What is Design for Manufacturing and Assembly (DFMA)?

Quick Points:

• DFMA combines Design for Manufacturing and Design for Assembly to reduce part counts, complexity, and production costs.
• Model-Based Definition ensures tolerances and requirements travel with the design, preventing costly miscommunication on the factory floor.
• Onshape brings DFMA and MBD into one cloud-native workflow, keeping every team and supplier aligned in real time.

If you’re embarking on a new venture with a ground-breaking product idea, you’ll need a working prototype or proof-of-concept to attract investors and get your business idea off the ground. Your prototype may include hand-made parts and off-the-shelf enclosures, or you may 3D print something close enough to the final design and use one of the many relatively inexpensive PCB printing services.

However, when approaching your prototyping, it should be noted that mass-producing a product requires a completely different mindset.

Designing your product so that it can be recreated consistently by people you don’t know is the only way to ensure that quality remains high and costs and warranty issues are kept to a minimum. You may need to redesign many of the parts of your product in order to consider all the necessary requirements for manufacture and assembly. Having parts that are difficult to manufacture or time-consuming to assemble will add too many costs up front before you start to realize any revenue.

The time to resolve these issues is now, during design.

What’s Manufacturing Design? What Does DFMA Mean?

Design for Manufacturing and Assembly (DFMA) means, simply put, optimizing your designs so they are easier and cheaper to manufacture and assemble at scale.

It combines two disciplines: DFM (Design for Manufacturing), which focuses on making individual parts easier to produce, and DFA (Design for Assembly), which focuses on reducing the complexity of putting those parts together. Used in tandem, DFMA, or sometimes called DFM/DFA, gives teams a complete lens for evaluating production readiness.

How you choose to manufacture each part has a huge bearing on how you approach this problem. The injection molding process, for example, yields highly repeatable, high-volume, low-cost parts, but with considerable upfront costs. So for injection-molded parts, you must ensure your design is correct before committing to tooling.

To make your design suitable for this process, you may have to add draft to every face, fillets to every corner and consider whether defects such as sink marks and warpage are acceptable – or if you can avoid them altogether. A good quality toolmaker should be able to answer these questions for you and give you advice and guidance. Some toolmakers may offer to do this work for you, for a fee, but make sure that you both agree on the final design before signing it off.

Injection molding also enables you to consider reducing your part count by combining the functions of one or more parts together or reducing the number of fasteners required by using snap fits. Fewer parts mean fewer assembly operations, fewer mistakes, and more throughput.

Ways to Lower Production Costs

Whether you’re applying DFM/DFA principles for the first time or refining an existing process, there are, of course, many different manufacturing methods available. When choosing the processes and suppliers that best fit with your design requirements and your budget, you can lower your overall production costs by finding ways to reduce the:

• Overall number of parts
• Number and types of fasteners or adhesives
• Fine tolerances and surface finishes
• Number of manufacturing operations
• Amount of jigs and fixtures required
• Overall cost of tooling
• Use of special tooling or tools required for manufacturing
• Use of exotic or expensive materials
• Skill levels required to assemble the product
• Number of asymmetrical parts to make assembly foolproof
• Fragile parts that can be easily broken during assembly
• Amount of packaging required for shipment, distribution and retail

How Onshape Helps With DFMA

Optimizing part designs to simplify manufacturing and assembly requires a vast knowledge of every available manufacturing and assembly process. Not every company has that depth of experience in house, and that gap in engineering design and manufacturing knowledge is where costly mistakes tend to happen. This is where it is prudent to involve people who understand each process and can advise you on the best way forward.

Real-Time Collaboration With Suppliers and Peers

Not only does Onshape allow teams to work together on the same project data, but it also enables interactive design reviews. Discussing designs with your peers or potential suppliers can be done in real time, at the time a question arises, if need be. There’s no need to wait until a scheduled design review rolls around. If you have access to the resources and the expertise, you can include them in the design process when it makes the most sense.

Built-In Manufacturability Analysis

Onshape includes a number of tools to help you design your products with manufacturing in mind. For injection molded or cast parts, there are Draft, Undercut, and wall thickness analysis tools to let you check that your parts can be easily manufactured and that you’re not adding too much cost.

Onshape’s unique Sheet Metal design tools also check for manufacturability as you design. These tools no doubt help, but DFMA considerations often affect several parts in an assembly at the same time, as each design change has a domino effect on the surrounding areas.

Branching and Merging for Parallel Design Exploration

It’s possible for multiple people to make multiple changes to the same design without stepping on each other’s toes by using Onshape’s built-in Branching and Merging.

Each designer can work in their own workspace that is temporarily independent from the rest of the design. Design ideas can then be tried, tested, reviewed and approved before being merged back into the main design branch.

Communicating Manufacturing Requirements With MBD

Good DFMA decisions are only as effective as the information behind them. A well-optimized part design is useless if your manufacturer doesn't know the precise tolerances and inspection requirements needed to make it work.

That’s where Model-Based Definition (MBD) comes in.

MBD is the practice of embedding all product and manufacturing information directly into the 3D model, rather than relying on separate 2D drawings. Tolerances, GD&T annotations, surface finishes, and material specs all live within the model itself, making it the single source of truth for everyone downstream – from machinists to QA inspectors.

In Onshape, MBD is a natural part of the workflow rather than a separate, manual process. Sketches and features are tolerance-aware at their core, ASME and ISO standards are embedded natively, and completed models can be shared instantly with suppliers via Onshape Publications. Manufacturing requirements travel with the design, so there is no risk of instructions getting lost between your team and the factory floor.

Keeping Your Bill of Materials Lean

Keeping tabs on your Bill of Materials (BOM) is essential when trying to keep costs down. For every new part, there are added manufacturing, assembly, and inventory costs, so having fewer parts in your product can save a lot when it comes to scaling up production.

One way to reduce the item count in your BOM is to combine multiple parts into one. This can be difficult to do if the parts themselves are complex or they interact with many other parts in the assembly at the same time.

Onshape’s Managed In-Context Editing feature can help here: You can graphically edit one part relative to several others and combine features from each part together. This mechanism is much more robust and much easier to implement and use than the “in-context” editing you will find in file-based CAD systems.

A BOM That Stays in Sync Automatically

BOM table information is traditionally displayed in tables on drawings of the final assembly with balloon callouts and quantities. Quite often, engineers have had to create a drawing just to get the final BOM. These tables can also get out of sync with the assembly if an engineer forgets to open the drawing and update the views.

Onshape brings assembly design and BOM management together – where they should be. As new parts are added or removed from an assembly, the BOM table in the flyout tab is updated automatically. You can then view and edit the data in the table and see dynamically how it relates to the 3D parts on screen. This makes it easier to track changes and develop products that are easier to manufacture.

Put Good DFMA into Practice with Onshape

Putting good DFMA principles into practice is much easier with the right tools behind you. From built-in manufacturability analysis to MBD that travels with your design from day one, Onshape gives hardware teams everything they need to move from prototype to production with confidence.

(This blog was originally published February 21, 2019.)