Why Custom Enclosure Modifications Matter (And How to Design Them)

Nearly every electronic system needs an enclosure, but not all designs can use a standard model. In some cases, full customization is required, but for many designs, modifying an off-the-shelf enclosure is faster and more cost-effective. This is particularly true in applications where aesthetic value is as important as performance.

The role of enclosures is multifold. They communicate functionality in industrial settings, influence consumer preferences with visual appeal, and maintain brand messaging and identity. Modifications such as painted enclosures and screen-printed graphics help to fulfill these expectations. Customization can also help designers keep up with changing markets accelerated by the Internet of Things (IoT).

While there are many advantages, there are also numerous pitfalls in the customization process that can lead to product delays, cost overruns, and customer dissatisfaction.

This article provides a basic introduction to enclosures for electronic systems. It then lays out a strategy for successful enclosure modification. It focuses on smaller enclosures from Hammond Manufacturing for IoT devices in applications such as building and home automation systems, handheld test and measurement devices, and operator interfaces for commercial equipment.

The basics of enclosures for electronic systems

The primary function of an enclosure is to house an electronic system, protecting it against environmental factors such as dust, moisture, ultraviolet (UV) radiation, and physical damage. An enclosure can also play a vital role in heat dissipation as well as shielding against electromagnetic interference (EMI) and radio frequency interference (RFI).

Meeting these goals starts with the selection of appropriate material. The options include acrylonitrile butadiene styrene (ABS) plastic, polycarbonate, extruded and die-cast aluminum, and various steel grades. Each material has unique tradeoffs in cost, weight, durability, and appearance.

An example of enclosure variety is the 1554/1555 series from Hammond Manufacturing (Figure 1). These enclosures are available in inexpensive ABS plastic for general purpose, low-cost use, or rugged polycarbonate for more demanding applications. The latter option is rated up to the National Electrical Manufacturers Association (NEMA) 4/4X and 6/6P for water-tight and submersible applications and has a flame rating up to UL94-5VA. The enclosures use a gasket tongue-and-groove seal to provide ingress protection (IP) up to IP68.

Figure 1: The 1554/1555 series enclosures are rated to NEMA 4/4X and 6/6P and use a gasket tongue-and-groove seal to provide ingress protection (IP) up to IP68. (Image source: Hammond Manufacturing)

Enclosures must also enable the physical securing of the electronics by providing mounting points such as studs, printed circuit board (pc board) slots, and DIN rail mounting tabs. For example, the 1554/1555 series features slots molded into the interior that accept vertically mounted 1.6 millimeter (mm) pc boards.

Another example is the 1455NHD series of aluminum enclosures (Figure 2). These feature seven horizontal slots that accept the 100 × 160 mm single Eurocard. The extruded aluminum enclosure can also serve as a heatsink, with six heat-dissipating fins integrated into the design for this purpose.

Figure 2: The 1455NHD enclosure integrates seven PC board slots to easily mount Eurocards and has six heat-dissipating fins . (Image source: Hammond Manufacturing)

Common enclosure modifications

One of the primary reasons to modify an enclosure is to create holes and cutouts for features such as:

• Entry points for power and data cables
• User interfaces including lights, buttons, and displays
• Maintenance access and battery replacement
• Exhaust fans and other environmental controls

An enclosure can also require the addition of various parts, including:

• Mounting points, such as an internal metal panel to support heavier components
• A transparent or translucent faceplate to enable visual inspection of the system and any internal readouts
• Accessories to aid cable routing, portability, and other functions

Figure 3 illustrates a 1554 series enclosure modified with many common alterations.

Figure 3: The 1554 series enclosure can be extensively modified by the manufacturer. (Image source: Hammond Manufacturing)

Most of these modifications require machining of the enclosure to ensure the proper sizing and alignment of the holes, cutouts, and mounting points.

To avoid costly and time-consuming rework, obtaining a sample of the modified enclosure is necessary to verify an accurate fit. Getting a sample can also improve the overall design by revealing opportunities for changes that can simplify the assembly and maintenance of the product.

Material failures and the need for quality control

Machining can also lead to material failures. For plastic enclosures, excessive mill feeds can melt the plastic, causing deformation and stress cracking. Reactions with tooling coolants can also cause fractures.

Metal enclosures present their own challenges, primarily that the materials are more difficult to work with, requiring specialized tools and skills. Small or intricate openings are particularly challenging with metal enclosures. Machining can also impact the porosity of some materials, like die-cast aluminum. Other damage can occur from pressing in hardware such as studs, as well as sharp edges and burrs left behind by poor machining.

These factors can alter an enclosure’s IP rating and damage its structural integrity. These machining flaws can be difficult to detect, so it is critical to have a robust quality control process.

Painting, screen printing, and other finishes

The appearance of the enclosure is important. A clean visual design can help users locate, identify, and utilize a system’s features. An example is a 1553T handheld case designed specifically for instrumentation. It features screen-printed graphics that indicate the functions of the user controls (Figure 4).

Figure 4: A 1553T case meant for handheld instrumentation exemplifies the need for user-friendly graphics. (Image source: Hammond Manufacturing)

An appealing design can go even further, helping to uphold a brand image and motivating customers to choose a product over the competition. For designers, starting with an enclosure with the desired look and feel is important.

Figure 5 shows the 1557 series, an example of an enclosure family designed to meet current aesthetic trends. These enclosures are noteworthy for their rounded corners and faces. They provide a modern look while maintaining traditional designs' durability and IP ratings.

Figure 5: The 1557 series enclosures provide a modern, rounded look for greater appeal to aesthetic-sensitive customers. (Image source: Hammond Manufacturing)

Figure 5 also demonstrates the substantial role of external finishes. Powder coating, anodization, and other finishes can provide a polished look while protecting an enclosure against UV radiation, corrosive chemicals, and other environmental hazards. Screen printing can add engaging visuals and critical information about a system's function and use.

However, poorly executed finishes can be a detriment to an enclosure’s appearance and performance. Screen-printing errors such as misalignment or incorrect colors can damage a brand’s reputation. Bubbling and flaking paint can make a product unappealing and reduce sales. If the coating plays a protective role, flaws in the finish may also expose the system to damage.

As with machining, tight quality controls and early sampling are critical to avoiding these issues and meeting the project objectives.

Choosing an enclosure modification strategy that minimizes risk

Given the attendant risks, the challenge for engineers is how to best approach modification. One option is to perform modification in-house, but if the in-house team is inexperienced or lacks the necessary tooling, this can lead to poor execution.

Another option is to purchase standard enclosures and then send them out to a secondary source for modification. The risks of this approach include:

• Challenges in communicating design specifications
• The possibility of multiple revisions
• Long delays in receiving the finished products

To avoid these issues, engineers now have the option to have their enclosures modified directly by the manufacturer. The key benefit of this approach is that the manufacturer already knows the full specifications of their enclosures, how to change them, and how to test the results to ensure a quality product. This approach gives engineers more predictable outcomes and a shorter time to market.

How to select an enclosure manufacturer

Manufacturers have varying capabilities, requirements, and processes, so it is essential to start by assessing candidate manufacturers and selecting one whose offerings meet the project demands. The first step is to ensure the manufacturer can complete the order size on the required timeline. For example, Hammond has a typical minimum order quantity (MOQ) for modified items of only 25 pieces and can fulfill many orders in only a few weeks.

The next step is to verify that the manufacturer can implement the required modifications. For example, Hammond can execute the following:

• Holes, cutouts, tapping, threading, and countersinking
• Pressed-in hardware, such as studs and standoffs
• Printed artwork, including logos and labels
• Special sizes and colors
• Pre-installed accessories

Finally, ensuring that the manufacturer has rigorous quality control and can provide samples ahead of production is critical. The process Hammond follows illustrates this point:

• To ensure the enclosure is built to specifications, the company provides an approval drawing and the required artwork proof for review before beginning work.
• Once approved, Hammond will build and carefully test a single sample for flaws.
• The company then receives the sample piece for inspection and testing. If the design requires tweaks, Hammond can overnight a new sample with the required changes. Full production only starts after the sample is approved.

Hammond takes several other steps to ensure quality. For example, all painted enclosures needing holes and cutouts are modified before being painted, ensuring the edges around the cutout have factory-quality paint coverage.

How to collaborate with an enclosure manufacturer to optimize design

Working directly with an enclosure manufacturer opens opportunities for design optimization. For any given project, there are many enclosure options. Consulting with the manufacturer can help the designer narrow their search of enclosure options and rapidly identify the ideal solution.

It is also worth investigating what kinds of information the manufacturer requires. Some manufacturers, like Hammond, can accept documents as simple as rough sketches, while others require specific formats. Resolving this question early in a project can save considerable design time and effort.

The manufacturer may also offer ways to simplify long-term engagements. For example, Hammond assigns every customized enclosure a unique part number so that additional quantities of the same design can be ordered later.

Conclusion

In addition to physical protection for electronic systems, enclosures enhance the user experience and safety, distinguish the product, and reinforce the brand. By leveraging an enclosure manufacturer’s expertise, designers can navigate the challenges of customization and successfully balance functional requirements, aesthetics, cost, and time to market.

Additionally, Hammond’s two dedicated modification facilities, one in North America and one in Europe, can customize boxes with holes, cutouts, silk screening, special length extrusions, and so forth.