Electronic Enclosure Types — Making the Choice Before Design

A critical step in planning and developing an optimal product design architecture includes determining the most appropriate custom electronic enclosure, both materials and process.  The selection defines enclosure development methodology based on production level and process.  This defines design rules.  Having its roots in manufacturing, NETBased knows the areas of flexibility and limitations within each set of materials and processes.  For instance, in a sheet metal enclosure, if the design calls for an irregular hole, a bridge lance, cardguide or tab, can it be run on inexpensive machinery or will it take more expensive machinery plus multiple secondary operations?  Knowledge of machinery, programming methods, setups, capabilities, etc., makes a difference as it defines the design rules and ultimately the reoccurring production costs.  If it’s the more expensive route, what are the alternatives to reducing production cost?  Designing to each processes strengths is key to reducing manufacturing costs and time-to-market.

Injection molding is not always the most appropriate choice for plastic enclosures.  There’s also pressure forming that can provide similar detail and definition to injection molding with the proper concept and execution.  Structural foam, gas-assist injection and reaction injection molding or RIM are also used for plastic enclosures.

Sheet metal, when properly designed, can provides inherent EMI containment.  Extrusions and die-casting can also be considered where unique part geometry, structural strength and EMI containment are desirable.

The design rules change from fabrication to stamping and from injection molding to RIM or thermoforming. Intimate knowledge of materials behavior, tooling design and production methods all play a part in making optimal material, process, design and geometry choices.  The correct choices save cost.

  Process Pros Cons Volume Tooling Part
Sheet Metal Fabrication Design flexibility for regular shapes
Small to large parts
No or minimal tooling
EMI containment
Labor intensive
Secondary process for hardware
Secondary processes (plating/painting)
L – M  0 – $ $$$
Sheet Metal Stamping Design flexibility for regular shapes
Increased structural design shapes
Thinner material thickness than fabrication
EMI containment
Tooling costs
Tooling production time
Tooling modifications
Secondary process for hardware
Secondary processes (plating/painting)
M – H $$ – $$$  $ – $$
Injection Molding Flexibility for design geometry
Uniform wall thickness
Large selection of materials and properties
Tooling costs
Tooling production time
Tooling modifications
Secondary process for EMI containment
M – H  $$ – $$$ $
Reaction Injection (RIM) Flexibility for design geometry
Thick and thin wall thicknesses
Labor intensive
Secondary processes (EMI & painting)
L – M  $$  $$
Pressure Forming Mid to very large part size
Somewhat flexible part geometry
Mid to very large part size
Somewhat flexible part geometryabor intensive
Secondary component assembly
Secondary processes (EMI/plating/painting)
L – M  $$ – $$$  $$ – $$$
Extrusion Some design flexibility
Small to medium parts
EMI containment
Limited material options
Secondary operations (trim/threading/machining)
Secondary processes (plating/painting)
L – M $$ $$
Die Casting Flexibility in design geometry
Increased structural strengthen
EMI containment
Limited material options
Secondary operations (trim/threading/machining)
Secondary processes (plating/painting)
M – H  $$$  $ – $$

Additional Considerations:

  • Market
  • Customer perception
  • Production levels
  • Products’ physical size
  • Environment
  • Industry compliance
  • Tooling budget
  • Reoccurring costs
  • Material selection (limited for some processes and a wide variety for others)
  • Tooling production which affects time-to-market
  • Tooling material (in some cases)
  • Tooling design
  • Part design intricacy
  • Secondary processes
  • Plating
  • Painting
  • Coatings for emissions and immunity