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The easiest way to approach such a project is to trace a product from raw material right through to its end of life and consider how much energy it consumes along the way.
Embedded energy
One important concept that you won’t generally find quoted on a material’s datasheet is embedded energy. The embedded energy of a material is all of the energy taken to produce a certain quantity of it.
This information is readily found using Google. For example, each kilogram of aluminium extracted from bauxite will take between 227 and 342 megajoules of energy to produce. A typical plastic from crude oil would take 82 to 108 megajoules. Unfortunately, it’s not that simple because a kilogram of recycled aluminium will take just 11 to 17 megajoules. So, it pays to delve a bit deeper for answers.
How much material to use
At first sight if you use less material, then you are using less embedded energy, but when you begin manufacturing you also need to factor in manufacturing and delivery into the final parts’ embedded energy calculation.
Even then it’s not that simple. Increased manufacturing can make massive in-service savings. For example, in the aerospace industry grams of weight saving can save kilos of fuel over an aircraft’s life. Lightweighting is also important in the automotive industry for the same reasons. Making parts more effective, in terms of fuel efficiency and serviceability, further contributes to reduced lifecycle cost.
In-service sustainability
Products that last longer and do not need replacing have less environmental impact than a shorter-lived version. This can throw up some surprising results; for example an organic farming group actually found that it is more environmentally friendly to use plastic crates on their farms instead of wood when they factored in the number of times they used them.
Finding the right answer
So how can you make your products and their parts more durable and/or lighter? The answer is to prototype, test and reiterate your design. When you get it right you will give your customers a better-performing product that will save them costly replacement, repair and servicing costs – which in turn cuts down the lifetime energy and monetary costs for them.
This is where rapid prototyping makes a real difference because normally the first iteration of a design is not the best solution. Modern technology allows you to fail fast, without blowing your budget, before you succeed. In the first stage you can upload your CAD into a software program which will both quote you a cost and provide a design for manufacture analysis – an automatic sense check if you like.
After that you can have a prototype delivered in as little as a day. This means you can design, test and reiterate your design for a lightweight durable product in next to no time.
Design for serviceability
When we consider designing more sustainable products, we need to think about more than durability. We also need to think through how easy it will be to service, maintain and repair it through its life. Think about access for spanners and other tools. Is a part easy to replace? Do you use helicoil for higher-strength threads so that replacement does not damage the product?
Recycling
And when your product does come to the end of its life, you need to think about how you can make your product simple to disassemble and recycle. You must also understand what your WEE obligations are.
This brings us full circle to considering what materials you use. Virtually all metals can and should be recycled. With plastics some can and some can’t. Also, while you could use a 100% recycled metal product, a plastic’s quality decreases each time it is reused because its polymer chain grows shorter.
But this does not mean that you should always turn to metal, because the right plastic in the right application can last a long time and when plastic does replace metal it often provides a lighter alternative – something that is key to saving “in use” carbon for some industries.
Also, we are starting to see the development of ecoplastics, many of which are easier to recycle and/or are biodegradable.
Clearly, choosing the most sustainable answer for your part or product is not easy. At Protolabs we deal with many industries and customers that are seeking more sustainable products, so why not contact us for advice.
For further information, please visit www.protolabs.co.uk.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.