IT Metal Enclosures Made of Sheet Metal: Properly Addressing Cooling, EMC, and Grounding Through Design

At first glance, an IT metal enclosure has a simple purpose: to protect electronics. Upon closer inspection, however, it is the result of several requirements, some of which are contradictory. Ventilation openings for airflow compromise EMC shielding. Powder coating for corrosion protection interrupts grounding paths. Fasteners designed for easy maintenance increase the complexity of the enclosure structure and, consequently, the effort required for tolerance management.

Those who fail to take these factors into account during the design phase will end up having to resolve them during manufacturing or operation—often at significantly greater cost. This article explains the requirements that IT metal enclosures made of sheet metal must meet and how these are implemented in terms of design and manufacturing.

BVS Blechtechnik manufactures metal enclosures for IT equipment, from prototypes to mass production.

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What IT Metal Enclosures Must Be Able to Do

Metal enclosures for IT infrastructure combine multiple functions into a single component. They provide mechanical protection for the installed components against impacts and unauthorized access. At the same time, they must dissipate the heat generated by the components’ power loss—passively through ventilation slots and perforations, and, in cases of higher heat loads, additionally through active fans.

In addition, they perform electromagnetic and electrical functions. They protect sensitive components from interference fields generated, for example, by servers, power supplies, or the fans themselves, and ensure safe equipotential bonding to dissipate hazardous contact voltages. At the same time, they must comply with the dimensional requirements of the 19-inch standard according to IEC 60297 and DIN 41494 so that they can be integrated precisely into standardized rack systems.

None of these requirements is unusual on its own—the complexity arises from their simultaneous interaction.

Passive cooling through hole patterns and perforations

Passive cooling in metal IT enclosures works through convection. Air enters on one side, absorbs heat, and flows out again on the opposite side or the top. This airflow is controlled by the perforations in the sheet metal.

Punching tools can be used to create various geometries directly in the material. Round perforations ensure even air distribution while maintaining high surface stiffness. Slotted perforations increase the open area and thus the airflow. Gills and cutouts enable targeted airflow and combine forming and perforation in a single manufacturing step, which is particularly cost-effective in mass production.

The geometry of the perforations influences two opposing characteristics. A higher open area ratio improves airflow but simultaneously reduces the sheet metal’s rigidity and increases the risk of spurious radiation. The optimal balance depends on the power dissipation of the installed components, the enclosure size, and the mechanical requirements. At BVS Blechtechnik, this optimization is routinely carried out in collaboration with customers as early as the quotation and design phases.

Design Principles of EMC Shielding

Effective electromagnetic shielding requires continuous electrical conductivity throughout the enclosure. Any interruption, gap, or unpainted joint can significantly reduce the shielding effectiveness. Long, open slots are particularly critical, as they act like slot antennas and can radiate or couple electromagnetic interference. Shielding effectiveness decreases as frequency increases, while smaller opening geometries improve it.

From a design perspective, this can be addressed, among other things, by using overlapping edges at parting lines to prevent continuous gaps from forming. For moving components such as slide-in modules, contact studs embedded in the sheet metal ensure that a conductive connection is maintained even without rigid screw fasteners. If design measures alone are not sufficient, EMC strips are used as a supplementary measure.

Ventilation openings can also be designed to comply with EMC requirements. Arrays of many small individual holes significantly reduce the shielding effect less than single large openings, even when the total area of the openings is comparable. Relevant standards for IT equipment are EN 55032 and IEC 61000; shielding attenuation tests are conducted in accordance with DIN EN 61587-3. Compliance with these standards is a prerequisite for CE conformity and interference-free operation in data centers.

Acoustics and Vibration Damping in Sheet-Metal Enclosures

Server fans and drives generate continuous vibrations. Large, unsupported sheet metal surfaces can enter into resonance due to this excitation and become sources of noise themselves. This is not a rare problem, but one that is regularly underestimated in the design process.

The most effective measure involves the sheet metal itself: beading and embossing—so-called stiffening formations—increase the panel’s stiffness without adding material and raise the natural frequency of the sheet metal surface. This shifts the resonance out of the typical excitation range of fans and drives.

Where this is not sufficient, insulation mats are added; these are applied either over the entire surface or in specific areas on the interior walls of the enclosure to reduce structure-borne noise and sound transmission. The measures required depend on the specifications and the operating environment. The range extends from simple stiffening ribs in standard enclosures to combined insulation concepts for environments with particularly low noise limits.

Grounding for Powder-Coated Enclosures – Plan Early Instead of Retrofitting

Powder coatings are typically not electrically conductive. Therefore, without additional measures, a fully coated enclosure has neither a secure ground connection nor a functional equipotential bonding system. This is not a design flaw, but it must be taken into account early in the planning process.

From a process standpoint, the solution is clear. Contact surfaces and grounding tabs are defined and specifically masked off before coating to ensure these areas remain free of powder. The location and size of the areas to be kept free depend on the housing’s eventual electrical wiring and are therefore coordinated closely with the customer. Grounding tabs are also integrated as fixed structural elements and recessed accordingly.

In practice, this step is more labor-intensive than it initially appears. If contact surfaces are not defined until after the production run has begun—or even after coating—the rework is time-consuming and often only possible to a limited extent. Early coordination between design, manufacturing, and surface treatment is therefore essential for a reliable and reproducible solution.

Maintenance-friendly housing designs

In data centers, ease of maintenance is often referred to as “tool-less design.” The goal is to be able to replace components without tools in order to minimize downtime as much as possible. In practice, however, this concept can only be fully implemented to a limited extent.

In practice, BVS has found that sliding mechanisms for enclosure lids and inserts, as well as snap-fit connections for removable assemblies and insert elements for plug-and-play components, have proven particularly effective. This simplifies the most common maintenance tasks without requiring the entire enclosure to be opened. However, such systems are generally not entirely tool-free.

Another design-wise measure is to reduce the number of different connection types. If all screw connections are the same size, the technician needs only a single tool for all tasks. This reduces assembly errors and, at the same time, simplifies documentation and service.

Dimensional Accuracy and Tolerances in Rack Systems

IT metal enclosures for rack mounting must consistently comply with the specifications of the 19-inch standard as defined by IEC 60297 and DIN 41494. One height unit (HU) corresponds to 44.45 mm; the external width, front panel dimensions, and mounting spacing are also clearly standardized and are required by rack manufacturers without any additional tolerance.

For enclosures consisting of multiple sheet metal parts, the dimensional deviations of the individual parts add up to the total tolerance of the entire assembly. Even if each individual part falls within the permissible general tolerance, the finished enclosure may still be too large or too imprecise for rack installation.

Therefore, the design is critical. Individual parts should be manufactured as close as possible to the target dimensions, mating parts should have opposing tolerances, and prototype parts should be fully measured before production begins. This allows fitting problems to be identified and avoided early on.

Enclosure design is more than just sheet metal fabrication

IT metal enclosures made of sheet metal are not off-the-shelf products. Cooling, EMC shielding, grounding, acoustics, maintainability, and dimensional accuracy are structurally interrelated and influence one another. Taking these interactions into account early in the design process helps avoid time-consuming corrections during manufacturing and operation.

BVS Blechtechnik manufactures IT metal enclosures—from prototypes to mass production—offering a full range of services under one roof, including stamping, press braking, welding, assembly, and surface finishing.

We provide support for cooling, EMC, grounding, and tolerance concepts—from prototypes to mass production

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IT metal enclosures made of sheet metal must simultaneously meet requirements for cooling, EMC shielding, grounding, acoustics, maintainability, and dimensional accuracy. Early coordination between design and manufacturing is crucial—especially regarding perforation, coating, and tolerance specifications. BVS Blechtechnik supports this process from prototype to series production.

FAQ

What perforation pattern is best suited for cooling IT metal enclosures?

For IT metal enclosures made of sheet metal, the appropriate perforation geometry depends on the specific application. Round perforations offer a good balance between airflow and sheet metal stiffness and are suitable for a wide range of applications. Slotted perforations increase the open area but reduce the sheet stiffness to a greater extent. Gills and cutouts enable directed airflow and can be formed directly into the sheet metal using punching tools. The geometry should be tailored to the power dissipation of the installed components and the mechanical requirements, rather than chosen on a one-size-fits-all basis.

How is EMC shielding ensured at expansion joints and ventilation openings?

EMC shielding is ensured through several design measures: At separation joints, overlapping edges—rather than straight joints—ensure that no continuous gap forms. For removable inserts, contact studs embedded in the sheet metal establish a conductive connection. Ventilation openings are designed as arrays of holes with many small individual openings, as this maintains the shielding effect significantly better than a few large slits. Where these design measures alone are insufficient, EMC tapes are used as a supplementary measure.

How do you integrate grounding points into a powder-coated enclosure?

Contact surfaces and grounding tabs are identified and masked off before powder coating so that these areas remain uncoated and electrically conductive. This step must be planned during the design phase. If grounding points are not determined until after coating, there are very few options for correction without rework.

Is it possible to perform completely tool-free maintenance on IT metal enclosures made of sheet metal?

Not entirely, in most cases. What can be reliably implemented: sliding mechanisms for covers and trays, snap-fit connections for removable assemblies, and plug-and-play trays for components. In addition, it makes sense to standardize all screw connections to a single size so that only one tool is needed for all maintenance work.

What dimensional standards apply to IT metal enclosures in rack systems?

The 19-inch standard according to IEC 60297 and DIN 41494. It specifies the external width, height units (1U = 44.45 mm), front panel dimensions, and mounting spacing. Enclosures must consistently comply with these dimensions, as rack manufacturers do not allow for any tolerance. For multi-part enclosures, the total tolerance of the assembly must be taken into account, not just the tolerance of the individual parts.