- 2017年11月16日10:10 来源：互联网
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3D printing——A third-world dimension
A new manufacturing technique could help poor countries as well as rich ones
EVERY summer, Seattle holds a raft race in Green Lake, a park that is the eponymous home of the water the rafts must cross.
Entries for the Milk Carton Derby have to be made from old plastic milk bottles.
The result is a wonderfully Heath-Robinson collection of improvised craft.
But this year one stood out: the entry from the University of Washington's engineering department actually looked like a boat.
The students who built it, Matthew Rogge, Bethany Weeks and Brandon Bowman, had shredded and melted their bottles, and then used a 3D printer to print themselves a plastic vessel.
No doubt the Milk-Carton-Derby rules will be tightened next year—though in the end, the team came only second.
But they did come first in a competition that mattered more.
On October 19th they won $100,000 in the 3D4D Challenge, organised by a charity called techfortrade.
3D printing is all the rage at the moment.
Several varieties of the technique exist, using a wide range of materials as the ink.
One of the most popular methods, though—and the one used by the team—works by extruding a filament of molten plastic.
In the case of the team's printer, this plastic was high-density polyethylene from milk bottles.
The print head makes repeated passes over the thing being printed, leaving a plastic trail as it does so.
It thus builds up a three-dimensional structure.
3D printing is now taken seriously by manufacturers as an alternative to cutting, bending, pressing and moulding things.
It is also a popular hobby among those of a geeky disposition.
What it has not been used for so far is to help people in poor countries improve their everyday lives.
Mr Rogge, Ms Weeks and Mr Bowman intend to employ their prize money to do precisely that.
They plan to form a firm that will, in partnership with a charity called Water for Humans, custom-build composting toilets and rainwater collectors.
The partnership will look for suitable local entrepreneurs in poor countries and will train them how to build, use and maintain the printers.
Once the technology is established for toilets and water collectors, other products will be introduced.
The local partners will know what products are needed and how much people are prepared to pay for them—and therefore what is worth making.
The operation will thus run on a commercial basis.
But the software that controls the printers will be open-source and available to all, as will many of the designs for things the printers can make.
That way, the technology can spread.
A trial will begin soon in Oaxaca, Mexico.
The crucial point about the team's printer is that it combines size and cheapness.
Printers used by hobbyists are not expensive, but they are small.
Many would find it hard to make anything larger than a coffee cup.
Those used by engineering companies cost serious money—and even they might balk at printing an object the size of the Milk Carton Derby boat.
The team's printer is built around a second-hand computer-controlled plasma cutter.
This directs the movement of an extruder that melts flakes of plastic into a thin stream which can be squirted out as required.
It is able to create things with dimensions of up to 2.5 metres by 1.2 metres by 1 metre.
Appropriately, many of its parts were themselves manufactured on a desktop 3D printer.
The ink is cheap, too. High-density polyethylene is as common as muck—literally, for a lot of it ends up on refuse tips.
Chop it up, though, and it is grist to the mill.
Mr Rogge estimates that if he and his colleagues had printed their boat from commercial plastic filament it would have cost them $800.
Instead, 250 clean, empty milk bottles set them back just $3.20.
Some technical questions remain.
High-density polyethylene shrinks when it cools.
That stresses the object being printed and can sometimes tear it apart.
The students are therefore working on a second prototype that prints things faster, allowing the layers of plastic to cool almost simultaneously.
They are also experimenting with making things from other types of waste plastic that suffer less from shrinkage.
And until a production version of the printer is ready and priced, it remains to be seen how competitive its output really will be with mass-produced items.
Mr Rogge doubts, for example, that a 3D-printed bucket—even one made from milk bottles—will ever be cheaper than one made in a factory.
Boats, though, could be a hit.
One of the judges at the 3D4D Challenge noted that many small vessels in West Africa are made from trees, such as teak, that are becoming scarce.
Making them from waste plastic instead would be an environmental twofer: rare species would be conserved and less rubbish thrown away.