Design for Manufacture and Assembly (DFMA)

What is it?

Design for Manufacture and Assembly is a critical part of the product development process and early consideration can be crucial in ensuring a successful product outcome.

DFMA (or DFM in its shortened form) is the approach of designing products or components to minimise manufacturing costs. It is estimated that about 70% of a product’s manufacturing costs are determined by design decisions such as material and manufacturing methods. Each component within a product has an important role to play in this process  – be it as simple as selecting a common fastener that is used across an assembly, or a higher-level decision such as choosing a suitable manufacturing process; one that suits the expected production volumes and operational conditions.

The real challenge and craft of DFMA is achieving the key performance, usability and quality requirements of the product whilst still ensuring optimal cost and manufacturability goals are achieved. Cobalt recognises the importance of early consideration of DFMA and it has become an integral part of our NPD (new product development) process. During our DFMA process, we typically consider the following key elements:

Number of parts
Minimising the number of parts provides benefits through reduced inventory, part handling and assembly steps. However, this needs to be balanced against making parts overly complex that will result in increased unit and/or tooling costs.

Performance requirements
The physical demands on a product will often drive early decisions on the most suitable manufacturing process and material. For example, a product may have both high mechanical demands, but also requires electrical isolation leading to a high strength, non-metallic construction such as an engineering plastic or composite. This drives direction of the proposed manufacturing process, but these are then considered against other factors such as cost, availability, environmental and product compliance/certification needs.

For example, stainless steel provides superior corrosion resistance but is often more difficult to process for common sheet metal or forming processes. Use of a carbon steel plus a protective coating may provide more cost-effective approach.

Part Standardisation
Use of standard parts has many benefits including reduced manufactured cost, development cost and lead time. Also, standard or OEM parts will often have well defined performance and reliability data that can be used to reduce the development time of interfacing custom components.

Design for modularity
If product is intended to have multiple models, each with varying features or options, design for modularity can significantly reduce design and inventory requirements. For example, a product could be designed to have a common enclosure or structure with an array of mounting features designed for assembly of various internal components that are integrated depending on the model or product type. A desktop PC case is a good example of this – standard slots and mounting points are used to allow configuration of various internal components such as CPUs, power supplies, video and network cards.

Handling and part orientation
For example; eliminate assembly error through integration of assembly features (poka-yoke1), or reducing the need to rehandle the product during assembly.

Design for ease of assembly
Consideration of assembly and fabrication techniques can significantly reduce overall production cost. Use of alignment features such as lead-ins or guide pins, minimising tight fitting features and adding compliance between parts where possible can significantly reduce assembly time.  Secondary processes such as painting, polishing or finish machining should be minimised and only specified on compatible combinations of materials and processes.

Precision and tolerance
Understanding finished part precision and variation depending on manufacturing process is important when considering DfM. High precision will increase cost – therefore limiting this to only critical features is important, while also ensuring the selected manufacturing process can produce parts to meet this requirement. Often cost efficiency can be found by using secondary processes such as machining or grinding to achieve precise and localised features.

Testing and Inspection requirements
Consideration of in-process inspection testing of critical individual parts or sub-assemblies to minimise risk of rework. Design plays an important role here with features included to allow quick visual checks of correct component assembly, use of go/no-go features and utilisation of sub-assembly methodology.

Maintenance or servicing
Knowledge and consideration of post-production maintenance or service requirements will impact the DfM approach. For example, snap fits provide a cost-efficient method to join parts together by reducing assembly time and eliminating the need for separate fasteners. However, snap fit components are often difficult to disassemble and can become damaged during the disassembly process.

Design for automation
Automation is now commonplace in mass production. Automated production processes have a unique set of demands that include handling, part identification and accessibility considerations.

Minimising Development Effort

Incorporating DFMA into the NPD process from the start will reduce development time and in many cases development costs. Early DFM consideration often eliminates the need to redesign or reengineer parts or assemblies after the concept has been developed. Developing the DFMA approach during the concept ideation phase ensures concept designs are formed on a practical, real-world basis, often requiring input from a range of disciplines and roles from design to engineering to manufacturing operations.

DFMA Casestudy

An example of our approach was a high-volume consumer product which had to meet an ultra-competitive price point, that Cobalt designed for a midsized client with inhouse manufacturing.  The product had to appeal to architects, so the overall industrial design result needed to be high. It also had critical performance and reliability demands, and housed electronics, electrical, mechanical and heating elements. Early electronics engineering input identified the need for RF/EMI shielding, which would have driven the material and/or surface coating costs. In this case, considering both design and DFMA early in the concept phase, we were able to:

  • Recommend an enclosure design which removed the need for a separate EMI shield.
  • Industrial design of the form, finish and usability features allowed the client to charge a premium for the final product, whilst increasing sales.
  • Engineered the body to enable model variations to be configured during assembly, thereby significantly reducing inventory and warehousing requirements.
  • Optimised detail design so that assembly was faster than the outgoing model
  • Overall result; higher sales; higher RRP; lower COGM; higher profitability

If you have a product that requires design for manufacture or assembly input or if you want to know more about our new product development process, contact us today for a confidential discussion.

References

  1. https://en.wikipedia.org/wiki/Poka-yoke