DFX : Design for Excellence

Introduction

In today's competitive world, with rising costs of energy, resources, and human labor, the success of a product depends very much on its optimal design.

This optimal device design takes into account several aspects that affect quality as well as cost. Examples of aspects that an optimal design should take into account are:

• Safety and compliance with legal requirements.
• High reliability over the estimated service life.
• Feasibility in a standard production process.
• Low cost of parts used (e.g., tolerating high variability of parts used).
• Minimized negative impact on the environment.
• Low testing costs in the manufacturing process.
• Easy diagnostics (serviceability).

One of the key solutions that help improve design is DFX - Design for Excellence.DFX focuses on optimizing a design in terms of various factors, such as quality, cost, reliability, safety, and more. This article will examine the DFX concept and its main elements, advantages, and limitations.

Design for Excellence

Design for Excellence is a set of technical recommendations that can be applied when designing a product to optimize it[1].

The main idea behind DFX is that many quality and cost issues can be solved early in the design process before they are implemented in reality. DFX promotes holistic thinking and collaboration between different engineering disciplines. Design for Excellence is the linking of many different areas of design. The following list shows the most common aspects:

DFM - Design for Manufacturing

DFM focuses on designing a product with ease of manufacturing in mind. This includes the proper selection of materials and geometries so that the production of that part allows the use of standard tools and processes. DFM is a rather broad concept related to designing for easy and low-cost production. Aspects of assembly and cost reduction are also elements of DFM. These areas of DFM are often distinguished as separate methods, referred to as DFA (Design For Assembly) and DFC (Design For Cost). Read the article: DFM - Design for Manufacturing.

DFA - Design for Assembly

DFA is a subset of DFM, focusing on assembly, i.e., joining multiple parts (components) together. The main goal of DFA is to minimize the number of parts and complex assembly operations. In this aspect, designers try to simplify the manufacturing process through such measures as standardizing the parts used (e.g., introducing a single screw length), symmetrizing or completely asymmetrizing parts, etc. An interesting technique is to add features to the design to implement poka-yoke solutions (e.g., a locating hole in a component, a different shape or color of the part, etc.). Read the article: DFA - Design for Assembly.

DFR - Design for Reliability

DFR focuses on product reliability through failure risk identification, mitigation, and reliability impact analysis. Failure identification relies on tools such as D-FMEA, FMEDA, FTA, computer simulations, PoF (Physics of Failure), etc. Risk reduction should improve the design concept, increase robustness, and apply adequate safety margins. The entire process employs the evaluation of prototypes, various tests (e.g., HALT), failure analysis (FA), and design improvement based on the testing and analysis results. For more information read the article: DFR - Design for Reliability.

DFT - Design for Test

DFT focuses on ensuring that a product is easy to test and diagnose during production. Aspects such as the ability to connect a diagnostic interface (e.g., JTAG, UART), access to test points, and the ability to put the product into a test or a diagnostic mode and then easily check its functions are taken into account. For more information read the article: DFT - Design for Test.

DFE - Design for Environment

DFE aims to minimize a product's environmental impact. This includes designing for product disassembly and material recycling, selecting parts with less negative environmental impact, etc. DFT is related to aspects like Life Cycle Assessment (LCA) and ecodesign. Read the article: DFE - Design For Environment

DFC - Design for Cost

DFC includes consideration of the cost of parts and the assembly process at the initial stage of the design phase when the product concept is still fluid. Sometimes, using slightly cheaper parts significantly increases the cost of the assembly process, ultimately increasing the cost of the entire device. Considering an overall cost is a crucial aspect of the DFC approach. For more information read the article: DFC - Design for Cost.

DFS - Design for Serviceability

DFS strives to ensure that the product is easy to service and maintain throughout its lifetime. Designers pay attention to making access to components, replacement of parts, and repair as easy and quick as possible. For more information read the article: DFS - Design for Serviceability.

Other methods

We can meet other terms such as Design for Quality, Design for Supply Chain, etc. These terms are similar to those explained above and overlap in scope.

Product concept vs. DFX

DFX activities should be carried out in parallel with the design activity. DFX should be considered as early as possible. In my opinion, the key phase is the concept phase, where the most important decisions related to the idea of the product design are made. At this stage, "strategic mistakes" can be made, causing considerable costs to the project later. Already at the concept stage one can:

• Risk reduction. Using D-FMEA, risky aspects of a project can be identified and activities can be focused on those aspects first. Sometimes, the product concept can be changed so that a given risk cannot occur physically. You can also try to reduce the severity of the failure, as in the following example: an electronic system measures temperature from a thermistor connected via wiring. A wiring failure causes a temperature reading error. Solution: implement the concept of "pausability check" and implement a safe mode in the operation of the device
• Design simplification. Removing, standardizing parts or delegating product functions to another system/product. For example, a single FPGA chip can be used instead of multiple digital gates, converters, and processors. Fewer parts reduce PCB size and increase the design flexibility.
• Process simplification. Changing concepts and parts to eliminate some processes. For example: changing THT connectors to SMT results in the elimination of the wave soldering process.

DFX advantages

• Higher quality. DFX helps ensure a higher quality product or service from the very beginning of a project.
• Cost reduction. Solving problems at the design stage is usually cheaper and faster than correcting them after implementation.
• Increasing competitiveness. DFX can help create products or processes that are more competitive in the marketplace.
• Customer satisfaction. A product that delivers higher quality and meets customer expectations.

DFX disadvantages

• Additional workload. Implementing DFX requires spending additional time and resources during the design phase.
• Need to apply interdisciplinary knowledge. DFX requires collaboration between different engineering disciplines and specialists.
• Emphasis on early decisions. DFX requires a systematic approach. Management's emphasis on quick results can result in rushing and overlooking some DFX principles, especially at the conclusion stage.

Summary

DFX - Design for Excellence is a design approach that promotes optimization of product design in terms of manufacturability, cost, reliability, and other factors. Implementing these DFX principles can help create products that are more competitive, more efficient, and more satisfying to customers. At the same time, cooperation between different engineering disciplines is required, and an awareness is needed that quality, price, and design reliability are key aspects starting at the early design stage.

If you are interested in how Elon Musk implements DFX principles with a bit more perspective, read our article: Five-step design method by Elon Musk.