Aluminum extrusion porous mold is an effective method to improve production efficiency. The most influential part of porous mold production includes mold design, mold making, extrusion production and mold repair. This article briefly introduces the precautions and production experience of each link.
1 mold design
1.1 mold cavity shrinkage given:
Firstly, according to the single hole shrinking principle, the overall shrinkage is given (the shrinkage rate of different alloys is different, such as the shrinkage rate of the 6063 material is 1%), and then the pre-deformation amount of the mold elastic deformation is given according to the position of the die hole, as shown in the figure;
1.2 mold structure design
1.2.1 Cavity placement
The two-hole cavity is generally placed by left and right discharge (symmetric or co-directional) and upper and lower discharge (symmetric or co-directional).
The general method for placing the three-hole cavity is as follows: three-hole flat discharge, product-shaped discharge, and inverted-shaped discharge.
Other porous cavity placements are basically placed on the principle of two-hole and three-hole.
Symmetrical discharge: the feeding and discharging are completely the same. The length of the mold design does not need to be considered. After the extrusion, the saw is convenient for surface treatment. It is necessary to use a plurality of different materials to store the material, which affects the working efficiency of the saw.
Co-feeding: The discharge direction of each hole is the same, no special distinction is needed in the rear saw. The operation of the rear saw is relatively simple, but the design flow rate is high, and the length of each hole is difficult to control.
1.2.2 Splitter design
Existing porous molds are most commonly used in porous single feed and porous integral feed configurations. Figure:
Porous individual feeding structure (Fig. 3): When squeezing, the whole rod is first divided into two identical contoured rods and then into the dividing hole. Advantages: The difference in the length of discharge of each hole is small, and the mold has strong anti-ballistic ability. Disadvantages: low economics. Compared with other structures, it requires a larger mold size, and the outer diameter of the aluminum rod diameter of the same specification is small.
Porous integral feed structure (Fig. 4): The aluminum flow directly enters each split hole during extrusion, and the feed balance of each type of hole is achieved through a separate welding chamber. Advantages: high economical efficiency, easy to make holes in the mold design. Disadvantages: The difference in the length of discharge of each hole is large, which requires higher processing precision; the anti-ballistic ability of the mold is weak.
1.2.3 Bridge thickness design
The bridge thickness (Fig. 6) is proportional to the bridge span (5). The bridge spans long, the thicker the bridge thickness, the better the strength of the mold, the larger the mold size, and the higher the extrusion force. Therefore, it is only necessary to ensure sufficient aluminum flow welding, and the bridge span is as short as possible.
1.3 Work belt given
Personally think that the speed of profile outflow mainly depends on the proportion of the split hole, the working belt is only used as auxiliary forming, but the opening of the "U" shaped material, the color difference of the "T" shape and the surface quality of the large plane have a great relationship with the given work zone. . The working belt ratio is generally 1.2 to 3.5 times the wall thickness.
1.4 Material selection
Compared with the single-hole mold, the porous mold has a large change in the extrusion process, which provides a good foundation for the stability and service life of the mold. It is necessary to select a steel with good toughness.
2 production and processing
2.1 Processing points
Most of them use CNC machining, except slow-cutting cutting cavity, outer circle, EDM working die and clearing angle. The upper mold working belt needs to make high and low points; when processing the lower working belt, each hole needs to be discharged at the same time. The mold is equipped with a full fit to use a clearance fit, and the fit clearance is generally between 0.02 mm and 0.06 mm.
2.2 Heat treatment points
The hardness is maintained between 48 and 50 HRC, and the hardness difference between any position on the mold is between 2 HRC. Pay attention to the position of the hardness test to avoid affecting the strength of the mold and the fit support.
3 extrusion process
3.1 Extrusion process parameters
Porous molds are most prone to uneven length of discharge, so as not to affect the judgment of the mold, the extrusion process must be carried out according to standards. The temperature difference between the positions of the mold is within 5 °C. By adjusting the extrusion speed and the temperature of the aluminum rod to achieve consistent exit temperature, the temperature of the 6063 material extrusion outlet profile is controlled at 520 ° C - 530 ° C. The extrusion speed (the advance speed of the extruder master cylinder) should be adjusted according to the stage. The last two rods before the order is completed are speeded up. After the speed increase is recorded, the maximum extrusion speed is found. The target profile outflow speed is 30m/min.
Our extrusion parameters are as follows
3.2 Use of the dispensing device
In order to prevent the mutual extrusion of the profiles extruded in the extrusion process, it is necessary to install a multi-component material device at the receiving table to create a separate movement interval for each extruded profile to avoid mutual contact and reduce Scrap due to scratches. Figure 7
3.3 Cooling wind speed adjustment:
When the profile is out of the receiving table, the knife bending phenomenon often occurs, causing the profiles of the holes to overlap after being mixed, and the straightening elongation will become larger to remove the bending phenomenon, causing the profile to scratch and straighten the excessive surface. Orange peel and size do not meet the requirements. In order to achieve simultaneous cooling, a gas pipe or outlet can be installed at the receiving station to use nitrogen cooling.
4 mold repair
The biggest problem of the porous mold is that the length of the holes and the thickness of the holes are uneven. The first step of the mold repair is to carefully check the molds, confirm that the holes are in full compliance with the drawings, and then repair the mold. The mold maintenance concept is to repair slowly. Repair the shape and repair the length.
The reasons for the influence of porous mold discharge are design factors, mold processing, extrusion equipment precision, process and operation. The precision, process and operation of mold processing and extrusion equipment can be directly controlled to ensure compliance with standards. Only in this way can we truly reflect Mold design issues and subsequent stable production. According to several years of production tracking, the production efficiency of porous molds is more than 50% higher than that of single-hole molds, especially for profiles with large order quantities. The porous extrusion efficiency far exceeds the single-hole extrusion efficiency, so the production efficiency of porous molds is high. Improvement has a big advantage.
Each company has its own main products, but there are also many products with a small order quantity. For example, the amount of single order is small. If the number of extruded rods is too small, the production cost will be too high. Multi-type molds, especially the existing wear-insulating insulation materials, the two wearing sub-pieces will generally receive orders at the same time. If one-to-many type can be realized, many flow-through links in production can be reduced.
Therefore, the development of porous molds still has a lot of room for development, and there are also many technical improvement spaces. It is necessary to communicate with the industry and work together to promote the development of the aluminum industry.