What is DFM and How Do I Do it?
Design for Manufacturing
What is DFM?
Design for Manufacturability, also known as DFM or DFMA (Assembly), is a guiding engineering design principle that has many advantages when incorporated into product development. The main goal of every organization using DFM principles is to optimize the product design by saving money while improving the product offering. It could be argued that the Design for Manufacturing principles have been around since the Industrial Revolution in the late 1700’s. During this period, companies began to understand that improved efficiency also improved their bottom lines since higher volumes were able to be reached for the first time. DFM is a critical engineering design process, and it became the foundation for the entire branch of industrial design engineering. Other terms that are closely related to DFM are DFI (Design for Inspection) and DFA (Design for Assembly), which we don’t cover in-depth in this article, but they are branches of the same tree and many commonalities exist.
5 Principles of DFMA (Design for Manufacturing/Assembly)
Process
When in the design process, engineers and designers need to think about the manufacturing process. Although the actual transition from prototype to production may not be for months or years, some decisions of the downstream manufacturing processes will be made in a project charter. A project charter is an essential tool in product development and management that establishes the goals, scope, and stakeholders of the project.
A good example of DFM could be an ice press, or really any product design that needs CNC machined. Think about how the product will be fixtured, what tools will be used, and the programming time involved. Try to minimize the number of tools required. (ie, if possible make all fillets in the design with the same arc radius.) If the design has a need for anodization, then including design geometry that could minimize chip drags or other chances of failure during programming/machine operation. Maybe design the product so the surface is easily polishable so that the anodization can take evenly. When we were just starting out, we ran into major supply chain issues when units had to be sent back for rework as the surface finish criteria required for anodizing were not met. Or better yet, design the product so that the plating company can create a rack to easily hold and dip many of your assemblies at once.
Another process to consider is DFAM (Design for Additive Manufacturing). We’ve been designing and prototyping on FDM, SLA, and SLS manufacturing process 3D printers for many years. Hands-down the most important thing when taking a 3D printed design to manufacture is choosing the right manufacturing process. FDM has distinct advantages and disadvantages, as do SLS and SLA. We wrote about these different types in this 3D printing article.
Design
Optimizing part cost is largely the design engineer’s job in many engineering organizations. It is the DE’s job to gather information on the manufacturing process, material, product design criteria, and stakeholders’ expectations (cost, timeline, and function aka the Scope).
For example, if you know that the product design is an ABS plastic injection-molded door handle, then you need to include the draft angles and ejection pin sites in the design of the product right after conceptualization. Not only will it make the design’s production possible and ease the manufacturer’s burden (if you are outsourcing) but also your and your stakeholder’s expectations are aligned and delays from confusion are avoided.
Another thing to think about in design is tolerance. Try not to design parts with tight tolerances. As a matter of fact, the opposite is true. When optimizing a part for manufacturing, you want your tolerance loose when possible. And it makes sense; the looser the tolerance, the faster the machine can run and part cost will decrease as a result.
Material
When DFM for CNC machining, softer materials are better since they can be run at higher feeds. The wear on the tool is less with soft metals, with engineering aluminum being an incredibly versatile material. We prefer 6061 when machining for production and even for prototyping.
Environment
Regulatory Compliance
Why should I DFM?
Simply put, thinking about the manufacturing process in the design stage will save you or your organization time and money. Whether it be non-recurring engineering time spent on the design or cascading errors in the tooling production, margin and profit will be left on the table if DFM isn’t incorporated. Or worse, the project will fail entirely, especially if your industry has cost-based pricing.
When Do I start DFM for my Product?
As engineers, when we ask the Design for Manufacturing question to mentors, we’re often met with two opposing answers: right from the start or towards the tail-end of the design process. When it fits into your project or entire organization depends on many factors, And the short answer is that it is entirely dependent on the product that needs to go to market (consumer product, medical device, defense contracting) , and that product is dependent on many factors (cost, value, volume, etc). HOWEVER, we’ve found that once the design is in CAD and it works functionally, DFM principles can have meaningful guidance to streamline the design process. That way, if the stakeholders’ expectation of cost or product function cannot be achieved within the project’s constraints, then the company can choose to shelf the project without tying up resources longer than needed.
Now, the DFM process can start earlier, and you should have it in the back of your mind from the get-go, but there really isn’t a point in optimizing a design for manufacturing if it doesn’t work in the first place. That’s why, even in an article that’s meant to explain the importance of DFM, we are taking time to point out that minimum functionality needs to be present before making decisions on manufacturability.
For example, when designing a consumer product that has cost-based pricing, DFM principles need to be followed immediately to maintain any semblance of a timeline. Otherwise, you will design a beautiful product that hits every point on the design matrix except for cost, which happens to have the most weight. A major factor when designing consumer products will be your COGS (Cost of Goods Sold) since the end product will be competitively priced and margin needs to be incorporated