Assembly often takes a back seat in the design process. Engineers have a habit of zeroing in on performance solutions and features, while ease of assembly becomes an afterthought. Granted, the assembly process is built to work but not necessarily to work efficiently, thus highlighting the need to align production line realities with design intent before parts hit the shop floor. Otherwise, if assembly wastage is spotted after the fact, then the fix won’t be cheap.

Essentially, an overt focus on performance and product features can lead to a drop in assembly efficiency. Those production line waste costs could have been dealt with by prefacing the process with a Design for Assembly (DFA) stage that streamlined whatever mechanical component assemblage operations were involved.

What’s the big idea behind DFA?

If we’re leaning into the technical side of things, Design for Assembly (DFA) optimizes product design by using key productivity principles. Component counts are minimized and standardized wherever possible. Steps are reduced or moved over to modular assembly stages, simplified so that overly complex production work is cut. The result is a faster, cost-effective manufacturing cycle, one that focuses on bottleneck reducing assembly streamlining and a higher, error-free throughput.

Key DFA principles include the aforementioned parts standardization and modular design processes. A bias toward symmetry and mistake-proofing techniques like poka-yoke further enhance assembly efficiency, preventing elementary errors like improper component orientation. Just like the basics of quality assurance, addressing rudimentary assembly constraints early in the design process improves manufacturing, reduces production costs and boosts overall product reliability.

Getting into automated tooling

All of the above might seem terribly obvious if the assembly process is manually operated. The workersThe WALKMAN continues to be the most referenced DFA example. Image Source: SONY stand or sit, a rubberized belt brings multiple parts forward, and the assembly operation is completed. What Design for Assembly is being asked to do today, though, is come up with streamlining solutions for automated or robotic parts integrating labor. The above strategies still apply, obviously, but now we add features like top-down assembly, machine geometries that are vertically aligned so that the various EOAT (End of Arm Tooling) machines can do their job.

Still on the subject of automation, here’s a short list of machine-oriented features a system designer would expect to see when applying Design for Assembly (DFA) principles in practice:

• Top-down or vertically aligned machine arm and EOAT access must be made available as a consistency-conserving measure to ensure reliable part placement.
• Locating features that incorporate lead-ins and slots, which make it easier for computer sensors to detect so that the assembly process accounts for machine vision limitations.
• Standardized tooling interfaces for grippers and suction cups to hold parts. Flipping and rotation are manipulation actions to be expected but can be reduced when possible.
• Assuring symmetry in a DFA-optimized design helps reduce assembly errors and speeds up orientation decisions, especially for robotic systems.
• Mechanically manipulated sub-assembly modules. This aspect of the DFA strategy also makes scalability a more flexible option, as different modules can be swapped out.
• Parts keying is incorporated to eliminate potential component connection errors. The unique keyways can only be oriented and plugged in one way.
• The use of built-in fasteners reduces the steps taken for machine tools to assemble a module. If the tool lifts to conduct its operation, the fastener is already in place.

Expect to find all of these solutions and more in use in advanced manufacturing environments, including automobile and smartphone factories, in any electronic or mechanical parts integration operation that is susceptible to costly processing bottlenecks.

The advantages of DFA in a manufacturing process

Bigger productivity margins and cost savings, those are the two obvious benefits. If automated arms have a hold of symmetrical components and can press or screw inbuilt fasteners with a greater degree of repeatability, mechanical components go together faster, with fewer errors and less manual intervention. This improves throughput, reduces rework and streamlines quality assurance all the way down the line.

Even assuming part of the process is manually performed, Design for Assembly still pays off. Simplified assemblies, standardized parts, and intuitive orientations reduce training time and handling complexity. Operators make fewer mistakes, assembly speed improves and the hours consumed by manual workers are reduced. Those workers are also a tad more flexible, not in the habit of being programmed when a new assembly stage modification is added, other than by a couple of days’ worth of in-house training.

With larger machine assemblies, think marine engines, robotic gantries or CNC machine frames, the benefits are amplified. These builds often involve heavy components that require cranes or jigs for positioning. DFA-minded design reduces the number of alignment steps, incorporates self-locating features and ensures that parts can be mated in a single orientation without fuss. That means fewer shims, fewer heavy equipment driven retries and less downtime waiting on fixture adjustments.

DFA for fewer assembly bottlenecks and more productivity

A process agnostic viewpoint was assumed while researching this post. That means symmetry held true and certain component integration methodologies were judged to be predictable. That’s not always the case, though. With real-world constraints, such as tight engineering tolerances and varied material/alloy behavioralism, DFA needs to be adaptive. In other words, what works in CAD space doesn’t always play nice with tooling on the factory floor.

That’s why the most successful DFA efforts aren’t just rule-based. In part, collaborative efforts, from assembly technicians to manufacturing engineers, help shape the assembly process. For the rest, there’s the ‘there’s an app for that’ approach.’ We found several software suites that have been specifically coded to aid in the streamlining of assembly workflows. The Siemens PCB manufacturing assembly and test software incorporates DFA analysis as part of an error-free solution. Boothroyd Dewhurst has a dedicated DFA product simplification software package as well. It’s used to calculate the theoretical minimum number of parts required to assemble an item without loss of quality or functionality.

On the Boothroyd Dewhurst Design for Assembly web page, there’s a deeper look at the DFA mindset, plus a brief mention of “Fostering a Collaborative Culture.” Digital solutions won’t get you all the way, then. The true value of DFA emerges when designers, engineers and line technicians sit down together, blueprints in one hand and end-product sales figures in the other, to talk it out and trim the industrial fat using every tool they can access.