Product designers have always had to choose between additive processes such as 3D printing and subtractive processes like machining. Now they can have both
If you hadn't heard, there's a new industrial revolution sweeping the world. This revolution, say the champions of this new kind of making, is the result of three factors that together change the nature and economics of manufacturing.
The first is free software for designing complex 3D objects; the best known example being Google Sketchup.
The second is 3D printing in which computerised machines turn virtual designs into physical models that you can prod, fondle and squeeze.
Finally, there is the precipitous drop in the cost of 3D printers and other rapid prototyping techniques. This suddenly makes it practical and profitable to make-on-demand instead of mass producing products.
That's led to a huge increase in the number of websites where you can buy things that are made-on-demand, things like bespoke Lego-like bricks for example. You place your order via a website, the order is sent straight to a 3D printer that makes the brick which is then sent to you in the next post. The designer, who doesn't even see the brick, simply pockets the profit.
At least, that's how this revolution is being promoted. The reality is that if you want to make anything more complex than a plastic brick, you'll soon run up against the limitations of rapid manufacturing processes.
These processes fall into two categories: additive and subtractive. Subtractive techniques such as high speed machining are fast but cannot create certain complex shapes. Additive techniques such as laser sintering of metal powder (a type of 3D printing) cannot easily make big solid objects because internal stresses build up in the solid parts as they cool, leading to distortions.
These problems, or at least ones like them, have troubled manufacturers for centuries. So it's no surprise that they threaten to derail the new industrial revolution before it has gained much momentum.
Today, however, Olivier Kerbrat and pals at the Institut de Recherche en Communications et Cybernétique de Nantes in France, say they've dreamt up a way to tackle this problem.
Their solution is a program that analyses a design and works out how difficult it is to make with a given manufacturing technique. It takes into account factors that influence manufacturability, such as the size of the object, its volume, the flexibility of a given cutting tool and the distance of parts of the object from the centre of the manufacturing platform (and so may need extra support) and so on.
It then colour codes the virtual object according to its difficulty of manufacture (see picture above). The designer can then make changes that improve matters.
That's a new way of thinking about manufacture. In the past, designers simply focused on the suitability of a product for its purpose, be it an engine part or a building brick. They would have had a manufacturing technique in mind and simply had to accept its advantages and disadvantages.
What Kerbrat and co make possible is a new way of thinking in which manufacturers can see which parts of a product are best suited to different types of manufacture. The designs can then be modified or even broken up so that different parts are made in the most cost effective way. (Of course, these parts have to be assembled again later and this needs to be taken into account.)
But the key point is that manufacturers can use both additive and subtractive manufacturing processes at the same time.
So-called design for manufacture is not a new idea but it has always been more of a black art than a form of engineering. By building this way of thinking into the tools used in standard computer aided design, it's just possible that Kerbrat and co will make it much easier. That should cut lead times, lower costs and, arguably, improve quality.
All we need now is Google to include this idea, or something like it, in Sketchup. For free.
Long live the revolution!
Ref: arxiv.org/abs/1106.3176: A New DFM Approach To Combine Machining And Additive Manufacturing
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