JAY Leno, the most popular talk-show host on American television, has one of the best collections of old cars and motorbikes in the United States. He keeps them in a large garage in the San Fernando Valley, down the road from the NBC studios in Burbank, California, where “The Tonight Show” is taped.Mr Leno is an admirable collector. His vehicles are not trophies for show, but curious examples that he likes to put in running order—so he can drive or ride them himself and enjoy the essence of a bygone age. A crew of professional mechanics is on hand to help restore and maintain the vehicles. Parts that have become obsolete are fabricated on the premises, using a battery of computerised tools that any machine shop would be proud to possess.In a monthly column he writes about his motoring passion for Popular Mechanics, Mr Leno recently described how his “Big Dog Garage Team” fabricated a feedwater heater for his 1907 White Steamer. The aluminium part had become so porous with age that steam could be seen seeping through. Being heavily impregnated with oil, patching it up by welding a plate in place was impossible. The answer was to fabricate the part anew.First, they used a 3D scanner to create a detailed digital model of the part at 160,000 dots per inch. Next, they fed that model to a 3D printer, which used the file to print, layer by layer, an exact copy of the part in plastic. Finally, the replica part made of plastic was used to make a mould for casting the finished component in aluminium. The scanning was a breeze, but printing the part took 33 hours. Still, having the item sent out for drawings to be made and then the part machined from solid metal would have taken weeks.As might be expected, Mr Leno's tools are among the best available—a $3,000 scanner from NextEngine and a $15,000 printer from Dimension, not to mention a Fadel CNC machining centre, which must have cost upwards of $100,000. Apart from a hydraulic lift and a plentiful supply of compressed air, your correspondent's humble workshop has nothing to compare. But his three old cars present similar problems.The good news is that the kind of rapid-prototyping technology used in the motor, aerospace and medical industries (not to mention Mr Leno's garage) has fallen in price dramatically over the past few years. While an industrial 3D printer (also known as a fabricator or a rapid prototyper) would once have cost over $100,000, a perfectly adequate machine for home use can now be had for less than $2,000. Those prepared to assemble their own can buy kits for $500 or so.There are drawbacks, of course. The size of products that can be made using a desktop 3D printer is usually limited to something that can fit within a five-inch (12.7cm) cube. Industrial fabrication machines can make parts six times larger. Even so, a desktop 3D printer will suffice for a surprising number of components used in cars and around the home.As a manufacturing process, 3D printing is what is known as an “additive” technology. Instead of removing material wastefully (by milling, boring, grinding and cutting), 3D printing uses what is effectively a modified ink-jet printer to deposit successive layers of material until the three-dimensional object is built up completely, with very little scrap. The material used is usually a thermoplastic such as ABS (acrylonitrile butadiene styrene), polylactic acid or polycarbonate, though metallic powders, clays and even living cells can be employed, depending on the application.While some hobbyists download ready-made designs to fabricate, many users create their own engineering drawings by taking advantage of free software like Google's SketchUp or Blender from the Blender Foundation in the Netherlands. For a price, professional packages can be had from Alibre Design, Autodesk and SolidWorks. Once the drawing is finished, the file is saved in a format the 3D printer recognises. On being loaded into the printer, the device's built in software analyses the digital design and works out the optimal way to trace the successive layers of the product being fabricated.The grandaddy of all desktop 3D-printers is the open-source RepRap project conceived in 2005 by Adrian Bowyer and colleagues at the University of Bath, in Britain. The RepRap (short for Replicating Rapid Prototyper) concept's main purpose is to make a machine that can replicate itself and evolve in the process. To date, three generations of reference designs have been released into the wild, each named after a famous biologist (Darwin, Mendel and Huxley). RepRaps are now reproducing around the world like rabbits.

The aim is to enable people—especially those in poorer parts of the planet—to make complex products for themselves without the need for industrial infrastructure and heavy capital investment. As an open-source project, anyone is free to use the design and improve it, so long as they make their additions freely available to others.



The personal-manufacturing movement—exemplified by Thingiverse for sharing user-created 3D files and Fab@Home to exchange ideas about hardware and software—resembles nothing so much as the era when the MITS Altair 8800 kit, with its eight-bit Intel processor and S-100 bus, prepared the ground for the PC revolution that was to follow.



Bre Pettis, one of the founders of MakerBot Industries, which runs Thingiverse on the side, believes personal manufacturing is currently going through much the same phase as personal computing did in the 1970s. In many ways, that makes MakerBot the MITS of today. It has sold over 5,000 of its Thing-O-Matic 3D printers, which retail for $2,500 fully assembled or $1,299 in kit-form. Meanwhile, a newcomer from the Netherlands called Ultimaker, which costs $1,700 as a kit, is winning fans for its raw speed and ability to handle larger jobs. Some wonder whether the Ultimaker could be personal manufacturing's Apple II.



Over the past week, Brook Drumm, an internet entrepreneur and workshop tinkerer in Lincoln, California, raised more than $155,000 in “kickstarter" funding on the internet from people who pledged money in exchange for one of his clever little Printrbot machines. Mr Drumm offers everything needed to assemble his basic 3D-printer for $500. Could that be today's equivalent of the Sinclair ZX81, the world's most popular PC in the early 1980s?



Two recent developments make your correspondent believe that personal manufacturing is about to go mainstream. One is the arrival of much cheaper printing goop. Thermoplastics like ABS and polylactic acid cost around $30 a pound. Metal powders can cost even more. Now a group at the University of Washington, in Seattle, has come up with a concoction based on artists' ceramic powder blended with sugar and maltodextrin. The material costs less than $1 a pound.



The other encouraging sign is how 3D design software is becoming much easier to use. Autodesk, the maker of professional software for architects and industrial designers, is offering a free PC program, called 123D Catch, that turns 50 or so digital photographs taken of an object from various angles into a 3D printing file. Preparing a 3D product for fabrication cannot get much easier than that.



As much as your correspondent would prefer a 3D scanner like Mr Leno's NextEngine, software such as 123D Catch could do a pretty good job in the meantime. But it surely cannot be long before Japanese camera-makers add features to their pocket-sized products that let them digitise 3D objects photographically. Then, personal manufacturing will literally become point, shoot, upload and print solid objects in three dimensions. And many an old car or lawn mower will run sweeter as a result.