revise a document/ technicalwriting

Document 9.1 | Draft of the Description of 3D Printing

3D Printing

A 3D printer is a device that enables you to create a three -dimensional object by creating it layer

by layer. A layer is a thin cross -section of the object you are building. Each layer is attached

seamlessly to the layer ben eath it until the whole object is built. Even though there are different

kinds of 3D printers, they all work the same way in that you need to begin with a computer -aided

design (CAD) file, which provides the blueprint that the 3D printer uses to create the object. You

can either create this CAD file using special 3D modeling software, or you can scan an actual

object and create the CAD file that way. Then the software in the 3D printer “slices” the design

into really thin horizontal layers, like a meat slic er does to a thick ham at the supermarket. There

can be hundreds of these slices, or even thousands. Then the 3D printer “reads” the exact

specifications of each slice and transforms the material into the exact specifications of the slice.

The materials ca n be plastic, gold, other materials — even chocolate!

When a sculptor carves a statue, he is using what is called a subtractive process. This means he

starts with a big block of stone or marble or wood and cuts away material until what is left looks

like the thing he is carving, such as a bear. The industrial versions of this are cutting, milling, and

machining. When a 3D printer is used, it is using an additive process. This means that the person

starts with nothing, then adds layer after layer (using the in structions from the software) to build

up the object you are creating.

If you don’t own a 3D printer, you can still use one. There are several companies that let you

upload your CAD file and they will “print” the object for you and send it back to you.

At Nike, they use 3D printing to “print” prototypes of new shoe designs using materials very

much like the ones that will make it into t he sneakers. If they don’t like the way the prototype

turns out, they can change the design in the software and print a new prototype. This way, they

save thousands of dollars and many weeks of time. Other companies use 3D printing not to make

prototypes b ut actual objects, such as jewelry and some kinds of clothing, that people buy. There

is a company called RepRap which sells 3D printer kits that let you assemble your own 3D

printer for around $1,000. (One day, you might be able to buy a kit, assemble the 3D printer,

then have it create more 3D printers!) Google has some freeware for creating CAD files so you

don’t even have to buy expensive commercial -grade software. One technology used in 3D

printing is called stereolithography (SLA). The way it works is that a beam of UV light is

concentrated on a vat of photopolymer resin, making it soft. When a bead of that resin is drawn

out of the vat it hardens in the light, creating the slice. Another technology used is called Fused

Deposition Modeling (FDM). FDM u ses extrusion, pushing a beam of melted thermoplastics into

a layer, then adding another layer. FDM is used in such products as LEGOs that are made of

ABS plastic or biodegradable polymer. Another method is called Selective Laser Sintering

(SLS). SLS is li ke SLA but instead of using liquid in a vat it uses powders such as glass, nylon,

ceramics, or metals. The powder is fused (the technical term is “sintered”). Document 9.1 | Draft of the Description of 3D Printing

3D printing is now used in medicine, where researchers are starting to create human tissue and,

eventually, entire organs. Pharmaceutical companies are also using it, as are architects who are

creating 3D models of buildings without having to make them out of cardboard or other

materials. Artists were among the first people to see the potential for 3D printing, turning CAD

files into unique, beautiful objects out of all kinds of plastics and metals. Archaeologists are

creating 3D m odels of priceless fossils for use in schools and museums. There is even a 3D

replica of King Tut’s tomb!