Join us for a comprehensive overview of design for manufacturing, or DFM. It’s a term that’s often used but rarely explained, so today we’re going to explore the details and show why it’s so important for getting the most out of product development.
What is Design for Manufacturing?
Design for manufacturing (DFM), also known as “design for manufacturability”, is a method of analysis that helps to determine the suitability of a product design for the process(-es) that will be used to fabricate it.
Rather than a single discrete action or set of rules, it employs many different analytical tools to arrive at evidence-based conclusions.
This procedure is sometimes called “performing a DFM”, but regardless of the terminology, the logic can be applied to virtually any industry. It yields valuable insights that help to lower production costs and improve quality while also reducing waste and inefficiency.
The following is a general overview of how best to employ the discipline of DFM. Specific industries may need to modify this approach to suit their unique manufacturing requirements.
General DFM questions
What is the purpose of DFM?
The purpose of DFM is threefold: to identify the best method for fabricating a finished part; to ensure the design of the part is optimized for the process to reduce defects, and to lower costs while maintaining product quality and performance.
Who is responsible for the DFM review?
Ideally, a DFM review should be performed in a partnership between the product designer and the manufacturer. This review should include input from everyone in the process who is responsible for making the finished part or related tooling. For complex projects, this list can be quite lengthy and might include a variety of engineers, tool designers, fabricators, colorists, material specialists, etc.
Each person has an area of expertise that, taken collectively, yields a complete understanding of the project and how to optimize for it.
When should DFM be performed?
A DFM should be performed as early as possible in the design stage, and certainly well before any commitment is made to build a set of tools or purchase raw material stock.
This is because altering a design later in the development process becomes exponentially more difficult and expensive the further along it is, and after a certain threshold it simply may not be possible. Therefore, the greatest cost savings come from perfecting the design – both for the finished part and any related tooling – before actual production begins.
How long does a DFM take?
The time required to do a thorough DFM review correlates directly with the complexity of the design. Some projects are relatively simple, perhaps representing an application of a well-known and stable manufacturing method. In that case, a few hours might suffice. But it’s not unusual for some plastic injection molding projects to require weeks of computer modeling, testing, modification, and re-testing before the ideal solution is achieved.
How does DFM support cost savings?
In addition to eliminating design errors, a DFM review can also reveal potential cost savings in the following ways:
- Reducing the number of processing steps
- Reducing unnecessary or redundant design features
- Creating modular or multi-purpose designs
- Reducing the number of connectors or fittings
- Using off-the-shelf components
- Using standard or recycled raw materials
- Reusing or modifying existing fixtures
- Simplifying assembly / disassembly
- Loosening tolerances
- Reducing the number of Critical To Quality (CTQ) dimensions
Why Is Design For Manufacturing Important?
Because of all the benefits listed above, you can see why DFM should not be considered as an afterthought but rather as an essential component of a completely new product introduction strategy.
Good DFM is all about clear communication between the designer and the manufacturer and is the best way to avoid any preventable mistakes further along the product development journey.
Performing A Design Manufacturing Analysis
As we’ve mentioned, every new product development project is unique, so we can’t offer a single guide that covers all aspects of every industry. But let’s consider a hypothetical part made in a modern CNC machine shop as an example.
Principle One: Clarify the Objectives
What are the design objectives?
What is the product or part meant to do, for whom, under what conditions, and why? These questions are all related, and the manufacturer should know the answer from the beginning of a project. The product designer must determine what their priorities are, which might include combinations of the following:
- Strength / durability / corrosion resistance
- Cosmetic appearance
- Environmental impact
- Time to market
… and many others. Only by clearly understanding the designer’s intent can the manufacturer offer insights, or present alternative methods, that can help meet the customer’s goals in the most efficient way.
Principle Two: Manage Expectations
To achieve the design intent, it’s almost always necessary to compromise on low-priority areas in order to achieve more important objectives.
For example, very precise, complex parts made from exotic materials are not going to also be inexpensive or quick to produce. Therefore, a DFM analysis begins by pointing out areas of compromise – what a manufacturer calls “managing expectations.”
Principle Three: Design for the Process
Designs should be created with the production method in mind – not forced to fit a process for which it’s not suited.
For example, a child’s rubber duck can be plastic injection molded very quickly and economically. The same would not be true if it were CNC machined from a solid block of material.
In this regard, product developers should listen to the advice of the manufacturer, who will recommend specific areas in the design that may need to be modified to suit the requirements of the equipment and the process.
Principle Four: Design for the Materials
Product designers must respect the unique characteristics of the raw material they use, while also ensuring that the material fits the process. If there is a change in material then it might entail a change in process, so this must be resolved in advance.
Also, a good DFM analysis will point out any place where the desired material isn’t a good fit for the application. That’s why manufacturer’s should know this upfront, so they can suggest useful alternatives.
Principle Five: Confirm Dimensions and Tolerances
Regardless of what the end product is, every drawing should clearly specify the nominal dimensions of every major feature as well as the allowable deviations from the nominal.
This is as it should be, of course. But in our experience, the single most common error in design comes from making dimensions unrealistically and unnecessarily tight.
A comprehensive DFM review will look carefully at all dimensions and will question any that appear too tight. This is because tight tolerances are much more difficult to make, require more time, are more expensive, and often don’t even yield a better end result.
Standard tolerances, as provided by a competent CNC machine shop using modern equipment, are more than adequate for all but the most demanding jobs. This is the single best way to save time, money, and frustration on most CNC machining projects, and the general rule applies to many other types of manufacturing processes as well.
Principle Six: Resolve Design Conflicts
A conflict is one in which the desired feature cannot be made via the manufacturing process, or not without compromising some other aspect of the design.
An example of this for a CNC machined part is an undercut. Because CNC machine tools work in the direct line of sight of the machine spindle, they cannot make undercuts if the access to that area is blocked.
In such a case, the design would need to be changed to remove the undercut. This is another reason why product designers need to consult manufacturers early in the design stage before they have committed themselves to invest in a part that can’t be made.
Design For Manufacturing Overview
The above has been an overview of the major considerations affecting a design for manufacturing review. Some of these points may also be affected by other factors, such as the intended production volumes or the need to account for batch shipments.
In all cases, this is why we recommend forming a good partnership with your manufacturing supplier and consulting with them as early as possible in the development phase.
This is the best way to ensure success on your next project.
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