To manufacture a set of high-quality aluminum extrusion dies, not only must there be good processing equipment and skilled extrusion die manufacturing workers, another very important factor is to have a good extrusion die design. For more complex heat sink hot extrusion molds, the quality of the mold design accounts for 85% of the quality of the mold. An excellent mold extrusion tool design is: on the premise of meeting customer requirements, do When the processing cost is low, the processing difficulty is small, and the processing time is short, the mold can produce qualified products in the shortest time. To do this, not only fully comprehend the customer requirements, but also require the mold designer to have an understanding of the extruder, the structure and processing technology of the extrusion mold, and the processing capabilities of the factory. As a heat sink hot extrusion dies supplier, if you want to improve the design level of the extrusion dies, you should do the following:
Heat Sink Hot Extrusion Moulds
1. Familiar with the size and deviation of aluminum profiles
The size and deviation of the aluminum profile are determined by the extrusion die, extrusion equipment, and other related process factors.
2. Choose the right tonnage of aluminum extrusion machine
The selection of the tonnage of the extruder is mainly determined according to the extrusion ratio. If the extrusion ratio is lower than 10, the mechanical properties of the aluminum profile product are low; if the extrusion ratio is too high, the aluminum profile product is prone to defects such as surface roughness and angle deviation. Solid aluminum profiles often recommend an extrusion ratio of around 30, and hollow aluminum profiles around 45.
3. Determine the shape of the extrusion die
The external dimensions of the extrusion die refer to the outer diameter and thickness 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 the extrusion die
For aluminum profiles with large wall thickness differences, the thin-walled parts and edge corners that are difficult to form should be appropriately enlarged in size; and for the die holes of flat and thin thin-walled profiles and wall panel profiles with a large width to thickness ratios, The size can be designed according to the general profile. In addition to the factors listed in the formula, the web thickness must also consider the elastic and plastic deformation and overall bending of the extrusion die, and the distance from the center of the extrusion cylinder. In addition, the extrusion speed and the presence or absence of a traction device also have a certain effect on the die hole size.
5. Reasonably adjust the flow rate of aluminum metal
Reasonable adjustment of the flow rate of aluminum metal is to ensure that every particle on the aluminum profile should flow out of the die hole at the same speed. When designing the extrusion die, try to adopt a porous symmetrical arrangement. According to the shape of the aluminum profile, the difference in wall thickness of each part and the difference in perimeter and the distance from the center of the extrusion barrel, the unequal length sizing belt is designed. Generally speaking, the thinner the wall thickness of the aluminum profile, the greater the circumference, the more complicated the shape, and the farther away from the center of the extrusion barrel, the shorter the sizing zone. If it is still difficult to control the flow rate of aluminum metal with a sizing belt, the cross-sectional shape of the aluminum profile is particularly complicated, the wall thickness is very thin, and the part far from the center can use a flow angle or a guide cone to accelerate the aluminum metal flow. For those parts with much larger wall thickness or very close to the center of the extrusion cylinder, the obstruction angle should be used to supplement the obstruction to slow down the flow rate here. In addition, you can also use process balance holes, process margins, or use anterior chamber molds, diversion molds, change the number, size, shape, and position of the distribution holes to adjust the flow rate of aluminum metal.
6. The extrusion die strength check
Because the working conditions of the mold are very bad when the aluminum profile is extruded, the strength of the heat sink hot extrusion dies is a very important issue in the design of the mold. In addition to rationally arranging the positions of the die holes, selecting appropriate die materials, and designing a reasonable die structure and shape, it is also very important to accurately calculate the extrusion force and check the allowable strength of each dangerous section. There are many formulas for calculating squeezing force, but the modified Berrin formula still has engineering value. The upper limit solution method of squeezing force also has a good applicable value, and it is relatively simple to calculate the squeezing force using the empirical coefficient method. As for the check of the strength of the mold, it should be carried out separately according to the type of product and the structure of the mold. Generally, the flat mold only needs to check the shear strength and flexural strength, the tongue mold and the flat split die to need to check the shear, flexural and compressive strength, and the tongue and needle tip also need to consider the tensile strength. In recent years, the finite element method can be used to analyze the stress and check the strength of, particularly complex molds.
7. Reasonable working belt size
Determining the working band of the split mold is much more complicated than determining the half mold working band. Not only must the wall thickness difference of the profile, the distance from the center be considered, but also the situation that the die hole is covered by the split bridge. The die hole under the shunt bridge has to be considered thinner due to the difficulty of metal flow in. When determining the working band, first find the thinnest wall thickness of the profile under the shunt bridge, that is, the place with the largest metal flow resistance. The minimum working band here is set to twice the wall thickness. The thicker wall or metal is easy to reach The working zone should be properly considered for thickening, generally according to a certain proportional relationship, plus the easy-to-flow correction value.
8. The structure and size of the die hole empty knife
The empty knife of the die hole is the structure of the cantilever support at the outlet end of the die hole working belt. When the wall thickness of the aluminum profile is ≥ 2mm, a straight air knife structure that is easier to process can be used; when the wall thickness of the aluminum profile is <2mm, the oblique air knife can be processed at the cantilever.