Design for Manufacturing (DFM)
Design for Manufacturing (DFM) is the process of designing parts, components or products for ease of manufacturing with an end goal of making a better product at a lower cost.
This is done by simplifying, optimizing and refining the product design.
The acronym DFMA (Design for Manufacturing and Assembly) is sometimes used interchangeably with DFM.
Five principles are examined during a DFM. They are:
Ideally, DFM needs to occur early in the design process, well before tooling has begun. In addition, properly-executed DFM needs to include all the stakeholders — engineers, designers, contract manufacturer, moldbuilder and material supplier.
The intent of this “cross-functional” DFM is to challenge the design i.e. to look at the design at all levels such as component, sub-system, system, and holistic levels , to ensure the design is optimized and does not have unnecessary cost embedded in it.
Changes become more expensive, as well as more difficult to implement, as the design progresses through the product life cycle. Early DFM allows design changes to be executed quickly, at the least expensive location.
Pulling stakeholders together early in the design process is easier if you’re developing a new product, but even if you’re dealing with an established product, challenging the original design is a necessary element of a thorough DFM. Too often, mistakes in a design are repeated by replicating a previous design. Hence question every aspect of your design.
- Look at the original drawings.
- Tear down the product.
- Look at competitive and near-neighbor products, as well as lead users such as medical and automotive.
- Talk to your contract manufacturer — who may have solved the problem with a different customer?
- Has someone else solved this problem a different way?
- Is there a way to make it better?
5 Principles of DFM :
The manufacturing process chosen must be the correct one for the part or product. You wouldn’t want to use highly-capitalized process like injection molding which involves building of tools and dies to make a low-volume part that could have been manufactured using a lower-capitalized method, such as thermoforming. That would be equivalent to using a tank to squash an anthill — a classic case of overkill.
In determining the manufacturing process, the DFM took into consideration the quantity of parts being made, the material being used, the complexity of the surfaces, the tolerances required and whether there were secondary processes required.
Design is essential. The actual drawing of the part or product has to conform to good manufacturing principles for the manufacturing process you’ve chosen.
In the case of plastic injection molding, for example, the following principles would apply:
- Constant wall thickness, which allows for consistent and quick part cooling
- Appropriate draft (1 – 2 degree is usually acceptable)
- Texture – need 1 degree for every 0.001” of texture depth on texture side walls
- Ribs = 60 percent of nominal wall, as a rule of thumb
- Simple transitions from thick to thin features
- Wall thickness not too small – this increases injection pressure
- No undercuts or features that require side action – all features “in line of pull/mold opening”
- Spec the loosest tolerances that allow a good product – and consult the trade organization for your manufacturing process on what is reasonable for that process
Be sure to discuss the design with your contract manufacturer, who can ensure that your design conforms to good manufacturing principles for the selected process.
It’s important to select the correct material for your part/product.
Some material properties to consider during DFM include:
- Mechanical properties – How strong does the material need to be?
- Optical properties – Does the material to be reflective or transparent?
- Thermal properties – How heat resistant does it need to be?
- Color – What color does the part need to be?
- Electrical properties – Does the material need to act as a dielectric (act as an insulator rather than a conductor)?
- Flammability – How flame/burn resistant does the material need to be?
Again, be sure to discuss the material with your contract manufacturer, who might have access to existing materials in their portfolio which would allow you to secure lower material pricing.
Your part/product must be designed to withstand the environment it will be subjected to. All the form in the world won’t matter if the part can’t function properly under its normal operating conditions:
All products must comply with safety and quality standards. Sometimes these are industry standards, others are third-party standards and some are internal, company-specific standards.
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