Enclosures
Key factors to consider when specifying plastic electronic enclosures
Specifying the perfect plastic enclosure for your electronics has never been easier because the range of standard models is so wide. But virtually identical housings can offer very different technical features and benefits, so it pays to get specialist advice. OKW explains more.
F
irst come the obvious questions. Who is the device for? What is its intended purpose? How and where will it be used? Will it sit on a desktop in an office? Or be mounted on a wall, machine or bulkhead in a factory?
Ergonomics will always be important, especially if the electronics are handheld or wearable. Few users will want to hold or wear a device for long periods of time if it feels awkward or uncomfortable. OKW Enclosures Ltd marketing director Robert Cox said: “Initial impressions always matter. The enclosure is the first thing a user will see and touch, so its aesthetics and ergonomics are critical.”
Many desktop enclosures feature a sloping top that presents a display or controls at a more convenient angle. This also makes these housings ideal for wall mounted applications such as access control keypads. A recessed top to protect a membrane keypad or product label is a standard feature on many models, be they desktop, wall-mounted, handheld or wearable. Some housings, such as OKW’s desktop/wall-mountable EVOTEC, offer a flat or sloping top as standard. UNITEC, for dual-user applications such as point-of-sale, has two operating faces and a wraparound recess for an all-over product label. Whether or not the enclosure will be used outdoors will have a bearing on the materials used. In the past, Acrylonitrile Butadiene Styrene (ABS) used to be the default choice for many plastic enclosures, and it remains very popular. ABS is highly durable, has good resistance to heat and many chemicals, and is easy to mould, machine and finish.
38 February 2025
But ABS isn’t as resilient as polycarbonate, which can withstand much higher impact forces: up to 850 joules/metre compared with 200 j/m for ABS. PC is made up of long chains of carbonate groups linked by strong bonds. This gives it exceptional rigidity, allowing energy to be absorbed and distributed across the material – making it highly impact resistant.
So, enclosures such as SOLID-BOX are moulded from a PC+ABS blend. This enables it to be specified for industrial applications where once a metal housing might have
Components in Electronics
been the first or only option.
Furthermore, ABS can be weakened by ultraviolet light. This vulnerability prompted the development of Acrylonitrile Styrene Acrylate (also known as Acrylic Styrene Acrylonitrile). ASA copes better with UV light because it replaces the polybutadiene rubber found in ABS with acrylate rubber, which is inherently more UV resistant. ASA retains many of ABS’s desirable properties (toughness, durability and ease of manufacturing) while adding superior resistance to UV light. It also withstands heat,
rain and temperature fluctuations better. Enclosures such as PROTEC are moulded from an ASA+PC blend which is robust and UV resistant. ASA typically has an impact strength of 160 to 400 j/m so the 850 j/m of PC adds substantial durability. You will sometimes see ASA+PC described as ASA+PC-FR because this plastic has superior flammability resistance: UL 94 V-0, compared with UL 94 HB for other plastics. Flammability ratings are based on tests involving factors such as ignition times, burn rates, whether burning
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