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The ‘right’ enclosure is not necessarily a ‘bespoke’ enclosure

25 June 2013

Every electrical device reaching the market has its own set of requirements in terms of the enclosure that houses it. Alan Lewis looks at the design criteria of modern electrical applications and suggests that 'bespoke' need not always be the way to go.

The last thing an OEM wants to do is compromise the design of their latest product to suit the enclosure that is available, especially with a short-run item that does not justify the cost of designing, tooling and producing a bespoke product.

Modern electromechanical devices are available in a myriad of shapes and sizes; from key fobs used to disarm alarms, to desktop control and monitoring equipment, medical devices - the list goes on. When seeking an enclosure to house the device, the designer is faced with the fact that each application is likely to have a slightly different set of requirements.

While some projects will justify the investment in a completely bespoke enclosure, it is fair to say that the majority won't. And in these cases, designers and production teams should be aware that their needs may already be catered for by a product that is available off-the-shelf.

Product footprint
As technology develops, users are placing increased value on how small a device can be made. Ultimately, the size of the enclosure defines the overall dimensions of a product, therefore it is important to consider the ideal size during specification.

Obviously there is no point in specifying an enclosure which is too small, but ultimately you may reduce the functionality and desirability of your product by specifying an enclosure with dimensions that are larger than necessary.

Most leading enclosure manufacturers are aware of the increased pressures on design engineers to offer reduced sizes, and this is reflected in the numerous dimension options across their product ranges.

My company, for example, offers a range of sizes which span from small key fobs all the way up to 19in instrument cases which are compatible with industry standard racks as well as being suitable for desktop applications.

Design outline
When asked to describe an enclosure, the first word that many people reach for is 'box'. This term may be misleading as it summons images of a uniform rectangular shape which offers little room for flexible design innovation.

While it's true that many enclosures are indeed ‘boxes’ – it is, after all, the optimum shape in terms of maximum volume for internal wiring – a well rounded product range (no pun intended) should cater for those requirements that go beyond this simplistic view of an enclosure.

For example, a lot of manufacturers offer enclosures designed specifically for hand held devices. Here, the important design criteria include comfort in the hand and an understanding of the expected dexterity of the average user.

By rounding off the corners and producing edges which feature a slight curve, manufacturers are able to make products which fit comfortably in the hand. Equally, they may reduce the width and depth of the product to allow the thumb of the hand holding the device a wider range of movement.

Slightly more difficult to accommodate are desktop enclosures which may be required to sit in many different locations or offer a variety of viewing angles. A standard approach by some manufacturers is to offer the traditional 'box' that can be ‘customised’ according to the purchaser’s needs.

Bespoke tooling can be costly, however, and typically results in increased lead times. To counter this, my company has developed an extended range of desktop products to accommodate the majority of industry requirements. This includes instrument cases with retractable feet, so the enclosure can either lie flat on a surface or at an angle, and sloping enclosures with a viewing panel that is raised at a second, steeper angle.

Internal layout
As important as the external dimensions of an enclosure are, the internal design ultimately determines the suitability of a product for any given application. Different fixing points will be required depending on the internal wiring of the product.

For instance there may be a requirement to fix a terminal block in place or to securely mount a PCB. Battery powered applications may also require separate compartments which can be accessed independently.

If you work with OEMs across many industries for long enough, you get a good idea of what is required. As an example, my company is able to offer a range of internal 'maps' for each of its product series which means the majority of designs can be accommodated within the product range.

Options include PCB mounts integrated into the internal enclosure wall, which allow a PCB to simply slide into place, and compartments with separating walls for standard size batteries.

When specifying an enclosure the best way to ensure that you get the right product for your application is to find a manufacturer that will act as a ‘specification partner’ rather than simply a supplier.

Speak to them about your design and ask how different products in their range might suit your needs. While customisation is a fantastic way of tweaking a design to your needs, finding a standard product which closely matches them in the first place will save you time and money further down the line.

Alan Lewis is business development manager for Retex UK

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