Through this positioning it is also possible to meter the dye with relatively low pressure.
Faster Nozzle Changing at the Spray Mixing Head
The mixing heads used in Structural Component Spraying (SCS) have also been further developed. In this process technology, layers made up of fiber mats and honeycomb cores are sprayed with unreinforced PU, inserted into a mold and pressed into shape. SCS permits outer layers with low thickness, so that the manufactured components are particularly lightweight.
Flat-fan nozzles and air-assisted circular jet sprays are available for the spraying process. Flat-fan nozzles produce a fan-like flat jet and are suited for large-format coating of the PU mixture on relatively level, large-sized components. The air-assisted circular jets produce a finer spray and have a lower output capacity than the flat-fan nozzles. They are used primarily for component areas with challenging geometry.
The newly developed nozzle-changing component by KraussMaffei now makes it possible to equip spray mixing heads with both nozzle varieties. In the manufacturing of the component, both nozzles can go into action alternately. This has the advantage of making the cycle time shorter.
KraussMaffei Technologies GmbH
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