# Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion
## 2 Die Design  
In this study, the cross-section geometry of the product is asymmetric, the wall thickness varies from 2.0 to 5.0 mm, and the main body region of the product attaches four snap-fit elements. Figure 2 shows the 3D model (Figure 2a) and the essential dimensions of the geometry of the extruded product (Figure 2b). [PERSON] and [PERSON] [29] evaluated the complexity of product geometry through a geometric classification of extrusion profiles, where solid profiles were classified into seven groups from the simplest geometry group (group A) to the most complex geometry group (group G). The product profile in this study is in group F, which has geometries with abrupt and thin wall cross-sections or wide cross-sections. Therefore, the 3D model shown in Figure 2 is a complex geometry profile. The maximum height and width of the products are 240.35 and 40 mm, respectively. Based on the largest size of the product profile, the traditional flat die and pocket die are selected to extrude on a machine with a container diameter of 310 mm (corresponding to a 4000-ton extruder); the spread die is chosen to extrude on an extruder with a container diameter of 186 mm, (corresponding to an 1800-ton machine). Figure 3 shows the layout of the die exit of the flat-face die and the 3D model of the flat-face die. Die structure consists of the main die plate, die bearing region, and three run-out steps. The maximum diameter and height of the die are 360 and 90 mm, respectively. The maximum taper angle of run-out  
is \(3^{\circ}\). The geometry of these steps is determined empirically to ensure the die strength and to provide enough safety when the extruded metal flow does not touch the run-out surfaces. Figure 4 displays the layout for the die orifice with basic dimensions, and the 3D model of the pocket die. The maximum diameter and height of the pocket die are designed similarly to the traditional flat die, in which the depth of the cavity is 32 mm; the minimum distance of the entrance is 32 mm; the maximum circle diameter of the die entrance is 280 mm. The run-out of this die is also designed with the same geometry and structure as the traditional flat die. Figure 4: Design for the pocket die: (**a**) Layout for the entrance; (**b**) Simplified 3D model (unit: mm). Figure 3: Design of the traditional flat die: (**a**) Layout of the die exit; (**b**) the 3D model of the flat-face die (unit: mm). Figure 2: The geometry of the extruded product: (**a**) The 3D model; (**b**) The cross-section geometry with essential dimensions of the product (unit: mm). Figure 5a shows the structure, and main dimensions of the spread die. Figure 5b shows the 3D model of this die. With the same cross-section geometry of the product, the spread die uses the billet with a diameter smaller than the size of the product, which is the main difference in this die design compared to other dies. Therefore, it is necessary to use appropriate tactics to distribute the material evenly in the extrudate. Previous studies have shown that the structure and entrance geometry plays a vital role in the spread die design [26]. Thus, this led to the fact that this die design becomes very complicated. Although the design of spread die is complicated, this kind of dies offer some advantages over the other die types. In practice, designers and engineers often modify the entrance geometry of spread die design to meet the customer requirements. It is necessary to provide a suitable die structure and incorporate the use of supporting solutions such as bearing length adjustment or pocket to achieve a high-quality product. The spread die is designed with a maximum diameter of 360 mm, in which the maximum height of the leading die plate (lower die) and the spreader die (upper die) are 90 and 90 mm respectively, the maximum spread angle of the upper die is 30\({}^{\circ}\). The upper die consists of a step with a depth of 30 mm placed before the die entrance. Moreover, a pocket is designed in front of the die orifice of the lower die to support flow correction.