We frequently hear that design reuse is important. You don’t have to be an engineer to understand the benefits of reusing designs and inventory parts instead of designing them from scratch over and over again. The concept is intuitive, in part, because there are so many real-world examples. Here’s just a few:
- During design, incorporating off the shelf parts and assemblies save design time and manufacturing costs. If a part is not available commercially and has to be fabricated, reusing an existing design can still save significant time and money by accelerating design, testing and manufacturing ramp-up time.
- In manufacturing, using common parts across multiple product lines can lower the need for special tooling, improve workforce efficiency and reduce parts and raw materials inventory.
- A supply chain that manages a smaller parts portfolio and a smaller supplier base is leaner and more efficient.
- During service operations, common parts and assemblies reduce diagnosis and repair time and require smaller spare parts inventory.
If the benefits of design reuse are so obvious, why do we need to continue discussing it? Is there more to design reuse than meets the eye? I think so, yes.
By focusing on physical objects, parts and the accompanying artifacts such as 3D models and design drawings, we may be missing a less tangible yet potentially more powerful reusable commodity. Knowledge.
Knowledge
Design, testing, manufacturing and servicing products both use and create a wealth of knowledge and a wealth of experience. While some of this knowledge is encapsulated as formal methods, design rules and engineering software, most of it is manifested only as an outcome of knowledge and experience.
In other words, the rationale and intent behind design decisions are not captured and formalized; which is why finding and reusing knowledge isn’t easy.
Let’s consider why direct reuse and the accompanying tacit knowledge are important.
Design intent
In a previous blog
Check-in, Check-out, Check-in, …. Why bother? I know where my CAD Files Are! I described how an engineer modified a design during a cost reduction campaign and removed a bunch of presumably spurious resistors from an electronic circuit. The negative impact of that change was not detected until the vehicle was already in production. If the engineer had used a tested and proven design that included the rational for those transistors, this incident could have been avoided.
Manufacturing
The manufacturing process, especially during volume production ramp up is very knowledge intensive. In
Take Control of Your ECO Process, I discussed the frequency of manufacturing related engineering change orders (ECOs). In a study conducted at a manufacturer of heavy equipment, 36% of the ECOs were a consequence of manufacturing and assembly problems.
Reusing parts already in manufacturing instead of implementing a new manufacturing process for new parts eliminates the need for new tooling and work instructions and reduces the scrap and tool breakage that are typical in early manufacturing.
Yield, Quality and Warranty
Some of the design and manufacturing arguments I discussed above could be construed as relatively self evident. But manufacturing organizations can take knowledge reuse one step further – by analyzing the ramp up experience and overall product manufacturing and service of other products of the reused parts. Whether off the shelf or of unique design, product management can get a headstart in understanding the new product: ramp up, quality, and even service requirements and warranty expenses.
Build vs. Retrofit vs. Buy
Often, design engineers can choose one of three options:
- design and manufacture a part or assembly more or less from scratch,
- retrofit an existing part, or
- look for a commercially available part that meets the requirements
Although the rule of thumb should always give the highest priority to using off the shelf parts, designers and product owners often have reasons to argue the case for their own design, which may or may not be possible to prove using objective economic rationale.
Typical arguments for designing and manufacturing a part instead of using a commercially available alternative focus on early lifecycle phases, and make an argument for a design that meets the equipments better. But design engineers tend to overlook manufacturing and maintenance costs that, in many cases, can offset the benefit of the improved design. A design reuse culture that understands the value of manufacturing and service experience can improve the fidelity of build vs. buy decisions.
Recommendations
With clear business rationale for parts and design reuse, product organizations need to take a two-pronged approach.
First, facilitate process and a culture of reuse. This includes emphasizing the direct benefits in design time, cost, and inventory, as well as the indirect value of extensive application of tacit knowledge throughput the product lifecycle. Utilizing a centralized PDM system and “connectors” to other enterprise systems can help facilitate knowledge capture and reuse, and product organizations should review the existence of knowledge “islands” hiding in less formal tools such as spreadsheets and email exchanges.
Product engineering should also realize that simpler and modular product architecture is not only easier to design, build and maintain, but also facilitates easier reuse. At the same time, a modular approach leads to designs and actual parts and assemblies that are easier to reuse, thereby self-enforcing the process.
Cabe Atwell
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