Economics Report.When we print something,a flat page comes to mind.For example,you might use a photocopier.(SOUND)Photocopiers printin two dimensions.Now, imagine how thiswould work for three dimensions.A machine prints layersof material —usually plasticplastic—one on top of the other.The layers are verythin—usually one-fifthor one-tenth of a millimeter.The layers then combineto form a solid object.There are many versionsof this kind of technology.But the basic idea is the samefor most 3-D printers.The process is calledadditive fabrication.These 3-D printers havebecome powerful toolsfor product designers.Computer-aided design programsuse software to direct the printer.Designers can then createa solid model in a short timeand easily make changes and tests.The 3-D printing technologywas first developedin the nineteen eighties.But high cost put them outof the reach of manyresearchers and businesses.Early printers were limited.High cost and limited usesmeant the 3-D printer marketwas small.Now, lower-cost printersare available toa much wider market,including small businessesand individuals.In January, the globaltechnology company Hewlett-Packardagreed to sell 3-D printersmanufactured by Stratasys.Stratasys has made 3-Dprinters for years.Last year, it introducedone for less thanfifteen thousand dollars.More companies are using3-D printing to directlymanufacture some products.For example, Freedom of Creation,based in Amsterdam,the Netherlands,prints furniture and art.Bespoke Innovationsin San Francisco, Californiawants to design and printartificial limbs.Co-founder Scott Summit saysthese prosthetic limbscan be designed exactlyfor a patient's bodyfor less money thanexisting products.But 3-D printing still has limits.For example,metals are more difficultto print than plastics.However, airplane maker Boeingprints some airplane parts.And printers are being usedto create some rare partsfor old machines.For people interestedin new technology,a New York based company, Makerbot,sells kits to people who wantto build a small 3-D printer.Some kits cost less thanone thousand dollars.And that's the VOA Special EnglishEconomics Report,written by Mario Ritter.For transcripts and MP3sgo to 51voa.com.And follow us on Facebook, Twitter,YouTube and iTunesat VOA Learning English.