Modul BDD 40303
Transcript of Modul BDD 40303
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custom made and distinctive if possible 'ndividual trimmings and
technical details of cars demonstrate this impressively
Environmental requirements
.nvironmental compatibility and the ability to recycle products and theirpackaging determine the buying behavior of customers as subsequent
costs are dependent on them
Decreasing li etime o products
# drastic decline in the lifetime of all types of products is being
witnessed #ccording to leading market research agencies the period of
time over which a product can be placed pro%tably in the market has
nearly halved over the last /0 years Studies from various sources agreethat this trend will continue at a rate of about 1 per year 2)igure
!he speed of change will largely depend on the line of business 5hilst
the electrotechnical industry or suppliers to car manufacturers have,
owing to their intensive use of new methods, already e$hausted the
potential to a great e$tent, more conservative lines of business such as
the machine6tool manufacturing industry still have considerable
potential
Decreasing prices
!he price of a product is gaining increasing in+uence in the buying
decision 7lobal markets and fast communication between continents
enable a worldwide price comparison 7eographical niches can no longer
be occupied, at least not for long
1.1 Critical Factors for Succ ss a!" Co#$ titi% Strat &i s
8ritical factors for success are de%ned by Siegwart and Sieger
9S'.75#:!; < as measures by which single in+uences may be condensed,
thereby enabling the measurement of the degree of success of a company
!he in+uences discussed in the preceding section and the resulting
consequences for product development point to the following factors for
success&
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Shortening of the product development time
:eduction of costs
'ncrease in +e$ibility 2product and production
'mprovement of quality
!his list is not universally applicable but it does represent today=s
generally accepted consensus !he single critical factors of success are
not independent of each other in the mathematical sense* they represent
values that, when weighted and interrelated in a strategy, enable
conclusions to be drawn !he strategy of a company e$presses how it
considers its own interaction with its competitors #ll critical factors for
success of a product, especially time and cost, can be condensed into onekey element& the >time to market ? >!ime to market? means the time that
elapses between the decision to develop and produce a certain product
and its introduction into the market
!his dominance of time over money, typical for today=s products, has
not only an absolute but also a relative dimension 't is not solely a
question of making the right decisions within a short period of product
development* of equal importance is making those decisions as early
as possible 'n addition it should be reali"ed that although the
accumulated e$penditures for product development early in the
process are still low, a large percentage of future costs is already
determined over the course of the development
!he graph shows clearly that the relationships are even more dramatic at
the commencement of product development& 401 of the total costs are
already de%nitely %$ed after the idea and draft phase, although at thispoint in time only negligible costs of /1 to 31 of the total costs have been
incurred .ngineers are often surprised to discover that it is important not
only to make the right decision as early as possible, but also to make that
decision %nal !he later changes are made, the more e$pensive they will
be )igure shows that the costs for a certain late change to a product
grow e$ponentially with the progress of product development 'n a
logarithmic scale this appears as a straight line @ere the same change is
shown but at diAerent stages of product development
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)igure !he costs for identical changes of a product at various phases
of product development
't follows from this not only that changes to the design become more
e$pensive and time6consuming the further the product development has
progressed, but also that product de%ciencies recogni"ed too late can
result in costs that threaten the viability of the entire pro ect 5hoever
doubts these %ndings should bear in mind that the cost for an alteration to
a large machine tool can speedily reach several hundreds of thousands of
dollars and a recall of automobiles can easily top billions even though the
defective part may be valued at mere cents
!o summari"e, it follows that the minimi"ing of product development time
is the key management ob ective, thereby enabling optimal total pro%t to
be achieved and e$penditure to be considered a time6dependent variable'n times when people focus on cost reduction, this is an important point
1.' Mo" ls i! Ra$i" Pro"uct D % lo$# !t Proc ss
Cew product strategies take into account that the requirements on
products and thereby product development have changed !he following
subsections discuss the in+uence of models and prototypes on the optimalimplementation of these new strategies !he observations show that for
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new product development strategies it is important not only to use models
but also to consider how fast they are available, at what step of the
development process, and the interactions that occur !he accepted terms
and de%nitions of classical product development are used !he demands
on models diAer according to the degree of progress the product
development has reached 't is sensible to agree on a model de%nition and
to assign this to certain steps in the product development irrespective of
the question of how these models are produced 'n the relevant literature
a large number of various terms and suggestions for model de%nitions can
be found n the one hand they are often characteri"ed by the planned
use and by specialties typical for certain branches, and on the other hand
they are often too speci%cally orientated to rapid prototyping processesProportional model
Shows the outer shape and the most important proportions )acilitates
communication and motivation, supports fast e$change of
communication about the intended product properties, and enables a
fast consensus on the product idea !he production process must be fast,
simple and cheap Disposal and recycling are very important
-roportional models are often called >concept models? or >show6and6tell
models ?
Degree of abstraction& high* degree of detailed speci%cation& low*
functionalities& none
Ergonomic model
Supports the fast decision about feasibility 2is it possible to develop this
product and should it be done Shows important details for operation
and use, and also, if applicable, important partial functions
Degree of abstraction& medium* degree of detailed speci%cation&
medium* functionalities& some
Styling model
Shows the outer appearance as close as possible to the 2series sample
Surface %nish needs to have >showroom? quality Supports the fast
decision on construction and manufacturing methods .nables third
parties 2customers, sales, press, suppliers to pass their udgments at anearly stage, enables public relations work
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Degree of abstraction& low* degree of detailed speci%cation& partially
high* functionalities& some
Functional model
.nables the proving of the numerical simulation calculations and theearly testing of certain functions 2how it could be assembled, easy
maintenance, and kinematics Shows some or all important functions, if
necessary without showing the outer shape )orms the basis for inquiries
by customers and suppliers 7ives relevant information for tool and mold
manufacturing, for the construction and installation of the means of
production
Degree of abstraction& low* degree of detailed speci%cation& high*
functionalities& several
Prototype
:esembles the 2series sample closely or, if necessary, e$actly 's
produced according to production documents !he only diAerence from
the series product lies in the production process .nables the testing of a
single or several product properties 2how it can be assembled,
electability, start of special approval processes .nables the production
of tools 2rapid tooling .nables the preparation for market introduction
by press campaigns
Degree of abstraction& none* degree of detailed speci%cation& high*
functionalities& all
Sample
#lready produced in series, possibly a pilot batch, production batch,
preproduction, or principal batch .nables the entire testing of all product
properties Supports the training of production and maintenance
personnel, supports the start of mass production, enables the
ad ustment of production and assembly sequence Supports the detailed
planning of customers and suppliers
Degree of abstraction& none* degree of detailed speci%cation& high*
functionalities& all
Solid images
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8overing& -roportional models, ergonomic models and styling models or
>show6and6tell? models Eisuali"ing proportions and general appearance
Geometrical prototypes
!esting of handling, operation and use Eisuali"ing the e$act shapeincluding the desired surface qualities
Functional prototypes or models
8overing& )unctional models, prototypes and samples
Below shows the simpli%ed de%nition of model classes in relation to the
main product development steps as de%ned in )ig /
Figure !" Steps o product development in relation to various model
defnitions
#lthough engineers readily agree on the meaning and the terminology of
functional models, prototypes, and samples, the classi%cation into
proportional models, ergonomically models, and styling models is poorly
understood and the value of these models is generally doubted 't is,
however, a key process in product development to agree on the product
and its general reali"ation
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!he conventional model making process, however, does rely on the oint
database in the form of two6dimensional 2/D drawings and sketches, but
it usually changes the geometry in the course of necessary
>interpretations? of the /D drawings during the model making !his step isoften taken deliberately to create the %nal geometrical form which is then
measured and returned to the design process !his means that during the
time when the model is being made there e$ists no de%ned database to
which other members of the team could refer Simultaneous engineering is
therefore not feasible for the duration of the model making
1.( Ra$i" Protot)$i!& *istor)
!he development of :apid -rototyping is closely tied in with the
development of applications of computers in the industry !he declining
cost of computers, especially of personal and mini computers, has
changed the way a factory works !he increase in the use of computers
has spurred the advancement in many computer6related areas including
8omputer6#ided Design 28#D , 8omputer6#ided Fanufacturing 28#F and8omputer Cumerical 8ontrol 28C8 machine tools 'n particular, the
emergence of :- systems could not have been possible without the
e$istence of 8#D @owever, from careful e$aminations of the numerous :-
systems in e$istence today, it can be easily deduced that other than 8#D,
many other technologies and advancements in other %elds such as
manufacturing systems and materials have also been crucial in the
development of :- systems !able traces the historical development of
relevant technologies related to :- from the estimated date of inception
#a$le ! % &istorical development o 'apid Prototyping and related
technologies
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!he beginning of rapid prototyping techniques are available in the latereighties and were used for the production of prototype and models
@istory of :apid prototyping can be found in the si$ties #n engineeringprofessor, @erbert Eoelcker, thought himself of the possibilities of doinginteresting things with computer controlled and the automatic machinetools @e tried to %nd a way in which the automated machine tools can beprogrammed by using the output of a design program of the computer @edeveloped the fundamental tools of mathematics that clearly e$plains thethree dimensional aspects and resulted in the earliest theories of algorithmic and mathematical theories of solid modeling !hey formed thebasis of modern computer programs and are used for designing almost all
things mechanical, ranging from the small toy car to the tallest skyscraper8arl Deckard, from the Gniversity of !e$as, came up with a goodinnovative idea @e pioneered the layer based manufacturing, where hethought of building the model layer by layer @e printed 3D models byusing laser light for fusing metal powder in solid prototypes, single layer ata time Eoelcker and Deckard %ndings, innovations and researches hadgiven e$treme momentum to the signi%cant new industry known as :apid-rototyping 9Hfaster than what? or at least >how fast > !here is also a
certain danger in using the term >rapid?& it could mean that these
processes are intrinsically faster than others !his is not necessarily so
!here is no general rule to be found here !he speed of rapid prototyping
processes depends to a great e$tent on the geometry 5hoever needs
only a board of / O / O inch is better served by the semi %nished
product and a saw Co computer6aided model making process will be
faster
!he word >prototyping? is also inapt because many applications of
computer6aided production processes do not deal with the production of
prototypes in the strict sense #part from design models and
demonstration models, molds and tools are made and even 2small series
are produced
!he term rapid prototyping has, however, an unbeatable practical
advantage 't is engraved in everyone=s memory 't is viewed as a
synonym for computer6controlled and therefore automatic generative
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processes :apid prototyping together with its most prominent member,
stereolithography, are well known in this combination !hey are self6
e$planatory and thereby ful%ll the most important requirements of a
standard term
'n contrast, most of the other terms used and e$plained in the te$t or in
the appendi$ require additional e$planation by the user& >!hat is
something like rapid prototyping ? )or this the reason we call this process
>rapid prototyping? right from the start
!he terms rapid tooling and rapid manufacturing are subordinate to that of
rapid prototyping and relate to special uses and areas of application
:apid prototyping encompasses the science of generative production
processes and is therefore a technology wing to their newness, some
applications acquire their own terminology for techniques or strategies
2often called >applications? as well which are often used synonymously
with those of the technology 5hereas in milling machine technology there
is no diAerentiation in method between producing positives and negatives,
this is de%nitely the case in rapid prototyping technology where
compulsory standards are only partially available 't is, however, very
important to reali"e that the application of rapid prototyping technology is,
methodically, really a technique !herefore, concept models and geometric
prototypes 2solid imaging as well as functional prototypes and technical
prototypes 2functional prototyping on the one hand, and generative tool
making 2rapid tooling and generative series production 2rapid
manufacturing on the other hand, adopt the status of a strategy
irrespective of their practical signi%cance
Depending on the architecture of the machine and the material used, the
application of rapid prototyping technology leads to solid images or
concept modelsNgeometry prototypes or to functional prototypesNtechnical
prototypes as shown in )igure 3 #pplications especially for metal
materials have brought about the development of generative tool making
2rapid tooling and generative series production 2rapid manufacturing
-rototypers used for the production of solid images or concept
modelsNgeometry prototypes 2concept modeler and those used for the
production of functional prototypesN technical prototypes are
technologically similar 5hereas concept modelers are suitable for the
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production of relatively rough but cheap models, functional prototypers
produce more comple$, more detailed, and more precise P but also more
e$pensive P models
Because rapid prototyping processes are practically unlimited in theirability to form comple$ shapes, they can produce both positives and
negatives Cegatives are produced as dies or molds 2die or mold inserts,
respectively for preproduction or small6batch production with
corresponding positives 'n this case, it is called generative tool making or
rapid tooling :apid tooling is, therefore, of special importance because
the >step into the tool? is very time consuming, prone to faults, and
e$pensive for all product generating processes !he terms generative
series production or rapid manufacturing 2also& rapid production assumethat rapid prototyping methods can be used directly for the production of
all kinds of 2mass products !his is already being done with special
applications such as, for e$ample, medical implants 28-67mb@, 7ermany
or plastic aligners for straightening adult teeth 2#lign !echnology, 8#,
GS#
Figure !* 'apid prototyping technology and its applications
'f we follow the actual terminology the following de%nitions result&
'apid prototyping
:apid prototyping describes the technology of generative production
processes
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Solid imaging and functional prototyping describe the applications of rapid
prototyping technology Solid imaging includes the production of relatively
simple, mechanical6technological nonresilient models that nonetheless
display the outer form and the features of the %nal component relatively
well )unctional prototyping is the application of rapid prototyping
technology to prototypes made of plastic, metal, or other materials that
simulate one or more mechanical6technological functionalities of the %nal
series component 'n many cases solid imaging and functional prototyping
often become the time6determining factor during the %rst phase of product
development
'apid tooling
:apid tooling describes those applications that are aimed at making tools
and molds for the production of prototypes and preseries products by
using the same processes as those used in rapid prototyping !his
concerns both the model 2positive as well as the mold 2negative
#nglophones talk here of >pattern making? and of >mold making ? #gainst
this background, rapid tooling becomes the time6determining factor in the
second phase of product development, that of optimi"ing the actual
product, developing the means of production, and the production itself
'apid manu acturing
By rapid manufacturing or rapid production we understand rapid
prototyping applications that produce products with serial character !hese
can be positives produced directly with rapid prototyping methods 2e g ,
plugs in smallest series or tools produced with rapid prototyping
processes usable directly for the production of the required quantities !he
mechanical6technological properties of today=s rapid materials are in most
cases still far from the target characteristics of the products )or largerproduction quantities production times are still relatively lengthy )or these
reasons rapid prototyping is usually uneconomical and rapid
manufacturing, with a few e$ceptions, does not 2yet belong to the
production processes that are in use
!he possibilities of rapid manufacturing inspired the phantasies of
engineers immediately after details of the %rst rapid prototyping processes
were published Scenarios in which spare6part stocks are completely
eliminated and replaced by appropriate rapid prototyping installations
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> ust in time? have been known for some time now ne suggestion of
making the entire stock6keeping of naval units, for e$ample on an aircraft
carrier, super+uous while simultaneously guaranteeing a +e$ible provision
by using appropriate rapid prototyping 2metal installations was especially
discussed in detail
ther scenarios in which the use of rapid manufacturing methods alone
can enable the transport of tools and spare parts to distant celestial
bodies such as Fars are also being seriously discussed at present !hese
re+ections are of value only, however, if the prototypers are able to work
with the materials available there .ven if these scenarios still seem
unrealistic today, recogni"able development trends make such
applications ever more probable :apid manufacturing as a tool of >customi"ed mass production? processes will gain more importance in
future in view of the following development trends in rapid prototyping
processes and the demands made on the products&
shorter product life time,
increasing product comple$ity,
growing individuality of products,
smaller series)igure 4 shows the relationships of rapid prototyping, rapid tooling and
rapid manufacturing to the basic product development phases
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Figure !+ 'elating o rapid prototyping, rapid tooling and rapid
manu acturing processes to the $asic product development phases
1.0 G ! ric C+aract ristics of Ra$i" Protot)$i!& Tc+!olo&)
'ndustrial rapid prototyping systems on the market today are sub ect to a
high development speed Cew processes still in the laboratory stage or
under development today will break into the market #t the same time,
well tried and tested systems will be upgraded within a relatively short
time
#s the equipment presently on the market will be obsolete or approaching
obsolence over relatively short periods the physical6technological bases of
the various processes not only facilitates the assessment of the current
processes, but it also supplies the basis for the assessment of future
industrial processes 'n reality, however, overlaps and repetitions are
unavoidable :apid prototyping processes belong to the generative 2or
additive production processes 'n contrast to abrasive 2or subtractive
processes such as lathing, milling, drilling, grinding, eroding, and so forth
in which the form is shaped by removing material, in rapid prototyping the
component is formed by oining volume elements
#ll industrially relevant rapid prototyping processes work in layers Kike
the half6breadthplan of a ship, known from classical model making, single
layers are produced and oined to a component 'n the strict sense, rapid
prototyping processes are therefore /QD processes, that is stacked up /Dcontours with constant thickness !he layer is shaped 2contoured in an 2$6
y plane two6dimensionally !he third dimension results from single layers
being stacked up on top of each other, but not as a continuous "6
coordinate !he models are therefore three6dimensional parts, very e$act
on the build plane 2$6y direction and owing to the described procedure the
stepped in the "6direction whereby the smaller the "6stepping is, the more
the model looks like the original
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#lthough all rapid prototyping processes known today work in this way as
/QD processes, some processes 2e g , e$trusion processes are in principle
3D processes, which means they can add incremental volume elements at
any chosen point of the model
!he special characteristic feature of rapid prototyping processes is that the
physical models are produced directly from computer data 'n principle it is
thereby unimportant whence the data are provided as long as they
describe a 3D volume completely Data from 8#D design, from the
processing of measurings and reverse engineering or other measurements
9computer tomography 28! , magnetic resonance tomography 2F:! < may
be used equally well
'n this way model making has become an integral part of the computer6
integrated product development )rom the product development aspect
rapid prototyping models can, therefore, be regarded as three6dimensional
plots or facsimiles of the corresponding 8#D data !he decisive advantage
in contrast to classical manual or semiautomatical model6making
processes lies in the fact that the data remain unaltered by the model
making #s a result no data need to be taken from the model Because themaking of rapid prototyping models does not alter the common database,
rapid prototyping processes have become the most important elements of
modern product development strategies such as simultaneous engi6
neering !he generation of layer information is based on a purely
computer6orientated 8#D model !he 8#D model is cut into layers by
mathematical methods !his layer information is used for the generation
of physical single layers in a rapid prototyping installation, the so6called
prototyper !he total sum of the single layers forms the physical model
!his is the principle of model generation by rapid prototyping as shown on
)igure
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)igure !he principle of model generation by rapid prototyping
Proc ssst $
D scri$tio!
8onvert8#D modelto S!Kformat
8#D model is converted into S!K format that represents thesurface of the part by many triangles
rient part2s
perator uses e$perience to select best orientation fore$ample to minimise build time or to achieve tolerances onkey dimensions
7eneratesupports ifrequired
Software normally automatically generates supports whereneeded, however e$perienced operators can usually editthese for e$ample to minimise need for manual supportremoval during post6processing )igure 4 shows the design of a part with supports in place
8reate slice%les
Software generates the /D pro%le description of each layerof the part plus supports to be made
)abricatepart plussupports
/D pro%les are sent to the machine to drive part creation, fore$ample by controlling mirrors that allow lasers to scanacross a powder bed to sinterNfuse powder where required
-ost6process
5hen parts have been fabricated they need to be cleaned,for e$ample to remove e$cess unfused powder or to removesupport structures )urther work such as sanding,in%ltration, painting or electroplating may also berequired depending on the process used and the
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intended application for the part
1. Classi catio! Of Ra$i" Protot)$i!& S)st #s
5hile there are many ways in which one can classify the numerous :-
systems in the market, one of the better ways is to classify :- systems
broadly by the initial form of its material, i e the material that the
prototype or part is built with 'n this manner, all :- systems can be easily
categori"ed into 2 liquid6based 2/ solid6based and 23 powder6based
)undamentally, the development of :- can be seen in four primary areas
!he :apid -rototyping 5heel in )igure J depicts these four key aspectsof :apid -rototyping !hey are& 'nput, Fethod, Faterial and #pplications
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)igure J& !he :apid -rototyping 5heel depicting the four ma or
aspects of :-
-rof R - ruth suggests the later term T'ncrescent= means Ubecoming
gradually greaterU 25ebster Dictionary and is more general than UdepositUor UadditionU Some techniques use direct 3D solidi%cation 2e g holographic
polymeri"ation and do not really deposit material in successive layers
UFaterial 'ncress FanufacturingU clearly identi%es those techniques as the
antipode of UFaterial :emoval FanufacturingU !he classi%cations of
material incress manufacturing techniques are given bellow which relates
to the way material is created or solidi%ed
Ra$i" Protot)$i!&
Li2ui"/3as "
Kiquid6based :- systems have the initial form of its material in liquid state
!hrough a process commonly known as curing, the liquid is converted into
the solid state !he following :- systems fall into this category&
2 3D Systems= stereolithography apparatus 2SK#
2/ b et 7eometries Ktd =s -oly et
23 D6F.8=s solid creation system 2S8S
24 .nvision!ec=s -erfactory
2 #utostrade=s .6Darts
2J 8F.!=s solid ob ect ultravioletPlaser printer 2S G-
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2H .nvision!ec=s Bioplotter
Soli"/3as "
.$cept for powder, solid6based :- systems are meant to encompass all
forms of material in the solid state 'n this conte$t, the solid form can
include the shape in the form of a wire, a roll, laminates and pellets !he
following :- systems fall into this de%nition&
2 Stratasys= fused deposition modeling 2)DF
2/ Solidscape=s benchtop system
23 8ubic !echnologies= laminated ob ect manufacturing 2K F
24 3D Systems= multi6 et modeling system 2FRF
2 Solidimension=s plastic sheet lamination 2-SK N3D System=s
invision
Po4" r/3as "
'n a strict sense, powder is by6and6large in the solid state @owever, it is
intentionally created as a category outside the solid6based :- systems to
mean powder in grain6like form !he following :- systems fall into this
de%nition&
2 3D Systems=s Selective Kaser Sintering 2SKS
/ 2/ L 8orporation=s !hree6Dimensional -rinting 23D-
3 23 . S=s . S'C! systems4 24 ptomec=s laser engineered net shaping 2K.CS
2 #rcam=s electron beam melting 2.BF
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RAPID PRODUCT PROCESS
!he ob ective of rapid prototyping is to quickly fabricate any comple$6shaped, three6dimensional part from 8#D data :apid prototyping is an
e$ample of an additive fabrication process 'n this method, a solid 8#D
model is electronically sectioned into layers of predetermined thickness
!hese sections de%ne the shape of the part collectively
!he focus of this chapter is on those system elements that aAect the
shape of the part& the 8#D %le, the S!K 2stereolithography %le, problems
and repairs of S!K %les, and other %le formats 'n short, the modeling
principles of rapid prototyping will be discussed in this chapter
'.1 3ASIC AUTOMATION PROCESS
:apid prototyping is essentially a part of automated a$rication, a
technology that lets us make three6dimensional parts from digital designs
9 < !here are several advantages of automated a$rication over manual
fabrication and molding processes Some of these advantages are
computer6aided design, quick design changes, and precise dimensioning
)abrication processes, manual or automated, can be classi%ed as
subtractive, additive, or formative !hese processes are shown in )igure
/
Su$tractive Process 'n this process, one starts with a solid block of
material larger than the %nal si"e of the %nished ob ect, and then
material is removed slowly until the desired shape is reached
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CHAP
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
Subtractive processes include most forms of machining processesM
computer numerical control 28C8 or otherwise Fost widely used e$6
amples include milling, turning, drilling, planning, sawing, grinding,
electrical discharge machining 2.DF , laser cutting, water6 et cutting, and
many other methods
-dditive Process Gnlike the subtractive process, this process involves ma6nipulation of material so that successive pieces of it combine in the right
form to produce the desired ob ect !he rapid prototyping process 2layered
manufacturing falls into the additive fabrication category )igure / /
shows the additive layer6by6layer process of rapid prototyping .$amples
of :- processes include SK#, )DF, K F, SKS, solid ground curing 2S78 ,
direct shell production casting 2DS-8 , and 3D printing 23D-
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Fi&ur '.' #dditive layer6by6layer process
Formative Process 'n this process, mechanical forces are applied to ma6
terial so as to form the desired shape .$amples of the formative
fabrication process include bending, forging, electromagnetic forming,
and plastic in ection molding
!wo or three of these processes can be combined to form a hy$rid process
@ybrid processes are e$pected to contribute signi%cantly to the production
of goods in the future -rogressive press working is an e$ample of hybrid
machines that combine two or more fabrication processes 'n progressive
press working a hybrid of subtractive 2as in blanking or punching and
formative 2as in bending and forming is used
'.' PROCESS C*AIN
#ll prototypes made with both the current and evolving :- processes have
several features in common 9/, 3< # solid or surface 8#D model is elec6
tronically sectioned into layers of predetermined thickness !hese sections
de%ne the shape of the part collectively 'nformation about each section is
then electronically transmitted to the :- machine layer by layer !he :-
machine processes materials only at TTsolid== areas of the section
Subsequent layers are sequentially processed until the part is complete 't
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
is this sequential, layered, or lithographic approach to parts manufacturing
that de%nes :- !he :- process basically uses the following steps to make
prototypes&
8reate a 8#D model of the design
/ 8onvert the 8#D model to S!K %le format
3 Slice the S!K %le into /D cross6sectional layers
4 7row the prototype
-ostprocessing
!he %ve6step process is shown in )igure / 3
Fi&ur '.( )ive6step process of rapid prototyping
'.( (/DIMENSIONAL MODELING
!he %rst step in creating a prototype is the creation of a 8#D solid model:- requires that we make a fully closed, water6tight model such that even
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
if we were to pour water into the volume of the model, it would not leak #
solid is a volume completely bounded by surfaces, which means the edges
of all surfaces must be coincident with one, and only one, other surface
edge Gnlike wire6frame and surface modeling, solid modeling stores
volume information # 8#D solid model not only captures the complete
geometry of an ob ect, it can also diAerentiate the inside and the outside
of the space of that ob ect Fany other volume6related data can be
obtained from the model
!he creation of a 3D body is the indispensable prerequisite for the
production of a rapid prototyping model !herefore, the application of
prototyping is linked especially closely with 8#D processes )or this reason
3D 8#D processes will be looked into only as far as is absolutely necessary
for the understanding of the fundamental relationships in the production of
rapid prototyping models .very 8#D system uses certain data elements
and data structures to describe a component in detail !he data record
includes not only the component geometry but also the materials, the
quality of the surface, the production process, and much more !he
component geometry therefore comprises only one part of the
information !he complete information registered in the database of a 8#D
system for a component is called a 8#D model 2the product to be made 'f
the geometric description of a component is 3D then it is called a 3D 8#D
model
By choosing a certain 8#D system the user commits himself to its
database !he structure and the data elements decide to a high degree
the quality of a 8#D system and its compatibility with other systems via
interface 8#D models are de%ned by model types regardless of the kindof 8#D system 2)igure / 3 !he corner model de%ned by points is of less
practical importance 't is used, for e$ample as an intermediate model for
the semiautomatic transformation of grid data or of /D 8#D models into
3D 8#D models
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
)igure / 3 8#D .lements and Fodel !ypes
!he edge model too is more of historical interest today in regard to rapid
prototyping wing to its small amount of data it enables a fast graphic
representation of 3D elements even with low computer performance 'ts
importance is therefore growing again in connection with virtual reality
2E: applications and digital mockup 2DFG !he most important
disadvantage of the edge model is the missing information about the
e$act position of the surfaces and the volumes )or this reason it cannot
be recommended as a basis for the production of rapid prototyping
models
#ll 8#D6systems that process components as surface models in their
geometrical databases are in principle suitable for the issuing of data via a
rapid prototyping interface 5hen a component is de%ned by its e$ternal
surface, the user is usually able to calculate the e$act component volume
as well !his is usually achieved by appointing and storing an additional
normal vector for each surface pointing away from the inside of the
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
component )or the complete description of a component therefore it is
absolutely necessary that the orientation of the component volume is
known Solids are optimal for the modeling of 8#D models that 2among
other things are also used for rapid prototyping !he orientation of the
volume is preset e$actly and need not be e$plicitly appointed by the user
Solid models can be created using a 8#D software package such as
#uto8#D, -roN.ngineer, 8#!'#, Solid 5orks, or many other commercially
available solid modeling programs
'.- Data Tra!sf r a!" D li% r)
nce a solid model is created and saved, it is then converted to a special
%le format known as S!K 2stereolithography 94< !his %le format originated
from 3D Systems, which pioneered the stereolithography process
#ctually, the #lbert 8onsulting 7roup under contract to 3D Systems
developed the S!K %le format to support the new revolutionary
manufacturing technology, called stereolithography !hough not ideal, it is
suf%cient to meet the needs of today=s rapid prototyping technology,
which generally build monomaterial parts !he success of this %le formathas been impressive !oday, a decade later, the S!K %le format remains
the de facto standard for the rapid prototyping industry
!he success of the S!K %le format is due to its suf%ciency, its simplicity,
and its monopoly 9 < 'ts mathematical suf%ciency stems from the fact that
it describes a solid ob ect using a boundary representation 2B6rep
technique #n S!K %le format represents the virtual 8#D model of the
ob ect to be prototyped as a collection of triangular facets !hese
triangular facets, when taken together, describe a polyhedral
appro$imation of the ob ects= surface, that is, a polyhedral appro$imation
of the boundary between material and nonmaterial 'n short, an S!K %le is
nothing more than a list of . , y , and z coordinate triplets that describe a
connected set of triangular facets 't also includes the direction of the
normal vector for each triangle, which points to the outer surface of the
model
Fost 8#DN8#F software vendors supply the S!K %le interface Since ;;0,
many 8#DN8#F vendors have developed and integrated this interface into
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
their systems !essellation is the process of appro$imating a surface by
triangular facets !he 8#D S!K %le interface performs surface tessellation
and then outputs the facet information to either a binary or #S8'' S!K %le
format
!he output of S!K %le formats can be e$pressed in binary or #S8'' format
!he characteristics of binary and #S8'' S!K outputs are shown in !able /
)igures / 4 and / show a binary S!K %le format and an #S8'' S!K %le
format, respectively
!here are three steps to S!K %le creation 9J
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Default output type:eferred to as human6readable
format:eferred to as machine6readable
format
.asily read and understood by
humans
Fore compact and ef%cient, easier tomove
through networkN transmit
Cot very ef%cient, slower toprocess,
larger %le si"esCot easily read or understood by
humans
without some translation
Cot recommended if moving %les
through a network
Address Length Type Description/ 0/ char &eader in ormation
0/ + long Num$er o acets insolidFirst acet 12/ $ytes3%0+ + 4oat Normal 1. component300 + 4oat Normal 1y component35" + 4oat Normal 1z component356 + 4oat )erte. 1. component3// + 4oat )erte. 1y component3/+ + 4oat )erte. 1z component3/0 + 4oat )erte. " 1. component3" + 4oat )erte. " 1y component36 + 4oat )erte. " 1z component3"/ + 4oat )erte. * 1. component3"+ + 4oat )erte. * 1y component3"0 + 4oat )erte. * 1z component3*" " short -ttri$ute in o! 1notused3Second acet 12/ $ytes3%*+!!!
Fi&ur '.- Binary S!K format
#riangulation tolerance" -d7acency tolerance* -uto8normal generation 1on9o:3+ Normal display 1on9o:32 #riangle display 1on9o:36 &eader in ormation 1te.t3
S;ain old zF-?E# N;'>-< /!//////e@// !//////e@// "!6*+ +5e@/5;A#E'
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
+!//////e@//
)E'#EB +!//////e@// !+/////e@// +!//////e@//
)E'#EB +!//////e@// !+/////e@// *!//////e@//
END
Some of the features of triangulation tolerance are as follows&
Determines how smooth the appro$imation of the surface or solid will
be 'n other words, how close the triangles appro$imate the surface @ow close the sides of the triangles that lie along the edges are to
the actual edges of the surface
Gsually set to one half the desired accuracy of the :- process being
utili"ed
Default is set at 0 00/ in , or 0 0 mm
!he dramatic eAects of decreasing the values of triangle tolerances are
shown in )igure / J Some of the features of ad acency tolerance are as
follows&
't does not aAect processing of solids
/ !he default value is 0 00 in , or 0 / mm
3 !he system uses this value to determine if two surfaces will be
attached to one another
4 .dges whose length is smaller than the ad acency tolerance can
cause ad acency problems
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
Fi&ur '. .Aects of decreasing values of triangle tolerances
!he eAects of ad acency tolerance are shown in )igure / H Some of the
features of auto6normal generation are as follows&
't does not aAect processing of solids
/ 8hoose a base surface, check the normal, and calculate all others
from this surface
3 Default should be on
E5a#$l '.1
)or the ob ect shown in )igure / I&
2a Draw the part using -roN.ngineer or a similar 8#DN8#F system
2b 8reate S!K #S8'' %le with chord height of 0 and 0
2c Discuss the changes that take place when chord height is varied 2%le
si"e, number of triangles, etc
Solution
2a !o generate the solid ob ect, a simple rectangular protrusion was
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
%rst created Gsing the cut command in the %le menu, the
rectangular sections were $lind cut to the speci%ed depths !he
circles were then cut completely through the part !he solid ob ect is
shown in )igure / ;
2b !he part was saved in an #S8'' S!K %le format with the speci%ed
chord heights and is shown in )igure / 0
2c Earying the chord height changes the number of triangles created
5hen the chord height is decreased, there are more triangles, thus a
larger %le si"e !he smaller the chord height, the resolution is better
and accurate for the ob ect @owever, the more accurate model will
take longer to produce )igure / shows the ob ect sliced at
diAerent chord heights
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
)igure / ; !he solid ob ect
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
Fi&ur '.16 S!K #S8''
'.0 R %isio! a!" Pr $aratio!
!he %le is taken from its 3D model surfaces and converted to many
triangles, a step referred to as slicing! !he more comple$ the ob ect, the
more triangles are required, and thus the bigger the %le that makes up the
8#D model as well as a support structure for the part to be grown on !he
sliced ob ect is saved as an S!K %le and is now in a format the :-
computer recogni"es
'. Co!structio!
!he part is submitted to the :- computer and the machine runs until the
part is complete :- machines build one layer at a time from polymers,
paper, or
Fi&ur '.11 2a 8hord @eight 0 and 2 $ chord height 0
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powdered metals Fost machines are fairly autonomous needing little
human intervention Build times vary depending on si"e and number of
parts required
'. Post$roc ssi!&
!he %nal step in rapid prototyping is postprocessing 't essentially consists
of part removal and cleaning and of postcuring and %nishing !his step
generally involves manual operations where an operator does the
postprocessing with e$treme care therwise, the part may be damaged
and may need to be prototyped again 9Hreverse engineering > !he conversion of measured data
in the form of point clouds directly into solid body descriptions in a neutral
data format, possible in principle, should be done only in e$ceptionalcases 't is not usually possible to relate point clouds clearly even to
simple geometrical bodies, and they contain an enormous amount of data
'n any case, the geometrical information of the entire body or of single
layers must be converted for transfer via interface into a neutral format
9stereolithography language 2S!K , SK8 which is a entire 3D6Systems or
Stratasys slice contour format, @ewlett -ackard graphic language 2@-7K ,
etc < as only then is the access to diAerent rapid prototyping processessecured !he generation of au$iliary geometries such as supports and
similar ones, which are not necessary with every rapid prototyping
process, is done P depending on the process P either together with the
generation of geometrical data or separately with the aid of rapid
prototyping software )inally, all data, the geometry and the supports, are
together sliced into layers by mathematical means and provide the layer
information that, together with machine speci%c parameters, is necessary
for the production of each layer Depending on the process, the layer
information is either completely calculated and stored before the process
is started, or it is calculated for each layer simultaneously with the build
#n S!K is a type of standardi"ed computer e$change %le which contains a
3D model !he representation of the surface2s of the ob ect2s in the %le is
in the form of one or more polygon meshes !he polygon meshes in an S!K
%le are entirely composed of triangular faces, edges and vertices )urther,
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
the faces have assigned normals which indicate their orientation
2insideNoutside
!he name >S!K? is taken from its e$tension, stl, originally because
the %les were intended for the rapid prototyping process called
Stereolithography !he %le format has become a world standard for
e$changing 3D polygon mesh type ob ects between programs, and stl=s
are now used as input for virtually all rapid prototyping processes, as well
as some 3D machining
'.( STL Fil Pro8l #s
5hile the S!K %le format is meeting the needs of the industries that are
using :- and while it is the de facto standard in :- industry, it has some
inadequacies 9/, H< Some of these inadequacies are due to the very
nature of the S!K %le format as it does not contain topological data #lso,
many 8#D vendors use tessellation algorithms that are not robust
8onsequently, they tend to create polygonal appro$imation models, which
e$hibit the following types of problems&
Gaps 2?rac s, &oles, Punctures Indicating >issing Faces 5hen a
solid model is converted into an S!K %le format, the solid model forms are
replaced with a simpli%ed mathematical form 2triangles @owever, if the
simpli%ed operation is not done properly, it introduces undesirable
geometric anomalies, such as holes or gaps in the boundary surface !his
problem is more prone to surfaces with large curvature Such gaps are
shown in )igure / /
/ Inconsistent Normals 'n general, surface normals should be pointed
outward @owever, the normals of some surfaces could be +ipped over, as
shown in )igure / 3, thus, becoming inconsistent with the outward
orientation of the original surface
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3 Incorrect Normals Sometimes, surface normals stored in the S!K %le
are not the same as those computed from the vertices of the correspond6
ing surfaces
4 Incorrect Intersections )acets may sometimes intersect at locations
other than their edges resulting in overlapping facets 2)ig / 4
Internal all Structure 7eometric algorithms are used for closing
gaps in S!K %les @owever, faulty geometric algorithms could generate
internal walls and structures that can cause discontinuities in the solid6
i%cation of the material 2)ig /
J Facet Degeneracy Degeneration of facets occurs when they may
not represent a %nite area and consequently have no normals 7enerally,
there are two kinds of facet degeneracies& geometric degeneracy and
topological degeneracy # geometric degeneracy takes place when all the
vertices of the facet are distinct and all the edges of the facet are
collinear # topological degeneracy takes place when two or more verticesof a facet coincide Since it does not aAect the geometry or the
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
connectivity of the remaining facets, the faults can be discarded 2)ig / J
H Inconsistencies Sometimes two S!K %les are combined to create a
prototype 'f these S!K %les were created using diAerent tolerance val6
ues, it will lead to inconsistencies such as gaps
'.- R alit) a!" Not R alit) Co!structio! R sult
!he problems and inef%ciencies of the S!K %le format have prompted the
search for alternate translators .$amples of some of these translators are'7.S, @-7K, and computed tomography 28! data
IGES File 'nitial graphics e$change speci%cation is a common format
to e$change graphics information between various 8#D systems 't was
initially developed and promoted by the then #merican Cational Standards
'n6stitute 2#CS' in ;I
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
!he '7.S %le can precisely represent both geometry and topological
information for a 8#D model #n '7.S %le contains information about
surface modeling, constructive solid geometry 28S7 and boundary
representation 2B6rep !he Boolean operations for solid modeling such as
union, intersection, and di:erence are also de%ned in the '7.S %le 't can
precisely represent a 8#D model by providing entities of points, lines, arcs,
splines, CG:BS surface, and solid elements !he primary advantage of
'7.S format is its widespread adoption and comprehensive coverage
@owever, there are some disadvantages of the '7.S format as it relates
to its use as an :- format !hese are&
!he inclusion of redundant information for :- systems
/ !he algorithms for slicing '7.S %le are more comple$ than those for
slicing S!K %le
3 !he support structures that are needed for some :- systems cannot
be created using '7.S format
'7.S is a very good interface standard for e$changing informationbetween various 8#D systems 't does, however, fall short of meeting the
standards for :- system
&e(lett Pac ard Graphics
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
format )irst, since @-7K is a /D data format, the %les are not appended,
leaving hundreds of small %les needing logical names and transformation
Second, all the required support structures must be generated in the 8#D
system and sliced in the same way
/ ?# Data 8! scan data is a new format used for medical imaging !he
format has not been standardi"ed yet )ormats are proprietary and vary
from machine to machine !he 8! scan generates data as a grid of three6
dimensional points, where each point has a varying shade of gray
indicating the density of body tissue present at that point Data from 8!
scan are being regularly used to prototype skull, femur, knee, and other
biomedical components on )DF, SK#, and other :- systems !he 8! data
essentially consist of raster images of the physical ob ects being imaged't is used to produce models of human temporal bones
Fodels using 8! scan images can be made using 8#D systems, S!K
interfacing, and direct interfacing 8! data is used to make human parts
such as leg prostheses, which are used by doctors for implants @owever,
the main problem with 8! image data is the comple$ity of the data and
the need for a special interpreter to process this data
(.- STL Fil corr ctio! # t+o"
Since an S!K mesh is composed entirely of triangles, it is the simplest form
of mesh model format .ach facet is necessarily planar 'n principle, for
rapid prototyping processes, a completely closed ob ect is required, that is
to say, the mesh completely encloses a volume, with no holes, gaps, or
overlaps 5e sometimes speak of this as a >watertight solid? 'n addition,
the software controlling some processes requires that there is only one
ob ect 2volume in the %le
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
Each o the illustrations a$ove sho( one slice o an !S#< model! In
order produce the layer, the 'P machine so t(are needs a closed loop
that defnes an interior, (hich is then flled (ith the model material!
Some procedures use the !S#< normals to defne the interior (ith
respect to the e.terior o the curves, (hereas others use nestingin ormation!
'n actual practice, there may be some tolerance allowed Small errors or
gaps may be tolerated by the prototyping software, or can be quickly
repaired Some software may allow multiple and overlapping ob ects .ach
process and software will work diAerently, some are more error6tolerant
than others !herefore, in general it is best to aim to achieve a perfect
001 closed model, otherwise, depending on who is doing the prototyping
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RAPID PRODUCT DEVELOPMENT AND MANUFACTURING B D D 4 0 3 0 3
and what process is being used, it may be time consuming 2read&
e$pensive to %$
-rofessional service bureaus and frequent users of :- parts will have
speci%c software designed to manipulate and %$ stl models and prepare
them for prototyping ne e$ample of this might be Fagics by Fateriali"e
2B !his type of software is e$pensive, but has speci%c tools for analy"ing
the integrity of stl models and rapidly correcting defects 2often
automatically !hey may also have other functions that permit the model
to be cut into smaller parts, shelled, nested, etc
nce the stl is 001 correct and veri%ed, it can then be imported into the
machine6speci%c :- software which will generate the commands to run
the machine !his data is then sent to the machine 2like a printer and themodel construction is started
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LI9UID/3ASEDRAPID
PROTOTYPINGSYSTEMS
Fost liquid6based rapid prototyping 2:- systems build parts in a vat of
photo6curable liquid resin, an organic resin that cures or solidi%es under
the eAect of e$posure to light, usually in the GE range !he light cures the
resin near the surface, forming a thin hardened layer nce the complete
layer of the part is formed, it is lowered by an elevation control system to
allow the ne$t layer of resin to be coated and similarly formed over it !his
continues until the entire part is complete !he vat can then be drained
and the part removed for further processing, if necessary !here are
variations to this technique by the various vendors and they are
dependent on the type of light or laser, method of scanning or e$posure,
type of liquid resin and type of elevation and optical system used
-.1. (D SYSTEMS: STEREOLIT*OGRAP*Y APPARATUS ;SLAoutput? device like a laser
scanning system !he layer thickness is controlled by a precision elevation
mechanism 't will correspond directly to the slice thickness of the
computer model and the cured thickness of the resin !he limiting aspect
of the :- system tends to be the curing thickness rather than the
resolution of the elevation mechanism
!he important component of the building process is the laser and its
optical scanning system !he key to the strength of the SK# is its ability to
rapidly direct focused radiation of appropriate power and wavelength onto
the surface of the liquid photo6polymer resin, forming patterns of solidi%ed
photo6polymer according to the cross6sectional data generated by the
computer 0 'n the SK#, a laser beam with a speci%ed power and
wavelength is sent through a beam e$panding telescope to %ll the optical
aperture of a pair of cross a$is, galvanometer driven and beam scanningmirrors !hese form the optical scanning system of the SK# !he beam
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comes to a focus on the surface of a liquid photo6polymer, curing a pre6
determined depth of the resin after a controlled time of e$posure
2inversely proportional to the laser scanning speed
!he solidi%cation of the liquid resin depends on the energy per unit area
2or >e$posure? deposited during the motion of the focused spot on the
surface of the photo6polymer !here is a threshold e$posure that must be
e$ceeded for the photo6polymer to solidify
!o maintain accuracy and consistency during part building using the
SK#, the cure depth and the cured line width must be controlled #s such,
accurate e$posure and focused spot si"e become essential
-arameters which in+uence performance and functionality of the parts
are physical and chemical properties of resin, speed and resolution of theoptical scanning system, the power, wavelength and type of the laser
used, the spot si"e of the laser, the recoating system and the post6curing
process
-.1.0. Str !&t+s a!" = a7! ss s
!he main strengths of the SK# are&
2 'ound the cloc operation! !he SK# can be used continuously
and unattended round the clock
/ 2/ Huild volumes! !he diAerent SK# machines have build
volumes ranging from small 2/ 0 \ / 0 \ / 0 mm to large 2H3H
\ J3 \ 33 mm to suit the needs of diAerent users
3 23 Good accuracy! !he SK# has good accuracy and can thus be
used for many application areas
4 24 Sur ace fnish! !he SK# can obtain one of the best surface
%nishes amongst :- technologies
0 2 ide range o materials! !here is a wide range of materials,
from general6purpose materials to specialty materials for speci%c
applications
/!he main weaknesses of the SK# are&
2 'equires support structures Structures that have overhangs
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and undercuts must have supports that are designed and
fabricated together with the main structure
J 2/ 'equires post8processing! -ost6processing includes removal
of supports and other unwanted materials, which is tedious, time6
consuming and can damage the model
H 23 'equires post8curing! -ost6curing may be needed to cure the
ob ect completely and ensure the integrity of the structure
-.1. . A$$licatio!s
!he SK# technology provides manufacturers cost usti%able methods for
reducing time to market, lowering product development costs, gaininggreater control of their design process and improving product design !he
range of applications includes&
2 Fodels for conceptuali"ation, packaging and presentation
/ 2/ -rototypes for design, analysis, veri%cation and functional
testing
3 23 -arts for prototype tooling and low volume production tooling
4 24 -atterns for investment casting, sand casting and molding2 !ools for %$ture and tooling design and production tooling
Software developed to support these applications includes ]uick8ast !F , a
software tool which is used in the investment casting industry ]uick8ast !F
enables highly accurate resin patterns that are speci%cally used as an
e$pendable pattern to form a ceramic mould to be created !he
e$pendable pattern is subsequently burnt out !he standard process uses
an e$pendable wa$ pattern which must be cast in a tool ]uick8ast !F
eliminates the need for the tooling use to make the e$pendable patterns
]uick8ast !F produces parts which have a hard thin outer shell and contain
a honeycomb like structure inside, allowing the pattern to collapse when
heated instead of e$panding, which would crack the shell
-.1.> DLP ? Di&ital Li&+t Proc ssi!&
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DK- M or digital light processing M is a similar process to
stereolithography in that it is a 3D printing process that works with
photopolymers !he ma or diAerence is the light source DK- uses a more
conventional light source, such as an arc lamp, with a liquid crystal display
panel or a deformable mirror device 2DFD , which is applied to the entire
surface of the vat of photopolymer resin in a single pass, generally making
it faster than SK#^
#lso like SK#, DK- produces highly accurate parts with e$cellent resolution,
but its similarities also include the same requirements for support
structures and post6curing @owever, one advantage of DK- over SK# is
that only a shallow vat of resin is required to facilitate the process, which
generally results in less waste and lower running costs
@'>
-.'. O3 ET GEOMETRIES LTD.:S POLY ET
-.'.1. Co#$a!)
b et was founded in ;;I and has established itself as the leading plat6
form for high6resolution three6dimensional printing 23D- b et also has
proven installations worldwide where 3D modeling can be created in o(ce
environment 3 Gsing its patented and market6proven -olyRet_ ink et6head
technology, it is able to print out the most comple$ 3D models with
e$ceptionally high quality -olyRet6based systems are used in hundreds of
manufacturing sites across the world and across a wide spectrum of industries& automotive, electronics, toy, consumer goods, medical
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footwear and more 't has been awarded more than 40 patents with addi6
tional patents %led or pending internationally b et 7eometries Ktd is
currently headquartered at / @ol"man St Science -ark - Bo$ /4;J,
:ehovot HJ /4, 'srael
-.'.'. Pro"ucts
b et=s current line of -olyRet6based systems, the .den_ family, is a group
of four machines that can deliver high6resolution prototypes within an
o(ce environment 4 !he .den_ family consists of the .den 00E_, .den
3 0_N3 0E_, .den /J0_ and .den / 0_, giving options to the users in
terms of build si"e, productivity and budget requirements )or economical
and eAective small models, both .den / 0_ and .den /J0_ are able to
%t in a small o(ce .den / 0_ features of two printing modes, high
quality 2@] and high speed 2@S , for user to choose from in order to
produce high quality prototype .den /J0_ consists of I units of single
head replacement 2S@: to et identical amounts of resin compared to
.den / 0_ resulting in better and more even surface %nish .den
3 0_N3 0E_ are the medium build professional machines in the .den
series which features printing modes 2@] and @S and higher material
capacity !he .den 00E_ 2see )ig 3 I is the largest build system with a
build volume of 4;0 \ 3;0 \ /00 mm 't has the best features including
dual printing modes, I units of S@: and an automatic function to switch
between cartridges Speci%cations of the .den_ family of machines are
summari"ed in !able 4 /
!he .den_ systems utili"e b et )ull8ure V materials and b et Studio_
software to provide a complete 3D- solution for any :- application b et
systems provide a range of diAerent materials for user to choose from,
depending on the required properties #ll .den_ systems are able to print
high accuracy ultra6thin J `m layers, producing models with
e$ceptionally %ne details and ultra6smooth surfaces !he .den_ family
works on the same principle where the etting head lays both the )ullcure
F 2model material and )ullcure S 2support material on the build tray #t
the same instance, the GE light integrated with the etting head cures the
already ust6laid )ull8ureV
materials, virtually laying and curing the modelin a single process
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Fi&. -.B. E" ! 066V TM ;court s) O8 t G o# tri s Lt"
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of the building process is the cross section of the parts arranged
in the software
3 23 5ith the completion of a cross6sectional layer, the build tray
will be lowered for the ne$t layer to be laid !he z 6height of the
elevator is leveled accurately so that the corresponding cross6
sectional data can be calculated for that layer
4 24 Both the part material and support material will be fully cured
when they are e$posed to the GE light and most importantly the
nonto$ic support material can be removed easily by the water et
4 / Strengths and 5eaknesses
!he .den !F system has the following strengths &
2 &igh quality !he -olyRet_ can build layers as thin as
J `m in thickness with accurate details depending on the
geometry, part orientation and print si"e
/ 2/ &igh accuracy! -recise etting and build material
properties enable %ne details and thin walls 2J00 `m or less
depending on the geometry and materials3 23 Fast process speed! 8ertain :- systems require
draining, resin stripping, polishing and others whereas .den_
systems only require an easy wash of the support material
which is a key strength
4 24 Smooth sur ace fnish !he models built have smooth
surface and %ne details without any post6processing
2 ide range o materials b et has a range of materials
suited for diAerent speci%cations, ranging from tough acrylic6
based polymer, to polypropylene6like plastics 2Duruswhite to
the rubber6like !ango materials
2J Easy usage !he .den_ family utili"es a cartridge
system for easy replacement of build and support materials
Faterial cartridges provide an easy method for insertion without
having any risk of contact with the materials
J 2H S&' technology !he .den_ machines= no""les consist
of heads and no""les 5ith Single @ead :eplacement 2S@:
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these individual no""les can be replaced instead of replacing the
whole unit whenever the need arises
2I Sa e and clean process! Gsers are not e$posed to the
liquid resin throughout the modeling process and the photo6
polymer support is nonto$ic .den !F systems can be installed in
the o(ce environment without increasing the noise level
!he .den !F system has the following weaknesses&
H 2 Post8processing # water et is required to wash away
the support material used in -olyRet_, meaning that water
supply must be nearby !his is somewhat a let6down to the claimthat the machine is suitable for an o(ce environment 'n cases
where the parts built are small, thin or delicate, the water et
can damage these parts, so care in post6processing must be
e$ercised
I 2/ astage !he support material which is washed away
with water cannot be reused, meaning additional costs are
added to the support material
-.'. . A$$licatio!s
!he applications of b et=s systems can be divided into diAerent areas&
2 General applications! Fodels created by b et=s
systems can be used for conceptual design presentation, design
proo%ng, engineering testing, integration and %tting, functional
analysis, e$hibitions and pre6production sales, market research
and inter6professional communication
/ 2/ #ooling and casting applications! -arts can also be
created for investment casting, direct tooling and rapid, tool6
free manufacturing of plastic parts #lso they can be used to
create silicon molding, aluminum epo$y moulds, EK! Folding
2alternative rubber mould and vacuum forming
3 23 >edical imaging Diagnostic, surgical, J operation and
reconstruction planning and custom prosthesis design -arts
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built by -olyRet !F have outstanding detail and %ne features which
can make the medical problems more visible for analysis and
surgery simulation Due to its fast building time, prototype
models are always built for trauma or tumors Fost importantly,
it reduces the surgical risks and provides a communication
bridge for the patients
4 24 e(elry industry! -resentation of concept design, actual
display, design proof and %tting -re6market survey and market
research can be conducted using these models
2 Pac ing! Eacuum forming is an easy method to
produce ine$pensive parts and it requires a very short time for
the part to be formed