Design for Disassembly (DFD) is, and increasingly will be, at the heart of developing circular business models.
The technological revolution and rapidly changing trends imposed by marketing have led to shorter product lifecycles and increased demand for ever-new products.
Clearly, this trend is not sustainable. It is not sustainable on an environmental level, both in terms of the exploitation of natural resources and the production of waste. It is not sustainable economically, especially if there is no access to quality post-consumer raw materials.
How to get quality post-consumer materials?
Design for Disassembly is one sound answer!
It is a design methodology that, by evaluating characteristics such as shape, size, functionality, modularity and materials, is able to develop industrial products that can be easily disassembled. Their composing materials can thus be re-introduced into new production processes.
Design for disassembly principles
When designing products with the goal of achieving easy disassembly, 3 factors must be primarily considered:
- Minimise the number of components and materials;
- Use the designs and mechanical characteristics of components to facilitate mechanical and non-chemical assembly and disassembly;
- Use structures composed of easily separable sub-assemblies or modular parts;
- Maximise hierarchical simplicity of connections between parts by minimizing connections between sub-assemblies and between components;
- Maximise and simplify accessibility to harmful components and materials (to be properly disposed of) and those of higher economic value (to be reused, remanufactured, or recycled-up-cycled);
- Minimise the number of components that are difficult to handle;
- Minimise the operations required for disassembly.
Fasteners and joining systems play an essential role in order to increase the efficiency of the disassembly process. Best guidelines suggest:
- Minimise the number and types of fastenings used in assembly.
- Use fastening systems that are easy to remove and quickly reversible. For example, the use of adhesive substances or welding with additional material should be avoided.
- Use joining systems made of the same material as the components to be joined. This avoids the need of being separated/extracted.
- Maximise and facilitate the accessibility and recognizability of the joining points.
- Minimise the number and types of tools needed to remove the joining systems and avoid the need to operate on multiple points simultaneously.
The most time-consuming step in a manual disassembly process is precisely the localization of the fasteners, this accounts for 1/3 to 2/3 of the total disassembly time (Duflou et al. 2006; Peeters et al. 2015).
Making the localisation of joints easier and more visible
The functional and marketing requirements of certain product categories tend towards miniaturisation of devices. To make it easier to locate fasteners, research on such systems has led to the development of joining devices that are sensitive to:
- TEMPERATURE: such as tapes containing thermoplastic expandable microspheres (Bain and Manfre, 2006; Kawaguchi, 2004). These encapsulate a hydrocarbon liquid which gasifies and expands when exposed to heat. By increasing in volume, these tapes act as a pressure activator by being able to separate the surfaces adhering to it.
- PRESSURE: as when the joining systems is equipped with a cavity that contracts when the surrounding air pressure increases. Recently, a second generation has been developed that makes use of a closed-cell elastomeric foam which, due to the increase in pressure, causes a deformation that can unlock the geometric interlock. This technology succeeds in reducing size while retaining robustness (Peeters et al., 2015; Willems et al., 2007 a,b) and reducing disassembly time.
For example, for the housing of an LCD TV the disassembly time is seen to be reduced by 70 to 90% and the operational cost is assumed to be 30% of the cost of manual disassembly (Peeters et al.,2016).
A study published in the Journal of Cleaner Production (Peeters et al., 2016) assessed the environmental impact of implementing these fasteners in a television, a setup box, and laptop.
The impact was calculated based on the production of adhesives for temperature-sensitive systems, and the production of polystyrene and polybutadiene rubber for pressure-sensitive systems. Temperature-sensitive systems are found to be the least impactful.
A limiting factor in the economic recovery and recycling of complex assemblies/assemblies is indeed the separation of materials into pure material flows. This results is the outcome of the ability to obtain quality and economically sustainable post-consumer raw materials. Economic sustainability is strongly influenced by separation times during disassembly. These can be reduced through careful material selection. For example, elements and junctions of the same material may not be disassembled, yielding significant benefits by saving labor cost and time, thus making recycling and/or material recovery economically viable.
As such, designers should:
- Minimise the variety of materials, maximise material compatibility, and prefer recyclable materials.
- For example, in the case of plastics, it is good practice to avoid metal inserts or reinforcements or to use composite plastics. In order to give greater rigidity to the product, it is preferable to intervene on its geometry, foreseeing for example different types of ribbing and reinforcement patterns that can be square, rectangular, rhomboidal, triangular or honeycomb.
- Avoid or minimise surface treatments and adhesive labels.
- Codify different materials for easier identification and separation.
The materials challenge: combining design with Sustainability
Clearly, in an ideal situation, only one type of material should be used. But it is important to consider the different chemical-physical performances so that the choice falls on materials, or on a material, able not to compromise the structural requirements of the product. In fact, the material chosen must be sustainable at the source, but also during the use phase, guaranteeing durability and suitability for the function it will have to perform.
Together with the functionality, it is important to consider the volume and weight of the product. These characteristics, in fact, can impact on the transport phases, making them more or less environmentally impactful.
The choice of materials also influences the end-of-life phase, not only for the rate of recyclability and circularity of the product. Guaranteeing economic sustainability is fundamental. To achieve this, it is necessary to find materials that are already widely used, even in different contexts, so that they can effectively become part of the market for recycled raw materials.
Why should we implement Design for Disassembly techniques?
There are several good reasons:
- Reducing waste in manufacturing and recovery processes using DfD techniques can significantly reduce manufacturing costs and enable greater technical efficiency;
- The modular design principles within DfD techniques allow for greater flexibility during product development, shorter development times, and reduced development costs;
- Implementing DfD into a design specification allows the product and its components to be more suitable for reuse or recycling when it has reached end-of-life, thereby reducing the amount of resources required to create new products.
To recap, optimizing the disassembly process leads to numerous benefits. It offers the opportunity to reduce the time required, lowers the cost of operations, decreases the energy needs, and automates the process.
In the next article we will discuss a concrete example and we will draw the conclusions about the contribution of design for disassembly to the creation of sustainable business models and we hope that a lively debate in the issue will start after that.
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Alessia Cerasoli, Sustainability Consultant in Exsulting