machinery | Profile dies


velocity distribution was obtained at the die exit without exceeding a pre-specified pressure drop across the die. 3D flow simulation software for extrusion die design


allows designers to fine-tune an extrusion die before it is machined, which can reduce development time by 40-50% according to Mahesh Gupta, president of Plastic Flow, and a professor of mechanical engineering at Michigan Technological University. “However, virtual fine tuning of extrusion dies still


requires designers to modify the die geometry them- selves after each flow simulation, using their past experience,” he said. He says that the new software eliminates the need


for this ‘virtual trial and error’. After each flow simula- tion, the geometry is improved, and the simulation is run again. This cycle of geometry improvement, followed by a flow simulation, is repeated until a design with a uniform exit velocity distribution is obtained process. As well as eliminating the need for designer interven-


Below: Greiner has supplied an estimated 25,000 extrusion dies since its inception


tion for die improvement after each flow simulation, the new software is expected to further reduce the develop- ment time for extrusion dies, he says. Before an extrusion die can be optimised, its geometry is parameterised. That is, various dimensions of the die are defined as adjustable parameters which can be changed to modify the die geometry. This is done in SolidWorks, because for complex profile dies the geometry cannot easily be broken in simple elements such as bricks and prisms. The parameterised die geometry created within


SolidWorks is then passed through the extrusion die simulation software – Plastic Flow’s PolyXtrue – for flow simulation. PolyXtrue is available as an add-on to SolidWorks. The square die analysed by the software has a die channel that gradually changes into a thin-walled


Plastic Flow’s optimisation software improved the design of a square profile die


square cross-section. It was used to extrude a profile in ABS. The thin gap portion of the die consists of two different plates: the channel gap in the final plate near the exit is 2mm for the two horizontal walls, and 1.5mm for the vertical walls. The length of the final die plate is 1cm. The outer cross-section of the intermediate die plate is the same as that of the final plate near the exit. However, the channel gap in the horizontal and vertical portions of the intermediate plate is varied to balance the flow at the die exit. The length of the intermediate plate (2cm) is kept


constant during the optimisation process. As expected, with the larger channel gap (2mm) in the


horizontal walls in both the exit plate and the intermedi- ate plate, the exit velocity is higher in the horizontal walls and lower in the vertical walls. The flow at the exit of the square die was balanced by the die optimisation software by changing the thickness of the horizontal and vertical walls in the intermediate die plate. In order to accelerate the flow in the vertical walls, the software increased the thickness of the vertical walls in the intermediate plane from 1.5mm to 2.02 mm, while the thickness of the horizontal walls in the intermediate plate was decreased from 2mm to 1.69mm. “This software is expected to reduce the develop- ment time for extrusion dies by more than 50%,” said Gupta.


Long collaboration Greiner Extrusion recently supplied its 500th


extrusion


tool to leading German window profile producer Aluplast. The companies have collaborated since the 1970s, in


projects ranging from extrusion tooling, downstream equipment and co-extruders to the installation of new production locations. “We value the high quality of products from Greiner,


26 PIPE & PROFILE EXTRUSION | June 2017 www.pipeandprofile.com


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