Selecting a Manufacturing Method for Electronic Enclosures

Posted On 03/10/2022 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 commoditised 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 moulded enclosure is actually an assembly of multiple parts.

Injection Moulding

Plastic injection moulding 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 moulding example
Plastic moulded parts provide a lightweight option for enclosure design.

The prototype injection moulding 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 mould.

Round CNC machining endmills create the aluminium moulds that produce injection-moulded 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 mould 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-moulded parts.

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

The lead time for injection-moulded parts is generally 15 days.

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 moulding.

Most machined enclosures are one-offs for creating a specialised 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  injection moulding 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 anodised or chemical-coated to protect them from corrosion.

3D example 2
3D printing affords highly customised 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 moulding, 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