3d printer report page 18

7/29/2019 3d Printer Report Page 18

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1. INTRODUCTION TO 3D PRINTING

3D printing is a form of additive manufacturing technology where a three dimensional object is

created by laying down successive layers of material. It is also known as rapid prototyping, is amechanized method whereby 3D objects are quickly made on a reasonably sized machine

connected to a computer containing blueprints for the object. The 3D printing concept of custom

manufacturing is exciting to nearly everyone. This revolutionary method for creating 3D models

with the use of inkjet technology saves time and cost by eliminating the need to design; print and

glue together separate model parts. Now, we can create a complete model in a single process

using 3D printing. The basic principles include materials cartridges, flexibility of output, and

translation of code into a visible pattern.

1.1 Typical 3D Printer

3D Printers are machines that produce physical 3D models from digital data by printing layer by

layer. It can make physical models of objects either designed with a CAD program or scanned

with a 3D Scanner. It is used in a variety of industries including jewelry, footwear, industrial

design, architecture, engineering and construction, automotive, aerospace, dental and medical

industries, education and consumer products. A materials printer usually performs 3D printingprocesses using digital technology. The first working 3D printer was created in 1984 by Chuck

Hull of 3D Systems Corp. Since the start of the 21st century there has been a large growth in the

sales of these machines, and their price has dropped substantially.

FIGURE I: Worlds First Working

3d Printer


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2. BRIEF HISTORY OF 3D PRINTING

3D printing was developed by Charles Hull, the founder of 3D Systems in 1984. Mr. Hull, born

May 12, 1939, was an inventor of over 60 U.S. patents in the fields of ion optics and rapid

prototyping. In his patent for the Apparatus for Production of Three-Dimensional Objects by

stereo lithography, issued on March 11, 1986, he defined stereo lithography as a method and

apparatus for making solid objects by successively printing thin layers of the ultraviolet

curable material one on top of the other.

FIGURE II. Charles Hull

Originally called Stereolithography, in the early years the technological development of the 3d

printer systems by 3D System using the Stereo lithography technique was in parallel

development to Fused Deposition Modeling (FDM), invented in 1988 by Scott Crump, the

founder of Stratasys. In 1993 Massachusetts Institute of Technology (MIT) added to the

development of this field by patenting 3 Dimensional Printing techniques based on

modifications of 2D printer technologies, which was then licensed to Z Corporation for

development of their 3DP printers.

In the year 1996 the world saw the first major release of 3d printers by Z Corp, Stratasys, and 3D

Systems. At this time the use of 3d printer nomenclature became more widespread. In the course

of further development over the next decade printer technology developed in respect to


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resolution and software capability, culminating in 2005 with the launch of the Spectrum Z510,

the first high definition color printer in the market.

FIGURE III. Open-Source Collaboration with 3D Printing

The next year, in 2006, a breakthrough open source printing project, named Reprap, was

developed in England. The rep-rap was capable of manufacturing various plastic parts, roughly

50% of itself. The first version of the Reprap, the Darwin, was released in 2008. In continued

development of Reprap printers the next model developed was the Mendel. The Mendel

succeeded the Darwin in efficiency using a variant triangular core structure as opposed to the

square frame of the Darwin. Following the Mendel several different research projects took the

rep-rap in new directions, one of those directions being the Huxley, another the Prusa (a simpler

streamlined rep rap offering), and others including mini-Mendel systems. Concurrent

development of extruder technology has allowed for the modification of most Reprap

commercial printers, and with the capability of self-replication, these printers are an effective

means to generate additional copies and 3d printing capability.

FIGURE IV: First version of the Reprap, the Darwin


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3. BASIC WORKING

3.1. Workflow

The workflow can be easily understood with the help of the flowchart given below.

A 3-D prototype of a desired object is created in three basic steps and these steps are:

Pre-Process 3-D Printing Post-Process

The steps involved in the workflow are illustrated by the figure given below showing which

process has what type of sections involved in it.

FIGURE V: Figure showing what work process involves

There are several types of 3D printers. They may use different materials, but all involve the same

basic approach for printing an object: spraying or otherwise transferring a substance in

multiple layers onto a building surface, beginning with the bottom layer.


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Before the printing can occur, a person must first create a 3D image of the item they want printed

using a computer-assisted design (CAD) software program. That object is then sliced into

hundreds or thousands of horizontal layers, which are placed one on top of the other until the

completed object emerges.

FIGURE VI: Basic steps involved in 3D printing

3.2 PROCESS:

3.2.1 CAD Preparation (Pre-Process):

Computer-aided design (CAD), also known as computer-aided design and drafting (CADD),

is used to prepare a 3-D or 2-D model of the desired object. Additive manufacturing takes virtualblueprints from computer aided design (CAD) or animation modeling software and "slices" them

into digital cross-sections for the machine to successively use as a guideline for printing.

Depending on the machine used, material or a binding material is deposited on the build bed or

platform until material/binder layering is complete and the final 3D model has been "printed."

A standard data interface between CAD software and the machines is the STL file format. An

STL file approximates the shape of a part or assembly using triangular facets. Smaller facets

produce a higher quality surface. PLY is a scanner generated input file format, and VRML (or

WRL) files are often used as input for 3D printing technologies that are able to print in full color.

Some software available for making 3D model .stl file:

FREE ONES:Google SketchUp ,Autodesk 123D ,OpenSCAD Blender.PROFESSIONAL: Autodesk Inventor Professional, PTC Creo, Solidworks, CATIA etc


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FIGURE VII: CAD designing and final product

3.2.2 3D Printing:

To perform a print, the machine reads the design from a .stl file and lays down successive layers

of liquid, powder, paper or sheet material to build the model from a series of cross sections.

These layers, which correspond to the virtual cross sections from the CAD model, are joined or

automatically fused to create the final shape. The primary advantage of this technique is its

ability to create almost any shape or geometric feature. The 3D printer runs automatically,

depositing materials at layers ~.003 thick. This is roughly the thickness of a human hair or sheetof paper. The time it takes to print a given object depends primarily on the height of the design,

but most designs take a minimum of several hours.

Traditional techniques like injection molding can be less expensive for manufacturing polymer

products in high quantities, but additive manufacturing can be faster, more flexible and less

expensive when producing relatively small quantities of parts. 3D printers give designers and

concept development teams the ability to produce parts and concept models using a desktop size

printer.

Construction of a model with contemporary methods can take anywhere from several hours to

several days, depending on the method used and the size and complexity of the model. Additive

systems can typically reduce this time to a few hours, although it varies widely depending on the

type of machine used and the size and number of models being produced simultaneously.


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FIGURE VIII: Product being printed in 3D printer

3.2.3 Cleaning 3D Printouts (Post-Process):

Though the printer-produced resolution is sufficient for many applications, printing a slightlyoversized version of the desired object in standard resolution, and then removing material with a

higher-resolution subtractive process can achieve greater precision.

Some additive manufacturing techniques are capable of using multiple materials in the course of

constructing parts. Some are able to print in multiple colors and color combinations

simultaneously. Some also utilize supports when building. Supports are removable or dissolvable

upon completion of the print, and are used to support overhanging features during construction.

The three main steps used in the cleaning process are:

1. Powder Removal2. Heating3. Finishing touch


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FIGURE IX: Extra powder on a 3D printed model

Powder Removal:

This is the sculpture with most of the support dust removed and it is then dipped in special glue

that makes them stronger and more colorful.

FIGURE X: Powder removal after printing


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Heating

The models are heated to set the glue. Here the oven being used is a normal oven used at home.

FIGURE XI:

Model being

heated for setting

in a domestic grade

oven

Finishing Touches

The output of all existing 3D printers is rough. The textures vary from pronounced wood grain

to merely sandy, With a little elbow grease we can get stunning results.

FIGURE XII: Final touch up


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4. 3D PRINTING TECHNOLOGIES

Several different 3D printing processes have been invented since the late 1970s. The printers

were originally large, expensive, and highly limited in what they could produce.A number of additive processes are now available. They differ in the way layers are deposited to

create parts and in the materials that can be used. Each method has its own advantages and

drawbacks, and some companies consequently offer a choice between powder and polymer for

the material from which the object is built. Some companies use standard, off-the-shelf business

paper as the build material to produce a durable prototype. The main considerations in choosing

a machine are generally speed, cost of the 3D printer, cost of the printed prototype, and cost and

choice of materials and color capabilities.

Printers that work directly with metals are expensive. In some cases, however, less expensive

printers can be used to make a mould, which is then used to make metal parts. Following are the

few methods widely used in printers now-a-days:

1. Selective laser sintering (SLS)2. Stereolithography3. Fused deposition modeling (FDM)4. Laminated object manufacturing (LOM)

4.1 SELECTIVE LASER SINTERING (SLS)

Selective Laser Sintering (SLS) is an additive rapid manufacturing process that builds three

dimensional parts by using a laser to selectively sinter (heat and fuse) a powdered material. The

printing process begins with a 3D CAD file which is mathematically sliced into 2D cross-

sections. The SLS prototype or part is built a layer at a time until completed.

The process starts by slicing the 3D CAD file data into layers, usually from 20 to 100

micrometers thick, creating a 2D image of each layer; this file format is the industry standard .stlfile used on most layer-based 3D printing or stereolithography technologies. This file is then

loaded into a file preparation software package that assigns parameters, values and physical

supports that allow the file to be interpreted and built by different types of additive

manufacturing machines.


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With SLM thin layers of atomized fine metal powder are evenly distributed using a coating

mechanism onto a substrate plate, usually metal, that is fastened to an indexing table that moves

in the vertical (Z) axis. This takes place inside a chamber containing a tightly controlled

atmosphere of inert gas, either argon or nitrogen at oxygen levels below 500 parts per million.

Once each layer has been distributed each 2D slice of the part geometry is fused by selectively

applying the laser energy to the powder surface, by directing the focused laser beam using two

high frequency scanning mirrors in the X and Y axes. The laser energy is intense enough to

permit full melting (welding) of the particles to form solid metal. The process is repeated layer

after layer until the part is complete.

FIGURE XIII: SLS printer

MATERIALS:

Most machines operate with a build chamber of 250 mm in X & Y and up to 350 mm Z

(although larger machines up to 500 mm X, Y, Z and smaller machines do exist). The types of

materials that can be processed include stainless steel, tool steel, cobalt chrome, titanium &

aluminum. All must exist in atomized form and exhibit certain flow characteristics in order to be

process capable.


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4.2 STEREOLITHOGRAPHY

Stereolithography, also known as 3-D layering or 3-D printing, allows us to create solid, plastic,

three-dimensional (3-D) objects from CAD drawings in a matter of hours.

The Stereolithography Machine

This machine has four important parts:

1. A tank filled with several gallons of liquid photopolymer.The photopolymer is a clear, liquid plastic.

2. A perforated platform immersed in the tank. The platformcan move up and down in the tank as the printing process

proceeds.

3. An ultraviolet laser.4. A computer that drives the laser and the platform

The photopolymer is sensitive to ultraviolet light, so when the

laser touches the photopolymer, the polymer hardens.

The laser can be seen binding each layer if we stand near the

machine.

FIGURE XIV: Stereolithography Machine

by 3D systems

The Stereolithography Process

The basic printing process goes like this:

Create a 3-D model of the object in a CAD program. A piece of software chops this CAD model up into thin layers -- typically five to 10

layers/millimetre.

The 3-D printer's laser "paints" one of the layers, exposing the liquid plastic in the tankand hardening it.

The platform drops down into the tank a fraction of a millimetre and the laser paints thenext layer.

This process repeats, layer by layer, until the model is complete.


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This is not a particularly quick process. Depending on the size and number of objects being

created, the laser might take a minute or two for each layer. A typical run might take six to 12

hours. Runs over several days are possible for large objects (maximum size for the machine

shown above is an object 10 inches (25 cm) in three dimensions).

The SLA then renders the object automatically (and unattended). When the process is complete,

the SLA raises the platform. If the object is small, several pieces of them can be produced at the

same time if required. They all sit next to each other on the tray.

FIGURE XV: A tray after building is complete, with several identical objects that were

produced

Once the run is complete, rinse the objects with a solvent and then "bake" them in an ultraviolet

oven that thoroughly cures the plastic.

FIGURE XVI: The ultraviolet "oven" used

to cure completed objects


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4.3 FUSED DEPOSITION MODELING (FDM)

Fused Deposition Modeling (FDM) is an additive manufacturing technology commonly used for

modeling, prototyping, and production applications.

FDM works on an "additive" principle by laying down material in layers. A plastic filament or

metal wire is unwound from a coil and supplies material to an extrusion nozzle which can turn

the flow on and off. The nozzle is heated to melt the material and can be moved in both

horizontal and vertical directions by a numerically controlled mechanism, directly controlled by

a computer-aided manufacturing (CAM) software package. The model or part is produced by

extruding small beads of thermoplastic material to form layers as the material hardens

immediately after extrusion from the nozzle. Stepper motors or servo motors are typically

employed to move the extrusion head.

FIGURE XVII: Fused deposition modelling: 1 - nozzle ejecting molten plastic, 2 - deposited

material (modelled part), 3 - controlled movable table


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Fused deposition modelling Process

In this process, a plastic or wax material is extruded through a nozzle that traces the parts cross

sectional geometry layer by layer. The build material is usually supplied in filament form, but

some setups utilize plastic pellets fed from a hopper instead. The nozzle contains resistive heaters

that keep the plastic at a temperature just above its melting point so that it flows easily through

the nozzle and forms the layer. The plastic hardens immediately after flowing from the nozzle

and bonds to the layer below.

FIGURE XVIII: Components used and process in FDM

Once a layer is built, the platform lowers, and the extrusion nozzle deposits another layer. The

layer thickness and vertical dimensional accuracy is determined by the extruder die diameter,

which ranges from 0.013 to 0.005 inches. In the X-Y plane, 0.001 inch resolution is achievable.

A range of materials are available including ABS, polyamide, polycarbonate, polyethylene,

polypropylene, and investment casting wax.


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4.4 LAMINATED OBJECT MANUFACTURING (LOM)

Laminated Object Manufacture (LOM) cuts the component slices from thin layers of material

using a CO2 laser mounted on a 2D plotter. The system most commonly uses sheets of paper

stacked on top of another automatically and bonded together using an adhesive. The parts of the

sheet outside the model provide support. These unwanted areas are marked with intersecting

lines, which forms cubes that can be broken away from the model once complete.

FIGURE XIX: LOM Modeling

Laminated Object Manufacturing process:

The process is performed as follows:

1. Sheet is adhered to a substrate with a heated roller.2. Laser traces desired dimensions of prototype.3. Laser cross hatches non-part area to facilitate waste removal.4. Platform with completed layer moves down out of the way.5. Fresh sheet of material is rolled into position.6. Platform moves up into position to receive next layer.7. The process is repeated.


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FIGURE XX: Laminated object manufacturing: 1 Foil supply. 2 Heated rollers. 3 Laser beam.

4. Scanning prism. 5 Laser unit. 6 Layers. 7 Moving platform. 8 Waste.

Process Advantages:

Accuracy--Since materials used in the LOM process are in sheet form and the process does not

subject them to neither physical nor chemical phase changes, the finished LOM parts do not

experience shrinkage, warpage, internal stress, and other deformations.

A precise X-Y positioning table is used to guide the laser beam resulting in production of

accurate parts. Accuracy of 0.010" is easily achieved regardless of the size of the part.

Speed--The LOM process does not convert liquid polymers to solid plastics nor does it convert

plastic powders into sintered objects, but instead it uses existing solid sheet materials which are

glued using a hot roller and cut with a laser beam.

Unlike competitive technologies such as Stereolithography and Selective Laser Sintering, the

laser in the LOM process does not have to scan the entire surface area of each cross-section,


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rather it only has to outline its periphery. Therefore, parts with thick walls are produced just as

fast as those with thin walls.

FIGURE XXI: Special advantage of split pattern being used in LOM

The LOM process is especially advantageous for production of large and bulky parts which are

often encountered in the aerospace and automotive industries. The reason for this unique

advantage is the fact that the core manufacturing material does not need to be formed since the

laser merely determines the geometrical shape by removing excess material.

Variety of Materials--Paper, plastics, composites, and ceramics can be used in the LOM

systems. Commercial availability of various sheet materials allow the users to vary the type and

thickness of the manufacturing material for their specific applications.

Paper is the simplest and least expensive material, and it produces rigid and durable parts which

have properties similar to plywood. Plastic films are more expensive and they result in parts

which are more flexible.

Special adhesive pre-impregnated composite materials are currently under development targeted

to producing high strength functional prototypes and small batches of working components.

Simplicity--

The simplicity of the LOM process and systems allow them to be practical

extensions to many manufacturing and design environments. LOM machines can be thought of

as peripheral devices to a CAD workstation, allowing any designer to output any design directly

to an LOM system. The need to create additional support structures is completely eliminated

with the process; something which is essential for competitive stereolithography systems.

3d printer report page 18

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