Enclosure buyers can choose with confidence

Steve Gallon of Fibox offers an overview of the RoHS Directive and its impact on the enclosure market.

Under the RoHS directive, as of 1st July 2006, the use of certain selected hazardous substances in electrical and electronic equipment, including lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE), will be restricted, with some limited exceptions.

The directive mandates EU member countries to take measures to enforce these requirements, under their respective jurisdictions.

The purpose of the RoHS restriction is in order to both protect human health and the environment by restricting the use of certain hazardous substances in new electrical and electronic equipment, while at the same time complementing the Waste Electrical and Electronic Equipment (WEEE) Directive, which seeks to eliminate the usage of certain hazardous substances in products; specifically in electrical equipment, that will be treated and recycled at end of their life.

As the deadline approaches, some manufacturers have already withdrawn certain noncompliant enclosure products from the market; but as a buyer of those products, how do you choose?.

As it stands, the RoHS Directive does not require that compliant products carry any label.

Although some manufacturers are now using RoHS ready labels, the law does not require it and they are being used purely for marketing purposes.

This new directive relies solely on the "producer responsibility" approach to achieve industry compliance.

But in order for manufacturers to achieve RoHS compliance, each material contained in each component part, must also be compliant; which in turn means that component suppliers will be required to certify and provide documented support that each component falls below the maximum concentration levels stated in the directive.

The substance limits currently defined are: lead 0.1% by weight in homogenous materials; mercury 0.1% by weight in homogenous materials; cadmium 0.01% by weight in homogenous materials; hexavalent chromium 0.1% by weight in homogenous materials; polybrominated bipheryls (PBBs) 0.1% by weight in homogenous materials; and polybromised diphenyl ethers (PBDEs) 0.1% by weight in homogenous materials.

(Homogenous materials in RoHS terms means a component or material that cannot be mechanically disjointed into different materials by unscrewing, cutting, crushing, grinding, by abrasive processes or similar procedures).

After 1st July 2006 all products on the market not covered by exemptions will be assumed to meet the requirements of the RoHS Directive if sold in Europe.

The directive will have a significant impact on product design as it affects many of the current materials and components being used in existing enclosure products.

The designer may have to find cost effective and safe alternatives for the restricted substances.

Even though many of alternatives are available, they still have to be identified and evaluated before incorporating them into the production lines.

It is also essential that the functional performance of the product is not degraded or legal requirements and product safety issues not compromised.

The use of substitute materials may also have a significant impact on existing manufacturing processes.

Having chosen the alternatives, they then have to be sourced through suppliers that may be new and untried.

Managing and controlling the new supply chain is essential and is not easy.

Much of the risk of supplying nonconforming equipment is from outsourced components.

Manufacturers need to have a high level of confidence in the material contents but may have difficulty enforcing it down the whole supply chain.

Having obtained compliant materials and components, manufacturers will still need to manage and store a massive amount of extra information on material contents and their specific concentrations, gathered from supplier declarations or certification from recognised testing and chemical analysis specialists.

As mentioned earlier, sometimes the substituted substances may induce further problems during the manufacturing processes.

For example, the complete elimination of lead will require a complete change in current production technology.

Therefore, as a result of the new RoHS Directive, there are many changes required on the design, production and the choice of "lower risk" substitution materials needed for many products that fall within the auspices of the directive.

There will also be an impact on certain manufacturers, who will need to rapidly withdraw a number of their incompliant PVC enclosure brands that are currently being used across a wide spectrum of industrial applications.

In meeting the requirements of the RoHS Directive, the first step is to establish the compliance status of products as follows: analyse the bill of material (BoM) to identify parts purchased and suppliers; review material and component content of products to identify potential presence of restricted substances; provide means for suppliers to complete the declarations of substance concentration level in agreed format; collect substance concentration data from supply chain; identify homogeneous materials in products; analyse supply chain data; identify noncompliances; define allowable thresholds for suppliers; and obtain supplier material declarations.

In testing and measurement for RoHS compliance, manufacturers need to: first decide the testing policy; then prepare the testing plan; and then locate and contract suitable testing facilities.

Clearly the prime function of any enclosure is to protect the electrical or electronic components housed within it.

Engineers must first consider the environment in which the product is to be used in order make careful selections based on the manufacturer's data.

Other considerations such as ingress protection (IP ratings), impact resistance (IK rating), corrosion, thermal protection, UV stabilisation and materials must also be taken into the equation as they impact on the useful longevity of the product.

Once these points have been established, overall costs obviously play their part.

It's a fact that the ultimate reliability of the system you build and supply is often influenced by the initial choice and design of the enclosure, as it is by the components used to build the system itself.

More and more these days, manufacturers are being asked to produce customised products to meet new end user requirements for instance the inclusion of windows, DIN rail mounted MCBs, switches, pushbuttons or calibration devices, membrane keypads and displays requiring predrilled holes, cutouts and subassembly mounting devices.

EMC shielding is also a necessity in certain environments as electromagnetic protection is needed to protect delicate components from interference from neighbouring devices.

Panel and system builders are constantly building more and more complex systems in response to their customer's wishes, which in turn has inspired enclosure manufacturers to produce a wider choice of flexible and innovative enclosure solutions.

But remember, whatever your particular requirement, all bespoke enclosures started as a standard box.

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