By Larry Boulden
What happens when a product or machine we design reaches the end of its useful life? Too often, it ends up in a landfill or a furnace. But we have the opportunity to make design decisions that will allow the products or machines we design to be creatively destroyed when their useful life ends.
Designing for Destruction may include preparing a product to biodegrade, or perhaps to explode. But often the endgame for a new design will be eventual recycling, sometimes called demanufacturing. Typically, that involves designing a product so that it can be disassembled or shredded. And so that its components and constituent materials can be harvested and sent along for constructive re-use in future products or machines.
Today, universities and CAD vendors are exploring a variety of ways to support sustainable design. This report will look at design innovations from several sources to make recycling easier. And within the CAD industry, muted rumors tell of system upgrades to come that will simplify the task of designing with end-of-life issues in mind.
Support from SolidWorks…
Increasing concern for recycling and wise resource use has been driven by such legislative initiatives as the European Directives, RoHS, and ISO14000. These efforts help drive a variety of areas including the wise use of materials, chemicals, and end-of-life strategies for various products, most notably automobiles.
In the past, we engineers were charged with considerations such as Design for Manufacturing, Design for Assembly, cost targets, production targets, margin targets, tooling considerations, lead-time and other factors. Now, the new consideration is Design for Disassembly, sometimes referred to as Design for Destruction. Just as manufacturing or assembling is a process to be optimized, disassembly or destruction of products to be recycled is a relatively new process and needs to be optimized.
Professor Tim Gutowski of M.I.T. suggests the following ‘top 10 list’ of considerations during
design to help with later disassembly for recycling:
1. Reduce the number of components
2. Reduce the number of separate fasteners
3. Provide open access and visibility for separation points
4. Avoid orientation changes during disassembly
5. Avoid non-rigid parts
6. Use common tools and equipment
7. Design for ease of handling and cleaning of all components
8. Reduce the number of different materials
9. Enable simultaneous separation & disassembly
10. Facilitate the sorting of non-compatible materials
Eric Leafquist, Product Manager at SolidWorks, suggests the following procedures, and notes that his firm offers design tools to help.
Minimize material types and maximize the use of these materials. After European Directives mandated the recycling of automobiles, the manufacturers drastically reduced the number of plastics used in order to simplify recycling. In SolidWorks, the manufacturer can create its corporate ‘allowed materials’ database with all the structural, physical, thermal and other properties. These data are available for determining things such as weight and cost of the part. These data are also available to feed the SolidWorks Simulation tools to use finite element analysis (FEA) to help ensure material need and part strength. This shorter list of available (allowable) materials may initially make engineers feel constrained in their design options but simulation can help optimize parts. For molded plastic parts, Solution Partner products help simulate the manufacturing of these parts to speed part design and refinement and help develop key aspects like mold runner designs to reduce waste and the need to reprocess post-molding materials.
As designs are required to be packaged more efficiently, tools such as COSMOSFloWorks enable heat transfers checks to ensure proper thermal performance.
Hold products together: Eliminating fasteners typically speeds assembly and disassembly. SolidWorks includes an assortment of Fastening Features to speed the design of snap fit features, alignment bosses, etc – well suited for molded part design. Molding in fastening features often speeds assembly, disassembly and eliminates the cost and complications of metallic fastener and molded-in inserts. A product called Toolbox provides a library of fasteners and standard hardware. Design management can customize this to help control and limit the range of fasteners available for use by engineers in their designs. This helps ensure use of existing parts already qualified for design for disassembly.
Workflow management and design tracking: PDMWorks Enterprise is a product data-management tool. This enables the enterprise to track CAD data and manage the workflow in the product-development process. Materials recycling considerations for key products such as batteries and PCBs can be added to the components. PDMWorks Enterprise can track hazardous substances. This data can be shared with ERP/MRP systems and can further streamline certification processes like RoHS, ISO, and environmental compliance.
SolidWorks enables use of custom material libraries to control the number of materials used in a design.
PCB design and management: CircuitWorks provides two-way data translation between ECAD PCB design tools and SolidWorks. Using CircuitWorks to bring PCB designs into the mechanical product design helps to get accurate 3D representations of the PCB to streamline the packaging design process. This makes it possible to try various designs quickly to help improve the design and minimize material. Properties of the PCB design and electronic components can be imported to SolidWorks.
Design for separating and sorting: Parts made of magnetic materials can be separated by the use of electromagnets. Water can separate low-specific gravity materials such as certain plastics. The user-definable materials database in SolidWorks mentioned before can highlight properties such as specific gravity and magnetic properties. This can help in specifying the appropriate materials to streamline both function and recycling.
Visualizing the design: CAD models allow the design to be viewed from every angle to assess how the product is assembled or disassembled. Can common tools access the product for both of these tasks? How does the product go together or come apart? Exploded views can be created to explain the assembly and the disassembly process graphically, Leafquist concludes.
And from Autodesk…
Another CAD vendor to expand capabilities in this area, Autodesk has announced the Sustainable Materials Assistant. A software add-in available for use with Autodesk Inventor 2009 software, the tool leads to more responsible materials decisions that can reduce environmental impact while still meeting critical performance requirements.
The Sustainable Materials Assistant helps manufacturers incorporate environmental design considerations early through these new capabilities:
Expanded Materials Library: The Sustainable Materials Assistant adds new property fields for materials that are included in the Inventor materials library. Inventor software users can populate these new fields with information about the toxicity, recyclability, carbon footprint and regulatory compliance issues of any of these materials.
Sustainability Report Function: Accessible from the Inventor software’s Bill of Materials Editor, the Sustainability Report analyzes and aggregates the properties based on the materials and components that comprise a given design option. We’re told you can output a report in HTML
format to document, compare and communicate the sustainability of their designs with key stakeholders, helping design teams make informed, environmentally responsible product decisions.
PDMWorks Enterprise provides data management that can track use of hazardous materials in a design. This can be useful in designing plastic products, electronics and other applications.
Sustainable Materials Assistant Download: The Sustainable Materials Assistant is available as a free “technology preview download” on Autodesk Labs, at the web address shown at the end of this article. We’re told that the add-in will operate effectively with all language versions of Inventor 2009, although the Sustainable Materials Assistant’s user interface is English-language only.
More on how design affects recycling
Google “design for recycling” and you’ll find over 975,000 sources of information. One of the truly useful sources is the Systems Realization Lab at Georgia Tech. The SRL has compiled information on how the design of a product or machine affects its recyclability, and this leads to useful guidelines on design of a product that will someday be recycled. The SRL sets these priorities on recycling:
* Highest priority from environmental point of view
* All resources (material and energy) put into product during manufacturing are preserved
* Requires non-destructive disassembly
2) Material recycling
* Most common
* Only materials are preserved, all geometric details are lost.
* Allows for destructive disassembly
* Also done for recovery of valuable material (e.g. gold in electronics)
3) Energy recovery
* Only energy embodied in materials is preserved through incineration or pyrolysis
For remanufacture and re-use, the following processes are typically considered:
* Disassembly (non-destructive)
* Inspection and sorting
* Part upgrading or renewal
For material recycling:
* Material separation (disassembly)
Materials selection: In product design, the materials selected may be the most important factor in recyclability. Guidelines include:
* Avoid regulated and/or restricted materials. These often MUST be recycled, whatever the monetary cost of removal.
* Use recyclable materials
* Use recycled materials, where possible. This increases recycled content
* Standardize material types
* Reduce number of material types
* Use compatible materials if different materials are needed. Single material is preferred however.
* Eliminate incompatible laminated/non-separable materials
These are a major hassle.
Unverferth, a maker of ag equipment, is the latest Autodesk Inventor of the Month. Using design software and digital prototyping technology. Unverferth has virtually designed a pioneering series of soil tillers. Inventor has helped Unverferth to reduce the carbon dioxide released into the atmosphere by farm operations, thus lessening environmental impact of farming.
For manual separation:
* Avoid painting parts with incompatible paint.
* Avoid plastics that can be contaminated by paint.
* Eliminate incompatible laminated/non-separable materials.
For mechanical separation:
* Reduce number of materials as much as possible.
Probably two materials can be economically recovered.
* Choose materials with different properties (e.g., magnetic vs. non-magnetic; heavy vs. light), thus enabling easy separation
* Allow for density separation
* Maintain at least 0.03 specific gravity difference between polymers
* Isolate polymers with largest mass by density
* Eliminate incompatible laminated/non-separable materials.
Other major considerations covered in the SRL database include wiring, fasteners, adhesives, and assembly guidelines. Check them out at the Website cited below.
What is Sustainable Design?
Sustainable design (also referred to as “green design,” “eco-design,” or “design for environment”) is the art of designing physical objects to comply with the principles of economic, social, and ecological sustainability. It ranges from designing small objects for everyday use, to designing buildings, cities, and the earth’s physical surface.
According to Wikipedia definitions, machinery can be designed for repair and disassembly (for recycling), and constructed from recyclable materials such as steel, aluminum, glass, and renewable materials. Careful selection of materials and manufacturing processes can often create products comparable in price and performance to non-sustainable products. Even mild design efforts can greatly increase the sustainable content of manufactured items.
Detergents, newspapers and other disposable items can be designed to decompose in the presence of air, water, and common soil organisms. The current challenge in this area is to design such items in attractive colors, at costs as low as competing items. Since most such items end up in landfills, protected from air and water, the utility of such disposable products is debated.
Why original design is critical
We tend to think of recycling as a sweetness-and-light process that allows reuse of precious materials and saves the environment. Alas, that may be only half-correct when products are not properly designed to be recycled.
Another type of recycling takes place when brokers sell products to be recycled to impoverished buyers in third-world countries. There, far away from environmental controls and safety regulations, individuals crush and burn products to earn a tiny payment, while creating an environmental mess in their own land.
For example, old electronics like TVs and monitors may be shipped to places like Ghana and sold to impoverished residents who use unsafe procedures to harvest tiny bits of recyclable materials. Toxic components are burned over open fires. In one case reported in National Geographic, “Fumes thick with dioxins and heavy metals engulf a young man tending piles of smoldering computer wire in Accra, Ghana. Metals buyers won’t accept wire until plastic insulation is burned off.”
You can read about it in NG, Jan. 2008, pp. 64-87, “High-Tech Trash – Will your discarded TV or computer wind up in a ditch in Ghana?” Abuses like this point up the importance of proper design so that recycling can be cost-justified under safe, environmentally sound conditions.
Sustainable design vehicle tops 2800 mpg
Ladies and gentlemen, start your fuel-efficient engines” were the words that kicked off the 2008 Shell Eco-marathon Americas; and that’s what 300 students from North America did at the April 2008 contest. Mater Dei High School of Evansville, Ind., set a new mileage record at the 2008 Shell Eco-marathon Americas, a challenge to design, build and test fuel-efficient prototype vehicles that travel the farthest distance using the least amount of fuel. The team’s combustion-engine prototype vehicle achieved an astonishing 2,843 mpg. Competition was steep this year with three teams breaking the 2007 mileage record set by Cal Poly.
Mark Singer, global project manager for the Shell Eco-marathon said, “Students participating in this competition are the brains of the future, stretching the boundaries of fuel efficiency and providing solutions to the global energy challenge. Throughout the two-day competition, teams are constantly making improvements to their vehicles, exchanging ideas and inspiring one another to pay attention to their own energy footprint.”
Autodesk served as the sole software sponsor for the event. Check it out at www.shell.com/ecomarathon
Filed Under: 3D CAD, Green engineering, Software