Sungmin Kim

SEOUL NATIONAL UNIVERSITY

Smart Garment Design

4. Rapid Prototyping

Introduction NC Machining History

Since 1940s

Advantage

Most of industrial materials are available

Disadvantage

Intermediate steps are required

– NC tool path generation– Process planning, jig, fixture, etc.

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Introduction NC Machining Mills

Cut different materials

Lathes

Cut workpieces while they are rotated

Plasma cutters

Cut a material using a plasma torch

Electric Discharge Machining (EDM)

Material is removed from the workpiece by a series of rapidly recurring current discharges

Wire EDM

Uses spark erosion to machine or remove material with a traveling wire electrode

Water Jet Cutters

A tool capable of slicing into metal or other materials by using a high pressure jet of water

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Introduction Rapid Prototyping

Build a prototype in one step

Directly from the geometric model of the part

Does not require intermediate processes

– process planning, material handling, transportation between machining stations, and so on

Restricted to specific materials

Used for prototypes for actual manufacturing procedures

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Introduction Rapid Prototyping Overview

Generates physical objects directly from geometric data without traditional tools

– Layered manufacturing

– 3D printing

– Desktop manufacturing

– Solid freeform manufacturing

Technology had advanced to encompass many applications beyond prototyping

– Rapid prototyping and manufacturing (RP&M)

Form the cross Sections

of the object to be

manufactured

Lay the cross sections

layer by layerCombine the layers

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Introduction Rapid Prototyping and Manufacturing

Unnecessary Steps in RP&M

Feature-based design and feature recognition

Conversion of design features to manufacturing features

Definition of complex sequences of handling material

Consideration on clamping, jigs, fixtures

Design and manufacturing of molds and dies

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Introduction Rapid Prototyping and Manufacturing

Methods of RP&M

Polymerization of suitable resins by laser, light, or lamps

Selective solidification of particles or powder by laser beams

Binding of liquid or solid particles by gluing or welding

Cutting and laminating the sheet materials

Melting and resolidification

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Introduction Rapid Prototyping and Manufacturing (RP&M)

Specific Processes

Stereolithography

Digital Light Processing

Solid Ground Curing

Selective Laser Sintering

3D Inkjet Printing

Laminated-Object Manufacturing

Fused-Deposition Modeling

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Stereolithography Stereolithography

Overview

Patented by Charles Hull, co-founder of 3D Systems, Inc. in 1986.

The most popular RP&M process

Became a standard for other RP&M processes

Requires support structures when the part has undercuts

Support Structure

Undercut

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Stereolithography Stereolithography

Photosensitive polymer that solidifies when exposed to a lighting source is maintained in liquid state

A platform that can be elevated is located just one layer of thickness below the top surface of the liquid polymer

The UV laser scans the polymer layer above the platform to solidify the polymer and give it the shape of the corresponding cross section

The platform is lowered into the polymer bath to the layer thickness to allow liquid polymer to flow over the part to begin the next layer

Step 3 and 4 are repeated until the top layer of the part is generated

Post-curing is performed to solidify for part completely

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Digital Light Processing Digital Light Processing (DLP) Overview

Created in 1987 by Larry Hornbeck of Texas Instruments

Uses digital micro mirrors laid out on a semiconductor chip

– The same technology applied for movie projectors

One section of object is built simultaneously

– The printing speed is pretty impressive

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Other method DLP method

Digital Light Processing Volumetric Printing The Future of True 3D-3D Printing

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SGC Solid Ground Curing History

Developed and commercialized by Cubital Ltd. of Israel in 1986

Principle

Each layer is cured by exposure to a lamp instead of by laser beam scanning

All the locations in a layer are cured simultaneously and post curing is not required

Advantage

Good accuracy and High fabrication rate

Does not require a support structure because the wax is used to fill the voids

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SGC

The cross section of each slice layer is calculated from the geometric model of the part and the desired layer thickness

1The optical mask is generated conforming to each cross section

2After leveling, the platform is covered with a thin layer of liquid photopolymer

3

The mask corresponding to the current layer is positioned over the surface and the resin is exposed to a high power UV lamp

4The residual liquid is removed from the workpiece by an aerodynamic wiper

5A layer of melted wax is spread over the workpiece to fill voids. The wax is then solidified by applying a cold plate

6

The layer surface is trimmed to the desired thickness by a milling disk

7The current workpiece is covered with a thin layer of liquid polymer and steps 4-7 are repeated for each succeeding upper layer

8The wax is melted away upon completion of the part

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Solid Ground Curing

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SGC Solid Ground Curing

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SLS Selective Laser Sintering Definition

Additive manufacturing technique that uses a laser to sinter powdered material

History

Developed and patented by Carl Deckard and Joe Beaman at the Univ. of Texas at Austin

– In the mid-1980s, under sponsorship of DARPA– A similar process was patented without being commercialized by R. F. Housholder in 1979

Deckard and Beaman were involved in the resulting start up company DTM

– In 2001, 3D Systems the biggest competitor of DTM and SLS technology acquired DTM

Principle

Binding the material together by aiming the laser at points in space defined by a 3D model

SLS is a relatively new technology that so far has mainly been used for rapid prototyping

– Low-volume production of component parts– Roles are expanding as the commercialization of AM technology

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SLS Selective Laser Sintering Advantage

Support structure is not required

– Voids are filled by the unprocessed powder at each layer

Usable with any meltable powder

– Even metal powders if the laser is powerful enough

Indirect sintering process is used for metal powders coated with a thermoplastic binder

– The binder material melts and loosely binds the metal powders to form the desired shape (a green part)

– The green part is then post-processed in a furnace where the binder is burned off

– Metal powders are bonded by traditional sintering mechanics (a brown part)

– Infiltrant is added to the furnace to reduce the porosity through capillary action

– Resulting mold is durable enough to make 2,500~10,000 parts

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SLS Selective Laser Sintering

A part cylinder is located at the height necessary for a layer of powdered material to be deposited on the cylinder to the desired thickness. The powdered material being used for the prototype is applied from the feed cylinder by the leveling roller

1

The layer of powder is selectively raster-scanned and heated with a laser, causing particles to adhere to each other. The laser scan forms the powder into the required cross section shape. Note that this step starts with the bottom cross section

2

The part cylinder is lowered by the layer thickness to permit a new layer of powder to be deposited3

The new layer is scanned, conforming it to the shape of the next upper cross section and adhering it to the previous layer

4

Step 3 and 4 are repeated until the topmost layer of the part is generated5

Post-curing may be required for some materials6

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SLS Selective Laser Sintering

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SLM Selective Laser Melting Overview

Developed in Fraunhofer Institute ILT in 1995

The fine metal powder is intensively fused by applying high laser energy

– Metal powder melts fully and forms a solid object (stainless steel, titanium, chrome, aluminum)

Applied to parts with complex geometries and structures

– Thin walls, hidden voids or channels

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3D Inkjet Printing 3D Inkjet Printing History

Developed at MIT

Extended version of 2D inkjet printing

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LOM Laminated Object Manufacturing Feature

Generates a part by laminating and laser-trimming materials

The sheets are laminated into a solid block by heat

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LOM Laminated Object Manufacturing

Advantage

External support structures are not required

Entire geometry is stabilized and is prevented from distorting under its own weight

Disadvantage

Difficult to scrap unnecessary material after the part is built

Careful cleanup process is required

High material consumption

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LOM Laminated Object Manufacturing

Each sheet is attached to the block, using heat and pressure to form a new layer. Sheet material is supplied from a continuous roll on one side of the machine and taken up on the opposite side. The heated roller provides the pressure and heat needed for lamination

1

After a layer is deposited, a laser is traced on the layer along the contours corresponding to the current cross section

2

Areas of the layer outside the contours are cross-hatched by the laser3

Step 1-3 are repeated until the top layer of the part is laminated and cut4

After all the layers have been laminated and cut, the result is a part imbedded within a block of supporting material. This material is then broken into chunks along the cross-hatching lines

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The resulting part may then be coated with a sealant to keep out moisture6

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LOM Laminated Object Manufacturing

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FDM Fused Deposition Modeling Principle

Generates each layer by extruding thermoplastic material

Part is constructed by successive extrusion of layers

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FDM Fused Deposition Modeling Evolution of FDM

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Applications of RP&M Prototyping for Design Evaluation Need for a Physical Model

Design evaluation is better when the designer can touch and hold a physical model

Visualization of some parts is still very difficult

– Blinds holes, complex interior passageways, compound curved surface, etc.

There is no better way than to hold it, turn it around a few times, and look at it from all sides

– To be certain that a complex part contains exactly those features intended

Aesthetic design requires a physical object for evaluation in particular

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Applications of RP&M Prototyping for Function Verification

Verification of Originally Intended Functions

The practicality of complicated assembly

Kinematic performance

Aerodynamic performance

Limitation

Strength

Operational temperature limits

Fatigue

Corrosion resistance

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Applications of RP&M Rapid Tooling Process Direct Tooling Methods

Tools are generated directly by rapid prototyping

Core and cavity inserts for an injection mold are made by stereolithography or SLS

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Applications of RP&M Special Applications Reverse Engineering

Three-dimensional data is captured in computerized form from physical models or products Resulting geometric model is processed into a solid model

Flow Visualization

Transparent prototype is used for flow visualization User for automotive engine coolant circulation system design

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Applications of RP&M Special Applications Photoelastic testing

A method to determine the stress distribution in a material

Based on the temporary birefringence of a transparent material

Medical mold

Combined with scanning technology such as CT & MRI

Surgical simulation of complex reconstructive procedures

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Modeling Modeling in RP&M Part Preparation

Generation of STL (STereoLithography) file from geometric model

Determination of buildup direction

– Affects surface quality, build time, amount of support structure, amount of trapped volume– Determined based on experience and trial and error

Part placement or packing

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Modeling Modeling Guidelines Stick to Material Guidelines

Each and every printing material is different.

– Brittle, strong, flexible, solid, smooth, rough, heavy, light, and so on– An object should ideally be designed for a specific material

The choice of printing material simply pre-determines some of the basic design guidelines

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Modeling Modeling Guidelines Design for Real World Physics

Weight Distribution

– Review how your model’s weight will be distributed– Maybe your model needs a base, thicker legs, or multiple points of contact on the ground to hold it up

Sizing

– Size your model to fit your needs and the printers– Size is especially important for prints that fit together like puzzles or are worn, like rings

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Modeling Modeling Guidelines Make a Water-Tight Mesh

A water-tight mesh is achieved by having closed edges creating a solid volume

Check the normal vectors and make sure they all face outward

– Any flipped normal vector will be read as holes by the printer

Clean up any internal geometry that could have been left behind accidentally from booleans

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Modeling Modeling Guidelines Be Careful of Protruding Appendages

Outstretched appendages from the core of model might snap off during or after printing

– During the production process, some materials are very delicate like a sandcastle– In some cases, an air blaster is used in order to remove any support material

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Modeling Modeling Guidelines Hollow the Model with Escape Holes

Make an escape hole so the excess material can be removed

– Especially necessary for strong & flexible models – Should be large enough for the support material to escape

For SLS (Nylon)

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Modeling Modeling Guidelines Prepare Separate and Interlocking Parts

3D printing uniquely allows the creation of intricate, movable pieces without assembly

– The level of intricacy and detail that industrial 3D printers can produce is unparalleled– Make sure there is a large enough distance between tight areas

Making an oversized model

– Create separate parts that can interlock after printing

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RP in Fashion 3D Printed Cloth

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RP in Fashion Kinematic Dress Nervous System

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RP in Fashion Kinematic Dress

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RP in Fashion 3D Printed Collection

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RP in Fashion Smart Garment

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