# Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion

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## Abstract

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## 1. Introduction

## 2. Die Design

_{max}) is based on an empirical formula, which relates to the width of the product as follows:

_{max}= K

_{w}t,

_{w}is the coefficient of the effect of the die orifice width (or product thickness) and t is the main width of the die orifice (in this study t = 3.15 mm). The value of K

_{w}is from 2.0 to 3.0, which is often used in practice with a pocket combination. According to Miles et al. [13], K

_{w}from 1.4 to 3.5 were recommended. For the investigation purpose, this study adopts the values of K

_{w}= 2.5 for calculating the bearing lengths of the initial extrusion dies.

- The bearing area further away from the center will have a smaller length value.
- Bearing lengths for regions with complex geometries (such as grooves for assembling, branches with changing directions) will be shorter than that for adjacent areas (multiplied by a coefficient from 0.75 to 0.9).
- The bearing length at the tip of the product profile is calculated to be approximately 0.6 times smaller than the adjacent bearing.

## 3. Finite Element Modelling

## 4. Results and Discussion

#### 4.1. Extrusion Velocity of the Product

_{i}is the speed at node i; V

_{a}is the average velocity of all nodes; n is the number of nodes considered in cross-section of product. The smaller the VRD value, the better the flow distribution. Smaller VRD also means that product quality is better. The value of VRD for balancing metal flow is defined by the designer, which is expected when the die design is as small as possible. In this study, if VRD is less than 2% of the metal flow is considered to be balanced [11,27].

_{w}= 2.5. The velocity distribution on the product is uneven in this case. Velocity tends to be faster and uniform in the region near the center and slow in the region far from the center (region 1 and region 2). The velocity in region 1 is slowest, which can be explained by the obstruction formed by the complex geometry. The difference between the maximum and minimum velocity in the product profile is 20.37 mm/s. The calculated VRD value is 4.23%. However, this value is too large and needs to be further improved.

_{w}coefficient should be increased accordingly. Table 5 lists bearing lengths of the regions in traditional flat dies with different K

_{w}values. The simulation results of velocity distribution for K

_{w}coefficient of 3.5 and 4.5 are shown in Figure 9a and Figure 9b. It is observed that the differences between the maximum and minimum velocity are reduced from 10.37 to 5.37 mm/s. In other words, increasing K

_{w}leads to the fact that the material flow becomes more balanced. Hence, the traditional flat die must use a coefficient of K

_{w}= 4.5 (corresponding to the maximum bearing length of 14.2 mm) to balance the metal flow in the extrudate.

_{w}= 2.5), the material flow can be balanced. However, controlling the metal flow in the spread die is more difficult compared to the other dies.

#### 4.2. Extrusion Force

#### 4.3. Extrudate Temperature

_{i}is the temperature at node i; T

_{a}is the average temperature of all nodes; n is the number of nodes considered in a cross-section of the product. Figure 13 shows the temperature distribution in the extruded products at a ram speed of 1 mm/s. It can be seen that the temperature distribution for the traditional flat die is more uniform than those of other dies. This is attributed by two reasons: 1) the contact area between flat die and material in die exit region is less than that of other dies and 2) the bearing length in this area of the traditional flat die is longer than the other dies leading to increased heat transfer. The temperature tends to reach its highest value in the middle part of the product, and minimal temperature occurs at the left or right edges of the profile. As a result, the region near the center experiences severe deformation. The maximum temperatures for the traditional flat, pocket, and spread dies are 497.5 °C, 504.9 °C, and 490.6 °C, respectively. The higher temperature results from the increased friction and work required for the deformation process corresponding to the die with more contact area and the larger accumulative volume of material flow.

#### 4.4. Extrusion Die Deformation

#### 4.5. The Transverse Weld of the Pocket Die and the Spread Die

## 5. Conclusions

- Using the traditional flat die has the advantage of achieving a more uniform temperature distribution in the extruded product when compared to other solid dies. The extrusion force of this die is about 5% smaller than that of the pocket die. This type of die has a simple structure and is easy to fabricate. However, the needed bearing length is longer than other solid die types, which is undesirable in extrusion practice. Moreover, the deformation of the flat-face die is the largest, the maximum die deflection at a speed ram of 1 mm/s up to 0.17 mm; This may exceed the permissible tolerance of the product. Deformation reduction solutions for this die need to be considered further. When using the flat-face die, a low ram speed can be used to reduce die deformation. Finally, using the traditional flat die is not suitable for extruding complex profiles.
- Using the pocket extrusion die has many advantages compared to other types of solid dies, the velocity is more balanced; the deformation is minimal; transverse welding length is half shorter when compared to the spread die. Moreover, when the ram speed increases, the value of VRD changes little and the die deformation is maintained stably, and the welding line length does not increase significantly (about 221 mm when increasing the ram speed from 1 to 9 mm/s). This die type is the best choice to ensure quality and productivity in extruding aluminum products. However, the pocket and flat-face dies have the disadvantage of being unable to extrude products with sizes larger than the container diameter of the extruder.
- Using the spread die has the advantage that the required extrusion force is the smallest when compared to other solid dies, which is about 40% of the extrusion force required for pocket extruders with the same product profile. It is an extremely effective solution when it is necessary to reduce a large amount of extrusion force or extruding products on small machines with product sizes larger than the extruder diameter. This die type has been growing rapidly in recent years because it can increase the flexibility of production. However, this die type is difficult to design to be able to uniformly distribute the flow in extruded products. Hence, using a pocket and variable bearing lengths is necessary to balance the metal flow for extruding complex product profiles. The more complicated die structure makes the fabrication cost bigger than other types of solid dies. The difference in temperature distribution in the extrusion product of this die is much larger than in other cases, which can be overcome by the increase in temperature for the die plates. The spread extrusion forming the transverse horizontal welding length is twice as long as the pocket die, and the charge weld length is increased rapidly with increasing ram speed (about 3243 mm when increasing the ram speed from 1 to 9 mm/s).

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Product defects with an improper extrusion die design. The defects concern with significant bending and twisting of the profile.

**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 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 4.**Design for the pocket die: (

**a**) Layout for the entrance; (

**b**) Simplified 3D model (unit: mm).

**Figure 7.**Meshing for the extrusion dies: (

**a**) The flat-face die; (

**b**) The pocket die; (

**c**) The spread die.

**Figure 8.**Velocity distribution in the extrudate of the traditional flat die with the calculated bearing length of K

_{w}= 2.5.

**Figure 9.**Velocity distribution in the products of the traditional flat dies with different K

_{w}coefficients at the ram speed of 1 mm/s: (

**a**) K

_{w}= 3.5; (

**b**) K

_{w}= 4.5.

**Figure 10.**Velocity distribution in the products at the ram speed of 1 mm/s of the dies: (

**a**) The pocket die; (

**b**) The spread die.

**Figure 13.**Temperature distribution in extrusion products of the dies, (

**a**) The flat-face die; (

**b**) The pocket die; (

**c**) The spread die.

**Figure 16.**Die deformation: (

**a**) Traditional flat die; (

**b**) The pocket die; (

**c**) The lower die of the spread die.

**Figure 17.**The appearance of stop mark and charge weld in the continuous extrusion of solid dies. The formation of a transverse weld and its length (L

_{tw}) with distance from stop mark to starting position of charge weld (L

_{s}), and distance from stop mark to the cut-off location at the end of charge weld (L

_{c}).

**Figure 19.**Percentage of the new material with the distance of the charge weld in the extruded product of the dies: (

**a**) The pocket die; (

**b**) The spread die.

Bearing Lengths with K_{w} | Bearing Region | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

1 | 2 | 3 | 4 | 5 | 6,14 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 | 16 | 17 | 18 | |

(K_{w} = 2.5) | 3.1 | 5.2 | 5.9 | 3 | 5.3 | 6.9 | 7.9 | 3.9 | 6.5 | 3.6 | 5.8 | 5.7 | 3.4 | 5.5 | 3.9 | 3.4 | 2 |

**Table 2.**Material parameters of the constitutive equation [30].

$\mathbf{\beta}\left({\mathbf{m}}^{2}\mathbf{MN}{-}^{1}\right).$ | A (s^{−}^{1}) | N | Q (J · mol^{−}^{1}) | R (J mol^{−}^{1} · K^{−}^{1}) |
---|---|---|---|---|

0.04 | 5.90152 × 10^{9} | 5.385 | 1.4155 × 10^{5} | 8.314 |

**Table 3.**Physical and thermal parameters of the billet and tools material [4].

Material | Density (Kg/m ^{3}) | Young Modulus (GPa) | Poisson’s Ratio | Thermal Conductivity (W/m.K) | Heat Capacity (J/(kg °C)) |
---|---|---|---|---|---|

AA6063 | 2700 | 40 | 0.35 | 198 | 900 |

SKD61 | 7870 | 210 | 0.35 | 24.3 | 460 |

Extrusion Parameters | Traditional Flat Die | Pocket Die | Spread Die |
---|---|---|---|

Container diameter (mm) | 310 | 310 | 186 |

Billet length (mm) | 200 | 200 | 200 |

Extrusion ratio | 72.5 | 72.5 | 26.1 |

Billet temperature (°C) | 480 | 480 | 480 |

Container temperature (°C) | 450 | 450 | 450 |

Die temperature (°C) | 450 | 450 | 450 |

Ram speed (mm/s) | 1, 3, 5, 7, 9 | 1, 3, 5, 7, 9 | 1, 3, 5, 7, 9 |

Bearing Lengths with K_{w} | Bearing Region | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

1 | 2 | 3 | 4 | 5 | 6,14 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 | 16 | 17 | 18 | |

(K_{w} =3.5) | 5.2 | 8.6 | 9 | 4.4 | 7.3 | 10 | 11 | 5.5 | 9.1 | 4.8 | 8 | 7.9 | 4.7 | 8.5 | 6.2 | 5.4 | 3.2 |

(K_{w} =4.5) | 7.1 | 11.8 | 12.2 | 5.8 | 9.6 | 13.2 | 14.2 | 7 | 11.7 | 6.3 | 10.5 | 10.4 | 6.2 | 11.5 | 8.5 | 7.4 | 4 |

Max. Deflection of Dies (mm)(Mag) | Ram Speed (mm/s) | ||
---|---|---|---|

1 | 5 | 9 | |

Flat-face die | 0.17 | 0.18 | 0.19 |

Pocket die | 0.12 | 0.12 | 0.12 |

Spread die | 0.11 | 0.13 | 0.13 |

Ram Speed (mm/s) | Length of Transverse Weld | |
---|---|---|

The Pocket Die (mm) | The Spread Die (mm) | |

1 | 3497 | 5742 |

5 | 3624 | 7385 |

9 | 3718 | 8985 |

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## Share and Cite

**MDPI and ACS Style**

Truong, T.-T.; Hsu, Q.-C.; Tong, V.-C.
Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion. *Appl. Sci.* **2020**, *10*, 263.
https://doi.org/10.3390/app10010263

**AMA Style**

Truong T-T, Hsu Q-C, Tong V-C.
Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion. *Applied Sciences*. 2020; 10(1):263.
https://doi.org/10.3390/app10010263

**Chicago/Turabian Style**

Truong, Tat-Tai, Quang-Cherng Hsu, and Van-Canh Tong.
2020. "Effects of Solid Die Types in Complex and Large-Scale Aluminum Profile Extrusion" *Applied Sciences* 10, no. 1: 263.
https://doi.org/10.3390/app10010263