A DFM review anticipates manufacturing, assembly, and inspection challenges
Custom battery packs succeed or fail based on a multitude of factors. Thermal management, battery management, charge control algorithms, cell chemistry, and cell count and orientation all play essential roles in the performance of a battery. The right choices in these and other areas can deliver boosted battery performance and longevity.
But peak performance isn’t just about incorporating all the cutting-edge features available. Rather, battery design and manufacture are economic problems as well as engineering challenges. As we discussed in a recent article, liquid cooling is far more efficient than passive cooling, but it’s not the best choice unless it’s economically viable. The benefits of every system and indeed every component have to be weighed against long-term value.
In this article, we’re exploring the idea of Design for Manufacturability, or DFM. DFM is a design process or paradigm aimed at reducing lifetime costs and increasing return-on-investment with better design. The basic principle is this: design choices have enormous effects on how difficult and costly it is to manufacture and assemble a product. Thus, paying early attention to manufacturability pays enormous dividends, even though design makes up only a small part of the manufacturing process.
Read on to learn:
- What DFM is and why it matters
- Some of the core techniques of DFM
- The “soft” skills that make DFM possible, including communication and goal-setting
Aved’s goal is to provide high-performance and cost-effective battery solutions to our clients. As a part of our custom battery pack design, manufacturing, and testing services, Aved provides DFM review of designs. Contact us to learn more about the design and manufacture process or request a quote today.
What DFM is and why it matters
What’s the most expensive part of designing and manufacturing a custom battery? Some might rank materials, labor, and manufacturing as the main costs. Others might point to regulation and safety testing as major contributors to cost. These stages consume a lot of time in the overall process.
When evaluating costs, you should first focus on the design phase. While design itself might only account for a small portion of the total time and money spent on generating a new product, choices made in the design phase can be responsible for about 70% of total project cost.
This is an extraordinary claim, but the idea is actually quite simple: after the design phase, it costs money to make changes, and the further along in a manufacturing project you get, the more costly it is to make a change. Many major manufacture-stage problems can be traced back to insufficient design-stage review of the plans. Some of these include:
- Difficulty in procuring raw materials
- The discovery that a supplier doesn’t have the capability to fulfill orders or to produce components that meet the specified tolerances
- The realization that a component has been over- or under-specified
- High yield loss
- Inconvenient safety testing (or failed safety tests)
Thus, it’s essential to conduct a Design for Manufacturability (DFM) review as early as possible to avoid these pitfalls. DFM is closely related to the principles of Design for Assembly (DFA) and Design for Inspection (DFI). All three of these terms operate on the basic idea that a design should be evaluated holistically and as early as possible.
During the DFM review, all stakeholders—clients, designers, suppliers, manufacturing engineers, and testing laboratories—work together to challenge the design. They analyze every component and assembly to determine whether it is necessary, what the appropriate tolerances are, and whether it is easy to work with during manufacture, assembly, and testing.
A design optimized for manufacture and assembly:
- Incorporates relatively few parts, because this is generally easier for machines and humans to handle
- Uses standardized parts, to facilitate manufacturing and supply chain
- Uses modular sub-assemblies, which facilities assembly and testing
- Requires little or no reorientation or manipulation of the build during assembly
Let’s dive into the specifics of how a DFM review accomplishes these goals.
The techniques of DFM: minimize, standardize, modularize, and streamline
A DFM review can be highly technical and detailed. However, every DFM review uses a few core techniques to maximize efficiency: minimizing part count, standardizing and modularizing, and streamlining manufacture and assembly.
Let’s take a look at what these techniques mean in practice.
Reduce, combined, and relax parts
Part reduction boosts manufacturability and ease of assembly by reducing the number of suppliers and purchases needed, shrinking inventory, and simplifying manipulation by machines or humans. Minimizing part number in the design stage is a great way to reduce overhead costs down the line.
To cut parts from a design, designers and engineers iteratively challenge every component of a draft design, asking questions like:
- Is this part required for the core function of the device?
- Is this part required for assembly and disassembly?
- Must this part move relative to other parts?
- Must this part be made of a different material than the rest of the assembly?
Answering “yes” to one of these questions suggests that the part is necessary and may need to remain. But if you can answer “no” to all of them, you have found a good candidate for elimination or combination with another part.
Some components cannot be eliminated outright because their functions are absolutely required. But some components can be combined to reduce total part count while retaining their function. Fasteners are common targets in DFM reviews. In lieu of fiddly bolts and screws, snap tabs can be integrated into a battery casing to facilitate assembly. Likewise, a radiator or vent can be part of the structural housing of a battery pack, instead of a separate part.
Standardize and modularize
One of the best things you can do to improve manufacturability is to use standardized parts. This can mean components that are already mass-produced. Alternatively, using the same custom-manufactured across multiple designs provides many of the same benefits. Standardized components reduce lead times and manufacture costs, give higher part availability, and allow for simplified inventory. Plus, they give you well-known tolerance and reliability data.
Dividing a design into modular sections likewise aids assembly, manufacture, and testing. Separate sections of a modular battery pack can be assembled and tested independently of one another. Additionally, modular designs (along with standardized components) allow for easier redesign.
Optimize assembly processes
Designing a product with an eye towards assembly can dramatically reduce costs and increase convenience. Every manipulation, rotation, or reorientation of a component during the assembly process adds time and consumes resources, whether your assembly process is automated or done by humans.
Designs that require little physical reorientation are easy for both humans and machines to assemble. Vertical assembly is particularly useful for automated assembly; the Walkman was famously designed for downward-only moves.
The soft skills of DFM: goal-setting and communication
As we discussed, a DFM review requires the critique of every aspect of a design. Each component and assembly must be evaluated for utility, performance, tolerance, cost, manufacturability, and ease of assembly. This is a highly technical process, but it is undergirded by a very soft skill: goal-setting. To analyze a design, you need a crystal-clear definition of the end-user’s performance needs and the regulatory and testing requirements.
For battery design, this means defining the end device and its needs in terms of voltage, capacity, portability (in terms of mass and volume), discharge rate, cycle life, and other parameters. These definitions help you choose among different battery chemistries and then define cell count and arrangement. Knowing all this, you can identify the safety standard to which your battery must be certified and therefore which safety tests it must pass. Read more about safety and compliance on our blog.
All this is design 101, of course—you need to know all of this to begin with. But only with precise definitions of each of these goals can you properly challenge and analyze every simple component in terms of cost, performance, and tolerance.
Cost, performance, and tolerance are closely related; reducing cost often involves relaxing manufacture tolerances of certain components or changing materials, which can in turn impact performance. Only by precisely defining performance goals can designers find the optimum tolerance and cost points that still produce the desired performance.
However, accomplishing this requires communication among stakeholders. Critiquing a design requires collaboration because different parties have different knowledge. For example, slow production of a design might ultimately be traced back to a misunderstanding of a manufacturer’s ability to achieve the specified tolerances.
Sharing of knowledge avoids these problems. As Raytheon explains, the design team understands the relationship between performance and tolerance. Suppliers know their lead times and manufacturing capabilities—they understand the relationship between tolerance and cost. Only by working together can they produce designs optimized for cost-effectiveness and performance.
DFM optimizes design for manufacture and assembly
As designers and manufacturers of custom battery pack solutions, Aved strives to provide the best batteries for your needs. Part of that means selecting the right chemistry, thermal management techniques, and battery management systems for the job. But it also means making sure our designs are cost-effective according to your performance needs.
With in-house battery design, manufacturing, and testing teams and close relationships with our suppliers, Aved provides detailed Design for Manufacturability (DFM) reviews of our batteries. Close collaboration between these teams lets us critique our designs to ensure that every component is necessary and specified to the appropriate tolerances, is easy to work with during the assembly stage, and will deliver the performance demanded by our clients and the regulatory standards.
Contact us to learn more about our battery design and manufacture process and to get started on your custom battery pack solution, complete with DFM review.