ã€China Aluminum Industry Network】 The aluminum profile extrusion die is a crucial component in the aluminum extrusion process. It plays a vital role in ensuring that the final product has the correct shape, size, and dimensional accuracy. In real-world production, various issues may arise during the extrusion of hollow aluminum profiles, and specific repair methods are applied to address them effectively.
One common problem is the presence of a seam or poor weld in hollow aluminum alloy extrusions using a flat-flow split mold. During the extrusion process, metal flows through the welding chamber, which can result in a visible weld line. If the welding is not done properly, gaps may appear, leading to structural defects.
There are two main causes for these gaps. First, if the split hole is too narrow or the welding chamber is insufficiently sized, the metal flow may be inadequate, resulting in low hydrostatic pressure within the chamber and an incomplete weld. To resolve this, the split hole and welding chamber can be enlarged through grinding or milling, allowing for better metal flow and improved welding. Second, excessive or improper lubrication can also lead to poor welding. In such cases, using a dry extrusion process without lubrication can help achieve better results.
Another issue is the concave or convex surface on the wall of the hollow aluminum profile. This occurs when the core's work belt is shorter than that of the lower die hole, leading to uneven metal distribution. To correct this, a spacer can be placed between the core and the lower die to ensure the core's work belt aligns correctly with the lower die hole under stress. Additionally, reducing the thickness at the exit of the lower die can help balance the metal flow.
Prolonged use of the mold can cause wear on the core’s work belt, creating grooves and increasing friction, which leads to uneven metal flow and a convex wall. If the wall thickness allows, the work belt can be repaired or ground down to reduce resistance. In more severe cases, the mold can be preheated, reshaped, and polished before being used again. If the work belt is not worn, adjustments can be made to the outer and inner areas of the core to improve flow.
Streaks on the outer surface of the extruded aluminum profile, especially noticeable after anodizing, are often seen in areas with thick walls, branches, or threaded holes. These streaks can be caused by uneven metal flow due to design features, the location of the weld zone, or inconsistencies in the profile's cross-section. Poor cooling systems can also lead to black marks after anodizing, while imperfections in the billet material can affect color uniformity.
To address these issues, it's important to review the customer's drawings for any irregularities. The diverting bridge should be placed on non-visible surfaces, and the welding chamber should be as large as possible to ensure sufficient hydrostatic pressure. For profiles with internal features like "twig" shapes or threaded holes, polishing the die or adjusting the transition radius can help. Proper heating and annealing of the billet are essential, as well as maintaining consistent cooling conditions to prevent grain size variation and color differences after anodizing.
Lastly, bending or twisting of the aluminum profile can occur due to uneven metal flow caused by improper work belt design, asymmetrical or obstructed orifices, or imbalanced metal supply. To fix this, the die outlet or split holes can be adjusted or expanded, and any obstructions should be removed through sanding. Ensuring balanced metal flow is key to producing high-quality, defect-free aluminum profiles.
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