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Mechanical disassembly

Mechanical Disassembly which incorporates: Brute Force, Shredding / Fragmenting and Granulating

Brute Force: a form of manual separation in which products are broken into pieces to salvage reusable and recyclable parts, components and materials. when designing products consider the following:

  • suitable connections, e.g. integral clips or snap-fits with break points at defined positions,
  • break points to snap off non-recyclable parts,
  • and grasping parts can all help to speed up the disassembly process
  • brute force is often required to break a welded joint

Shredding/Fragmenting: a process in which products are fed into a shredder which fragments, grinds, rips or tears the product into pieces which are then sorted into different materials streams and recyclable or valuable materials extracted. ferrous metals (iron, steel and nickel) are extracted magnetically, aluminium is removed using induction currents. hazardous materials are identified and removed manually (which is costly) everything else becomes waste - however as plastics and other materials are more widely used, the residuals will have to be utilised to a greater degree.

Shredding is ideal for:

  • recovering metals from high metal content items - if the ferrous and non-ferrous materials = 75% or more the product could be shredded and recycled
  • large household appliances and some dispensing equipment.

Not suitable for:

  • appliances which do not have a high metal content as they are not economically viable for the shredding.

Design considerations:

  • increase the use of metals
  • avoid self contaminating combinations of materials
    • e.g. copper can dramatically reduce the value of steel.
  • avoid toxic substances such as cadmium, asbestos and mercury which may not be accepted for shredding.

Granulating: Granulating is the mechanical processing of production scrap, post-consumer plastic packaging, industrial parts, or other materials into fine particles.

Process: "Granulators consist of a feed hopper, cutting chamber, classifying screen, and rotating knives that work in concert with stationary-bed knives to reduce the plastic scrap until it is small enough to pass through the classifying screen. The resulting particles, called regrind, can vary in size from 3 mm to 20 mm" (Modern Plastics Encyclopedia 1995).

  • mechanical recycling of plastics involves melting, shredding and granulation of waste plastics.
  • plastics must be sorted prior to mechanical recycling into polymer types and/or colour.
  • the plastic is then melted down directly and moulded into a new shape or melted down after being shredded into flakes and then processed into granules called regranulate.

Design considerations:

  • granulating is ideal for products with a high plastic content such as small household or gardening appliances and power tools.
  • it is important that there are no contaminates i.e. hazardous materials / components present, therefore these may have to be removed manually prior to granulating. a specialist granulator is used to process WEEE so that different material streams can be easily separated.