In one line: Most of a product’s cost is locked in during design, so design to reduce manufacturing and assembly cost from the start, without sacrificing quality.
Core idea
By the time a design reaches the factory, its materials, part count, tolerances and assembly sequence, and therefore most of its cost, are already fixed. Design for manufacturing (DFM) brings manufacturing knowledge into design decisions early. Its sibling, design for assembly (DFA), focuses on the cost of putting parts together. The broader family, sometimes called DFX, adds test, service, sustainability, reliability and other “-ilities.” Ulrich and Eppinger present DFM as an iterative loop [1].
How it works
- Estimate manufacturing cost:
- components: standard parts plus custom parts, with material, processing and tooling
- assembly: labor and equipment
- overhead: support and indirect costs
- Reduce component cost: understand process constraints and cost drivers, redesign to eliminate processing steps, choose an economical scale for each process, standardize components, and use a “black box” approach to supplier-designed parts.
- Reduce assembly cost: integrate parts, maximize ease of assembly, and consider customer assembly.
- Reduce support cost: cut the number of unique parts, simplify the supply chain, and design so that mistakes are hard to make.
- Consider the impact on other factors: development time and cost, product quality, and external factors such as component reuse and life-cycle cost.
- Recompute the estimate, and repeat until it is good enough.
In practice
The program’s DFM assignment is an informational interview. You prepare structured questions and spend half an hour with a manufacturing expert, ideally at your own company, on how they approach design for manufacturing, assembly, test, serviceability, sustainability and cost, and whether a documented process exists. Engineers are often surprised by how much the expert knows about design decisions they thought were purely technical: a tolerance tightened “for safety” that triples machining cost, a connector choice that doubles assembly time, a part that can only be tested after it is sealed inside the product.
Questions to ask yourself
- Which design decision on my project most drives its manufacturing cost?
- Has anyone from manufacturing, test or service reviewed our design yet?
- Does my organization have a documented DFM/DFX process, and have I read it?
Connections
- Shaped by: Product Architecture. Feeds: Product Development Economics, Supply Chain Management.
- Quality partner: Robust Design. How to learn it: Informational Interviews.
- Capabilities exercised: Connecting Across Disciplines, Resourcefulness, Inquiry.