RAPID PROTOTYPING TECHNOLOGIES

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RAPID PROTOTYPING TECHNOLOGIES Prof. Dr.
Bilgin KAFTANOGLU www.mfge.atilim.edu.tr/kaftanogl
u Manufacturing Engineering Department ATILIM
UNIVERSITY ANKARA
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• WHAT IS PROTOTYPING?
• Essential part of the product development and
  manufactuing cycle
• Assesing the form, fit and functionality of a
  design before a significant investment in tooling
  is made.

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• Until Recently, prototypes
• were handmade by skilled craftsmen (i.e. High
  Cost)
• adding weeks or months to the product
  development time (increase time to market)
• So
• A few design iterations could be made before
  tooling went into production
• Seldom optimization of designed parts or at
  worst parts did not function properly.

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• Rapid Prototyping
• name given to a host of related technologies
  that are used to fabricate physical objects
  directly from CAD data sources
• These methods are unique in that they add and
  bond materials in layers to form objects.
• Other names Solid Freeform Fabrication,Layer
  Manufacturing

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• With Rapid Prototyping,
• Objects can be formed with any geometric
  complexity without the need for
  elaborate (very complex) machine setup and jigs
  and fixtures.
• Objects can be made from multiple materials
  (Such as Aluminum and Polyamide, Copper and
  Steel), or as composites, or materials can even
  be varied in a controlled fashion at any location
  in an object
• The construction of complex objects are reduced
  to a manageable, straightforward, and relatively
  fast process.

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• With Rapid Prototyping,
• time to market in manufacturing is reduced
• the product designs are better understood and
  communicated
• rapid tooling to manufacture those products are
  made.

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• The names of specific Rapid Prototyping
  processes
• Stereolithography (SLA),
• Selective laser sintering (SLS),
• Fused deposition modeling (FDM),
• Laminated object manufacturing (LOM),
• Laser Engineering Net Shaping (LENS)
• Inkjet Systems and Three Dimensional Printing
  (3DP).
• Each has its singular strengths and weaknesses.

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• STEREOLITHOGRAPHY
• The most widely used rapid prototyping
  technology.
• Builds plastic parts or objects a layer at a
  time by tracing a laser beam on the surface of a
  vat of liquid photopolymer (Self Adhesive
  Material).
• Liquid photoplymer quickly solidifies wherever
  the laser beam strikes the surface of the liquid.
  
• Once one layer is completely traced, it's
  lowered a small distance into the vat and a
  second layer is traced right on top of the first.
  
• The layers bond to one another and form a
  complete, three-dimensional object after many
  such layers are formed.

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STEREOLITHOGRAPHY
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The platform in the tank of photopolymer at the
beginning of a run.
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STEREOLITHOGRAPHY
The objects have overhangs or undercuts which
must be supported during the fabrication process
by support structures. These are either manually
or automatically designed and fabricated right
along with the object. Upon completion of the
fabrication process, the object is elevated from
the vat and the supports are cut off.
The platform at the end of a print run, shown
here with several identical objects.
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STEREOLITHOGRAPHY
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STEREOLITHOGRAPHY

• The second most accurate and best surface finish
  of any rapid prototyping technology.
• Wide range of materials with properties
  mimicking those of several engineering
  thermoplastics. Biomedical materials are
  available, and ceramic materials are currently
  being developed.
• The technology is also notable for the large
  object sizes that are possible.

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STEREOLITHOGRAPHY

• On the negative side,
• Material is expensive, smelly and toxic
• Removing supports may adversely effect surface
  finish
• Parts often require a post-curing operation in a
  separate oven-like apparatus for complete cure
  and stability. Post Curing ensures that no liquid
  or partially cured resin remains.

The ultraviolet "oven" used to cure completed
objects.
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FUSED DEPOSITION MODELLING

• Second most widely used rapid prototyping
  technology, after stereolithography
• A plastic filament is unwound from a coil and
  supplies material to an extrusion nozzle.
• The nozzle
• is heated to melt the plastic and has a
  mechanism which allows the flow of the melted
  plastic to be turned on and off.
• is mounted to a mechanical stage which can be
  moved in both horizontal and vertical directions.

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FUSED DEPOSITION MODELLING
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FUSED DEPOSITION MODELLING

• As the nozzle is moved over the table in the
  required geometry, it deposits a thin bead of
  extruded plastic to form each layer.
• The plastic hardens immediately after being
  extruded and bonds to the layer below.
• The chamber is held at a temperature just below
  the melting point of the plastic.

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FUSED DEPOSITION MODELLING

• Materials ABS and investment casting wax, and
  more recently polyamide materials
• Researches for embedding Ceramic and Metal
  powders in polymer filament is going on.
• ABS offers good strength
• Support materials
• Same material Problems during removing
• Break Away Support System Easily removed
• Water Works Water-soluble support material.
• (in ultrasonic vibration tank)

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FUSED DEPOSITION MODELLING

• Office-friendly and quiet
• Fairly fast for small parts or for those that
  have tall, thin form-factors
• Very slow for parts with wide cross sections
• The finish of parts have been greatly improved
  over the years, but aren't quite on a par with
  stereolithography.
• FDM offers great strength.

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INKJET

• Uses a single jet each for a plastic build
  material and a wax-like support material, which
  are held in a melted liquid state in reservoirs
• The materials harden by rapidly dropping in
  temperature as they are deposited
• After an entire layer of the object is formed by
  jetting, a milling head is passed over the layer
  to make it a uniform thickness

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INKJET
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INKJET

• Extremely fine resolution and surface finishes,
  essentially equivalent to CNC machines
• The technique is very slow for large objects
• While the size of the machine and materials are
  office-friendly, the use of a milling head
  creates noise which may be objectionable in an
  office environment.
• Materials selection is very limited and the
  parts are fragile
• Especially used in precise casting patterns for
  jewelry.

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INKJET
Jevelry Application
A production cut in the middle
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3D PRINTING

• Developed at MIT
• A measured quantity of powder is first dispensed
  from a similar supply chamber by moving a piston
  upward incrementally.
• The roller then distributes and compresses the
  powder at the top of the fabrication chamber.
• The jetting head subsequently deposits a liquid
  adhesive in a two dimensional pattern onto the
  layer of the powder
• The powder becomes bonded in the areas where the
  adhesive is deposited, to form a layer of the
  object.

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3D PRINTING
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3D PRINTING

• No external supports are required during
  fabrication since the powder bed supports
  overhangs
• Offers the advantages of speedy fabrication and
  low materials cost
• Probably the fastest of all RP methods
• Recently color output has also become available
• There are limitations on resolution, surface
  finish, part fragility and available materials.

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LAMINATED OBJECT MANUFACTURING

• object cross sections are cut from paper or
  other web material using a laser or a knife
• The paper is unwound from a feed roll onto the
  stack and first bonded to the previous layer
  using a heated roller which melts a plastic
  coating on the bottom side of the paper
• The profiles are then traced by an optics system
  or knife
• Areas to be removed in the final object are
  heavily cross-hatched with the laser to
  facilitate removal.
• Excess paper is cut away to separate the layer
  from the web. Waste paper is wound on a take-up
  roll

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LAMINATED OBJECT MANUFACTURING
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LAMINATED OBJECT MANUFACTURING
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LAMINATED OBJECT MANUFACTURING

• It can be time consuming to remove extra
  material for some geometries
• The finish, accuracy and stability of paper
  objects are not as good as for materials used
  with other RP methods
• Material costs are very low, and objects have
  the look and feel of wood and can be worked and
  finished in the same manner
• Application Patterns for sand castings.
• Limitations on materials, work has been done
  with plastics, composites, ceramics and metals.
  However, available on a limited commercial basis.

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Laser Engineered Net Shaping

• A technology that is gaining in importance and
  in early stages of commercialization.
• Designed for aerospace industry, especially to
  produce titanium parts.
• A high power laser (1400 W) is used to melt
  metal powder supplied coaxially to the focus of
  the laser beam through a deposition head.
• The head is moved up vertically as each layer is
  completed.
• Metal powders are delivered and distributed
  around the circumference of the head either by
  gravity, or by using a pressurized carrier gas.

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Laser Engineered Net Shaping
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Laser Engineered Net Shaping

• In addition to titanium, a variety of materials
  can be used such as stainless steel, copper,
  aluminum etc.
• Materials composition can be changed dynamically
  and continuously, leading to objects with
  properties that might be mutually exclusive using
  classical fabrication methods.
• Has the ability to fabricate fully-dense metal
  parts with good metallurgical properties at
  reasonable speeds
• Objects fabricated are near net shape, but
  generally will require finish machining.

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Laser Engineered Net Shaping
Before and after finish machining
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Laser Engineered Net Shaping
120x120x120 cm LENS Machine
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Selective Laser Sintering

• Sintering
• bonding of the metal, ceramic or plastic powders
  together when heated to temperatures in excess of
  approxiamately half the absolute melting
  tempertaure.
• In the industry, sintering is mainly used for
  metal and ceramic parts (Powder Matallurgy).
• After pressing (compaction) of the powder inside
  mold for deforming into high densities, while
  providing the shape and dimensional control, the
  compacted parts are then sintered for achieving
  bonding of the powders metallurgically.

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Selective Laser Sintering
Compaction
Sintering
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SINTERING
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Sintering in Rapid Prototyping

• Sintering process used in Rapid Prototyping
  differs from the Powder Metallurgy, such as
• Plastic based powders, in additon to metal
  powders.
• Local sintering, not overall sintering.
• Very short sintering period.
• Laser (heat source) is exposed to sections
  to be sintered for a very short time. Hard to
  achive an ideal sintering.
• In some applications, for achieving the ideal
  sintering, the finished parts are heated in a
  seperate sintering owen.

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Selective Laser Sintering

• Invented by Carl Deckard during his Phd. studies
  in Texas University in 1987.
• Offers the key advantage of making functional
  parts in essentially final materials.
• The system is mechanically more complex than
  stereolithography and most other technologies.
• A variety of thermoplastic materials such as
  nylon, glass filled nylon, polyamide and
  polystyrene are available. The method has also
  been extended to provide direct fabrication of
  metal and ceramic objects and tools.

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Selective Laser Sintering
Process 1) Laser beam is traced over the surface
the tightly compacted powder to selectively melt
and bond it to form a layer of the object.
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Selective Laser Sintering
Process 2) Platform is lovered down one object
layer thickness to accommodate the new layer of
powder
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Selective Laser Sintering
Process 3) A new layer of powder is coated on
the surface of the build chamber.
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Selective Laser Sintering
Process 4) The powder is supplied from the
powder bins to the recoater. This process is
repeated until the entire object is fabricated.
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Selective Laser Sintering

• The fabrication chamber is maintained at a
  temperature just below the melting point of the
  powder
• Heat from the laser need only elevate the
  temperature slightly to cause sintering. This
  greatly speeds up the process
• No supports are required with this method since
  overhangs and undercuts are supported by the
  solid powder bed
• Surface finishes and accuracy are not quite as
  good as with stereolithography, but material
  properties can be quite close to those of the
  intrinsic materials

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Selective Laser Sintering
Three Types of Laser Sintering Machines 1)
Plastic Laser Sintering Machine 2) Metal Laser
Sintering Machine 3) Sand Casting Laser
Sintering Machine
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Selective Laser Sintering

• Plastic Laser Sintering
• For direct manufacture of styling models,
  functional prototypes, patterns for plaster,
  investment and vacuum casting, for end products
  and spare parts.

• Volvo Steering Wheel
• Engine Block Pattern
• Plaster Invest. Pattern

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Selective Laser Sintering

• Metal Laser Sintering
• For direct production of tooling, including for
  plastic injection molding, metal die casting,
  sheet metal forming as well as metal parts,
  directly from steel based and other metal powders.

• A gear for Volvo Corp.
• Die Cast Parts (500 Al parts produced)
• Motor Housing

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Selective Laser Sintering

• Sand Laser Sintering
• Laser Sintering System for direct, boxless
  manufacture of sand cores and moulds for metal
  casting.

• V6-24 Valve Cylinder Head.
• Impeller
• Steering Block for a car

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METU SYSTEM

• EOS EOSINT P380 Rapid Prototyping System

General Properties
Plastic Laser Sintering System X,Y Axes Alternating Scanning
Technical Specifications
Work Envelope
-X Axis 340 mm
-Y Axis 340 mm
-Z Axis 600 mm
Layer Forming Thickness
0.15mm /-0.05 mm
Max Laser Power 50 W
Z Axis Production Speed 30 mm / saat
Max Scanning Speed 5 m/s
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Comparison Chart
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Additive Fabrication vs Subtractive Fabrication

• Additive Fabrication methods (RP) can not become
  complete replacement for the Subtractive
  Fabrication methods (Milling, Turning, EDM etc.)
• Subtractive methods
• have reached an extraordinary level of
  development and they continue to evolve.
• they are fast, versatile, inexpensive, readily
  available and well-understood by large numbers of
  practitioners.
• in many cases they are quite sufficient to make
  prototypes rapidly,
• no equal when it's necessary to make very
  precise parts in final materials.

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Additive Fabrication vs Subtractive Fabrication

• Additive technologies are instead complementary
  to subtractive ones, if the situation calls for
• complex or intricate geometric forms,
• simultaneous fabrication of multiple parts into a
  single assembly,
• multiple materials or composite materials in the
  same part.
• Additive technologies make it possible to
  completely control the composition of a part at
  every geometric location. Thus, RP is the
  enabling technology for controlled material
  composition as well as for geometric control.

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Limitations of RP Methods

• ACCURACY
• Stair Stepping
• Since rapid prototyping builds object in
  layers, there is inevitably a "stairstepping"
  effect produced because the layers have a finite
  thickness.

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Limitations of RP Methods

• ACCURACY
• Precision
• tolerances are still not quite at the level of
  CNC,
• Because of intervening energy exchanges and/or
  complex chemistry one cannot say with any
  certainty that one method of RP is always more
  accurate than another, or that a particular
  method always produces a certain tolerance.

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Limitations of RP Methods

• FINISH
• The finish and appearance of a part are related
  to accuracy, but also depend on the method of RP
  employed. Technologies based on powders have a
  sandy or diffuse appearance, sheet-based methods
  might be considered poorer in finish because the
  stairstepping is more pronounced.

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Limitations of RP Methods

• Secondary Operations
• Parts made by stereolithography are frequently
  not completely cured when removed from the
  machine. Final cure is effected in a box called a
  post-cure apparatus (PCA)
• Parts made by three dimensional printing (3DP)
  and MultiJet Modeling (MJM) can be very fragile
  and might not be able to take normal handling or
  shipping stresses. These parts are often
  infiltrated with cyanoacrylate adhesive or wax as
  a secondary operation to make them more durable.
• Metal parts will almost certainly require final
  machining and must usually undergo a thermal
  baking cycle to sinter and infiltrate them with a
  material to make them fully-dense.
• Other than powder-based methods all other methods
  require a support structure to be removed in a
  secondary operation which may require
  considerable effort and time.

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Limitations of RP Methods
Support structure (red material), water-soluble,
fused deposition modeling (FDM).
Support structure, stereolithography.
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Limitations of RP Methods
3) SYSTEM COSTS RP systems cost from 30,000
to 800,000 when purchased new. The least
expensive are 3D Printer and FDM systems the
most expensive are specialized stereolithography
machines. In addition, there are appreciable
costs associated with training, housing and
maintenance. For example it can cost more than
20,000 to replace a laser in a stereolithography
system.
4) Material High cost. Available choices are
limited.
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RP in Medical Applications
Oral Surgery
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RP in Medical Applications
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RP in Medical Applications

• Modelling in Medical Applications
• Models are created using medical imaging data
  obtained from
• a standard Computed Tomography (CT) or
• Magnetic Resonance Imaging (MRI).
• Bone structures such as skull or pelvis are all
  imaged using CT. Soft tissue structures such as
  brain and organs are best imaged by MRI. The
  slice data from CT or MRI are processed into 3D
  images by using sophisticated software.

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RP in Medical Applications
Oral Surgery
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RP in Medical Applications
Oral Surgery
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RP in Medical Applications
Prosthesis Applications
A bone structure which was produced from ceramic
powder embedded paper material in LOM.
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RP in Medical Applications
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RP in Medical Applications
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RP in Medical Applications
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RP in Medical Applications
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RP in Medical Applications
Bone Structure with the cranial vasculature
highlighted in red. This model was made using SLS
with a special material called Stereocol.
(Coloured when exposed to high power laser)
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RP in Medical Applications
TISSUE ENGINEERING
Actual living tissue cells are extracted from the
patient and seeded onto a carrier which
accomodates and guides the growth of new cells in
3D within laboratory environment.
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RP in Medical Applications
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