Electronics Protection Online - A Complete Guide to Enclosures and Protection

Electronics Protection

Standard, Modified, Configured or Custom Enclosures – It’s Your Choice
Marc Harvey, Verotec

For the majority of low to medium volume applications, specifying a standard enclosure is by far the most logical decision for the project engineer. There are numerous manufacturers from which to choose, and the variety of sizes, designs and styles is enormous. Long established general standards applicable to many uses, particularly the 19 inch width and “U” height, and the more specific requirements incorporated in various open bus structure specifications such as cPCI, mean that many of the size variables are removed from the decision making process.

The main advantage of standard enclosures is that the manufacturer have created products that will meet the majority of requirements. Factors such as EMC and thermal management have been considered, and there will normally be a good choice of sizes within the range. In addition, the user’s time to market is minimized, as there are no front end engineering and tooling charges. For many electronics companies, to invest in enclosure designers would make no sense. Enclosures are widely available off the shelf from both the manufacturers and through the distribution channel, so delivery time is unlikely to be a concern. The unit costs are attractive and the design is normally field proven in many different applications.

Specifying a standard enclosure naturally raises the question of the modification required to suit the project. Assuming the enclosure is a standard size, it will have to be machined with suitable apertures to accept the various components. It will also have to be silk-screened with legends and logos, and it may have to be painted in a non-standard color to meet corporate or branding requirements. To do this, the purchaser has three choices. Standard enclosures can be purchased and modified in-house and the modifications can be carried out by sub-contractors or the enclosure can be modified by the manufacturer and supplied as a finished ready for assembley.

Depending on the manufacturing capability, to modify the housing as part of the assembly process may be the best way to proceed, although in most cases, the more standard units required will have to be purchased to allow for set-up procedures and wastage. In addition, some electronics companies may not have the plant, equipment, expertise or interest in undertaking metalworking tasks in their own premises. If the modification processes are outsourced, there are the additional costs and logistics associated with the process of sub-contracting, often to multiple suppliers and potentially increasing the costs as each will require extra units to allow for first-offs and set up wastage.

By far the best option is for the original manufacturer to provide the modified enclosure. Enclosure manufacturers will make the CAD drawings of the standard product available to the customer, who can either update the drawing by hand or by using his own CAD system to show the required modifications. If the project requires a non-standard size of a standard design, the original manufacturer is the only possible supplier.

Configured systems are another way in which the enclosure manufacturer can save the user time and money. Typically, a configured system will consist of a desktop, rack mountable or portable enclosure, fitted with a subrack conforming to IEC297, IEEE1101.10 or 11, a backplane, power supply and cooling, normally meeting the requirements of an open bus specification such as VMEbus, cPCI or any of the increasing number of specialist derivatives based on the two main specifications. In this case, the hardware manufacturer provides the customer with a ready-to-run system where the customer can mount PCBs, power up the system, test and ship. The advantages are self-evident. The system will be configured to meet the customer’s specific needs and a unique part number can be ordered that defines the system exactly and without having to undertake assembly of various pieces of hardware arriving at different times. Finally, by working with the enclosure manufacturer, the system will have been tested and proven during the development phase.

Unless the product under development is destined for a consumer application that will require high volumes, the design effort and tooling time and cost required to develop a custom enclosure cannot normally be justified for typical medium run applications. It is likely that a standard enclosure that will do the job already exists, so why reinvent the wheel? Work closely with the chosen manufacturer to ensure that the enclosure both reflects the quality of the product itself and meets the technical and mechanical needs of the system.

For more information, please visit www.verotec.co.uk