Seven Design Decisions That Save Hours During Assembly

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• Assembly efficiency is often determined during design, long before production begins.

• Small design decisions around accessibility, alignment and modularity can significantly reduce assembly time, rework and manufacturing variability.

• McKinsey Electronics supports engineering teams with design-informed component selection and manufacturability-focused guidance that helps improve assembly efficiency, reliability and lifecycle performance.

Most assembly problems do not originate during assembly. By the time a technician struggles to insert a connector, reach a fastener or align two components, the decision that created the problem has usually been locked into the design months earlier. Manufacturing teams often encounter the resulting production challenges because production is where the problem becomes visible, but the root cause frequently lies in design choices that seemed insignificant during development.

As products become more compact, integrated and feature-rich, the relationship between design and manufacturing continues to tighten. A design that functions perfectly in CAD may still create unnecessary assembly complexity, longer production times and greater variability on the production floor.

The strongest products are designed not only to function, but also to be assembled consistently, tested efficiently and maintained throughout their operational life.

Here are seven design decisions that can save hours during assembly while improving overall manufacturability.

Why Some Products Take Longer to Assemble Than Others

The difference is often not manufacturing capability. It is the accumulation of design decisions made throughout development. Individually, each decision may seem minor. Together, they shape how quickly a product can be assembled, tested and serviced.

1. Design for Manufacturing Tolerances

CAD models create an idealized version of reality. Components align perfectly, holes sit exactly where they should and every dimension behaves exactly as intended. Manufacturing rarely operates under those conditions.

Every manufacturing process introduces dimensional variation. PCB fabrication, machining, molding and component placement all contribute small dimensional deviations. Individually, these variations may appear insignificant. When multiple parts come together during assembly, however, those dimensional variations create tolerance stack-up.

Connector alignment provides a common example. Two mating components may align perfectly in CAD yet become difficult to assemble because each individual part remains within its specified tolerance range. What appears to be a perfect fit on screen can become a frustrating fit on the production line.

Designing with realistic tolerances creates flexibility where it is needed. Small increases in clearance, alignment features and tolerance-aware interfaces often eliminate assembly issues before they ever appear. The objective is not maximum precision. The objective is predictable assembly under real manufacturing conditions.

2. Design for Connector Accessibility

Few assembly tasks consume more time than struggling with inaccessible connectors.

As electronic systems become denser, designers naturally focus on optimizing space utilization. The result is often connector placement that works electrically but creates unnecessary challenges during assembly and servicing.

A connector may technically fit within an enclosure while still requiring awkward cable routing, awkward insertion angles or limited finger access. In some cases, technicians must partially disassemble other sections of the product simply to connect a cable.

These issues become especially significant in products with multiple harnesses, higher production volumes or long operational lifecycles.

Good connector placement considers more than electrical connectivity. It considers how a technician will physically access, route and secure the connection. Connectors that are easy to reach reduce assembly time, minimize installation errors and simplify future service activities. In many products, a few additional millimeters of clearance can save far more time than the space they consume.

3. Design for Fastener Accessibility

Compact products often create a temptation to place fasteners wherever space is available.

The consequence is that assembly technicians frequently encounter screws located deep inside enclosures, positioned near obstructions or accessible only through specialized tools. What may save a few millimeters of packaging space can add valuable seconds or minutes to every assembly cycle. This issue becomes increasingly expensive as production scales.

An additional ten seconds per unit may seem trivial during development. Across thousands of assemblies, those seconds become hours of labor. Difficult-to-access fasteners also increase the likelihood of assembly errors, inconsistent torque application and service complications later in the product lifecycle.

Designing for fastener accessibility improves more than production efficiency. It improves repeatability. If a technician can consistently access a fastener, they can consistently install it correctly.

4. Design for Modular Assembly

Many assembly challenges originate because products are treated as single integrated systems rather than collections of smaller functional modules.

Modular design allows subsystems to be assembled, tested and validated independently before final integration. This reduces complexity during final assembly while enabling parallel manufacturing operations.

Consider a product containing a display, control electronics, power subsystem and communication module. If each section can be assembled and verified separately, problems are identified earlier and integration becomes more predictable.

The benefits extend beyond manufacturing. Modular architectures simplify troubleshooting, improve serviceability and reduce the impact of future design revisions. When a subsystem changes, the entire product does not necessarily require redesign.

As products continue growing in complexity, modularity increasingly becomes a manufacturing strategy rather than simply an architectural preference.

5. Design Alignment into the Product

Many assemblies still rely heavily on operator skill to achieve proper alignment. The problem with this approach is that people naturally introduce variation. Two experienced technicians may assemble the same product slightly differently, particularly when positioning components manually.

Good designs reduce dependence on operator judgment by incorporating alignment directly into the product. Features such as locating pins, alignment tabs, guide rails and keyed interfaces help components naturally move into their intended positions. Instead of asking operators to create alignment, the design itself establishes alignment automatically.

This approach reduces assembly time while improving consistency. More importantly, it transforms assembly from a skill-dependent process into a repeatable process. That distinction becomes increasingly valuable as production volumes grow.

6. Design for Testability

Testing is often considered after the design is nearly complete. By that stage, opportunities to simplify validation may already be gone.

A product that is difficult to test quickly becomes expensive to manufacture because every unit must still be verified before shipment. Poor access to test points, inaccessible interfaces and complicated validation procedures increase production time regardless of how well the product itself performs. Designing for testability means asking a simple question early in development:

How will this product be verified once it is assembled?

Engineers who consider testing during design often discover opportunities to simplify fixtures, improve accessibility and reduce validation complexity. The result is not only faster testing but also more consistent quality assurance. In many cases, a product that is easy to test is also easier to troubleshoot and maintain throughout its lifecycle.

7. Design for Serviceability

Assembly and serviceability are often treated as separate concerns. In reality, they are closely connected.

The same design decisions that complicate manufacturing frequently complicate maintenance. Hidden connectors, inaccessible fasteners and tightly packed assemblies may be manageable during initial production, but they become far more problematic when a product requires repair, inspection or upgrades.

This is particularly important in industrial and electronic systems expected to remain operational for years.

Products designed with serviceability in mind tend to be easier to assemble because both activities benefit from accessibility, organization and modularity. A technician performing maintenance encounters many of the same physical challenges as a technician performing assembly.

Designing for future access therefore improves more than maintenance efficiency. It strengthens the entire lifecycle of the product.

8. Assembly Efficiency Begins During Design

Manufacturing teams often inherit assembly challenges, but they rarely create them. Most production inefficiencies can be traced back to design decisions made long before a product reaches the factory floor. As products become more sophisticated and manufacturing timelines continue shrinking, the ability to anticipate assembly requirements during development becomes increasingly valuable.

The most successful designs balance functionality with manufacturability. They recognize that performance alone is not enough. Products must also be assembled consistently, tested efficiently and maintained throughout their operational life. The strongest engineering decisions are often the ones that save time long after the design work is finished.

Engineering support extends beyond component selection. Design decisions made during the earliest stages of development have a direct impact on manufacturing efficiency, testing complexity, serviceability and long-term product reliability. McKinsey Electronics works with engineering teams to evaluate technologies from a system-level perspective, considering manufacturability, lifecycle management and long-term performance, enabling you simplify production, improve product consistency and support more reliable electronic systems throughout their lifecycle.