Putting the cart before the horse: why early enclosure selection ensures efficient product design…

Author : Paul Raynor, Director of JPR Electronics

04 July 2018

First there is the brief, then the design process, the sourcing of components for the assembly – then selecting a housing to enclose the whole lot. Although this seems reasonable, by following this sequence, many things can start to go wrong – just when time is of the essence and pre-production is about to take place...

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What if the final assembly is too big for an available enclosure? Die cast enclosures are invariably more expensive as the depth required increases. The die required for a deep casting is not easy to create and such manufacturing tools are invariably high cost items – even when amortised over the final selling price of the casting.

Tall assemblies limit the choice of enclosure, increasing the time required to find a suitable housing. Having a box larger than the actual requirements means paying extra for unnecessary space; while a smaller box may need a circuit or component redesign. More time, more money. Some equipment manufacturers choose to make their own custom tooling, adding time and expense to their production costs and increasing their risk if the product fails to sell well.

What if everything is ready to go into production, but the chosen enclosure is no longer in stock – and worse, has a long lead time? Only limited options are available: choose an alternative enclosure with possible redesign of components – or simply wait until the stock is available. Both choices entail frustration, delays and (quite possibly) lost sales.

What if the chosen enclosure is low cost, the right size, and readily available initially – but then, it either rises in cost, loses quality, or is no longer available once full scale production of the project is taking place? Company credibility suffers when explaining to both clients and their end customers that their heavily promoted product has to undergo changes in size, shape and cost.

What happens if it is discovered that the IP rating, flammability rating or EMC rating of the project design depends on a special enclosure? Enclosures with special ratings have correspondingly high prices and should be included in the budget from an early stage.

Paul Raynor from JPR Electronics says that these are all typical examples of what he calls “putting the cart before the horse”. He suggests considering a different scenario: designing from the outside-in, where choosing an enclosure comes right at the very beginning of the process of product development. Once the brief is decided, manufacturers will then know whether the enclosure needs to be weather-proof, have special IP, flammability ratings, and so on.

Once the type of enclosure is decided, the next step is to choose an ideal size for the product and design to fit the box. The process then becomes infinitely more efficient and cost effective.

By making early decisions over enclosures, any customisation can be agreed – and time and money saved. By designing circuitry to fit the enclosure, costings are already in place, and product size well defined. Changes can be implemented if necessary (either to the circuitry or to the enclosure), while there is still time; however, when the enclosure is deemed satisfactory, it can be ordered ahead, so that production can proceed without time being lost waiting for stock to arrive.

Of course, it is important to ensure that there is reliability of quality and continuity of supply. Cheap options may be attractive initially, but, as many OEMs have found to their dismay, cheap items often have quality issues, or even simply don’t appear once production is underway.

Raynor asserts that, if the customer is willing to place a scheduled order, they will ensure that buffer stocks are held for the customer to be delivered as and when they are required. He also notes that JPR only work with reputable, well established suppliers who are able to consistently and reliably produce quality products over the long term, hence their growing relationship with Hammond Manufacturing.

Both JPR’s close working relationship with Hammond – along with their excellent facilities in guiding and supporting customers – help them to make the right choices early on in the process. CAD drawings of enclosures are easily downloaded so that specifications can be integrated right from the start. Machining, printing and drilling are carried out in the factory, all saving time and money.

Raynor continues: “We have found that by working together with our customers and key suppliers like Hammond from the start of a new product process, design and production times are optimised. There are less false starts and frustrations and the end product can be delivered on time and on budget. The horse and cart are a team, not just separate entities.”

By taking a holistic approach to design, it is simply common sense to choose first the item that is the most difficult to alter at a later stage. It is a risky fallacy to assume that in the last stages of the project design, it will be possible to find an appropriate enclosure from the thousands available.

Decision making at this point is time consuming and often fruitless. While components and circuitry can often simply be reorganised so that internal form alters – while still maintaining its function – the enclosure can only remain static.

Therefore, the moral of the story is, of course, to choose the enclosure first!

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