August 1, 2022

Selecting a Manufacturing Method for Electronic Enclosures

By Protolabs

Electronic devices are everywhere, from smartphones and laptops for consumers to sophisticated medical devices, critical aircraft flight controls, as well as safety, performance, and entertainment systems in electronic and other vehicles.

Despite their widely varying applications, many electronic devices have at least one thing in common—the circuit boards and other components that make them work are all in an enclosure.

A custom-designed enclosure can help a consumer and computer electronics products stand out from commoditized competitors. Other enclosures offer more practical benefits, such as protecting industrial and other equipment from moisture, heat, or chemicals, among other hazards.

Various manufacturing processes are available to create an enclosure that will meet the performance and aesthetics that most electronic devices require. These services can carry a project from prototyping to low-volume production while accelerating time to market and leading to savings over time.

This introduction covers the advantages and disadvantages of each process for manufacturing enclosures, including design considerations, material and assembly options, and advanced manufacturing techniques.

enclosure IM assembled
This plastic molded enclosure is actually an assembly of multiple parts.

Injection Molding

Plastic injection molding produces strong, durable parts. That makes it a good choice for medical and other small handheld devices like remote controls, laptop docks, and parts for smartphone bodies. Finishes range from almost shiny to matte. You can also get clear parts for buttons, lenses, or light pipes. Depending on their geometries, larger parts can be challenging to manufacture in-house and could be better suited for our Hubs manufacturing network. 

Injection molding example
Plastic molded parts provide a lightweight option for enclosure design.

The prototype injection molding process delivers parts within days, helping to cut product development cycles by weeks, sometimes months. Prototyping this way can be more costly when iterating before production but it also can serve as a bridge to production. As customers look for higher volumes of parts, Our on-demand manufacturing process offers unlimited shots from each mold.

Round CNC machining endmills create the aluminum molds that produce injection-molded parts, so designs should include a radius or a certain amount of rounding where part floors meet walls and at the tops of walls. Protolabs’ design for manufacturability analysis can identify where radii are in a part. The standard design review also evaluates wall thickness, where consistency improves plastic flow into the mold to produce a high-quality part. Side-actions will create holes for connectors or power supplies.

ABS/PC blends and glass-filled nylon are among the materials that give the best durability in injection-molded parts.

A medical instrument case or other enclosure that attaches to a mating piece with screws or bolts is a candidate for insert molding, an advanced manufacturing process in which threaded metal inserts are placed into the mold before plastic injection. Another advanced process, overmolding, involves molding a soft plastic or liquid silicone rubber component onto an already molded hard-plastic part, or substrate. The two parts are chemically or mechanically bonded together permanently.

The standard lead time for injection molded parts is as fast as 7 days.

Sheet metal example
Sheet metal is a popular option for enclosures and offers a variety of potential features, such as flanges slots, and screw holes with countersinks.

Sheet Metal Fabrication

The go-to process for making enclosures for computer parts, panel boxes, and electronics bus bars is sheet metal fabrication. Sheet metal enclosures or parts are cut from a thin, flat piece of metal, bent into shape with a press brake or folder and, sometimes, welded. Holes for cables or louvers for venting are laser cut from the sheet before the bending starts. Though light, metal enclosures are highly durable and the material typically is affordable.

Designs likely have to be less complex because of the limitations and safety concerns involved in manually bending a piece of metal. With fewer material choices than for other processes, most sheet metal enclosures are made from aluminum or stainless steel.

We have thousands of sheet metal hardware options for integrating nuts, pins, studs, and other connectors, or threaded or unthreaded standoffs to provide space between connected parts.

Powder coating—like a dry paint that is applied and baked onto any electrically conductive metal, is a popular finish for metal enclosures. It’s faster, cheaper, and more durable than paint, especially outdoors. Also, it looks great.

With a box-type enclosure, small notches or bend reliefs can keep the metal from bulging outwards and leaving a slight gap where two flanges come together. Or, those areas can be ground smooth, welded, and powder-coated so it looks like one solid part. Two design features to consider if you want to eliminate sharp edges on sheet metal enclosure parts a radius—or rounded corner—or an angled/beveled corner known as a chamfer.

A customer may need only a small number of sheet metal enclosures. But once the setup is in place to produce them, making more will cost less. Parts can be available as fast as three business days, but powder coating, hardware installation, and welding may add a day or two to that.

An endmill machines an enclosure.
An endmill machines an enclosure.

CNC Machining

Speed is the biggest reason for using CNC machining to make electronic enclosures, with parts ready in one to three business days. You can also machine more complex designs, but they might take a bit longer to produce. Machined parts are durable and our CNC machining process uses most of the plastics available for injection molding and most of the metals used in sheet metal fabrication.

Most machined enclosures are one-offs for creating a specialized replacement part or prototyping a new design. Because machining is a subtractive process—cutting the part or enclosure from a block of material—it is somewhat more expensive. For orders of 150 or more parts, going with sheet metal fabrication or injection molding may be cheaper in the long run.

Plastic parts are sent out as milled, so some tool marks may be visible. Metal parts can be bead blasted to have a matte finish. Metal parts also can be anodized or chemical-coated to protect them from corrosion.

3D example 2
3D printing affords highly customized enclosures made from durable materials.

3D Printing 

Stereolithography (SLA), selective laser sintering (SLS), and Multi Jet Fusion (MJF) are the primary industrial 3D printing processes used to make enclosures for electronic consumer products and industrial equipment. All three can produce prototypes or end-use parts in as fast as a day.

Stereolithography uses an ultraviolet laser that draws on the surface of a liquid thermoset resin to build parts using thousands of layers of material. This results in a smooth part surface finish. It creates concept models, cosmetic prototypes and complex parts with intricate geometries. When prototyping, designers may have a clear enclosure printed to see how circuit boards and other components will fit. Some electronic enclosure prototypes test for airflow by including small blocks representing transistors and other components, sending smoke into the box to see how it circulates. Just as with injection molding, functionally clear parts for buttons, lenses, or light pipes can also be printed.

3dp example
SLS and MJF are capable of printing durable enclosures with chemical and heat resistance properties.

While both SLS and MJF produce robust, durable nylon enclosures, they differ slightly in how the materials are processed. Selective laser sintering uses a computer controlled C02 laser to fuse layers of powdered materials from the bottom up. Multi Jet Fusion selectively applies fusing and detailing agents across a bed of nylon powder, using heating elements to fuse layers to form a solid component. Both processes result in a textured finish, very similar to denim blue jean material. Most of the material options for SLS and MJF (both filled and un-filled materials) afford chemical and heat resistance properties, making them ideal candidates for end use enclosures. Additionally, these materials can produce parts with flexibility, such as living hinges or snap features, making them ideal for single part enclosures that require secure connections.

Selective laser sintering and Multi Jet Fusion are ideal for low-volume production. This could be hundreds of parts although orders for smaller enclosures may easily run into the thousands. Nylon powder bed technologies are some of the fastest 3D printing processes, so they generally have the lowest per-part price, especially in larger quantities