6. Electromagnetic Compatibility (EMC)

In many applications, EMC is of no interest but in others, it can be a design consideration. Plastic enclosures have one specific weakness: by virtue of the intrinsic properties of the material itself, plastic, unlike metal, offers no EMC attenuation. 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, depending on the project requirements. By offering different materials in a range of thicknesses, the most cost-effective and technically competent solution can be provided.

If metal enclosures are designed in such a way that electrical continuity is present among the top, base, and removable panels and any painted or anodized finish is purely for external decorative purposes, they will provide a level of EMC likely to be more than sufficient for the majority of applications. A conductive gasket will be used to electrically link the two halves of the enclosure.

7. Fixing

Enclosure panels and covers obviously have to be secured to their mating half. There are two main methods for plastic and die-cast enclosures. In the first, a self-tapping screw is secured directly into the material of the base; in the second, a machine screw mates with a threaded bush molded into the base. A machine screw is preferable if repeated opening and closing is anticipated during the life of the equipment; a self-tapping screw is fine for “close-and-forget” uses. A further refinement, normally only appropriate for machine screw closures, is the use of captive screws, which do away with the possibility of one of the screws being lost during opening.

8. Downloadable Drawings and Support Materials

Any reputable enclosure manufacturer will provide a comprehensive library of technical information on its Web site. Typical downloadable resources should include dimensioned drawings to assist with the design and modification requirements, technical details, and key product attributes.

9. Manufacturer Modification Capability

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 setup and wastage quantities. Enclosure manufacturers will typically be able to provide milling, drilling, punching, engraving, screen printing, painting, and EMC coatings for their range of standard products. Manufacturers of molded enclosures can normally also offer enclosures molded in custom colors to meet any applicable identifying requirements or corporate branding needs.

10. Manufacturer and Distributor Technical Support

Standard enclosures for the electronics and electrical industries are produced in a huge variety of sizes, styles, and types by many specialist manufacturers. A molded, extruded, or die-cast enclosure may appear to be just a simple box but in fact, it is the result of extensive design expertise that has resulted in a feature-rich housing suitable for a use in a wide variety of applications and environments. A standard enclosure will inevitably need to be modified to make it fit for its purpose. Most manufacturers and distributors keep stocks of standard enclosures on the shelf and the modern trend is that distributors are now joining manufacturers in providing technical support to their customers, working with them at the design stage to help choose the most appropriate enclosure for the application.

Conclusion

A superficial glance at a molded or die-cast enclosure may give the impression that it is a simple box but in reality, it is the end result of a great deal of design effort and expertise that has been expended to create the most useful and feature-rich housing suitable for a use in a wide variety of applications and environments. Work with the enclosure manufacturer from an early stage in the project design cycle to tap the wealth of experience behind a standard enclosure.

This article was written by Russell Irvine, Sales Manager – Europe, at Hammond Manufacturing, Basingstoke, Hampshire, UK. For more information, visit here.