Design for X (DFX) Methods

Albert Einstein once said, “The best design is the simplest one that works.” But a simple design can be difficult and time-consuming to create.

However, putting too little work into engineering a new product can easily backfire in the latter stages of a project. It is more efficient in terms of overall time and money spent to take the time to consider the different aspects of a project before it leaves the drawing-room.

This is where design for excellence (aka design for X and DFX) comes in. The term “design for X” first made an appearance at the Keys Conference in 1990 and in the AT&T Technological journal. The papers even suggest that the two authors were not aware of each other, showing that the movement towards the same goal had started independently.

The DFX ideology helps build amazing products without the need for modifications in later stages, as its different areas take many of the most crucial aspects into consideration already in the design phase.

What is Design for X?

Design for excellence is an ever-evolving philosophy of a set of principles in design and manufacturing. It adopts a holistic and systematic approach to design, focusing on all aspects of a product – from concept generation to final delivery.

It provides good practices and design guidelines to ensure we get the design and manufacturing methods right the first time. All this is done before the product even reaches the shop floor.

Traditional Engineering Design vs Design for X

Think of design for X (DFX) as a whole new way to look at engineering design. There are many similarities between design for X and the traditional way of doing things. But the differences are so stark as well.

Having a good idea about how design for X can do so much more than good old engineering design practices will help us understand why more and more companies are taking the leap to design for X.

Conventional Product Development Process

Traditional engineering design follows a sequence from research to testing/improvement of design. A general sequence of engineering design is as follows:

• Identify a problem by observation, survey, experimentation or a combination of both.
• Research the problem in detail to gather as much relevant information as possible.
• Brainstorm possible solutions. Here we make an optimum selection after evaluating the pros and cons of each solution.
• Create the design and make necessary calculations.
• Create a prototype.
• Carry out testing on various fronts to ensure the prototype can solve the original problem.
• Improve the product as needed before mass production.

This kind of linear approach can be problematic and costly in many cases, preventing us from achieving the full potential of engineering design.

DFX Process characteristics

The design for X process comes with certain characteristics that make it a better alternative to its traditional counterparts.

Early correction of defects

Issues in the traditional engineering design process are usually identified and rectified after the design phase. Correcting these problems can prove extremely costly in many cases.

DFX shifts the addressing of these issues to an early design stage, which saves money as well as time.

Smaller number of product iterations

It is rare to see a designed product work perfectly the first time. Multiple iterations are needed to perfect a design. But creating these iterations is expensive, especially for plastic products that need custom moulds for injection moulding.

DFX strives to reduce the number of product iterations and try to get the design right the first time. This can be done by creating various virtual designs and carrying simulations instead of physical tests.

In cases where a physical iteration is needed, technologies such as rapid prototyping and generative design may be preferred. For example, instead of using injection moulding, additive manufacturing techniques such as 3D printing can be used to create iterations within a few hours at a low cost.

Requires fewer tools

Traditional engineering design requires the use of many tools. DFX reduces the number of tools needed for design by limiting it to a standard set for increased efficiency. This is one of the areas DFM (design for manufacturing) touches upon.

Broader scope of design

As stated before, the scope of DFX is broader and more inclusive than regular engineering design. By utilising the design principles within the various areas (for example, DFM and DFA), the DFX methodology increases the value while reducing the costs of products.

Inclusive design team

As DFX considers many aspects of product development, the design team’s role is much bigger than one in traditional engineering design. DFX encourages greater collaboration between designers, suppliers, and manufacturers.

Shorter time to market

By increasing communication and reducing rework cost, DFX considerably reduces the time to market for any product.

Some other salient characteristics of DFX that are quite self-explanatory are as follows:

• Reduced total product development cost
• Diminished product risk
• Improved operational efficiency
• Increased production yield
• Higher customer satisfaction

Types of DFX

Design for excellence is an all-encompassing philosophy that provides design guidelines for all aspects of a design and production process.

The “X” that stands for excellence can be substituted with a few letters to address a certain sub-section of DFX. These categories include manufacturing (DFM), assembly (DFA), quality (DFQ), supply chain (DFSC), etc.

Designers improve a product’s design in all these areas by implementing certain design principles in the process. The aim is to create a product that excels in these areas by making changes in the proposed design.

Design for X (DFX) has many such focus areas for design improvement. Some of them such as DFM, DFA, and DFMA are more popular than others.

Next, we shall cover some of these focus areas to get a better overall understanding of the design for X concept in different aspects of product development.

Design for Manufacturing (DFM)

Design for manufacturing refers to a design that brings convenience in the manufacturing aspect of product development. At every stage of the design, the ease of manufacturing the product is evaluated.

It is one of the most common and useful design for X categories as it provides techniques that help us create a better product at a lesser cost. Designers use them to enhance the design of parts, assemblies, and complete products.

For example, a metal product can be made using various fabrication processes. DFM enables designers to choose the right manufacturing and surface treatment methods for the best quality at the lowest prices. Part design then follows the chosen method to secure manufacturability.

Following the initial choice comes cost analysis. If the cost is still high, the above steps are repeated until reaching an optimal solution.

Design for Assembly (DFA)

In design for assembly, designers implement qualities in a product that make it easy to assemble. Fewer, simpler components that can be easily assembled by simple operations are encouraged to eliminate the possibility of mistakes. 

It also provides other advantages such as low maintainability due to fewer parts requiring testing and maintenance. The one question that is repeatedly asked of a design in DFA is “Does a part/component need to be separate from the entire product?”

Possible reasons for needing a part to be separate from the product body are:

• Functionality demands relative motion between part and product body.
• The part is made of a different material for functional/aesthetic reasons.
• The part may need to be disassembled for repair, maintenance, or access to other parts.

In the absence of the above reasons, the part must be combined with another part or with the product body to reduce the part count in the final assembly.

Design for Manufacturing and Assembly (DFMA)

DFMA

DFMA is a step ahead of both DFM and DFA. DFM focuses on the fabrication of a product/component, whereas DFA focuses on the product architecture.

DFMA combines both of these disciplines to deliver simpler, more efficient products that are easier to manufacture and assemble. Additional benefits include lower costs, increased reliability, and a shorter time to market. The DFMA design process creates about 40% time savings when compared to a conventional design process.

DFMA can also use the benefits of concurrent engineering. Design and manufacturing teams get together to design a better product than what each of them would have come up with were they to work alone.

Whereas DFM could opt for a combination of laser cutting and bending, DFA principles could prefer CNC machining services to produce more intricate but fewer parts, with less emphasis on the production costs.

DFMA brings the two methods together to create a more holistic view of the product development process while keeping different aspects in mind.

Design for Reliability (DFR)

IEEE defines the reliability of a part as “The ability of a component or system to perform its required functions under stated conditions for a specified period of time.” The aim of DFR is to build reliability into a product.

This must be done from the earliest stages of the design phase and evaluated at every stage after that. Integration into the entire product development process is a requirement to achieve the best results.

Designers must note that there are no industry standards available to measure reliability, as it varies from part to part. Equally important to knowing reliability testing methods is to know how to accommodate reliability into a product. 

In DFR, designers search for sources of part/product failure and work to eliminate this risk. Where elimination is not possible, they try to delay the failure to a timing equal to or greater than the product lifecycle. Many techniques such as FMEA and FTA help to test and design reliable products.

There are many other tools also available at a reliability engineer’s disposal. It is not necessary to use all the tools for every part but only ones that apply for a certain use case.

Reliability is inversely proportional to the cost of a product. In the quest to increase reliability, product costs can sometimes go well over budget. Thus, there is a need to reach a middle ground to balance both attributes of a product.

Design for Quality (DFQ)

The quality of a product is an attribute that has a direct impact on the product’s sales. The overall quality of a product is a measure of 8 different properties:

• Performance
• Features
• Reliability
• Conformance
• Durability
• Serviceability
• Aesthetics
• Perceived quality

To deliver a good quality product, quality checks must be built into the production system from the very beginning. This reduces quality issues before the product goes into production. Depending on only the final inspections to weed out bad quality products is usually not enough.

A good quality plan is essential to make this happen. It ensures that customers receive the best products without burdening the finances of a company too hard.

Design for Supply Chain (DFSC)

For a long time, the supply chain for a product was always an afterthought. Only after the product design and manufacturing processes were in place, the logistics systems were given a serious thought.

Logistics involves aspects such as packaging/transportation, parallel processing, and modularisation (standardisation) of parts.

DFSC proposes that the supply chain for the product be designed when the product itself is in its initial design phase. This helps us minimise supply chain costs, need for inventory, lead time and waste.

Design for Testing (DFT)

Testing refers to the quality checks that are carried out on all or a representative sample of a product or its prototype. This is to ensure that they meet predetermined criteria and standards set by the designers.

However, it is not easy to test all products. In many cases, testing consumes a good portion of the project budget, especially if testing methods are put in place after the design and manufacturing aspects have been finalised.

Design for testing refers to building testing methods into the product during the design stage to make it easy and economical to test the various product attributes and functions. The aim is to detect any crucial defects or issues with minimum intervention in the assembly line or during the packaging phase.

Design for Maintenance

This approach focuses on making the product easier to maintain. Both preventive and breakdown maintenance must be given due consideration in design.

Many products can be made easy to maintain by approaching the design process with a few points in mind that improve the maintainability of all products. A way to do this is by building in systems that show the real-time condition of a product. For example, a sight glass to show the oil level of a compressor. The sight glass allows for an engineer to check the oil level regularly and prevent any major breakdown.

Even when a major breakdown occurs, following design for maintenance gives easy access to the parts that could be the most probable culprits. For example, you can easily change spark plugs and the like in cars while accessing motor belts requires considerably more work. Having it vice versa would not make sense as changing plugs is a job that needs to be done with much higher frequency.

Another important feature that improves maintainability is developing a modular product. The ability to order and replace just the failed parts is an attractive feature for any product.

Designers must avoid designs that compel the user to renew large parts when small parts are at fault. For example, in a split AC, if the room temperature sensor is at fault, the design must allow for a quick replacement instead of having to change the PCB along with the sensor.

Design to Cost (DTC)

Design for cost and design to cost (DTC) are a set of DFX cost management techniques to control the cost of product development and manufacturing. The design intent is to create a product considering cost as a design parameter in addition to the schedule, scope and features. 

Generally, product design is responsible for 75% of the cost. Many hidden costs can emerge at a later point in product development such as the cost of redesign, rebuild, time to market delay, retesting, etc. Characteristics such as a simple design, easy assembly, manufacturability, efficient supply chain, reliability, etc. have a direct impact on the product cost.

By considering the overall cost of the product and engineering lower costs into the product from the initial stages of design, unnecessary costs can be prevented.

Design for Sustainability (DFS)

With environmental concerns growing every year in the 21st century, many companies desire for their products to have as small an impact on the environment as possible. This is further motivated by many governments now offering subsidies for green products and consumers actively seeking eco-friendly products.

The focus in DFS is on reducing the carbon footprint of the product by using recyclable materials and green manufacturing ideas for the product as well as its packaging.

DFS is a wide topic with many design rules that deserve a special discussion of their own. Besides the organisation, DFS extends to all the suppliers and manufacturers that contribute to the creation and maintenance of the product.

Design for Product Life Cycle (DFPLC)

A product life cycle refers to the entire life of a product from its introduction to its eventual withdrawal from the market. Design for product lifecycle focuses on increasing the profitability over the entire lifecycle of the product. It proposes methodologies, techniques and processes to make the product easier, cheaper and safer to manufacture, distribute, maintain, use and even dispose of.

Design for product life cycle takes into account potential changes that could be implemented into the product design in the future, cost savings, technology upgrades and infrastructure improvements. The suggested techniques make it easier to implement these changes for a smoother transition with minimal impact to the supply chain.

This is usually done by anticipating changes that are likely to occur and making provisions in the product design to accommodate them in the future. It also sets a limit on how much time would be permitted to complete this transition, as extended transitions can be very expensive.

Conclusion

As of now, industry experts have written extensive papers on 48 different DFX approaches. But the list for DFX is practically infinite. A DFX approach can be designed around any feature that is important to the product and the organisation.

At higher levels, organisations may level up to introduce Design for Six Sigma (DfSS). DfSS contains many design considerations and design guidelines to significantly improve the way an organisation creates products.

The enviable benefits of DFX are realised over the life cycle of the product. Some of these benefits are a simple yet effective design, shorter time to market and a cost-effective product.

Other benefits may not always be noticeable immediately, but they have the potential to usher in the long-term success of the product. They can greatly impact the competitiveness and market growth of an organisation.