In the post-processing stages after the extruder, particularly in the dryer, it is almost impossible to completely prevent the accidental detachment of equipment parts such as bolts. In some cases, even broken extruder blades may mix into the finished feed. Although a grading sieve is typically installed after the dryer, it may not effectively remove these occasional metal contaminants—especially when large-aperture screens are used for producing large-diameter feed. Therefore, installing a permanent magnetic drum before the finished product bin is still essential to ensure product safety and quality.