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Causes and solutions for the formation of surface particles of extruded aluminum profiles

May 31,2019.

Abstract: In the extrusion production of aluminum profiles, some small particles on the surface of the profile are adsorbed on the surface of the profile, and the touch is touched, which affects the surface appearance of oxidation, electrophoretic painting and sprayed profiles, and reduces production efficiency and Yield.Therefore, the formation mechanism is analyzed to take measures to reduce or eliminate  the appearance of defects in this type of material.


In the extrusion production of aluminum profiles, common defects are relatively straightforward, such as bending, twisting, deformation, slag inclusion.The defects of "adsorption particles" are difficult to find without careful observation or hand touch.The hazard is that in the production process of electrophoresis and spray profiles, it is difficult to remove, affecting the appearance of the profile and causing waste.Therefore, it is necessary to continuously observe and analyze in the practice of extrusion production, summarize its causes, and take timely measures to reduce or eliminate the emergence of such defects.



1 "Adsorption particles" performance and impact on product quality,

There are more and more ways to surface treatment of aluminum profiles. In addition to general oxidized aluminium profiles, electrophoretic aluminium profiles, spray profiles, fluorocarbon spray aluminium profiles, wood grain paint aluminium profiles, etc. have appeared one after another.The defects of "adsorption particles" have little effect on general oxidized materials, but have a great influence on other treatment forms, mainly hindering the appearance of these profiles.In extrusion production, the extruded profile "adsorbed particles" are carefully observed or slipped on the surface of the profile by hand.In the sawing and splicing process, most of the small particles can be removed by blowing or wiping with the wind.However, some of them are still adsorbed on the surface of the profile due to static electricity.After aging treatment, the particles adhere more closely to the surface of the profile.In the surface pretreatment process of the profile, some may be removed due to the influence of the concentration of the bath, but a small pit is formed on the surface of the profile, and some may not be removed to form a bump.This problem often occurs in the production of electrophoretic and spray profiles.


2 Reasons for the formation of “adsorbed particles”
The influence of the mold
In the extrusion production, the mold is operated under high temperature and high pressure, and the mold is elastically deformed under the influence of pressure and temperature.The working belt of the mold is parallel to the extrusion direction. After being subjected to the pressure, the working belt is deformed into a trumpet shape, and only the edge portion of the working belt contacts the profile to form a sticky aluminum, which is similar to the knives of the turning tool.During the formation of the viscous aluminum, particles are continuously carried out by the profile and adhere to the surface of the profile, causing "adsorption particles".As the aluminum sticking increases, the mold springs back and a bite defect is formed.If the sticky aluminum is piled up more and cannot be pulled out by the profile.



3 Measures to reduce “adsorption particles”

Problems that should be paid attention to in the design, manufacture and use of molds

The design of the mold must meet the calculation requirements of stiffness and strength to reduce the amount of elastic deformation of the mold under pressure.When determining the working belt, the length of the working belt, the form of the empty knife, the form of the neck and the form of the welding chamber should all be considered in the optimum value of the parameters.The selection of the coefficient such as the diversion hole and the diversion hole of the mold is as large as possible within the allowable range to achieve the purpose of reducing the pressure.



4 Conclusion

The influencing factors of "adsorption particles" are mainly three aspects: mold, cast rod and extrusion process.The operation level of the operator is also reflected in these three elements. On the basis of production practice, it is necessary to continuously analyze the problem and summarize the experience, which can reduce or avoid “adsorption particles”, sticky aluminum, rough surface, scratches, profiles. Defects such as tearing greatly improve the yield and production efficiency of the profile.