Environmentally Friendly Process
The facts that make die castings the optimum material and process choice to meet today’s environmental criteria
Most engineers, as concerned citizens, know that the problems of waste disposal in the U.S. are serious. Minimum-content laws have been passed by many U.S. states, mandating the use of recycled materials in new products.
Disappearing waste disposal sites are of even more concern in Europe. Legislation in several countries now bans incineration.
It is clear that the product designer is not only responsible for optimum function and easy fabrication of a product, but also is now required to account for the product's ultimate destiny at the end of its service life.
The Designer’s Material Choices
Other considerations being equal, what the designer of today’s products must distinguish between are theoretical or future possibilities of reprocessing a material, on the one hand, and in-place recycling, on the other.
The fact is that metals can claim the support of an existing world-wide infrastructure that economically collects, reprocesses and channels reprocessed materials back into manufacturing—and allows reuse at costs significantly less than that of virgin materials.
Supporting the automotive industry, a network of automotive dismantlers daily salvages metal auto parts and then places the remainder of the vehicle in the hands of "shredders." The shredding process, which has proven its economic viability, results in the recycling of almost 75% of the weight of a typical car— nearly all of this as ferrous and nonferrous metal. Over 85% of the aluminum in a car is currently reclaimed and recycled.
The nonmetallic portion of a product is generally regarded by recyclers as "fluff," consisting mostly of plastic. Nearly one-quarter of all solid waste is estimated to be plastics, and less than 3% of this plastic is being recycled.
Problems with plastic product recyclability were pointed up by a national task force which requested that plastics marketers refrain from use of the universal symbol for recycling in advertisements, since it was regarded as misleading in relation to plastics.
A Unique Environmental Position
Nearly all metals—and die castings in particular—have always been readily recyclable. Die castings are not hazardous waste and pose no problems in handling or reprocessing, as do some toxic nonmetallics.
Die castings are recyclable components with engineering advantages not available in other metalforming processes. The major cost and performance benefits of parts consolidation possible with plastic components can be carried forward in die casting designs with additional advantages.
Net-shape die castings can be produced with thinner walls than comparable plastic parts, and can provide greater strength and product durability over a longer life cycle—with added serviceability.
Die Casting’s Recycling Circle
Aluminum die casting alloy recycling has been in place almost from the beginning of custom die casting production.
Specifications for aluminum alloys have been developed that provide for a full range of compositions that can utilize various types of recycled metal. Carefully engineered and spectrographically controlled formulas result in precise specification ingot for each of the commonly used die casting alloys.
Over 95% of the aluminum die castings produced in North America are made of post-consumer recycled aluminum. Since the production of recycled aluminum alloy requires approximately 5% as much energy as primary aluminum production, there is a dramatic conservation of nonrenewable energy resources.
Die castings, as opposed to forgings or extrusions, for example, can make far greater use of recycled material. In selecting materials and manufacturing processes to meet consumer concerns, the product designer should ask these questions:
- Does the material allow for efficient and economical maintenance, repair, refurbishing or remanufacturing of the product to extend its life, where this is a design benefit?
- Is the material non-toxic and readily recyclable at the end of its useful life?
- Can the material be recovered and reused in high performance applications?
- Is the necessary infrastructure in place to make recycling of the reclaimed material a practical reality?