Causes of convex defects on the four walls of the square tube aluminum profile: After multiple extrusions or other reasons, the working belt of the extrusion die is worn out and pits appear, which hinder the flow of metal along the tongue surface, causing the outside flow rate of the profile to be faster than the inside, causing the four walls Convex. If only one wall or two or three walls protrude, it may also be caused by improper cooperation between the tongue working belt and the die hole working belt, that is, the tongue working belt protrudes from the die hole working belt too long, or it is caused by local wear of the "tongue" Caused by.

　　Repair method: When the wall thickness of the aluminum profile is too small, file the pits of the tongue work belt to reduce the friction resistance, or block the mold work belt. If the wall thickness does not allow filing of the tongue, then a new mold has to be replaced. When only individual wall thickness is convex, it can hinder the working belt at the corresponding wall.