Design for Manufacturing vs Design for Assembly: Are They Different?

Design for Manufacturing (DFM) and Design for Assembly (DFA) are now combined into a single discipline: Design for Manufacturing and Assembly (DFMA).

14 July 2021

One of the leading approaches used by top electronics engineers, the purpose of DFMA is to take in the entire development and manufacturing process and determine the most efficient and economical strategies.

DFMA then acts as a set of best practices or guidelines. Design and manufacturing engineers use these in the early development stages to guide design decisions, resulting in benefits like shorter development time, accelerated time-to-market, lowered production costs and early error detection.

But what do the two original tenets of DFMA mean once broken down? How do DFA and DFM differ? This post will explore each on its own.

Design for Assembly (DFA)

The focus of Design for Assembly is to reduce assembly costs and make the assembly process more efficient.

DFA specialists examine the number of parts involved in assembly and how easy they are to handle during each stage. The purpose is to eliminate any wrinkles or unnecessary complexities, resulting in a streamlined assembly process.

To achieve this, DFA follows these core principles:

  • Simplify assembly stages: Products should require the minimum possible number of parts. A DFA specialist will study the product’s function and parts to eliminate those that are redundant or unnecessary.
    DFA provides a framework for determining “necessary” parts, asking questions like “Does this part’s movement impact overall function?” and “Does this need to be an individual component, or can it be combined with another?”

  • Design a consistent assembly experience: Ensure there are no situations in which an assembler might confuse similar parts, omit a part, or install one incorrectly.

  • Avoid overly detailed steps: Parts should self-align and fit together like a puzzle; assembly should not require highly precise manual adjustments.

    For example, under the DFA methodology, designers may select rivets over screws and avoid excessive washers.

  • Ease of handling: Avoid parts that are challenging or dangerous for assemblers to maneuver, such as parts that are too sticky, sharp or slippery.

  • Ease of retrieval: Similarly, parts that are extremely small or have angles that easily tangle together make organization and retrieval more time-consuming.

Engineers working within the DFA framework will consider design features of every part like size, thickness, weight, fragility and hand-feel to ensure assembly is as practical and efficient as possible.

DFA allows engineers to eliminate guesswork in assembly and achieve a product of consistent and repeatable quality while keeping costs low.

Design for Manufacturing (DFM)

Both DFA and DFM are intended to reduce costs and optimize processes. The biggest differences between them are the methods and stages of production they address.

While DFA focuses on streamlining and reducing costs in assembly, design for manufacturing (DFM) – sometimes referred to as design for manufacturability – is concerned with reducing overall part production costs and simplifying manufacturing operations.

Leading principles of DFM include:

  • Modularity: Can you easily swap in other parts? Do any parts prove too complex?

  • Minimize reorientation steps: Limit the number of times a part requires repositioning during manufacturing.

  • Reduce the number of manufacturing steps: The process as short as possible and allow for fastest possible time-to-market.

  • Find the best technology: DFM specialists work to determine the best manufacturing method for a project while maximizing potential throughput.

  • Select materials best suited for the manufacturing process of choice: Casting, machining, and forming each have advantages and disadvantages when it comes to material selection. Using DFM, designers can determine the most suitable pairing of materials and manufacturing methods.

  • Review tolerances: Guided by DFM, engineers make tolerance choices that are appropriate for a given production method, or vice versa. This ensures the specified tolerances are reliably attainable.

  • Examine cost dependability of chosen materials: A crucial tenet of DFM is ensuring products can continue to be produced on budget in the long term. DFM specialists look for materials that are known to have significant price increases and will investigate more cost-effective alternatives if necessary.

  • Design for a particular manufacturing process: DFM experts may add insertions or flanges to a part so it can fit into an automated process.

As shown, both DFA and DFM methodologies are effective in creating a shorter, less costly, and more efficient product production. The major difference between them lies in where they focus those efforts: the assembly stage vs. manufacturing stage, respectively.

DFMA fuses these approaches together, allowing a more holistic understanding of the entire production process. In this way, specialists can better see how design and development are closely interconnected.

By following the principles of this combined discipline, engineers can see even faster production times at lower costs, with even fewer hiccups along the way.