Design for manufacture (DfM) was introduced as a conceptual way of ensuring challenges that appear in a project’s later stages are given due consideration early on when easier and cheaper to address.
When embarking on a new project the start point will be the ‘voice of the customer’ embodied in a detailed specification. Achieving this specification is the design team/engineering department’s responsibility. Initial steps are reviewing the specification and deriving a concept.
At this point, there are often as many questions as answers. Some will be answered by the specification, while others will need more input. Examples include:
• What is the product’s operating environment?
• Is weight an important factor?
• If battery-powered, how long must the device operate between charges?
• Must any safety standards be met?
• How/where will users operate the device?
In larger organizations, the engineering department may have specific teams dedicated to disciplines such as mechanical, electronics hardware, software development and interface/user experience, while in smaller companies, several disciplines may be the responsibility of a single person.
Supply chain, manufacturing, quality, sales and marketing will also have roles to play in the project. Often this involves giving input and opinions on key trade-offs, such as adding a larger display (reducing battery life) or adding functionality (making the product larger). The whole team must buy into these balanced decisions.
Concept of DfM
DfM aims to ensure the project’s later stages are considered from the outset, delivering a product that is easy to manufacture, whether in-house or subcontracted. Generally, the earlier stumbling blocks are identified, the easier, quicker and cheaper they are to resolve. This is best achieved by integrating product design and process planning under a single responsibility.
Most projects will require consideration of:
• Purchasing raw materials
• Approved supplier policies
• Production planning
• Test engineering
Often a set of design and manufacturing guidelines is put in place to ensure the wider project team considers and meets all DfM requirements, plus other project goals.
Communication is key, so decisions can be shared, risks identified and solutions bought into. For example, a suitable microcontroller may be available but not from an approved supplier. Likewise, a novel component may save on BoM costs but require thousands of dollars in tooling. The team needs to agree, as decisions may spawn new tasks.
DfM for procurement professionals
While the supply chain will be involved in most aspects of the project, areas of particular focus include:
Component choice: Once the initial BoM is available, questions include:
• Is a component already being used elsewhere to benefit from economies of scale/reduced inventory? If not, is a suitable component being used elsewhere?
• Many common discrete semiconductors and ICs are available in different package types. If one type is already being purchased, why has engineering chosen a different type? Is production tooling available for the new style?
• Over-specification of tolerances drives costs up, especially with passive components, such as capacitors and resistors where tolerance is important. Check if the design can accept a lower tolerance or different material as both can impact cost and availability.
Component availability: No matter how simple a component, non-availability will prevent production. Consequences range from downtime costs to lost sales revenue.
• A BoM risk assessment should be conducted with components at risk of shortages identified. New suppliers should be qualified early, with trusted suppliers preferable.
• Design guidelines should include alternate components where possible. Sole-sourced components must be highlighted and signed off. A special supply chain approach may be needed, such as increasing inventory of these components.
• Tools exist for early obsolescence warning and should be used to identify problems.
Make or buy?: This decision depends on design complexity, approvals and planned sales volume. Often seen as an engineering decision, the ramifications are wide and varied. With availability of modules or system-on-chip (SoC) ICs, there is greater opportunity to purchase pre-configured solutions.
• Home-spun designs achieve exact parameters, although some challenges include power and safety. Modules will carry approvals, making end product approval easier and cheaper. They will also be optimized for efficiency, EMI and space.
• While a module may cost a little more, the hidden costs of parts inventory and assembly should be considered. Generally speaking, the lower the anticipated sales volume, the more modules stack up.
Risks while sourcing: Prevalence of counterfeit components makes securing the supply chain more important.
• There are many ways counterfeit components and modules can enter the supply chain. Working with reliable suppliers—approved by manufacturers—is important, as is insisting on full component traceability.
• Unscrupulous suppliers may repackage an unrelated device inside a package purporting to be another. While many are easily detected, some may operate similarly but lack performance. These can be time-consuming and costly to identify. Only thorough testing (including x-ray) can confirm legitimacy.
• In certain applications, such as medical, safety compliance is incredibly important. Full documentation should be supplied with components, with particular attention paid when standards are revised to ensure the components meet the latest version.
Global issues: Events such as natural disasters, pandemics, wars and market instability can affect supply of components or the raw materials they depend on.
• If sourcing from one region or sole-source suppliers, keep abreast of local news.
• Shortages of raw materials can affect supply. Components that could be affected should be visible to the supply chain team.
• Be aware of seasonal fluctuations—for example, components used in gaming consoles can be hard to source running up to Christmas.
• Depending on a company’s ethical stance on issues such as the environment or modern slavery, ensure these issues are not lurking in the supply chain.
• A risk assessment for natural disasters is prudent, especially for factories susceptible to earthquakes or floods. This should include knowledge of whether the supplier uses sub-contractors as these can change and may alter the risk level.
Tools supporting DfM
Suppliers such as Mouser can advise on DFM strategies and provide helpful tools. For example, Mouser’s Forte BoM tool offers a free, convenient way of managing BoMs with features including:
• Configurable BoM import
• Correct part confirmation via confidence indication
• Evaluation of possible stock and obsolescence issues
• BoM amendments directly within the tool
• Checking price breaks for multiple quantities
• Export, share and print out BOMs