Design for Manufacture and Assembly (DfMA)

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Design for Manufacture & Assembly (DfMA) is an engineering design methodology designers and manufacturers should use to minimise cost and increase the quality of product designs.

What is Design for Manufacture and Assembly?

DfMA is a design methodology that emphasises manufacturing simplicity and assembly efficiency. As a result, a product’s design can be improved to enable faster, safer, more cost-effective, and more efficient manufacturing and assembly.

CNC Milling - Manufacture and Assembly
CNC Machining

Design for Manufacture and Assembly consists of two primary methodologies. One for manufacturing and another for assembly. They are Design for Manufacture (DFM) and Design for Assembly (DFA). DFM and DFA aim to optimise design while lowering labour, materials, and overhead costs.

What is Design for Manufacture?

DFM entails designing a product’s parts to be as simple to manufacture as possible. Therefore, choosing the most economical materials and production methods is essential, reducing the manufacturing process’s complexity.

Principles of DfM

  • The parts should be made to fit within the tolerance limits of the manufacturing process.
  • The part should be defined as a manufacturing process at an early stage
  • Part features should  be within the capabilities of the chosen manufacturing process
  • A designer should explore and improve all manufacturing functions, including fabrication, assembly, testing, procurement, shipping, service, and repair of parts and assembly

What is Design for Assembly?

Dfa entails designing a product to be simple to assemble. It focuses on minimising the number of assembly operations and lowering the cost of product assembly.

Typical products go through the following stages and checks.

  • Designed
  • Prototypes
  • Tested
  • Manufactured or procured
  • Inspected
  • Controlled
  • Documented
  • Life cycle managed

Since each part you design and introduce has to go through the above stages, the cost of managing a single component adds up; hence reducing the part is the most significant function of the DFA.

Principles of Design for Assembly

Recommendation by Ulrich & Eppinger (1995)

  • Reduce part count and part types
  • Strive to eliminate adjustments
  • Design parts to be self-aligning and self-locating
  • Ensure adequate access and unrestricted vision
  • Ensure the ease of handling of parts from bulk
  • Minimise the need for reorientations during assembly
  • Design parts that cannot be installed incorrectly
  • Maximise part symmetry if possible or make parts asymmetric
  • Eliminate processing steps
  • Choose the appropriate economic scale for the process
  • Standardise components and processes
  • Adhere to “Black Box” component procurement (describe what the component has to do, not how to achieve it)
  • Minimise system complexity

Advantages and Disadvantages of Design for Manufacture and Assembly

Advantages of DfMA

  • Reduced waste
  • Lower manufacturing
  • Fewer design changes during the later stages of the design process
  • DfMA significantly reduced the assembly cost by using fewer parts, requiring less labour, and using fewer unique parts.

Disadvantages of DfMA

  • Prices rise due to high startup costs for factories and a lack of demand for mass-produced goods.
  • Design for manufacture and assembly methodology is not always the cheapest option as it depends on quantity.