The "single-mold porous" technology, commonly referred to as the "porous mode," is an advanced extrusion process that significantly improves yield, production efficiency, and profile quality. This method is highly energy-efficient, reduces labor and land costs, and aligns with national energy-saving policies, making it a crucial factor in supporting sustainable development for enterprises.
1. **Mold Design and Manufacturing**
To achieve optimal performance in "single-mold porous" molds, careful attention must be given to the design of the mold structure. The strength of the steel material should be considered, and the spacing between holes should be neither too large nor too small. It is recommended to layout the holes horizontally based on symmetry. If vertical placement is necessary, staggered arrangements are advised. Advanced, high-precision equipment is essential during mold manufacturing to ensure accuracy. For instance, shunt holes and welding chambers are best processed using CNC machining centers, while cavity cutting should use slow wire cutting to maintain verticality, parallelism, and surface finish.
2. **Extrusion Production Process Control**
2.1 **Process Parameters**
2.1.1 **Bar Temperature**
For multi-hole flat molds, the bar temperature is typically maintained between 390°C and 480°C. A ladder-type cooling method is used, starting from the upper limit and gradually decreasing by 10°C for each stage until reaching the lower limit. For porous split molds, the bar temperature range is generally between 430°C and 500°C, following a similar control method.
2.1.2 **Mold Temperature**
The normal mold temperature should be kept between 430°C and 480°C.
2.1.3 **Barrel Temperature (Material Temperature)**
The barrel temperature is usually controlled between 410°C and 440°C, with the upper limit being acceptable under certain production conditions.
2.1.4 **Exit Temperature**
The exit temperature is generally maintained between 520°C and 580°C. Deviations from this range can negatively affect the hardness and quality of the extruded profiles.
2.2 **Process Operation Specifications**
2.2.1 **Aluminum Rod Heating**
Aluminum rods are heated in a bar furnace using zone-controlled heating, either from high to low or vice versa. To ensure proper warming, the porous mold is usually heated from high to low, with temperature settings adjusted according to the number of furnace zones.
2.2.2 **Mold Heating**
Mold heating time is typically limited to 6 hours to ensure even heating. The mold, along with the die pad and die set, should be heated together, but overheating must be avoided to prevent surface defects. When placing the mold in the furnace, it should be positioned away from walls and fan vents, maintaining at least 5 cm clearance between molds. The furnace must remain clean to avoid dust contamination that could lead to surface imperfections.
2.3 **Extrusion Process Control**
2.3.1 **Time from Mold Removal to Extrusion**
The time between removing the mold from the furnace and starting extrusion must not exceed 3 minutes to avoid material speed discrepancies.
2.3.2 **Short Rod Extrusion**
Only short rods (200–300 mm) should be extruded to ensure consistent quality.
2.3.3 **Initial Extrusion**
The front rod should be pressed with a “0†section, and extrusion speed should be gradually increased once the material flows smoothly.
2.3.4 **Discharge Port Protection**
High-temperature pads should be used at the discharge port to protect the surface from scratches. Graphite plates should separate each profile to prevent rubbing and damage.
2.3.5 **Traction Adjustment**
Intermittent adjustments of the tractor’s pulling force are necessary to meet geometric tolerance requirements. Initially, higher tension is applied, then gradually reduced once the material is stable.
2.3.6 **Extrusion Speed**
Normal extrusion speed is typically maintained between 30–40 m/min.
2.3.7 **Quenching**
Quenching must follow the alloy state requirements, either air-cooled or water-cooled.
2.3.8 **Production Interruptions**
Unplanned shutdowns must be more than 3 minutes. In such cases, the mold should be removed and reheated to 500°C. It is recommended to unload the mold after delivery and re-mount it on the machine to avoid potential damage caused by reinsertion.
2.4 **Exit Profile Temperature and Speed Control**
2.4.1 **Adjust Bar Temperature Based on Exit Profile Temperature**
Temperature adjustments should be made based on the exit profile temperature.
2.4.2 **Normal Exit Profile Temperature**
The ideal exit profile temperature range is 520–580°C. Temperatures below 520°C may result in insufficient hardness, while temperatures above 580°C risk over-heating and defects.
2.4.3 **Surface Observation**
If the discharged material appears black, the rod temperature and extrusion speed should be immediately reduced to prevent excessive heat.
2.4.4 **Operator Monitoring**
Operators must continuously monitor rod temperature, exit profile temperature, profile surface condition, and equipment operation. Any anomalies require immediate shutdown to prevent mold damage and extend its service life.
3. **Equipment Configuration for "Single-Mold Porous" Extrusion**
Successful implementation of the "single-mold porous" technology requires not only a stable extruder and high-quality dies but also advanced supporting equipment. This includes double tractors with flying saw machines, mold systems, aluminum rod heating furnaces, and long spindle furnace heat shear technology. These components work together to enhance productivity, improve output stability, and ensure consistent profile quality.
4. **Conclusion**
With continuous improvements in extrusion processes, the "single-mold porous" technology has significantly boosted production efficiency and yield. However, due to variations in equipment, mold materials, and extrusion methods across different companies, the development and application of this technology may vary. Despite these differences, its role in modern aluminum manufacturing remains critical.
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