bl2606-specifying-enclosures

SOLVING YOUR DESIGN CHALLENGES

Specifying the right metal enclosure for your electronics means answering some fundamental questions. Many of them concern earthing, cooling, finishing and (unsurprisingly) budget. Here are the answers to some of the questions we get asked most…

HOW CAN I REDUCE THE COST OF A FABRICATED ENCLOSURE?

Specifying a standard enclosure and having it customised is the quick, cost-effective alternative to a fully bespoke housing. Simplifying geometry and standardising features can cut costs without affecting performance.

Maximise savings by consulting us as early as possible in the design process; small changes early on can reduce complexity and save you money. Enclosures formed from one or two simple folded parts are consistently more cost-effective than more intricate designs. Avoiding tight bend radii, back-to-back folds and small flange heights enables faster forming. Designing bends to align with standard tooling rather than forcing the use of special punches also cuts costs.

Selecting the right surface finish matters too. Anodising and powder coating are not interchangeable in cost or performance so ask us how to reduce costs without compromising on quality.

ARE CUSTOM 19" ALUMINIUM ENCLOSURES EXPENSIVE?

Not necessarily. Our most versatile 19" rack cases (COMBIMET) are actually our most cost-effective. How do we manage it? The answer lies in smart design. COMBIMET was designed for fast and cost-effective customisation: this helps to keep costs down.

Not that much customisation is needed because the range is so big, with so many shapes, sizes and configurations available as standard. Modifications can be kept to a minimum. So you get a high-quality ‘electronics ready’ enclosure that can go straight from your Goods In to your production line. And all for a pleasantly sensible price.

HOW DO I EARTH A METAL ELECTRONIC ENCLOSURE?

For maximum reliability, we recommend self-clinch stainless steel fasteners. They’re strong and offer good earth bonding over long periods. Specify a dedicated protective earth (PE) stud – a self-clinching stainless-steel stud or nut on the primary structural chassis. Many METCASE enclosures feature earthing studs on every panel as standard.

Stainless steel is best for the inserts because it’s tough – resisting thermal cycling and vibration. Ensure good metal-to-metal contact between the insert and the aluminium substrate. The insert must be fitted to bare aluminium, with the bonding area masked during finishing. The self-clinching process is advantageous here, as it cold-flows the aluminium into the serrations of the insert, creating a gas-tight interface that is stable over time and much better than a tapped hole or loose nut.

All incoming protective conductors should terminate using a crimped ring terminal, secured to the earth stud with a stainless nut and serrated/star washer on the conductor side to maintain contact pressure and break any residual oxide film.

ARE VENTILATED RACK ENCLOSURES SUFFICIENT FOR HEAT DISSIPATION?

Sometimes. In low-power or convection-friendly designs, a well-ventilated enclosure can be quieter and more reliable than an actively cooled one – but it depends on the electronics. The thermal problem must be properly quantified. Trusting to ventilation without proper analysis is a frequent error in rack equipment design.

Ventilation slots enable natural convection: hot air rises and escapes, drawing cooler air in from below. But three conditions must be met:

• the total heat load must be modest
• there must be a clear vertical airflow path
• the pressure drop across the vents must be low.

In reality, a fabricated aluminium enclosure with a small ventilation area will dissipate only a few tens of watts by natural convection without an excessive internal temperature rise. Above this, temperature rises will be rapid and non-linear.

Ventilation slots alone may not be sufficient, especially if PCBs, wiring looms and subchassis disrupt convection paths. Fans, blowers or fan trays may become necessary – and the enclosure must support controlled airflow, rather than merely letting heat out.

WHICH FINISH IS BEST FOR ALUMINIUM ELECTRONIC ENCLOSURES?

We recommend fine-textured powder-paint finishes. They’re hard wearing, don’t scratch easily, and look smart. Extra-hard-wearing fine-textured powder paint offers an even more durable finish. We have a large range of these paints in stock, with no extra charge for special colours from our stocked paint list.

ARE ALUMINIUM ENCLOSURES SUITABLE FOR DISPLAY-MOUNTED ELECTRONICS?

Yes, they’re ideal. We have many 19", desktop/portable, wall-mount and VESA-mount aluminium enclosures that enable display mounting. Solutions include integrated metal brackets for flush mounting. Threaded standoffs and mounting plates are also popular.

Mechanically, folded aluminium sheet provides a strong stiffness-to-weight advantage. The folds do most of the structural work – even relatively thin material can be very rigid if the geometry is correct. Aluminium also offers benefits with regard to heat conduction and EMC protection.

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