One of the defects that occur on the surfaces of aluminum profiles after the extrusion process is surface lines. The main causes of this defect are as follows:

• Die surface imperfections caused by wire EDM cutting.
• Cutter marks in the die pre-chamber.
• Incorrect transition length.
• Improper nitriding.
• High billet temperatures.
• Incorrect extrusion speed.
• Core (inner tube) surface defects.
• Use of non-homogeneous raw material (billet).
• Incorrect graphite material used in the exit table.
• Improper transfer belts.
• Incorrect intermediate (bushing) distance.