The importance of design in the process of mold use

author:安迪模具 Release time:2015-12-17

 The mould in use process, and the design for manufacturing has a very important relationship, if the design is bad, can cause artifacts manufacturing various problems, affect the workpiece made beautiful, even will affect the use performance of the workpiece quality, so we need to know about the major points of the die design.

1. Dimensional analysis of aluminum extrusion parts
The size and deviation of the extruded parts are determined by the mould, extrusion equipment and other related process factors. Which affected by mold size change is very big, and the reasons that result in the change of mold size mold of elastic deformation, die temperature, the manufacturing precision of mould materials and mould and mould wear and so on. Squeeze ratio is the difficulty of squeezing the mold with numerical value. Generally, the squeezing ratio is applicable between 10 and 150. The compression ratio is less than 10, the mechanical performance of the product is low; Vice versa, the product is prone to surface roughness or Angle deviation. The solid profile is usually recommended for extruding ratio of about 30, and the hollow profile is around 45. The shape dimension of the extrusion die is the diameter and thickness of the outside of the mould. The dimensions of the moulds are determined by the size, weight and strength of sections.
2. Reasonable calculation of extrusion die size
When calculating the die hole size, the chemical composition of the main consideration is extruded aluminum alloy, the shape of the products, nominal dimension and its tolerance, extrusion temperature and mould material and squeezed under the temperature alloy linear expansion coefficient, product cross section geometry features and its changes during stretching, factors such as the size of the extrusion pressure and the elastic deformation of the die.
For the thickness of the wall thickness, the thin wall part and the edge of the edge should be appropriately enlarged. For generous than a big wide flat thin wall profiles and wall profiles of die hole, the size of the purlin section according to general profile design, and the size of the web plate thickness, besides to consider the factors listed in formula, still need to consider the elastic deformation of mould and plastic deformation and the overall bending, factors such as the distances from the center of the container. In addition, the compression speed, traction device and so on have a certain influence on the size of die.
3. Adjust the flow rate of metal reasonably
The so-called reasonable adjustment is to ensure that every particle on the product section should flow out of the die hole at the same speed in the ideal state. It is possible to use porous symmetrical arrangement, according to the shape of the profile, the difference of the thickness of each part of the wall and the distance from the center of the extruder and the distance from the center of the cylinder. Generally speaking, the thickness of the wall of the profile is thinner, bigger and more complicated than the circumference of the shape, and the farther away from the center of the extruder, the shorter the diameter of the diameter should be. When it is difficult to control the flow rate with a definite diameter, the thickness of the wall is very thin, the wall thickness is very thin, and the part that is far away from the center can be used to accelerate the metal flow through the Angle of flow or guide cone. In contrast, for areas with a much larger wall or close to the center of the extruder, the hindrance should be used to complement the obstruction to slow down the velocity here. In addition, the flow rate of metal can be adjusted by using the process balance hole, the residual amount of the process, or the number, size, shape and position of the front chamber die, the flow mould and the diversion hole.
4. Ensure sufficient mould strength
Due to the poor working conditions of the mould, the mould strength is a very important problem in mould design. In addition to the reasonable arrangement of die hole position, choose the right mold materials, reasonable design of die structure and shape, accurately calculate extrusion and check all the dangerous section of the allowable strength is also very important. There are many formulas for calculating extrusion pressure at present, but the modified Berlin formula still has engineering value. The upper limit solution of extrusion pressure has better application value, and it is easier to calculate the squeezing pressure by using the empirical coefficient method. As to the strength of the mould, the mould should be conducted according to the type of product and mold structure. The general plane mould only needs to check the shear strength and flexural strength. The tongue type die and plane shunt module needs to check the anti-shear, bending and compressive strength, the tongue and the tip of the needle also need to consider the tensile strength. An important fundamental problem in strength checking is choosing the appropriate strength theory formula and the relatively accurate allowable stress. In recent years, finite element method is used to analyze the stress situation and the strength of the test.
5. Work band width
Determine the effort of combination die belt than determine the mould work with much more complex, not only should consider profile wall thickness difference, from near and far, in the center of the surface and must consider the die hole covered with shunt bridge. In the die hole under shunt bridge, the work belt must be considered thinner due to the difficulty of metal flow. When determining the work zone, the first to find out the most thin wall thickness in triage bridge profile in the metal flow resistance of the largest local, the minimum work twice as the wall thickness, wall thickness thicker or metal is easy to achieve, work with due consideration of thickening, generally according to certain proportion relationship, plus easy flow of the revised.
6. The structure of die hole knife
Die hole knife is the structure of die - hole work belt. When the profile wall thickness t is greater than 2.0mm, it can be used to make the straight blade structure with easy processing. When t< 2mm, or with the cantilever can be used to the inclined empty knife.
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