Industrial Shredders and Crushers for Material Recycling

Crusher and shredder.
Size reduction of various materials (not only plastic) is usually
done with two types of equipment: the crusher and the shredder.
Each machine has its own features, but over the last few
years recyclers have increasingly been installing shredders, thanks to
such features as:

• longer operating life without operator intervention
• versatility
• durability
  Shredders differ in:
• the number of rotors (1, 2 or 4)
• the presence of an upper ram (for processing materials with
  low bulk density)
• the size of the feed opening
• various rotor parameters (length, diameter, material, the type
  and number of seats and of the knives themselves, rotation speed)
• the power of the main motor (it determines the first obvious
  parameter, throughput, as well as a second, less obvious one,
  the tearing force, which sets the toughest material
  that can be processed)
  These are the main parameters by which such equipment is selected;
  the remaining parameters are finer details and their choice depends on the
  specific project.
  One of the most widespread shredders in the Russian Federation is the one from
  GENOX, with a 37 kW motor, a capacity of up to 500
  kg/hour and a useful service life of at least 15 years (again,
  depending on operating conditions).
  The shredder is equipped with a hydraulic ram 800
  mm wide and a rotor diameter of 400 mm, while the large feed opening
  of 1400 x 1530 mm allows fairly large pieces of
  many materials to be processed.
  Among such materials, we have seen the processing of
  medical waste, leather, wood, chewing gum packaging,
  cable, bumpers, tires and so on.
  Crushers for polymers
  Crushers are divided mainly by power, feed opening size
  and knife type.
  The choice of crusher should be based on the material. After that
  you can determine:

1. Knife type — the most common is the "dovetail", which is
   named for the similar shape of the knives. The rotor usually has 3 rows
   of such knives, as well as stationary knives on the frame — 2 pairs — the knives on
   the frame are straight.
   This type of rotor is used for processing: films, sacks,
   big bags, canisters, barrels, thin-walled (wall up to 5 mm) pipes and other
   materials. Not processed: wood, fabric, leather, etc.
   These crushers are particularly suitable for PET recycling — this material
   is one of the most abrasive (it aggressively affects the
   cutting surface). And in a crusher the knives are easier to change than on a shredder
   (3 hours on a crusher, versus one working shift — up to 12 hours — on a shredder).
   Therefore, because of knife wear, the customer always keeps a spare set and
   sends the old one for sharpening.
   Various modifications exist based on this rotor
   (straight knife, dovetail knife split into 2 parts to relieve
   loads, and others).
   1.2. The second knife type is the "pyramid", also called the "claw",
   "stepped", etc. Its knives are arranged like a staircase; they are
   usually square and dense. A rotor can have from 4 and,
   for example, up to 20 of them (depending on rotor length). There are also
   stationary knives, as in any other crushers. These
   thick and strong knives make it possible to process dense materials with
   a thick wall (again, we are talking about plastics): thick-walled pipes, sprues,
   rejected injection-molded products and others.
2. Rotor — an important difference from the shredder is the rotor
   speed — in a shredder it reaches 80 rpm, while in a crusher it can be up to
   500 rpm; there are low- and medium-speed crushers, but even so it is from
   150 rpm. For this reason the shredder has an advantage — it is more
   durable and, if foreign material gets into it, the damage to the
   equipment is minimal.