Die design is a common problem faced by food engineers working with extrusion processes. In new product development, balancing the flow distribution in the die is critical to stable production. Dies are typically balanced by opening and closing the die land and adding internal obstructions to accelerate or slow down the flow of material where needed. Balancing the die with CFD rather than physical experiments eliminates the need to build and test multiple dies and saves time and material on the extrusion line.

The first example below shows a dough extruder head assembly that was redesigned from a round shape to an eight-point star configuration. The velocity contours at the exit of the die revealed a maldistribution problem. The CFD model was used to determine the internal baffle configuration required to provide the proper flow resistance and distribute the dough evenly across the head.

A non-uniform velocity profile across the die face can lead to a twisting of the extruded product. An example of a twisted pasta product is shown in the second figure below. This flow simulation illustrates how CFD can be used to design extrusion dies that will result in specific extruded shapes, depending upon the rheological properties of the pasta dough.

Model of a redesigned 10-die dough extruder head assembly (left). Contours of dough velocity at the exit of the die, indicating the maldistribution at the points of the star design (right).

Click on the image to view the animation