Feature Enclosures & air movers

Specifying the right enclosure

F

or the overwhelming 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” width and ‘U’ height, and the more specific requirements incorpo- rated 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 advantages of standard

enclosures are that the manufacturer will have created products that will meet the majority of requirements. Factors such as EMC and thermal man- agement will have been considered, and there will normally be a good choice of sizes within the family. In addition, the user’s time to market is minimised, as there are no front

When it comes to selecting an enclosure, do you opt for a standard, modified, configured or custom product? Peter Curtis of Verotec comments

with legends and logos and it may have to be painted in a non-standard colour to meet corporate or product branding requirements. To do this, the purchaser has three

choices. Standard enclosures can be purchased and subsequently modified in-house; the modifications can be carried out by sub-contractors; or the enclosure can be modified by the man- ufacturer and supplied as a finished unit ready for the electronics and other equipment to be assembled in to it. Depending on the manufacturing

capability in house, modifying the housing as part of the assembly process may be the best way to proceed although, in most cases, more standard units than are actually required will have to be purchased to allow for set-up procedures and wastage. In addition, some electronics

One option available is ‘modification’

end engineering and tooling charges. Indeed, for many electronics compa- nies, investing in enclosure designers would make no sense at all. 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. In addition, the unit costs are attractive and the design will have been field proven in many different applications.

Modifying to suit the project

Specifying a standard enclosure, however, raises the question of the mod- ification required to suit the specific project. Assuming that the enclosure is a standard catalogue size, it will typi- cally have to be machined with suitable apertures to accept the various compo- nents. It will have to be silk-screened

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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 compli- cations associated with managing the process of sub-contracting, often to multiple suppliers, potentially further increasing the costs as each process will require extra units to allow for first-offs and set up wastage. The best option is for the original manufacturer to provide the modified enclosure. Enclosure manufacturers will normally 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. Obviously, if the project requires a non-standard size of a standard design, realistically the original manufacturer is the only possible supplier.

Configured systems

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,

Configured systems are another way in which the enclosure manufacturer can save the user time and money

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, into which the customer can mount his PCBs, power up the system, test and ship. With this approach, the system will

be configured to meet the customer’s specific needs for the project; he can order a single, unique part number that defines the system exactly, and he will not have to undertake assembly of various pieces of hardware arriving at different times, possibly from different suppliers. Finally, and most impor- tantly, by working with the enclosure manufacturer, the system will have been tested and proven during the development phase.

Meeting project requirements

Unless the product under develop- ment is destined for a consumer application that will consequently 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 highly likely that a standard enclosure that will do the job already exists, so why reinvent the wheel? It is important, therefore, to 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.

Verotec T: 02380 246900 www.verotec.co.uk

Enter 210

The main

advantages of standard

enclosures are that the manufacturer will have created products that will

meet the majority of requirements

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