Minimize Part Count and Levels of Assembly

Minimizing part count and levels of assembly is an important principle in ergonomics in DFMA. Here are strategies for this principle.

Minimize the number of levels of assembly

Some subassembly is good, but don't go overboard. By decreasing the number of assembly levels, you:

• Simplify specifications

• Facilitate the assembly process

• Simplify factory layout

• Minimize numbers and types of fasteners, cables, etc.

The addition of a single screw to a product doesn't add just the cost of the screw, but also the cost of:

• Having someone align it and screw it in

• Drilling and tapping the hole, and the machinery to do it

• Overhead for inventory

• Time and space necessary for the assembly process

The same goes for different types of cables and connectors in electronic equipment, as well as many other examples.

Encourage modular, interchangeable assemblies

Designing interchangeable parts with specific qualities makes customization easy.  

Other advantages:

• Reduces final assembly time

• Simplifies inventory

• Facilitates automation

• Reduces post-assembly adjustments

• Improves serviceability

Build in self-fastening features

This goes hand-in-hand with reducing the number of fasteners and using special characteristics of the material. Snap-fit items are easily molded from plastics, and fold-over tabs are easily stamped from sheet metal.

This example shows how a snap-fit tab can take the place of a separate screw. Not only does one eliminate the screw, but also time is saved because the tab is self-aligning.

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