Design for assembly (DFA) is a design strategy that strives to make products as easy, straightforward, fast, and inexpensive to assemble as possible. It refers to assembly during the manufacturing process, rather than customer assembly post-purchase. When done well, DFA reduces the number of parts to assemble, the cost and time of production, and material waste from assembly errors.
The two most important principles in design for assembly are to minimize the number of parts or components in a product and to minimize the number and complexity of assembly operations needed to put the product together. When designers seek to minimize part count, they can use ingenuity to develop more durable products that are easier to manufacture, repair, and maintain. Designers practicing DFA work toward a low part count and pursue simple part shapes, which can be faster and less complicated to assemble.
Minimizing the number and complexity of required assembly operations optimizes a product’s assembly process to be as fast, consistent, cost-effective, safe, and error-free as possible. There are many factors to consider to make a product as simple to assemble as possible, including designing the parts to be easy to handle, symmetrical, or oriented so they can only be aligned and inserted correctly. Using standardized, modular parts can make components more interchangeable.
Also important are a part-assembly sequence with accessible fixings that can be reached without specialist tools, and minimal amounts of bespoke jigs or fixtures required to hold parts during assembly. Finally, whether assembly will be automated or manual affects assembly logistics, as well as the balance between up-front costs vs. efficiency.
Design for assembly may encompass factors like material selection and manufacturing processes when those choices could affect assembly. However, DFA is often considered simultaneously alongside design for manufacturing (DFM), which seeks to make manufacturing processes as simple and cost-effective as possible. When product developers design according to production considerations, DFA and DFM are essentially two sides of the same coin, and they go by the combined term of design for manufacture and assembly (DfMA). This is the full integration of design with production.
Using modular and off-the-shelf parts and components can make assembly designs faster and more efficient because they’re more standardized and interchangeable. This also makes them more scalable and flexible for adapting to different applications. By contrast, custom-machined parts can have the opposite effect.
If aiming for scale, products are more likely to be designed for automated assembly rather than manual. Automation can make assembly faster and more efficient than manual assembly, but automation usually requires higher upfront costs. Automation also affects design for assembly because designers and engineers need to design parts and components that match the assembly capabilities of their automation. Design for automated assembly focuses on parts that can be easily gripped and manipulated by the common tools and grippers on automation and robotics systems, such as electro-magnets, vacuum cups, and three-finger grippers.
Several other DFA considerations apply, regardless of whether the assembly will be automated or manual. For example, minimizing the number of fasteners used in an assembly design—screws, nails, bolts, and so on—can speed up assembly. Rather than using fastening parts, built-in fasteners such as snap fits are often great DFA choices because they’re unlikely to loosen over time. However, snap fits can be susceptible to breakage during disassembly. If disassembly is anticipated, other fastener types would be better.
Designers can also ease assembly by making their assemblies mistake-proof, a method called poka-yoke by its 1960s Japanese innovator, Shigeo Shingo. Mistake proofing means making a product not just easy to assemble, but also very difficult to assemble incorrectly. Designers can do things like place notches or other obstructions that block incorrect assembly procedures. In addition to self-fastening parts, designers can help to mistake-proof DFA products by making part assembly unidirectional and designing self-locating, self-aligning, and self-inserting features.
Most of the assembly design process happens using design for assembly software before physical prototyping begins so that designers can make many changes freely without associated physical costs. However, prototyping comes into play to ensure that self-fastening and other mistake-proofing and DFA features have their desired effect of simplifying assembly.
Taking advantage of design for assembly can lead to benefits throughout a product’s lifecycle of design, manufacturing, and maintenance.
Designs with fewer and simpler parts that implement DFA principles from the beginning can save time in the manufacturing and assembly processes.
Using fewer parts that are easier to assemble can lower manufacturing and assembly costs, and reducing errors through DFA lowers waste expenses as well.
Product developers optimizing assembly design use fewer parts, which can lower a product’s failure rate.
Design for assembly can reduce material use by to helping streamline the number of parts in a product and reduce material waste by simplifying assembly and reducing assembly errors.
The more simplified a product assembly design, the more likely that manufacturers could automate the assembly with robotics systems and other machines in order to make the process more efficient.
Design for assembly makes assembling a product easier—and can sometimes also make disassembly easier, thereby simplifying product repair and maintenance. Note that DFD—design for disassembly—can also require extra considerations and does not always align perfectly with DFA.
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BRYDEN WOOD
London design and engineering firm Bryden Wood, an early DfMA adopter, slashed costs and timelines by manufacturing components with a platform system similar to automotive production for the Forge commercial complex, the UK’s first net-zero office building.
Image courtesy of Bryden Wood
GAMMON CONSTRUCTION
As part of Hong Kong’s reindustrialization, digital contractor Gammon employed the offsite manufacturing of components using DfMA for the 1.1-million-square-foot Advanced Manufacturing Centre. Making thousands of modules at offsite factories helped streamline the installation time from weeks to days.
THE BOLDT COMPANY
An in-depth Autodesk University presentation lays out the valuable lessons the Boldt Company has learned during its long experience with applying design for manufacturing and assembly (DfMA) principles to prefab and modular building products.
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Learn more about CAD software for machine design, which is a form of design for assembly software. Products like Autodesk Fusion and Inventor integrate DFA and DfMA technology, including real-time feedback on manufacturability.
Applying design for manufacture and assembly (DfMA) to prefabricated construction makes the building industry more like advanced manufacturing and amplifies prefab’s benefits by making it faster, cheaper, safer, and more eco-friendly.
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The design for assembly (DFA) concept is to make a product’s assembly simpler, faster, less expensive, and error-free—with the simultaneous goal of reducing waste in materials and labor. Designers accomplish this by minimizing the number of parts needed to assemble and making those parts efficient to assemble.
DFA done well can reduce the cost and time of production, as well as reduce material waste, while resulting in products that are more reliable or easier to repair.
The principles of DFA are:
Design for assembly (DFA) and design for manufacture and assembly (DfMA) are closely related methods in the larger design for excellence (DFX) philosophy. DFA focuses on optimizing designs for quick and error-free assembly, generally by striving to make simpler and fewer parts.
DfMA combines DFA and design for manufacturing (DFM), in which the design focuses on materials selection and the ease and efficiency of manufacturing processes. DfMA can deliver more reliable products, reduce time to market, and lower costs by producing simpler—yet just as functional—products that are more efficient to manufacture and assemble.
