5-Zone Mixing Screw Improves Melt Quality
September 19, 2013
The five-zone HPS-M mixing screw by KraussMaffei has four years of proven success in many applications which involve adding color master batches directly on the injection molding machine. Its five-zone geometry allows gentle materials processing and minimizes machine wear. Thanks to its excellent mixing action, it is ideal for quick color changing.
Trade fair promotion gives customers a high degree of assurance
KraussMaffei will be offering a special promotion for HPS-M screws at the K 2013 in Düsseldorf (hall 15, booth B27/C24/C27/D24). Visitors can have their component checked for quality and discuss with KraussMaffei's experts the potential for improvement offered by the HPS-M screw. If the quality of the component cannot be enhanced despite the use of the HPS-M screw, KraussMaffei will take it back without fuss - guaranteed. This means that customers have better security on their investment and can convince themselves of the advantages of the HPS-M screw.
Direct coloring is gaining market share
Injection molders are faced with to ever-increasing demands with regard to cost-effective manufacturing and flexibility. This trend is reflected in the increasing use of color master batch which enables plastics to be colored directly on the machine and reduces compounding costs. The use of master batch allows the injection molding plant to be operated flexibly and economically, particularly when multiple color variants are required in quick succession.
Screw geometry protects material and machine
Three-zone screws often do not deliver perfect color homogeneity. "This is where the HPS-M screw by KraussMaffei comes in. The color pigments are distributed homogeneously in the plastic melt through the intelligent combination of shearing and mixing zones. That way the homogenization process no longer has to take place under high backpressure which, firstly, causes an unwanted increase in melt temperature during plasticization and, secondly, leads to premature wear of the screw and cylinder," stresses Markus Bauer, Head of Service at KraussMaffei. A rheologically optimized screw geometry protects both the plastic and machine, resulting in long screw and cylinder life. "Existing injection molding machines, including earlier model series, can easily be retrofitted with our HPS-M screw because the fitting dimensions are identical to those of the three-zone screw and existing screw tips can still be used. 750 screw assemblies on the market speaks for itself," adds Bauer.
Closing the gap between the three-zone screw and the high-performance screw
The screw is ideal for polypropylene, PE and ABS plastics in applications which involve frequent color changes and using colors that are difficult to mix. Although static mixers can also be retrofitted easily to injection molding machines, they lead to higher injection pressures and lengthier color changing times. In addition, they are prone to becoming damaged if the plastic injected through the mixing elements is not fully molten at the start of production. "The HPS‑M screw is a good alternative to three-zone screws, as it combines their fitting dimensions with the geometric characteristics of high-performance screws. In even delivers good results if color streaking and uneven mold filling occur with the standard screw," says Bauer. This means that it closes the gap between three-zone screws which are best suited to technical plastics and high-performance screws which are designed for extremely short cycles times thanks to larger effective screw lengths ranging from 23 to 26 D, but they require longer screw cylinders. For example, color changing times have been reduced by over 20 percent compared to static mixers by using an HPS-M 5-zone screw for direct coloring of ABS.