How to design a product for manufacturing
DFM challenges, tips, and examples
|Michael Corr, Founder and CEO, Duro|
Every manufactured product was once just an idea, whether a chair or the latest smartphone. Their inventors needed confidence, determination, and resources to realize their dream.
Bringing a new hardware product from concept to production can be daunting, so optimizing the process as much as possible by breaking it into smaller steps is necessary. Designing for manufacturing (or manufacturability) is an essential part of this process.
What is Design for Manufacturing (DFM)?
Design for Manufacturing (DFM) involves changing the design of your parts, products, or components to optimize the manufacturing process using available equipment to mitigate mistakes and discrepancies while maximizing yield at the lowest possible cost. Almost all modern manufacturers use it, although its implementation highly depends on the specific technology involved. In addition, applying DFM principles helps identify problems during the design phase when they’re less expensive to fix than when a product is near or already in production.
More specifically, DFM goes beyond making a functional electrical circuit or mechanical assembly design; it involves making decisions to improve the ease of manufacturing. As such, DFM may have nothing to do with the functional purpose of the product. Instead, DFM may mean changing, for example, the draft angle on a mechanical part or rearranging how your passive components are laid out on your circuit board to improve the efficiency and yield for manufacturing.
Why is DFM so important?
In today’s manufacturing environment, product designers and manufacturers are typically siloed. They may work in different environments or even other countries, so information between the two teams can be delayed or miscommunicated. Additionally, each manufacturer is unique regarding the type of equipment they use and the space and process they have. Addressing their unique environment using DFM is essential to:
Reduce cost to manufacture: Speed up manufacturing time and improve ease of manufacturing.
Increase yield: Increase the number of functional units that are produced.
Suppose a customer orders 1000 finished units from their manufacturer. The yield rate will be less than 100%, so the manufacturer must build more than 1000 units to ensure a complete 1000 working unit order. The lower the yield rate, the more units manufacturers have to build and the higher the expenses incurred for reworking the failed units.
Design for manufacturability helps increase yield because the more complex or the lower the margins are for a successful manufacturer, the higher the probability that you have failures or parts or assemblies that are non-compliant with specific test parameters. By mastering DFM, companies can reduce the cost of rework and more accurately forecast sales goals. In addition, it helps to ensure that your products get to market on schedule at the lowest possible cost without compromising quality.
How to factor DFM into your engineering process + examples
The overall goal of DFM is to reduce manufacturing costs without reducing yield. It’s about making decisions specific to the manufacturing resources and capacity or performance of the equipment or processes a vendor has on hand.
For example, if you were assembling products using a hammer and nails, you would need to consider several factors to achieve 100% yield:
- How much force can the hammer exert to drive a nail?
- How much surface area is required for the hammer to distribute that force evenly on the nail head?
- What type of nail can handle the force exerted by the hammer? (Thin, low gauge nails may not stand up to the force exerted by the hammer)
- How many nail breaks occur per 100 assemblies?
Examining these factors allows you to determine the most compatible nail type to pair with your hammer. For example, a stronger nail would lead to fewer nail breaks and a higher overall yield during the assembly process. You would then calculate the cost increase of higher-grade nails against the cost of nail breaks in the original assembly.
Some other examples include:
There’s a little taper on the inside of injection-molded parts called the draft angle. When the liquid plastic is injected into the negative cavity of the mold and cools, it can create friction between the plastic part and the mold if the angle is straight. This causes the part to get damaged when removed from the mold. Proper draft angles make pulling the part from the mold easier without any damage.
One example of DFM is designing for the specifics of the mold and the temperature constants and materials that would result in the least amount of breakage or damage while maximizing the speed of extraction. This change might be subtle, for example, adjusting the draft angle from 1.0 to 1.5 degrees. But the machines used to manufacture the part might then result in yields of 95% rather than 60%.
In electronics, many little parts, such as capacitors, require keen attention to detail. On a PCB, the space between these elements is critical. As a designer, the closer you place these components on the circuit board, the more likely you’ll have short circuits as the solder flows from one capacitor to the next, resulting in higher failure rates. Therefore, from a DFM perspective, ensuring these elements are correctly spaced is essential.
Reflow ovens melt the solder during manufacturing before it eventually cools and hardens. And so the hot air flow’s cubic feet per minute (CFM) will determine how efficiently the solder melts and then sticks to the pads (which also affects how closely you can put the parts together). Since reflow ovens have different airflows, designing PCBs with the correct separation of capacitors is essential. In other words, designers must design PCBs compatible with the machine’s airflow capacity to achieve the desired yield.
4 Essential Steps to Achieve DFM Success
At the most basic level, DFM has two layers:
- Designing for the process itself. You need to understand how the product will be assembled, for example, injection molded versus CNC, or surface mount reflow versus cold wave solder.
- Understanding the capacities, capabilities, and tolerances of the machines used to manufacture the product to get the best result.
However, to truly succeed with design for manufacturing, designers, engineers, and manufacturers must work together, communicate, and focus on limiting the number of parts a product needs, standardizing parts and materials, and accounting for the various manufacturing equipment and processes required to create the product. Follow these four steps to improve your results with DFM:
1. Involve manufacturers early to gather feedback on designs
For DFM to succeed, relationships are key, meaning you must share ideas. The more information a design engineer has, the better. It’s not just about going to a book and reading the best practices but talking to the manufacturer and asking, “How would you manufacture this design before you release it? How can I provide feedback?”
By starting this dialogue early, you can better grasp the tolerances of the manufacturer’s equipment and plan for changes, helping you reduce the costs associated with change management. If you wait to give feedback until after the design has been released and is in the manufacturer’s hands, you will face an increased cost to fix it. Fixing an issue in the design cycle is much easier than during production.
2. Understand the manufacturing equipment
Another critical step in DFM includes taking time to learn what specific equipment or processes your vendor has available and designing around them for compatibility. It would help to understand how parts and assemblies are manufactured and alter your design and bill of materials to match their capabilities. This will significantly accelerate the manufacturing time and overall yield of your product.
Visit the factory floor, review the steps required to manufacture your products and see if there are any efficiencies you can make in the design to make their processes easier. Another important aspect of this process is reviewing the limitations of the environment concerning any materials and parts you’re using. For example, identify the temperatures and pressure they can withstand during manufacturing.
3. Don’t skip the prototyping step
In the early development phase, you might skip a prototype under the assumption that you can figure it out later in production. This is generally done to save money, but failing to iron out the production-specific bugs at this step can lead to increased costs later as you scramble to make changes once the product is in the customer’s hands.
4. Create a feedback loop between engineers and manufacturers
Communication between engineers and manufacturers must be continuous throughout the entire process. Your designers and engineers must be involved to ensure that technical elements and decisions aren’t left up to your manufacturer exclusively – they may miss something that makes or breaks your product.
A manufacturer’s job is to produce parts and put them together. Their job is not to determine what is best for your product or how it will work in the marketplace. Good manufacturers have insight into that. Still, it’s a fraction of the insight that you, your designers, or your engineers have, not only because they understand these processes from a market perspective better but because they’ve been working on this product for months, sometimes years.
Learn how Duro streamlines communication between design teams
DFM should be present throughout the product life cycle, from concept to release. In particular, it involves testing throughout this process to identify and correct problems at the earliest possible stage.
Duro can help businesses streamline product development and manufacturing — lowering costs, boosting productivity, and improving product quality and team collaboration. Contact us today to schedule a demo.