Originally published on fastradius.com on December 2, 2020
Electricity is a powerful, yet delicate force that is the key to our modern world. At any point, a person might wear or interact with several electronics at once, from cell phones to smartwatches and life-saving medical devices. While consumers might take these devices for granted, a tremendous amount of work goes into designing the various enclosures that protect the electric circuitry and wiring that ensures their functionality.
The delicate nature of these electronics often requires that they be housed within some kind of enclosure or cage to protect their circuitry and wiring from damage. These enclosures serve not only to keep chemicals, dust, moisture, and other environmental elements from adulterating the electronics, but also protect end-users from electric shocks and potential fires. Typically, the enclosure is the only part of the device that the consumer sees.
Electronics enclosures take a wide variety of shapes and sizes — from phone and computer housings to protective enclosures for power and telecommunications systems — and the specific manufacturing method best-suited for a particular job will depend on a number of factors, including material selection, price point, production volume, and design considerations.
Here’s what product teams need to know.
Key Material Selection Considerations for Electronics Enclosures
The design process for electronics enclosures should be “reverse-engineered” — designers and engineers can work backward, using what they know about the critical requirements for the final application to inform the design, material selection, and choice of manufacturing method.
The selection of the materials best-suited for the job will be determined, in large part, by the degree to which the enclosure will be subjected to stress and environmental wear. The housing for a bicycle speedometer, for instance, has strict material demands: it needs to be able to withstand rain, dirt, and constant intense vibration to prevent the device from malfunctioning. In contrast, a graphing calculator is far less likely to be exposed to high amounts of physical wear, which can significantly expand the pool of viable materials for the enclosure.
While some electronics might feature wood or acrylic materials (record players or handheld gaming devices, for instance), the vast majority of consumer electronics enclosures will be made from rigid plastics or metals. Metal enclosures tend to be stronger and more durable than their plastic counterparts, and are typically made from aluminum or carbon, galvanized, or stainless steel. One significant advantage of metal materials is that they are electrically conductive, which helps to negate incoming and outgoing electromagnetic interference and radio frequencies. Metal enclosures must be electrically grounded to provide shock resistance.
On the other hand, plastic enclosures are generally lighter in weight and less expensive to manufacture, and some engineering thermoplastics can even provide greater strength than metals such as aluminum, aluminum alloys, and magnesium alloys. They are also nonconductive — meaning that energized wires do not create shock hazards if they come in contact with the inside of the enclosure — and will not trigger circuit protection systems. If a conductive surface coating is needed for a plastic enclosure, one can be added in post-production, though the additional time, materials, and labor will increase the cost per part.
Unlike metal enclosures, plastic enclosures do not generate heat. When thinking about end-use applications, it’s important to remember that metals will get significantly more hot than a piece of plastic. If the electrical components inside the enclosure will generate enough heat to impact the material, opting for a plastic enclosure will generally be the safer option; humans would much more easily pick up a plastic shell than a metal one.
Many thermoplastics — polypropylene being one common example — are extremely moisture-resistant, but will degrade when exposed to ultraviolet light over prolonged periods. However, this effect can be mitigated by incorporating UV stabilizers into the enclosure material, or by covering the enclosure’s surface with paint or another UV-resistant finish. In some cases, the flexibility and rubber-like qualities of less rigid plastics can improve the part’s durability or provide watertight seals.
Common Methods for Manufacturing Electronics Enclosures
Ultimately, the material selection for a particular electronics enclosure will determine which manufacturing method is most efficient. Some of the most common methods include the following:
1. CNC Machining
CNC machining is a versatile, subtractive manufacturing process that uses digital CAD files to direct tools in shaping a part from a block of raw material called a “workpiece” or “blank.” The process is highly repeatable — meaning the same design file enables engineers to produce identical copies of a part simultaneously on multiple machines — and can be used to create both plastic and metal enclosures.
While other manufacturing methods are limited to creating relatively simple housings, CNC machining enables greater geometrical complexity to be incorporated into part design while providing super part tolerances. Another advantage of employing CNC machining is that enclosures machined from a single metal workpiece will not display any open seams, creating a clean, visually-appealing product. However, shelling a block of material on a mill might not be a cost-effective option, as you are likely paying for more material than what you’d end up using in the final product.
2. Sheet Metal Fabrication
Sheet metal fabrication is an economic and efficient means by which to produce electronics enclosures. Typically, these enclosures have significantly lower material expenses than their CNC-machined counterparts, in part because with just three bends, a sheet can be transformed into an open-faced housing.
The cases of desktop computers and many outdoor electronics enclosures are common examples of enclosures made via sheet metal fabrication, and what they lack in aesthetic value they make up for in durability. The initial tooling costs associated with sheet metal fabrication can be high, but cost per part rapidly decreases as production volume rises.
3. Injection Molding
The injection molding process involves repeatedly and rapidly filling durable metal molds with molten plastics, thereby enabling the large-volume production of identical parts. Manufacturers often use this method to create simple enclosures from rigid or non-rigid plastics, such as those used in game controllers, electronic keys, kiosk displays, and many other products.
Tooling time and expenses increase the lead time and initial overhead for injection-molded enclosures, but parts become incredibly cost effective when produced in high volumes. Insert molding, a process similar to injection molding, also allows electronics to be firmly embedded within an enclosure for additional protection.
4. 3D Printing
3D printing, or additive manufacturing, uses CAD files to create parts one layer of material at a time, which often allows multi-part assemblies to be condensed into single pieces. 3D printing grants greater geometric freedom — enabling the addition of features such as curved internal channels that are extremely difficult or impossible to produce via other methods.
Further, 3D printing allows for electronics to be fully enclosed within their casings, which often eliminates the need for additional assembly. Generally not suited to large-volume production, additive processes are effective and affordable for prototyping and small- to medium-volume runs. Both metal and plastic components can be 3D printed.
Manufacture Electronics Enclosures of Superior Quality
As digital technologies become evermore ingrained into daily life, maintaining the long-term functionality of electronic devices becomes more important than ever. Electronics enclosures provide critical protection, but engineers and product teams need to ensure that material choice and part design are optimized to deliver maximum benefit.
Choosing a manufacturing partner like SyBridge means that you will gain firsthand access to our decades of collective expertise and knowledge. We’re an on-demand digital manufacturing platform specializing in the efficient and economical production of superior products. Contact us today to discover how we can help transform initial design ideas into fully functioning, durable parts.