By: Stephen Field
Senior Consultant, Product Design
15th March 2017
So you want to put some electronics in a ‘box’, how hard can that be? The world is full of electronics in boxes…. it’s easy, isn’t it?
Of course, there is a world of difference between a sophisticated electronic device in a demanding aerospace environment and a cheap-as-chips, perhaps even disposable, consumer product. However, many of the same considerations apply at both ends of this range.
In common with other areas of design, the ‘thing’ that the mechanical designer creates very much depends upon the demands of the customer as itemised in the requirements specification. In an ideal world, the customer knows enough to be able to create a comprehensive specification document. This is often not the case and so the designer will use their knowledge and experience to steer the design in the right direction.
This short piece introduces some of the elements the mechanical designer has to contemplate as they embark on the creation of a new electronics enclosure. I hope, through this discussion, the reader will begin to appreciate the many aspects that influence the design of the humble ‘box’. It is the designer’s experience and innate feel for their subject that allows them to create products from a blank page.
Depending on the requirements placed upon the designer, some of the things to consider are listed below. Many of these constraints are customer wishes. Some, especially regarding safety, are legislated for by national, EU or international agreements.
Size and weight – seldom are these unimportant to any customer. Even if it is not a specific requirement, these parameters become significant when it comes to considering the cost of packing and shipping the product.
Ergonomics and aesthetics – the user experience is an important factor especially, but not exclusively, for consumer products. In my long career, I have never met a customer, or a fellow team member for that matter, who does not have a view on how a product should look.
They often do not know what they want until they see some conceptual ideas. One of the key skills of the designer is to create tangible schemes from the often vague notions of others. Later, the designer must be able to hold all the relevant requirements in mind as these same others try to steer into impractical cul-de-sacs with words like ‘just’, ‘only’ and the ubiquitous ‘something’.
Heat dissipation – any power used will generate heat. Excessive heat may cause degradation of performance and/or reduced component life. Many factors can affect what strategies can be put in place for heat removal.
Specialist knowledge and software are sometimes needed to optimise the thermal design of a system. However, this route often takes time, resources and experience. An understanding of the general principles, coupled with some early empirical evaluation is sometimes more beneficial.
Ingress protection – protect products from the intrusion of everything from screwdrivers and fingers to dust and high-pressure water spray.
EMC protection – ensure to protect from harmful radio signals and to ensure there is no leakage from the product that might be detrimental to other devices.
Protection from vibration and impact – accidents can happen and protection is needed for a whole host of scenarios. This can range from: products being bulk transported, consumer use and misuse and products being dropped. You might need to consider the vibration encountered in a lorry engine bay or the launch environment of a space satellite.
Each case is different. Sometimes experience and sound practice are sufficient to ensure a reliable product. Occasionally, analysis and testing are necessary to be absolutely sure the product is fit for purpose and, crucially, safe.
Safety from electrical shock – always make sure that you are protecting the user, whether they are a skilled technician or an inquisitive child.
Electrostatic safety – many semiconductor components can easily suffer damage by being subjected to electrostatic discharge.
Electrostatic discharge safety – specialist products that are required to operate in explosive atmospheres have to be designed to eliminate the chance of them generating or propagating a spark.
In parallel with considering the above requirements, the designer must adapt their design approach to suit the expected manufacturing volumes. This will inform the choices of materials and the manufacturing techniques employed.
The manufacturing techniques are also influenced by the budget available for setting up the manufacturing capability; the tooling as well as the expected country of manufacture, the assembly process used and the market for the product.
In recent times, the designer has had to begin to consider the ease of disposal and recycling at the end of the product life. This is a good example of where international treaty and agreement between governments can be used to enforce behaviour that would not come about through market forces.
Holding a good understanding of these requirements and knowing which ones are essential and most desired; so that trade-offs and compromises can be agreed upon to best meet the overall goals is key to a successful product design process.