Car crushers are large machines that turn a car into a large bucket of scrap steel and the rest of the car into non-ferrous materials, plastics and waste called automotive shredder residue. The glass, fabric, plastic, and all other non-ferrous materials are separated by eddy current magnets in place of heavy media separation. The non-ferrous materials may be referred to as "zorba".[1] Often the profit from the non-ferrous materials covers the operating cost for the shredder.

When a metal shredder starts, the material enters into the tear box through the feeding system. The tear blade is loaded on the box. The material is torn into small pieces through the tear, extrusion and shear of the tear blade, and is discharged from the lower part of the box.

Metal scrap recycling, also called secondary metal processing, is a large industry that processes, in the U.S. alone, 56 million tons of scrap iron and steel (including 10 million tons of scrap automobiles), 1.5 million tons of scrap copper, 2.5 million tons of scrap aluminum, 1.3 million tons of scrap lead, 300,000 tons of scrap zinc and 800,000 tons of scrap stainless steel, and smaller quantities of other metals, on a yearly basis