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The DFA, translated by Design for Assembly, brings together product design rules to improve the assembly of the product once in production. 


The DFA brings together a whole range of rules whose objective is to optimize the assembly process of a product. The challenge is to help designers to design a product whose production will generate the minimum cost reducing the number of parts, reducing the number of assembly steps, movements…

The method is based on the study of an existing product or prototype to improve the assembly process.

Beyond the 10 principles of design and project management presented below, there are 3 methods to implement the DFA :

The 10 design principles of DFA

When setting up the DFA (Lucas method or other), we will begin our study by performing a DFA analysis (see Excel file on your left) which is based on the elements below.

They will help us search for “good ideas” to identify the minimum number of really useful parts that adhere to DFA design principles. Assign a score for each Principle according to the following rule :

  • 0 : the condition is respected
  • 1 : the condition is correctly respected
  • 2 : the condition is moderately respected
  • 3 : the condition is not met but with a small financial impact
  • 4 : the condition is not met and has a strong financial impact 

For scores of 3 or 4, improvement actions will be needed.




1. Reduce the number of part

Reducing number of parts allows us to significantly improve the problems (quality, logistics …) and costs during assembly.

2. Standardize parts

Obvious principle, it will facilitate the problems of logistics, training, will limit the errors …

We will use an interchaFngeable module design.


3. Design parts that do not generate errors

Use the principles of Poka Yoké for the assembly to become “automatically” As for example to make symmetrical parts.

We will ask ourselves the following questions. Can you :

  • Forget the piece
  • Assemble it badly
  • Put the wrong piece



Design pieces that fit independently with the left or right hand and in all directions.

If a piece can not be symmetrical, then make it really asymmetrical.

4. Design parts that do not require adjustments and adjustments or holding in position

Minimizes production errors and time.


5. Minimize reorientations during assembly

Provide space, make elements more easily visible…


6. Design parts that are easy to handle

Avoid holes, closed parts, small / large parts, parts with edges, burrs…

This will prevent them getting tangled and allow the use of vibrating bowl, rail…


7. Concevoir des systèmes de fixations simples

Screw systems are long and complex. Where they are needed, it will be necessary to standardize.


8. Design parts that fit together easily

Avoid the use of tools, glue, provide forms that help insertion, limit assembly efforts.


9. Design a product that flips up and down

The design should allow to begin the assembly by a large piece of base, on which we will fix the others by the top.


10. Avoid soft parts

More complex to mount, they are also more fragile and complex to store.


The 10 tips of the project management

  1. All key players must be present when designing the product.
  2. Create renderings and prototypes of the finished product.
  3. Divide the product architecture into a module or assembly group.
  4. Perform a time and cost analysis of its assembly.
  5. Generate a cost reduction idea list.
  6. Use creative tools to improve design.
  7. Select the best ideas.
  8. Select materials, parts and processes by integrating suppliers as soon as possible.
  9. Set target costs for each part.
  10. Conduct a detailed analysis of the new product.
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