The ultimate guide to DFA (Design For Assembly)

The Concept of Assembly

Assembly refers to the assembly of components into a product that can achieve the quality of a variety of products. The concept of assembly can be derived from the meaning of assembly:

a) Put the components together;

b) Realize the corresponding functions;

c) Achieve great quality of the product.

The most important thing in assembly is to achieve the product functions requirement and product quality requirement, not simply locking the screw or putting together the components. Therefore, assembly is a way to realize product function and product quality.

A product needs to go through the process of assembly before it can be manufactured and become a product. Products contain anywhere from a few to millions of parts. A stapler has dozens of parts, a cell phone has hundreds of parts, a car has tens of thousands of parts, and an airplane has more than a few million parts. Assembly is an important part of the product manufacturing process, and the assembly process has a great impact on product quality, product cost, product development cycle, and so on.

There are seven steps in the typical assembly process: 

Step-1  Place the base; The base of a part does not necessarily refer to the fixture bench, it could also be a part. For example, in the winding of the stator, relative to the enameled wire, the stator rack is a part serving as a base.
Step-2 Identify the parts; Identifying parts is also important in the assembly design process. For example, if the color of the O-ring and the parts are all black, it is difficult to recognize different parts in terms of the vision system.
3) Grab the parts; The difference between manual assembly and automated assembly needs to be considered. If the part is too soft, or too slippery, it’s difficult to grasp it for assembly.
4) Move the part to the assembly position; Parts are best assembled once in place with no interference along the way.
5) Adjust the parts to the correct position; Sometimes we need to consider adding guide features to assist the adjustment. 
6) The parts are fixed; The parts of each process are preferably fully constrained, and then proceed to the next process.
7) Inspection; This is the end of a process.

The process of manual assembly and automated assembly will be slightly different. But all assembly design requirements stem from these seven basic steps, so it’s important to remember.

Mechanical designers can generally understand the assembly process based on these seven steps, but assembly process engineers need to know more, such as the location of incoming materials, the arrangement and efficiency of fixture benches, and the specific assembly methods of production line workers. Therefore, after the mechanical engineer completes the DFA (Design for Assembly), it is necessary to discuss it with the assembly engineer.

The Difference Between A Good Assembly Design And A Bad Assembly Design

Design For Assembly (DFA)