How to specify rugged, lightweight plastic enclosures for harsh environments
OKW Enclosures’ VP marketing, Robert Cox, outlines key considerations for selecting durable plastic enclosures capable of delivering strength, protection and long-term reliability
Smart design is helping plastic enclosures survive harsh industrial and outdoor environments. Strong and light plastic housings offer a practical alternative to diecast aluminum models in some applications. However, correct specification is crucial.
Any enclosure destined for industry or the outdoors must be tough: preferably rugged enough to merit an IK impact rating. Look for either IK07 or IK08. IK07 (2 joules) is equivalent to dropping a 0.5 kg mass from a height of 400 mm; IK08 (5 joules) is the equivalent of a 1.7 kg mass being dropped from 300 mm. This may not sound like much but it is enough to cover day-to-day knocks.
However, strength is about more than just the thickness of the plastic. Key design features also come into play. Enclosures such as OKW’s Solid-Box (IK08) feature deep side recesses to help shield connectors and interfaces. Subtle beveling can help to deflect impacts, as well as enhancing the esthetics.
In-Box is another proven and popular impact-rated enclosure: IK07 for the ABS version, IK08 for polycarbonate (PC). Adding polycarbonate variants to the range also enables OKW to offer In-Box with a transparent lid for displays.
ABS has often been seen as a go-to plastic for enclosures because it has a good balance of resilience and processability. However, PC is stronger, primarily because its polymer chains contain rigid rings linked by carbonate groups. These rings make the molecular backbone very stiff and resistant to deformation. At the same time, the spacing and bonding between the chains allow them to absorb and dissipate energy without snapping. When force is applied, polycarbonate tends to deform slightly and distribute the stress through the structure, rather than cracking.
However, ABS is easier to mold and is generally more cost-effective than PC. Blending the two plastics gives designers the best of both worlds. Another excellent blend is ASA+PC because it has greater UV stability than ABS. PC+ABS and ASA+PC are both rated UL 94 V-0 for flammability, better than UL 94 HB.
Good ingress protection is also vital: IP 66 (temporary flooding) and IP 67 (temporary shallow immersion). Go beyond that, such as IP 68 for deeper or more prolonged immersion or IP 69K for regular high-pressure jet washing, and you may need a diecast aluminum enclosure.
However, a good IP 6X rating is only half the story. Think about where the enclosure will be installed and how often it will need to be reopened. Consider ‘lid closed’ installation if there is often a lot of dust or spray in the air. Solid-Box (IP 66, IP 67) and Smart-Box (IP 66) both feature lid closed installation, with fixing screws hidden beneath trims. Smart-Box’s trims are hinged so they remain attached to the strap-secured lid.
A wide choice of accessories is also important. Models such as Robust-Box (IP 66) can be specified with color-coded trims, DIN rail fastening elements, wall mounting brackets, hinges, security kits, PCB supports, pressure equalization elements and cable grommets.
When it comes to customization, it pays to partner with a manufacturer that carries out all the work in-house: CNC machining, lacquering, printing, laser marking, decor foils, special materials, RFI/EMI shielding and installation/assembly of accessories.
OKW Enclosures’ VP marketing, Robert Cox, said: “Working with a single-source supplier ensures quality and accountability throughout the entire manufacturing process. This also saves time and money and there’s no shipping between suppliers so it’s better for the environment.”
www.okwenclosures.com
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