Atrain can comfortably last operationally for half a century. Yet the value chains behind many train parts aren’t nearly as resilient. Scale manufacturing only works well above certain volumes, otherwise costs such as mould development, warehousing and transport logistics grow beyond a reasonable point. Pretty soon, the only viable alternative is to buy a new train.

But what if you could print your parts right where you need them? Yes, this is a point that was used several years ago to promote 3D printing. Today, almost everyone agrees that the hysteria around 3D printing – more formally called additive manufacturing – has died down to a whimper of its promises. But while the hype of consumer 3D printing boiled over, underneath, the science fermented into something of real commercial and societal significance.