Mold structure design
Reasonable arrangement of die holes: The theoretical center of gravity of the die hole should be placed in the center of the mold. The porous mold should be arranged on a concentric circumference as much as possible to ensure symmetry, while considering the strength of the mold, the surface quality of the product and the uniformity of metal flow.
Optimize the design of the split hole: Design a reasonable shape of the split hole according to the profile structure, the shape is as simple as possible, and the number is as symmetrical as possible, so as to ensure that the mold will not sink on one side after the pressure and cause the core head to deflection.
Design a suitable hollow knife structure: when the wall thickness of the aluminum profile is ≥ 2mm, a straight hollow knife structure can be used; When the wall thickness of the aluminum profile is < 2mm, the inclined hollow knife can be selected.
Die hole size calculation
Consider a variety of factors: When calculating the size of the die hole, it is necessary to consider the chemical composition of the extruded alloy, the shape and nominal size of the product and its allowable tolerance, the extrusion temperature, the coefficient of thermal expansion, the geometry of the product section, the size of the extrusion force and the elastoplastic deformation of the mold.
Special profile treatment: For profiles with large wall thickness differences, the thin-walled parts and sharp edges that are difficult to form should be appropriately enlarged; For the die holes of flat and thin-walled profiles and siding profiles with large width-to-thickness ratios, in addition to conventional factors, it is also necessary to consider factors such as elastic deformation and plastic deformation of the mold, overall bending, and distance from the center of the extrusion cylinder.
Metal flow rate adjustment
Use the sizing belt: Generally speaking, the thinner the wall thickness of a certain part of the profile, the larger the circumference, the more complex the shape, and the farther away from the center of the extrusion cylinder, the shorter the sizing belt should be.
Use flow promotion or hindering structure: For parts with particularly complex shapes, very thin wall thickness, and far from the center, flow promotion angles or guide cones can be used to accelerate the flow of metal; For parts with much larger wall thicknesses or very close to the center of the extrusion cylinder, a barrier angle is used to supplement the barrier to slow down the flow rate here.
Other adjustment methods: the flow rate of the metal can also be adjusted by using process balance holes, process allowances, or by using front chamber molds, deflection molds, and changing the number, size, shape and position of diverter holes.
Mold strength check
Choose the appropriate formula: At present, there are many formulas for calculating extrusion force, the modified Berlin formula still has engineering value, the upper limit solution method of extrusion force also has good applicable value, and the empirical coefficient method is relatively easy to calculate the extrusion force.
Type verification: generally, flat molds only need to check the shear strength and flexural strength; The tongue mold and planar shunt mold need to check the shear, bending and compressive strength, and the tensile strength of the tongue and needle tip part also needs to be considered. For particularly complex molds, the finite element method can be used to analyze the stress and check the strength.
Work belt size determination
Consider a variety of factors: Determining the working belt of the split combination die is much more complicated than determining the working belt of the half die, which not only takes into account the difference in the wall thickness of the profile and the distance from the center, but also the fact that the die hole is obscured by the split bridge.
Reasonably determine the minimum working belt: the die hole under the diverter bridge must be considered thinner due to the difficulty of metal flowing. When determining the working belt, first of all, find out the thinnest part of the wall thickness of the profile under the diversion bridge, that is, the place with the greatest metal flow resistance, the minimum working belt here is set to be twice the wall thickness, the wall thickness is thicker or the metal is easy to reach, the working belt should be properly considered for thickening, generally according to a certain proportional relationship, plus the correction value of easy flow.
