any industrial equipment and instruments in modern industry, such as precision instruments and weak current equipment, require fine, thin-walled, precision extruded aluminum tubing with very accurate cross-sectional dimensions, and their dimensional tolerance control requirements are very strict. The smallest wall thickness of the precision aluminum tube is only 0.4 mm, and its tolerance requirement is ±0.04mm. The requirements for the equipment, molds, and processes of the extrusion production process are quite strict. The industry usually refers to this extrusion technology as precision extrusion. Precision extruded aluminum tubing are generally solved by cold drawing and fine drawing after extrusion, because fine drawing can achieve a dimensional tolerance within 0.02, and can also achieve a high straightness.
Precision extruded aluminum tubing
1 Technical requirement for precision extruded aluminum tubing
Generally speaking, aluminum alloy hot extrusion has a large degree of deformation, changes in extrusion temperature and speed, neutrality of extrusion equipment, deformation of molds, etc., are likely to affect the accuracy of profile dimensions, and it is difficult for them to interact with each other. overcome.
1.1 Requirements for casting rod material
The composition and structure of the cast rod are not uniform, and defects such as inclusions, segregation, coarse grains will affect the flow and deformation of the metal, and cause the size of the product to vary. For precision extrusion, the requirements for the material of the cast rods are more stringent, which must be homogenized, and the crystal grains should be controlled within one level.
1.2 Requirements for equipment
The quality of the extruder affects the accuracy of extruded products. Generally, the tension column of the extruder is required to be a pre-stressed overall structure, and the rigidity and alignment of the equipment should be good. Generally, the maximum allowable deviation between the extrusion shaft, the extrusion cylinder, the die, and the feeding manipulator is less than 1.5mm, usually controlled at 1.2mm Within. For precision extrusion, the center deviation of the mold, extrusion barrel, and extrusion rod should be less than 0.2mm. The extruder used for precision extrusion should have an isothermal extrusion control system and a constant velocity extrusion control system. Speed squeeze control.
1.3 Requirements for tools and molds
The mold is the most direct factor affecting the dimensional accuracy of precision aluminum tube extruded products. To ensure that the size of the extruded precision aluminum tube is unchanged or changes little in the production interruption surface, the rigidity, heat resistance, and wear resistance of the mold must reach a certain level. Requirements.
2 Examples of precision extruded aluminum tubing
The machining tolerances of some small precision aluminum materials are more than half smaller than the special grade tolerances of the JIS standard. Generally, the dimensional tolerances required for precision extruded aluminum tubing are between ±0.04~±0.07mm.
The minimum wall thickness of A1050, A1100, A3003, A6061, A6063 (low and medium strength alloys) small precision extruded aluminum tubing is 0.5mm, and the minimum cross-sectional area is 20mm2. A5083, A2024, A7075, (medium and high strength aluminum alloys) small precision extruded aluminum tubing. The minimum wall thickness is 0.9mm and the minimum cross-sectional area is 110mm2.
Examples of dimensional tolerances of precision extruded aluminum tubing
Size/mm Allowable tolerance of size/mm
JIS special grade small and precise
A 2.54 ±0.15 ±0.07
B 1.78 ±0.15 ±0.07
C 3.23 ±0.19 ±0.07
3 concluding remarks
Precision extrusion is a comprehensive technology. The material, design, and manufacturing of the mold are required to be very strict; the extruder must be advanced equipment; according to different product sections, choose large|different extrusion methods and processes; the aluminum rod needs to be homogenized, and its organization, The performance must be uniform. Only in this way can the requirements of precision extrusion be met.