FEATURE RACKS, CABINETS & ENCLOSURES Specifying enclosures for Industry 4.0
Russell Irvine from Hammond Electronics explores some of the key considerations when specifying enclosures for Industry 4.0 applications
I
ndustry 4.0, the deployment of distributed automation and data
exchange in manufacturing technologies, is based on the Internet of Things (IoT) and cloud computing to create the "smart factory". The move to complex distributed computing brings with it some high level technical issues: IT security, greatly aggravated by the inherent need to open up previously closed production systems, requires encryption. System reliability, repeatable low latency and stability are needed for critical machine-to-machine communications so that production processes cannot be compromised. Hard wired, Wi-Fi and Bluetooth connectivity enable processing and communicating throughout the IoT under different communication protocols. In addition to these macro-level
concerns, at the micro level the widespread distribution of electronic modules and sub-systems into the factory environment requires considerable thought to be given to the selection of the housings that provide the physical protection required. Given that the selected enclosure must provide a secure and physically robust environment for the electronics, there are several criteria to consider when specifying the best enclosure for the job. Selecting a standard enclosure from one
of the many suppliers has the obvious benefits of no up-front non-recurrent design, engineering and tooling charges; products are on the shelf ready for immediate delivery, so time to market is low; the unit costs are attractive and the design will have been field proven in many different applications. Compared with an application-specific custom enclosure, designed specifically for the project, standard products are immediately available and, certainly in volumes up to the low thousands, are extremely cost-effective. However, a standard product will need to be modified for the specific use. In order to make a standard enclosure
suitable for a specific application, it will need to be modified. The best option is for the original manufacturer to provide a modified enclosure configured to the specific requirements of the project, so there is no need to over-order to allow for set-up and wastage quantities.
20 NOVEMBER 2018 | ELECTRONICS To achieve higher levels of sealing in
metal, plastic and extruded small enclosures, a gasket, typically made from a preformed compressible material, is sandwiched between the two mating surfaces. A metal enclosure can be painted without having to mask the gasket area; the gasket can be easily replaced if it is damaged.
Small enclosures
are usually made from die-cast or extruded aluminium or are moulded from polycarbonate, flame retardant or standard ABS. The choice of material will depend on the required impact and abrasion resistance, resistance to chemicals and UV stability. Industry 4.0 requires electronic modules and systems to be installed on the factory floor, close to the equipment that is being monitored and controlled. The question of the level of protection against the ingress of dust and water therefore becomes significant. EN 60529 defines IPxx, where the first digit defines the protection against solid objects and the second the protection against water ingress. An enclosure for general purpose use would typically be rated IP54, whereas one for use in hostile environments would typically be rated at a minimum level of IP65. Satisfactory IP54 sealing is readily achieved by using a tongue and groove construction to the joint between the body of the enclosure and the removable lid. No gaskets are used; the seal is achieved through the combination of a recess in the base section that mates to the corresponding mirror profile in the lid.
Figure 1, 2 & 3: Hammond enclosures
EMC PERFORMANCE In many applications EMC capability is irrelevant, but in the potentially electrically noisy factory floor environment, it can be a consideration. Plastic enclosures have one specific weakness: they offer no inherent attenuation to the passage of electric or magnetic fields. If EM radiation emitted by the housed electronics or their susceptibility to external fields is a potential problem, the lack of screening could be an issue. Internal coatings in a variety of materials can be applied to the inner surfaces of a plastic enclosure to give different degrees of attenuation dependent on the project requirements. By using different materials in a range of thicknesses, the most cost-effective and technically competent solution can be provided. Metal enclosures, providing they are manufactured in such a way that electrical continuity is present between the top, base and removable panels and that any painted or anodised finish is purely for external decorative purposes, will provide a level of EMC likely to be more than sufficient for the majority of applications. With small low power systems, heat
dissipation is not usually an issue, but if systems are generating sufficient waste heat it can become a problem. As with EMC, metal and plastic enclosures have significantly different properties. Metal enclosures have greater ability to provide conduction and convection cooling because of their greater conductivity; indeed some extruded enclosures are designed with increased surface area to improve cooling performance. All types of enclosure can be modified with arrays of holes to improve convection cooling if required.
Hammond Electronics
www.hammondmfg.com 01256 812812
/ ELECTRONICS
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