ENCLOSURES
enclosures speed up installations but can be harder to reopen. This could be an issue (or a bonus if you wish to deter tampering). Some clip-together enclosures can be swiftly reopened with a special tool – giving you the best of both worlds.
Other factors to consider are the breadth of the range for your chosen model. Are there enough sizes? You may need more than one size if your products are to share a common design language. And opting for industry-standard sizes makes it easier to replace existing housings. Ideally, partner with an enclosures manufacturer that carries out all the customisation work in-house: machining, printing, lacquering, decor foils, laser marking, EMC shielding and installation/ assembly of accessories. This ensures quality and accountability. It also saves time and money – and CO2 emissions, because housings don’t have to be shipped between multiple suppliers.
Another key customisation option is special materials. Look for a manufacturer that rating, or in different colours. Specifying a custom colour at the moulding stage may obviate the need for lacquering later on. (Though lacquering is always worth considering because of the extremely wide available.)
For decades, the go-to plastic for electronic enclosures was Acrylonitrile Butadiene Styrene (ABS). It is strong, light and generally exhibits good resistance to a variety of chemicals. ABS has good dimensional stability, can be easily moulded and coloured, and is not brittle so it doesn’t chip or crack during machining. It remains a good standard material for many enclosures.
But ABS can be vulnerable to the damaging effects of the Sun’s rays, becoming discoloured and fragile over time. Hence the development of UV-stable Acrylonitrile Styrene Acrylate (ASA) which replaces the UV-sensitive butadiene rubber found in ABS with UV-resistant acrylate rubber. Elegant STYLE-CASE handheld enclosures are moulded from ASA: the high- clean – making these housings perfect for medical applications such as wired hospital bed controllers.
Blending ASA with polycarbonate (PC) adds extra strength, leading to the increasing popularity of ASA+PC (UL 94 V-0) for enclosures such as SMART-PANEL for intelligent building control systems. Polycarbonate is the plastic used for riot shields and bulletproof glass so its strength
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It has never been easier to specify your perfect enclosure at a tempting price point. But conversely, the vast range of
standard models can be bewildering – and there are some important guidelines to bear in mind when selecting a housing.
is well documented. It also has good heat resistance, stays strong at low temperatures and is a good electrical insulator. However, it is susceptible to scratching and can also be damaged by solvents, acids and alkalis. Enclosures moulded from ABS as standard ASA+PC – it’s always worth checking. Polymethyl Methacrylate (PMMA) is infrared permeable, making it a prime contender for wireless remote control applications. Ranges such as award-winning MINITEC offer PMMA as standard. PMMA has excellent UV resistance and is less likely to scratch than polycarbonate. However, it is more brittle than ABS or PC and can also be damaged by solvents. Furthermore, PMMA begins to soften at 80° to 90° Celsius, making it unsuitable for applications in which it will be exposed to high heat or hot electronic components.
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Thermoplastic elastomers (TPE) are soft- touch thermoplastics that behave like
rubber but can be extruded or injection plastic enclosures. Used as an intermediate ring between two case shells, a TPE plastic such as a thermoplastic vulcanisate (TPV) creates a pleasant tactile feel, helps with ingress protection and adds a stylish dash of colour – as demonstrated by the wearable/ handheld BODY-CASE (IP 65). TPVs are a class of thermoplastic elastomers. They are typically a blend of polypropylene (PP) and dynamically vulcanised Ethylene Propylene Diene Monomer (EPDM) rubber. Their tensile superior to those of most unvulcanised TPEs, including SEBS.
of TPE with better UV resistance than some other TPE types. It is particularly well-suited to compatibility and weather resistance – making it a popular choice for wearable electronics and soft gasketing in enclosures. So which is better? TPV or SEBS? TPV is tougher and more resistant to tearing but expensive. SEBS is good for device grips, while TPV is better for gaskets and seals. Polyamide (PA) is noted for its mechanical strength. It is particularly well suited to enclosures that require structural integrity under load, repeated use or rough handling. This is why it is often used in connectors, cable glands and some rugged industrial housings. Some parts in the RAILTEC C range of open supports for DIN rail electronics are moulded from PA 66, a grade of polyamide that is favoured when mechanical performance under heat is essential. PA 66 has higher crystallinity compared with PA6. This gives it greater stiffness, strength and
JULY/AUGUST 2025 | ELECTRONICS FOR ENGINEERS 15
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