Analysis of main reasons

Because of the insufficient air cooling at the exit of extruder, aluminum profile contacts the swing bed at a higher temperature. The cooling speed of contact part is different from other positions, and there is coarse Mg2Si phase precipitation, which turns black gray after anodizing.

terms of settlement

1. Strengthen the air cooling strength, avoid the interval of profile on the swing bed is too small, and ensure the temperature gradient of air cooling;

2. The factory with conditions shall adopt the method of atomization water cooling and air cooling to completely eliminate black spots.