Many industries and, indeed, companies have their own unique definitions of design for manufacturing (DFM), including how to apply it and the benefits it brings to themselves, their customers, and the end user. For the sake of clarity, we'd like to suggest a methodology that we've used successfully with thousands of customers over the years. With some slight modifications, we believe this approach can work in just about any industry making any type of finished product.
The purpose of DFM
At its core, DFM serves three main purposes:
- Identifying the correct processing steps necessary for making a finished part;
- optimizing the part design and manufacturing process to achieve maximum economy and quality with minimal waste;
- ensuring the raw materials are appropriate for the design intent and the manufacturing process.
Manufacturers often have insights on how to achieve these objectives that many product developers are not aware of, which is why a certain amount of design flexibility is critical to the success of a project.
Who is responsible for the DFM review?
Comprehensive DFM analysis must be done in partnership between the manufacturer and the product developer. This entails questions and back-and-forth communication to establish the design intent.
We define the manufacturer as anyone who is directly involved in transforming the raw material into a finished product. This list might include tooling engineers, machine operators, QC personnel, painting specialists, and so forth. 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?
DFM analysis should be performed at the earliest possible opportunity during the product design phase and long before any commitments are made for tooling or raw material.
The importance of this can’t be overstated. We are still astonished when we receive a complete set of design drawings that are "set in stone" by the customer. The design has been vetted and approved by any number of people in the command structure of a large corporation, and yet we discover the part can't be made, or not as designed.
We know from experience that altering a design late in the development process becomes much more difficult and expensive the further along it is. Therefore, the greatest cost savings come from perfecting the design well in advance, and that should be done in collaboration with the manufacturer.
How does DFM support cost savings?
In addition to eliminating design errors, a DFM review can also reveal potential cost savings by:
- 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.
Performing a DFM essentially boils down to six key steps.
1. Clarify the design intent
The product designer should know what the priorities are, and these should be clearly communicated to every stakeholder. They might include:
- Strength, durability, and corrosion resistance;
- cosmetic appearance;
- accuracy and precision;
- environmental impact;
- production lead time.
This list is not exhaustive. Only by clearly understanding the designer’s intent can the manufacturer then offer insights, or present alternative methods, that can help meet the customer’s goals in the most efficient way.
2. Manage expectations
Every manufacturer is familiar with the uneasy relationship between price, quality, and speed. Only two of these three can ever be achieved at any given time. Therefore, once the design priorities are clearly established, this necessary compromise must be explained to the client so they have a realistic understanding of what to expect in the course of their product's development.
3. Design for the process
A design should be created with the production method in mind — not forced to fit a process for which it's not suited.
This may seem obvious, but you would be surprised by the number of times we've seen design drawings that were originally intended to be CNC machined, only later to be asked: "Oh, can't you just injection mold it instead?" No, every process imposes its own discipline upon the design, not the other way around.
4. Design for the material
Molders are well aware that there are thousands of unique resin compounds available on the market, and even "generic" varieties can differ subtly from one resin supplier to another. Changes in material chemistry greatly affect molding temperatures, cooling strategies, packing pressure, and much else. This must be accounted for at the very beginning of a project.
5. Confirm dimensions and tolerances
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 product. And as we know, shrink rates of plastic resin can vary widely, thereby making consistent and repeatable tight tolerances even more problematic.
6. Resolve design conflicts
A conflict is one in which a desired feature cannot be made via the manufacturing process, or not without compromising some other aspect of the design or the injection mold. Of course, it's possible to make minor changes to a tool during trials, but major design changes might require completely different tooling strategies altogether — another reason why it's best to resolve design conflicts before any metal cutting begins.
Partnering for success
The above has been an overview of the major considerations affecting a design for manufacturing review. Some of these points may also be influenced 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.
About the author
Gordon Styles is the founder and president of Star Rapid. Utilizing his background in engineering, Styles founded Star Rapid in 2005 and under his leadership the company has expanded to 250 employees. With an international team of engineers and technicians, Star Rapid combines advanced technologies — such as multi-axis CNC machining — with traditional manufacturing techniques and high-quality standards. Prior to Star Rapid, Styles owned and managed the United Kingdom’s largest rapid prototyping and rapid tooling company, STYLES RPD, which was sold to ARRK Europe in 2000.