What are the design points of aluminum profile extrusion die?

Eight key points in the design of aluminum profile extrusion die

1, size and deviation of aluminum profile

The size and deviation of aluminum profile are determined by extrusion die, extrusion equipment and other related technological factors.

2. Choose the correct tonnage aluminum extruder.

The tonnage of extruder is mainly determined according to the extrusion ratio. When the extrusion ratio is lower than 10, the mechanical properties of aluminum profile products are low; If the extrusion ratio is too high, aluminum profile products are prone to surface roughness and angle deviation. The extrusion ratio of solid aluminum profiles is often recommended to be around 30, while that of hollow aluminum profiles is around 45.

3. Determine the shape of the extrusion die

The external dimensions of the extrusion die refer to the diameter and thickness of the outer circle of the extrusion die. The external dimensions of the extrusion die are determined by the size, weight and strength of the profile section.

4. Determination of die hole size of extrusion die

For aluminum profiles with large wall thickness differences, the dimensions of parts that are difficult to form such as thin-walled parts and sharp edges should be appropriately increased; For open-width thin-walled profiles and wall profiles with large width-to-thickness ratio, the dimensions of stringers can be designed according to general profiles, and the dimensions of web thickness should consider the factors listed in the formula, such as elastic deformation and plastic deformation of extrusion die, overall bending and distance from the center of extrusion cylinder. In addition, the extrusion speed and the presence or absence of traction device also have certain influence on the die hole size.

5. Reasonably adjust the flow speed of aluminum metal.

Reasonable adjustment of the flow velocity of aluminum metal is to ensure that every particle on the section of aluminum profile flows out of the die hole at the same speed. When designing the extrusion die, the holes should be arranged as symmetrically as possible. According to the shape of aluminum profile, the difference of wall thickness and specific perimeter of each part and the distance from the center of extrusion cylinder, sizing belts with different lengths should be designed. Generally speaking, the thinner the wall thickness, the larger the circumference and the more complex the shape of aluminum profile. The farther away from the center of the extrusion cylinder, the shorter the sizing area here. If the sizing belt is used, it is still difficult to control the flow speed of aluminum metal. The cross-sectional shape of aluminum profile is particularly complex and the wall thickness is very thin. The flow angle or guide cone can be used to accelerate the flow of aluminum metal in the part far from the center. However, for those parts with much larger wall thickness or close to the center of the extrusion cylinder, the plugging angle should be used for supplementary plugging to slow down the flow rate here. In addition, the flow rate of aluminum metal can be adjusted by using process balance holes and process allowance, or by using front chamber die and shunt die and changing the number, size, shape and position of shunt holes.

6, extrusion die strength inspection

Because the working conditions of the die are very bad when aluminum profile is extruded, the strength of the die is a very important issue in die design. In addition to reasonable arrangement of die hole position, selection of suitable die material and design of reasonable die structure and shape, it is also very important to accurately calculate extrusion force and check allowable strength of each dangerous section. At present, there are many formulas for calculating extrusion force, but the modified Buel-Lin formula still has engineering value. The upper bound solution of extrusion force also has good application value, and it is relatively simple to calculate extrusion force by empirical coefficient method. As for the check of mold strength, it should be carried out separately according to the product type and mold structure. Generally, the plane die only needs to check the shear strength and bending strength. The shear strength, bending strength and compressive strength of tongue die and plane parting need to be checked, and the tensile strength of tongue and needle tip needs to be considered. An important basic problem in strength checking is to choose a suitable strength theoretical formula and a more accurate allowable stress. In recent years, finite element method can be used to analyze stress and check the strength of particularly complicated dies.

7. Reasonable workspace size

It is much more complicated to determine the working area of split-flow combined die than that of half-die. Not only the wall thickness difference and the distance between the center and the surface of the profile, but also the situation that the shunt bridge blocks the die hole should be considered. Because it is difficult for metal to flow into the die hole under the shunt bridge, the thinner working area must be considered. When determining the working area, we must first find out the place where the wall thickness of the profile under the shunt bridge is the thinnest, that is, the place where the metal flow resistance is the greatest. The minimum working area here is set to twice the wall thickness. Where the wall thickness is thick or the metal is easy to reach, the working area should be appropriately thickened, generally according to a certain proportion, plus the easy flow correction value.

8. Structure and size of die hole empty knife

The die hole empty cutter is a structure with cantilever support at the outlet end of the die hole working belt. When the wall thickness of aluminum profile is ≥2mm, the straight hollow cutter structure which is easy to process can be adopted; T 1t2mm, you can choose to process the inclined empty knife at the cantilever.