The Streaks Formation in Hollow Profile Extrusion

In the last years the application of aluminum extruded profiles for the architectural market and for products with aesthetic requirements widely increased. A common concern related to the production of this type of profiles is the appearance of surface defects and in particular any difference in term of color homogeneity on the surface. Among the others, extruded profiles streaks represent one of the most difficult imperfections to deal with especially due to the lack of knowledge on the formation and evolution of this defect. Finally, an important industrial issue is related to the appearance of this kind of defects: immediately after extrusion it is often impossible to determine whether the profile surface is correct or faulty because the streaks usually appear only after profile anodizing thus generating the rejection of the whole batch at a late stage of the production chain with an obvious economical consequences.