ENVIRONMENTALLY CONSCIOUS DESIGN (ECD) PRIMER
PRINCIPLES OF ECD
Good Design Principles are:
1. Teamwork - The difference between
good and bad designs,
2. Minimize the number of parts,
3. Design so the assembly can be completed in a layered process,
4. Consider easy part handling,
5. Design mating parts that are easy to insert and align,
6. Avoid expensive fastening operations, i.e. use threaded fasteners,
7. Avoid parts that will cause tangling with identical parts,
8. make parts symmetrical to aid in automatic orientation,
9. If symmetry can't be achieved than exaggerate the asymmetric features,
10. Avoid adjustments.
According to T.E. Graedel and B.R. Allenby (1995) following principles for ECD should be accomplished:
* All material that enters a
manufacturing process should leave as part of a product,
* All energy should result in useful work,
* Products should be made of abundant, nontoxic materials,
* Products should be designed so that useful products can be made from them at the end of their life,
* Pursue minimum packaging and maximum material recycling / reuse
Products should be design to promote the practice of 3R's :
- Remanufacturing, and
In addition, designers must cooperate with manufacturing processes to ensure
that design decisions don't create environment-related manufacturing problems.
It has to be considered how materials, fasteners, structure, treatment, geometry impact ECD and 3R principles.
An estimate of environmental impact of the designed part can be obtained by defining reprocess ability indexes RPI. They have to characterize following parameters of the analyzed part:
* Removable features,
* Relative stress level,
* Amount of mating (moving) contact areas.
Examples of RPI terms:
The goal is to minimize the RPI computed as: