DFMA: SHOULD COSTING
DFMA: PRODUCT SIMPLIFICATION
What is part consolidation?
Part consolidation is the practice of redesigning a product to combine multiple separate parts into fewer parts that perform the same functions. A bracket, a housing, and two stiffeners become a single casting. Three sheet-metal pieces and six spot welds become one stamping. The functions remain; the part boundaries disappear.
Part consolidation is not guesswork. The DFA (Design for Assembly) methodology provides three systematic criteria for evaluating every part in an assembly to determine whether it genuinely needs to exist as a separate piece—or whether it can be combined with an adjacent part.
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Why part count matters
Part count is the single strongest predictor of product cost, quality, and time-to-market. Every additional part in a product adds cost across multiple dimensions:
This is why part consolidation produces outsized returns compared to other cost-reduction methods. Optimizing the manufacturing process for an individual part might save 10–15%. Eliminating the part saves 100% of everything associated with it.
The three criteria for minimum part count
The DFA methodology, developed by Boothroyd and Dewhurst, provides three criteria for evaluating whether each part in an assembly needs to be a separate piece. A part must be separate only if it meets at least one of these criteria:
Does this part need to be separate?
- Relative motion: Does the part move relative to all adjacent parts during normal operation? (e.g., a hinge pin, a sliding contact, a rotating shaft)
- Different material: Must the part be a fundamentally different material for functional reasons? (e.g., an electrical insulator adjacent to a conductor, a rubber seal against a metal housing)
- Assembly/disassembly: Must the part be separate to allow assembly or disassembly of other parts that meet criteria 1 or 2?
If a part doesn’t meet any of these three criteria, it is a candidate for consolidation with an adjacent part. This doesn’t mean it must be consolidated—manufacturing feasibility, cost, and other factors still apply. But it means there is no functional reason for it to be separate.
- Rotating shafts, bearings, moving linkages (criterion 1)
- Seals, gaskets, insulators, lenses (criterion 2)
- Removable covers for service access (criterion 3)
- Separate brackets, stiffeners, and reinforcement plates
- Multi-piece housings split for manufacturing convenience
- Decorative covers on internal components
- Most standard fasteners (screws, washers, clips)
What consolidation eliminates
When you consolidate two parts into one, you don’t just save the cost of the eliminated part. You save everything that part carried with it:
| Cost element | What disappears | Typical impact |
|---|---|---|
| Manufacturing | The part’s entire production cost (material, process, setup, tooling) | Direct cost savings |
| Fasteners | Screws, washers, clips, adhesive that joined the parts | $0.02–$0.50+ per fastener × volume |
| Assembly labor | Handling, insertion, alignment, and fastening operations | 3–12 seconds per eliminated part |
| Tooling | Separate fixtures, molds, or dies for the eliminated part | $5K–$100K+ per tool |
| Inventory | SKU, storage, ordering, receiving, and tracking | Carrying cost + stockout risk |
| Quality | Inspection, tolerance stackup, and potential failure mode | Fewer defects, less rework |
| Supply chain | Supplier management, POs, receiving inspection | Procurement overhead |
The cascade effect
Part consolidation often triggers a cascade of secondary savings that amplify the initial benefit:
Eliminating a part typically eliminates 2–6 fasteners. Those fasteners had their own handling, insertion, and tightening time. In high-volume production, this adds up fast.
Every joint between two parts introduces tolerance stackup. Consolidation reduces the number of interfaces, improving dimensional accuracy without tightening individual part tolerances.
Fewer parts means fewer stations, fewer grippers, fewer feeders, and simpler programming. Assembly automation becomes more feasible and less expensive.
Every interface is a potential failure point: a seal that leaks, a fastener that loosens, a joint that fatigues. Consolidation eliminates interfaces and the failure modes they create.
Manufacturing processes that enable consolidation
Part consolidation often requires changing the manufacturing process to one that can produce more complex geometry in a single operation:
Combine multiple machined or fabricated aluminum/zinc parts into a single near-net-shape casting. Excellent for complex housings and structural components.
Consolidate snap-fit assemblies, integrate living hinges, and combine structural and cosmetic functions in a single molded part.
Produce complex internal passages and thin walls that would require multiple machined pieces. Ideal for consolidating valve bodies and manifolds.
Progressive dies can form, pierce, and bend complex bracket assemblies from a single blank, eliminating welded or fastened multi-piece brackets.
3D printing removes nearly all geometry constraints, enabling consolidation that no traditional process can achieve. Best for low-volume, high-complexity parts.
Custom extrusion profiles can integrate mounting features, channels, and stiffeners that would otherwise require separate attached parts.
DFM analysis compares the cost of the consolidated design across process alternatives, ensuring the chosen process delivers the lowest total product cost—not just the lowest individual part cost.
The cost tradeoff: part cost vs. product cost
A common objection to consolidation is that the consolidated part will be more expensive than any single original part. This is often true—and completely irrelevant. Here’s why:
| Cost element | Before (3 parts) | After (1 part) | Change |
|---|---|---|---|
| Part A (bracket) | $2.40 | $4.80 | |
| Part B (housing) | $3.60 | ||
| Part C (stiffener) | $1.20 | ||
| 6 fasteners | $0.72 | $0.00 | −100% |
| Assembly labor | $1.85 | $0.30 | −84% |
| 3 separate tools | $1.10 amort. | $0.65 amort. | −41% |
| Total product cost | $10.87 | $5.75 | −47% |
The consolidated part costs $4.80 vs. $7.20 for the three original parts—a 33% reduction in part cost alone. But the product-level savings are 47% because you also eliminate fasteners, assembly, and tooling. This is why you must measure consolidation at the product level, not the part level.
Worked example: motor controller housing
An illustrative DFA-driven part consolidation on an industrial motor controller housing:
| Metric | Before | After | Change |
|---|---|---|---|
| Total parts | 29 | 8 | −72% |
| Separate fasteners | 16 | 2 | −88% |
| Assembly time | 210 sec | 72 sec | −66% |
| DFA index | 7% | 62% | +55 pts |
| Manufacturing cost | $41.20 | $22.60 | −45% |
The original design used CNC-machined aluminum parts bolted together. DFA analysis identified 21 parts that failed all three minimum-part-count criteria. The redesign consolidated the housing into a single die-cast part with integrated mounting features, snap-fit covers, and molded-in cable routing—eliminating 14 fasteners and 21 parts.
Values are illustrative. Actual results depend on your design, volume, and process. DFMA calculates these from your specific assembly.
When to pursue consolidation
- Assemblies with DFA index below 20% (most parts don’t meet minimum-part criteria)
- Products with high fastener count relative to functional parts
- Multi-piece housings, brackets, or structural assemblies
- Products moving from low-volume machining to higher-volume production
- Competitive teardowns revealing simpler competitor designs
- Consolidated parts that exceed process capability (too large, too complex)
- Tooling investment that doesn’t amortize at current volumes
- Service/repair access requirements that mandate separability
- Regulatory requirements for inspectable joints or replaceable components
Frequently asked questions
What is part consolidation?
Part consolidation is the practice of combining multiple separate parts into fewer parts that perform the same functions. It reduces assembly time, fastener count, tooling, inventory, and total product cost. The DFA methodology provides systematic criteria for identifying which parts can be combined.
How do you identify part consolidation opportunities?
DFA (Design for Assembly) analysis applies three criteria to every part: (1) Does the part move relative to its neighbors? (2) Must the part be a different material? (3) Must the part be separate for assembly or disassembly? If the answer to all three is no, the part is a candidate for consolidation with an adjacent part.
What are the benefits of part consolidation?
Fewer parts means less assembly time, fewer fasteners, less tooling, lower inventory cost, fewer suppliers, fewer quality failure points, lower weight, and simpler supply chains. Typical DFMA case studies show 40–60% part count reductions with proportional cost savings of 20–50%.
Does part consolidation make individual parts more expensive?
Sometimes yes. A consolidated part may be more complex and slightly more expensive than any single original part. But it replaces multiple parts plus their fasteners, handling, and assembly operations. The total product cost almost always decreases because assembly cost reductions and eliminated parts far outweigh any increase in individual part complexity.
How does DFA analysis support part consolidation?
DFA analysis systematically evaluates every part in an assembly against minimum-part-count criteria, identifies which parts are candidates for consolidation, quantifies current assembly time and cost, and projects the assembly time and cost of the consolidated design. It provides both the roadmap and the business case.
What manufacturing processes enable part consolidation?
Die casting, injection molding, investment casting, 3D printing/additive manufacturing, and sheet metal forming are particularly well suited because they can produce complex geometries in a single operation. DFM analysis compares process alternatives for the consolidated design.
Find the parts that don’t need to exist
Bring an assembly. We’ll run the DFA minimum-part-count analysis and show you exactly which parts are candidates for consolidation—with the cost impact quantified.
