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Buy cheap, buy twice

A co-strip

An inherent part of the digital age, the emergence and development of the ‘connected’ or ‘smart’ vehicle is gaining ground around the globe, both in the commercial and military arenas.

However, the digitalisation of vehicle functionality brings with it the need not only for ever more sophisticated electronic and software systems, all of which need protecting, not just from electromagnetic interference (EMI), but also from environmental elements such as dust, dirt and water. Having a suitable IP (Ingress Protection) rating, which indicates the resistance of a product to such hazards, is becoming an increasingly important characteristic of the latest EMI shielding gaskets and seals and EMI sealed enclosures often have to meet a variety of environmental requirements as part of their application.

The trick for designers of vehicle assemblies and systems is to consider these needs at the conceptual stage of a project, rather than the common industry scenario of giving it a cursory thought towards the end.

By working from the beginning with a specialist in EMI shielding technology will pay significant dividends as materials can be developed purposely for the application.

Contrast this to specifying a budget solution at the last minute, and the levels of compromise (and cost) will be plain to see.

As an old adage goes: ‘buy cheap, buy twice’.

A considered approach

By taking a considered approach to gaskets, the brand of a vehicle manufacturer can be protected. After all, customers quickly become disgruntled when faced with failures due to poorly designed systems.

Military vehicles are also becoming more aware of the need for gaskets and seals able to provide both electrical and environmental protection. Today, more than 20% of vehicle designers (commercial and military) who have approached Parker Chomerics for an EMC (electromagnetic compatibility) solution, also require a suitable IP rating, and this percentage is growing year-on-year.

With such a marked customer-driven trend, it is important to specify the optimum IP rating for an EMI shield. However, the rating depends very much on where the EMI shield will be located on the vehicle, and to what threats it will be exposed.

Typical vehicle applications range from automotive control boxes through to a host of requirements in the engine and undercarriage, with the latter proving particularly demanding from an environmental perspective.

At Parker Chomerics, we are finding that among the common IP ratings increasingly requested for vehicle applications include IP65, IP66, IP67 and IP69.

The first numeral of an IP rating, in this case ‘6’, indicates full protection against dust and other particulates even with a vacuum inside the enclosure. In short, the unit is deemed to be dust tight.

The second numeral is the differentiator in applications of this type. For example, if the second number is ‘5’, it means the product is protected against low-pressure jets of water from any angle. Here, solutions such as CHO-SEAL Co-Extruded gasket profiles LD55 and LH10, when used as elastomer gaskets in a groove, have proved themselves to be suitable. Stepping up to an IP rating with a second numeral of ‘6’ means protection is assured against more powerful jets of water – as issued by a 12.5mm diameter nozzle, rather than 6.3mm for IP65.

Above: EMI shields with high IP ratings

A second numeral of ‘7’ equates to protection against temporary immersion for up to 30 minutes at depths between 15 and 100cm. Again, a CHO-SEAL Co-Extruded gasket in a groove provides a very good all-round solution to this requirement. Some stipulations here include making sure the EMI gasket is of sufficient size, and that the surface finish of the enclosure is good enough to create an effective seal.

As an aside, the ‘8’ rating is not applicable in vehicle applications as it relates to protection against continuous immersion.

So, what of IP69? Well, the ‘9’ equates to protection against both high-pressure and high-temperature jets of water, while an IP69K rating adds resistance to wash-down and steam-cleaning procedures.

In an application such as a car door, the door itself will of course deflect most of the water pressure encountered during road use, with the rubber seal being secondary (jets of water will not come into direct contact with the gasket). However, this fact does not mean the seal is of secondary consideration.

Elastomer gaskets with deflection characteristics, along with appropriate mechanical design factors, are recommended for IP69 and IP69K requirements.

Cost effective

For all applications where a cost-effective solution is required, a well sized – preferably 3mm rather than 1mm – solid O-section that is paired correctly (galvanically) would deliver protection against both EMI and water. In fact, trying to maintain a rating such as IP69 with a 1mm flange width would be exceptionally difficult.

The galvanically treated aspect is vital in applications where the gasket might be in contact with a component such as a military vehicle hatch, as

conductivity factors come into play. Compatibility between metals must be ensured.

Aside from dust and water, there are many other threats to be considered when specifying a suitable shield/seal. For instance, in undercarriage applications, extreme temperature requirements can be experienced in certain countries, particularly in the height of winter or summer. Heavy rain or flooding events are also increasingly commonplace, while coastal locations mean that vehicles could be subject to salt spray. In addition, fire retardant and chemical resistant products are required in specific circumstances.

There is of course a solution at hand for all applications, no matter how challenging: work closely with a specialist experienced in solutions for both EMI and environmental protection.

At Parker Chomerics, for example, materials are subject to comprehensive internal spray and immersion tests that are application-specific, in line with customer requirements.

Using an expert resource will identify what EMI materials and sizes are best suited to the task in hand, taking the guesswork out of the gasket/seal selection process. And although the growing connected vehicle and electric car markets are currently driving up demand for IP-rated EMI shields, even standard vehicles need to be protected environmentally and electrically.

Ultimately, the principal aim is to shift the current mindset on gasket requirements from an afterthought to that of a forethought.

Leaving it late, in the design cycle, means that customers could end up with gaskets that are not sufficiently robust. After all, what price can be put on customer satisfaction and brand reputation?

Author details: Tim Kearvell is Elastomer Product Manager, Parker Hannifin Chomerics Division

Author
Tim Kearvell

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