research article digital microdroplet ejection technology ...downloads.hindawi.com › journals ›...

Research ArticleDigital Microdroplet Ejection Technology-Based HeterogeneousObjects Prototyping

Na Li Jiquan Yang Chunmei Feng Jianfei Yang Liya Zhu and Aiqing Guo

Jiangsu Key Laboratory of 3D Printing Equipment and Manufacturing Nanjing Normal University Nanjing 210042 China

Correspondence should be addressed to Jiquan Yang yjfsmilenjnueducn

Received 6 October 2015 Revised 10 January 2016 Accepted 12 January 2016

Academic Editor Yuankai Huo

Copyright copy 2016 Na Li et al This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

An integrate fabrication framework is presented to build heterogeneous objects (HEO) using digital microdroplets injectingtechnology and rapid prototyping The heterogeneous materials part design and manufacturing method in structure and materialwas used to change the traditional processThe net nodemethod was used for digital modeling that can configure multimaterials intimeThe relationship ofmaterial color and jetting nozzlewas builtThemain important contributions are to combine the structurematerial and visualization in one process and give the digital model for manufacture From the given model it is concluded thatthe method is effective for HEO Using microdroplet rapid prototyping and the model given in the paper HEO could be gottenbasically The model could be used in 3D biomanufacturing

1 Introduction

The structure of biological body is heterogeneous such asbone which is of different density It means the biologicalproducts should be made in heterogeneousness for func-tion realization Nonhomogeneous materials were used fordesign andmanufacture tomeet the functional requirementsand they contain a variety of materials [1] Heterogeneousobjects break the limit of traditional parts that containsingle material Design theory and manufacturing method oftraditional homogeneous objects cannot be applied directlyExploring the design theory and manufacturing method ofthe heterogeneous objects is the current study hot spotsTraditional methods and molding method are based onrapid prototyping (RP) Traditionalmanufacturingmethod isbased on the functionally graded materials mainly includingvapor deposition method plasma spraying method self-propagating high-temperature synthesis method powdermetallurgy laser cladding method and centrifugal castingmethod These traditional manufacturing methods for func-tionally graded parts have some disadvantages as in thefollowing sides it is not possible to manufacture three-dimensional structure precisely and the bond strengthbetween the gradient layer and the substrate is low which is

easy to crack and material distribution cannot be controledaccurately [2] Yakovleva et al study the laser direct formingmethod for three-dimensional objects with gradient material[3] Lappo et al developed multimaterial selective lasersintering (SLS) equipment which is based on the discretemolded used to make continuous multimaterial prototypes[4] Cho et al reported the molding equipment developedbased on the three-dimensional printing (3DP) processproposed by the MIT and the device uses multiple digitalprint nozzles injection molding material to create a three-dimensional model [5] Yang and Evans developed the SLSprocess based multimaterial powder spray equipment usedto produce three-dimensional functionally gradient materialcomponent [6] Bremnan et al developed multimaterial lay-ered manufacturing equipment that can be commercializedand used to process electric ceramic pieces [7] Choi andCheung research on multimaterial laminate manufacturingprocess based topology level path planning [8] Li et alhave a research on geometry and material informationdescription of CAD model for ideal material parts slicingthe algorithm of CAD model [9] They developed a moldingsystem prototype of the ideal material the system uses screwextrusion continuous jet and the nozzle squeeze the moltenABS silk to produce multifunctional material components

Hindawi Publishing CorporationInternational Journal of Biomedical ImagingVolume 2016 Article ID 5057347 7 pageshttpdxdoiorg10115520165057347

2 International Journal of Biomedical Imaging

Zhang et al studied multibranch multilayer structure andthe artificial bone bracket containing heterogeneous porousstructure with gradient function of the bioengineering orga-nization [10] Zhizhong et al study the forming process ofcomplex shapes silicon carbide ceramic components based onstereolithography technology manufacturing [11ndash15]

Some molding material was applied in these moldingmethods which is very limited and some lower moldingprecision and the molding efficiency are low and formedcertain limitations for controlling the multiphase material inthe space within heterogeneous objects precisely Althoughthis molding method or system is not yet mature or perfectit gave a basis for the rapid manufacturing of heterogeneousobjects

The RP-based manufacturing method for heterogeneousobjects due to the discrete-accumulation principle makessimultaneous molding in geometry and material distributionpossible and occupies an important position in terms offorming heterogeneous objects in recent years [12 16 17]Domestic and foreign research institutions and departmentsare committed to the RP molding of heterogeneous objectsand have achieved preliminary results [18 19] This paperpresents a digital microdroplet ejection technology of manu-facturing methods for heterogeneous objects and a designedprototyping system A good and effective heterogeneousmaterial injection shaping models were given for 3D digitalmanufacturing

The structure of this paper is as follows the instructionwas given in Section 1 The art of manufacturing was givenin Section 2 The CAD model of heterogeneous objects waspresent in Section 3 The CAD model data processing forheterogeneous objects was given in Section 4 The dropletsinjection molding of multiphase material parts was given inSection 5 And the conclusion was given in Section 6

2 Design and Manufacture Processes ofHeterogeneous Objects

Heterogeneous objects especially themanufacturing of func-tionally graded materials must be formed in a single man-ufacturing which is difficult for traditional manufacturingmethod to cope with due to the materials and structuresThecharacteristics of accurate injecting and accumulation pro-cess point-by-point of the 3D printing in rapid prototypingprovide a possible means of production for heterogeneousobjects and are capable of unifying the preparation of mate-rials and manufacturing of parts The system structure is inFigure 1

A molding method for heterogeneous objects combinesthe designingCADmodel [20] of themultimaterial 3Dprint-ing technology compositematerials preparation process anddesign and manufacturing process is shown in Figure 1 Thisprocess includes three parts CAD model of heterogeneousobjects designing the molding data processing and formingequipmentThe object was first described in point clouds andtransformed into STL file with the points which store the keyinformation of material and structure of object The slicingcodes were translated to print road of the forming equipment

Table 1 The material distribution definition for nodes

Nodes Node material values indicate1198751 (1 0 0 075 0 0 1 +infin 0 0 minus1 0 0 0 0)1198752 (075 025 0 067 minus133 0 minus1 2 0 0 minus1 0 0 0 0)1198753 (05 05 0 05 minus15 0 minus1 15 minus05 0 minus1 0 0 0 0)1198754 (025 075 0 0 minus2 0 minus1 133 minus067 0 minus1 0 0 0 0)1198755 (0 1 0 0 minusinfin 0 minus1 0 minus075 0 minus1 0 0 0 0)1198756 (05 05 0 05 minus15 1 minus067 15 minus05 1 minus067 0 0 0 minusinfin)1198757 (033 033 033 1 minus1 15 minus05 1 minus1 15 minus05 1 minus1 0 minus2)1198758 (016 016 067 1 minus1 2 0 1 minus1 2 0 1 minus1 05 minus15)1198759 (0 0 1 0 0 +infin 0 0 0 +infin 0 1 minus1 067 0)

The forming equipment is called three-dimensional printing(3DP) which is used for fabricating prototypes directly fromCAD models in a layer-by-layer manner There was a largevariety of 3DP processes introduced in the past decadeSuccessive layers of prototype are printed using digital modeluntil the whole prototype is fabricated

3 The CAD Model of Heterogeneous Objects

31 Design Process of Heterogeneous Objects CAD modelof heterogeneous objects includes structural model andmaterials model and materials model design is based onthe structure model and the design process is as shown inFigure 2

Firstly from CAD STL model of heterogeneous objectswhich aim for the contour surface geometry the vertexof each STL triangular facets could be gained that is thenode data Then subdivide the model node grid basedon the design requirements and functional requirementsof heterogeneous objects Before the process of assigningthe material for nodes material definition of the featurenodes should be decided and the subsequent interpolationoperation is carried out on thematerial interpolation betweenthe nodes

32 Node Material Assignment The functionally gradientmaterial planemodel is shown in Figure 3 for example whichis composed of three metallic materials Zn Al and Cu Theouter feature points 1198751 1198755 11987511 11987510 constitute the outlineframe and the device feature points 1198752 1198753 1198754 1198756 1198757 1198758and 1198759 constitute the subdivision feature nodes and could beappropriately subdivided as in Figure 3(a)

The definition of the feature nodes in the CAD model ofthe heterogeneous objects is according to (1) and Table 1 forthe feature node material assignment

119875119894 = (1199041 1199042 119904119897 1199091 11990910158401 1199101 119910

10158401 119909119895 119909

1015840119895 119910119895 119910

1015840119895)

119896

sum119897=1

119904119897 = 1 119904119897 isin [0 1]

119909119905 =119872119875119905+1 (119904119905 119909)119872119875119905 (119904119905 119909)

International Journal of Biomedical Imaging 3

middot middot middot

Monochrome STL

model

Color heterogeneous

objects model

Model

orientation

Heterogeneous objects prototype

Support

generation

Nozzle

control

system

Material

control

system

Detection

system

Energy

control

system

CAD

model

design

3D CAD models

Point clouds

Mesh refinement and

optimization

Forming

equipment

Molding

data

processing

Color conversion

Halftone conversion

Machinery

Model

slices

Process

parameter

settings

Processing

file

generationMachining

simulation

Material information

Geometric information

Topology information



Functional requirements

Design requirements

Figure 1 Molding process of HEO prototype system

1199091015840119905 =119872119875119905minus1 (119904119894 119909)119872119875119905 (119904119905 119909)

119910119905 =119872119875119905+1 (119904119905 119910)119872119875119905 (119904119905 119910)

1199101015840119905 =119872119875119905minus1 (119904119905 119910)119872119875119905 (119904119905 119910)

(1)

where 119896 is the total number of material species containedin the model 119904119897 represents the body components of the 119897thmaterial at 119875-node 119897 is the sum of body components of allmaterials119909119905 and1199091015840119905 are the distribution vectors of 119905thmaterialat the two opposite directions along the 119909-axis respectivelyindicating the changes trend of the material The value isthe ratio of the material body component between the nodeand next node along 119883 direction The greater the absolutevalue of the vector the more intense the material changearound this pointThe vector is equal to 1 andmeans the samebody component of the node and the next node 0 means the

Geometric

representation

of the outer

contour

Contour node

extract

Node mesh

subdivisionMaterial definition

for feature nodes

Node

material

interpolation

Material

interpolation

between nodes

Figure 2 CAD design process models for heterogeneous objects

contour pointsminus1means the samematerial body componentwith the prior node +infin means that the point does notcontain this material but the neighboring direction containsthe material 119910119905 and 1199101015840119905 are similar to 119909119894 and 1199091015840119894 definition

There are two special cases according to material defini-tion description above In one case the neighboring nodesdo not contain the material four material vectors of a node


control point

Material distribution

P1 P5

P11P10

P2 P3 P4

P6P

P7

P8

P9

Cu Al

Zn

x

y

x998400

y998400

(a) The definition for materials distributed control points (b) Material distribution renderings

Figure 3 Material distribution definition

Figure 4 Material definition mesh subdivision

are zero and the material body component is nonzero Inanother case it is called the material mutations area whenfour material vectors of the node are +infin which stands forthe material fracture area

33 Material Node Subdivision In order to improve theaccuracy of material distribution definition set further gridrefinement as shown in Figure 3(a) The refinement principleis based on the material distribution vector of the originalnodes that is the material changes the curvature and thegreater the change of the curvature the higher the subdivisionpoint density as shown in Figure 4

The definition of the nodes in Figure 4 was given as inTable 1 The density of nodes was related to the number ofmaterials types The node density was given as 119889119899 = 2119899 times 1198890where 1198890 is the density of a single material

34 The Material Interpolation Method between the NodesThe material distribution among the nodes gradually isdesigned according to the existing material value of the

above-mentioned nodes using the linear interpolation equa-tion (2)

119872119875119895(119909120572119894) = (1 minus 120572119894 (119909))119872119875119894(119909) + 120572119894 (119909)119872119875119894+1(119909)

119872119875119895(119910120572119894) = (1 minus 120572119894 (119910))119872119875119894(119910) + 120572119894 (119910)119872119875119894+1(119910)

120572119894 (119909) =119889 (119875119895 (119909) 119875119894+1 (119909))119889 (119875119894 (119909) 119875119894+1 (119909))

120572119894 (119910) =119889 (119875119895 (119910) 119875119894+1 (119910))119889 (119875119894 (119910) 119875119894+1 (119910))

0 le 120572119894 (119909) le 1 0 le 120572119894 (119910) le 1

(2)

where 119875119895 means the random interpolation points betweenpoints 119875119894 and 119875119894+1 119889(sdot sdot) denotes the Euclidean distancebetween any two points in space and 120572119894(119909) stands for thematerial linear interpolation rights of 119894thmaterial 119878119894 along the119883 direction between points119875119894(119909) and119875119894+1(119909) 120572119894(119910) stands forthematerial linear interpolation rights of 119894thmaterial 119878119894 alongthe 119884 direction between points 119875119894(119910) and 119875119894+1(119910)

The gradient distribution of three materials of is shownin Figure 3(b) based on the node assignment and nodeinterpolation method

4 The CAD Model Data Processing forHeterogeneous Objects

After the completion of the material assignment on eachnode STL model should be sliced into layers to get theseries slices Each slice is composed of a plurality of contoursand the material distribution of each contour vertex can beobtained by the linear interpolation Each grid is quadrilateralafter refining the mesh within each slice Material valuesof each grid node are gotten from interpolation operationaccording to (2) based on the vertex material values of theouter contour Subsequently the material distribution within


188

442

228

142

P

C 37

M 87

Y 45

K 28

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

(a) The material component (decimal) of an arbitrary point

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

C = 00100101

M = 01010111

Y = 00101101

K = 00011100

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

m1 = 00010011

m2 = 00101100

m3 = 00010111

m4 = 00001110

(b) Material component digitized (bina-ry)

h1

h2

h3

h4

(c) Nozzle operation timing diagram

Figure 5 The material component of arbitrary point correspondence relationship with nozzle actions

each grid can also be obtained one by one in order to get thematerial distribution at any point within each slice

The color layout of desktop publishing industry hassimilarities with the material distribution within two-dimensional geometric plane Two-dimensional cross sectionof multimaterial model can be seen as a color image toestablish the mappings between color space and materialsspace

According to the integration method of design andmanufacturing for the HEO any point 119875119911 can be representedby the expression (3) in the molding process

119875119911 (119896 119894 119895 119898119897) (3)

where 119875119911 is located in the 119896-layer in 119911 direction 119894 and 119895 arethe 119894th row and 119895th column pixels of geometric informationin CMY mode graphics of the slice layer and 119898119897 isin 119872is the material distribution matrix of the point (materialinformation)119872 matrix in (4) is determined by material information

of the point in the modeling process The example shownin Figure 5 is containing four kinds of material for hetero-geneous model The material components of any point 119875can be obtained through design process in the followingsequence firstly the aforementioned color-material mappingand secondly material assignment for nodes and finallymaterial interpolation between nodes Figure 5(a) gives thecolor component and material proportion occupied by eachcomponent of the point 119875 and each point within theheterogeneous entity shall be in accordance with (4) and thesum of the volume of the materials components is 1

4

sum119897=1

119898119897 = 1 (4)

To get precisely the material distribution of the model foreach point within the heterogeneous entity the moldingprocess should be precisely on material volume componentand be accurately controlled on thematerial molding For thedigitized droplet injection molding method the relationshipof nozzle and the material is one-to-one and in order tofacilitate the subsequent digital ejection for nozzles the mate-rial points are converted in proportion to the correspondingbinary value The body components of 1198981 1198982 1198983 and 1198984

materials were 188 442 228 and 142 as seen inFigure 5(b)

Drop-on-demand method is used for microdroplet ejec-tion system with multinozzle and the injection controlsystem is shown in Figure 5(b) It shows that material binaryvalue of each point is carried out by high-speed switchingoperation After one nozzle completes ejection the nextnozzle begins to eject other materials The correspondingoperation time sequence chart of the nozzles is shown inFigure 5(c) in order to accurately achieve thematerial stackedfor each point within every layer

Binary manner is used here for every material Whatshould be noted is that the injection time is an integermultiple of the minimum pulse period Therefore there willbe error caused by transforming problems inevitably theinjection system expands the material body fraction to 100times to reduce for the material forming deviation androunding method is used to round the number of injectionpulses of every material The injection pulse frequencies ofmaterials at the point 119875119911 were 1878 4416 2284 and 1421respectively in accordance with Figure 5(c)

5 The Droplets Injection Molding ofMultiphase Material Parts

Our group proposed and developed a new molding methodthat is the digital microdroplet ejection technology-basedheterogeneous objects directly manufactured based on theresearch results of multimaterial droplet injection moldingand rapid prototyping and the improvement of polymermaterials use experience The main idea of the method isto carry on the concurrent design of the geometry andtopology shape (monochrome STL surfacemodel data) basedon the color STL model and the material structure (colorinformation) is according to the functional requirementsof parts Slice the layer of color STL model containing thestructural and material information which obtains a seriesof colored slices in order to analyze the color informationand structural information of each processing unit Newmicrodroplet ejection technology and rapid prototypingtechnology are used in molding process The microdropletejection of the concentrated suspension contained materialparticles and UV photosensitive resin or low melting point


(a) Model definition (b) Material definition

(c) STL model for slice (d) Multimaterial model prototype

Figure 6 Heterogeneous objects model color prototypes

Table 2 The HEO model information

Dimensions (mm) 205012 times 143032 times 88049Volume (mm3) 235410123Triangles before Remesh 3550Triangles after Remesh 36248Layer thickness (mm) 01

alloy melt through a fine nozzle thereby obtaining the HEOprototypes

Figure 6 used the parallel design and manufacturingmethod of the heterogeneous objects to produce the irregularhemispherical bone possessing two materials (model data inTable 2) The common STL model only has rough geometricinformation without material information Figure 6(a) is themodel of the bone Figure 6(b) stands for the foundationfor material information description accurately Figure 6(c)is the aforementioned refined STLmodel which gavematerialinformation and its renderings Figure 6(d) is the prototypesprocessed by heterogeneous material molding system Themanufacture parameter was gotten as shown in Table 2Dimensions (mm) were the manufacturing area volume(mm3) is the amount of the material consumed triangles arethe sliced information and the layer thickness (mm) is themanufacture height in one layer

The modeling method for heterogeneous objects basedon the STL format and space microtetrahedron is proposedadopting STL common data formats in RP areas and themicrotetrahedral mesh refinement is uniformed based onpart features The heterogeneous object was decomposed

layer-by-layer giving material information to grid nodesAnd grid was constructed on the surface including internalstructure and material information The method realizedparallel design of structure and materials for heteroge-neous objects Such space microtetrahedral-based model-ing method of heterogeneous objects integrated the designprocess of structural design material design and modelvisualization which has the following advantages comparedwith other methods

(1) It is easy to dock with the existing CAD design soft-ware and RP molding equipment using STL commondata format and provided the data protection forCADand CAM integration of heterogeneous objects

(2) It gave the foundation for fine and fast visualizationof heterogeneous objects in CADmodels in followingthe process During the rendering process only thecolor of the STL facets located on the surface ofheterogeneous objects needs to be set simplifying thedisplayed processing problem within the microtetra-hedron It is efficient in color processing time

(3) It is a new way for point cloud in CAD data toreconstruct heterogeneous objects using the gridnodes definition

(4) Facilitate the storage of heterogeneous objects orderlyusing data in layer-by-layer formal and it is easy forhierarchical processing and molding of CAD model

The modeling method of heterogeneous objects is still in thestage of perfection Future research will focus on the fol-lowing aspects dynamic modeling of heterogeneous objects


finite element analysis of CAD models for heterogeneousobjects rapid prototyping methods and formation mecha-nism of heterogeneous objects

6 Conclusions

The above-mentioned research has important theoretical andpractical significance meanings in several aspects good forenhancing the integration of digital design and manufactureof heterogeneous objects useful for a further understandingand revealing a complex physical phenomenon and mecha-nism generated during the manufacturing process and goodto improve the molding quality and other aspects of theheterogeneous objects

This manufacture method integrated the designing andforming approach including structural design materialdesign and model visualization integration using digitaldroplet injection technology and rapid prototyping technol-ogy It can also combine the polymer materials low meltingpoint alloymaterials ceramic particles and other organic andinorganic substances This method provides a new model forfast and precise manufacture of heterogeneous objects

Conflict of Interests

The authors confirm that the paperrsquos content has no conflictof interests

Acknowledgments

Thisworkwas financially supported byNatural Science Foun-dation of China (nos 61273243 and 61304227) Open Fundof Hubei Key Laboratory of Intelligent Vision Based Mon-itoring for Hydroelectric Engineering Jiangsu Science andTechnology Key Project of Infrastructure (no BM2013006)and University Nature Science Foundation of Jiangsu (nos15KJB510018 13KJB460011 and 14KJB480004) The authorswould like to thank all the people who gave support andadvice to the team especially Dr Georges Fadel Clem-son University and his research team about modeling forheterogeneous objects and they would also like to thankMaterialise Belgium for their help in data processing

References

[1] N Hopkinson R Hague and P Dickens Rapid ManufacturingAn Industrial Revolution for the Digital Age JohnWiley amp SonsHoboken NJ USA 2006

[2] Y Jiquan and X Guocai Rapid Prototyping Technology Chem-ical Industry Press Beijing China 2006

[3] A Yakovleva E Trunovaa DGreveyaM Pilloz and I SmurovldquoLaser-assisted direct manufacturing of functionally graded 3Dobjectsrdquo Surface and Coatings Technology vol 190 no 1 pp 15ndash24 2005

[4] K Lappo B Jackson KWood et al ldquoDiscretemultiplematerialselective laser sintering (M2SLS) experimental study of partprocessingrdquo in Proceedings of the Solid Freeform FabricationSymposium pp 109ndash119 The University of Texas Austin TexUSA August 2003

[5] W Cho E M Sachs N M Patrikalakis and D E Troxel ldquoAdithering algorithm for local composition control with three-dimensional printingrdquo Computer Aided Design vol 35 no 9pp 851ndash867 2003

[6] S Yang and J R G Evans ldquoA multi-component powderdispensing system for three dimensional functional gradientsrdquoMaterials Science and Engineering A vol 379 no 1-2 pp 351ndash359 2004

[7] R E Bremnan S Turcu A Hall et al ldquoFabrication of electro-ceramic components by layered manufacturing (LM)rdquo Ferro-Electrics vol 293 no 1 pp 3ndash17 2003

[8] S H Choi and H H Cheung ldquoA topological hierarchy-based approach to toolpath planning for multi-material layeredmanufacturingrdquo Computer-Aided Design vol 38 no 2 pp 143ndash156 2006

[9] R Li Y Rui and G Dongming ldquoConcurrent design of geom-etry and material for no-homogeneous objectsrdquo MechanicalEngineering of China vol 19 no 4 pp 461ndash465 2008

[10] R Zhang Y Yan F Lin et al ldquoLow temperature rapid pro-totyping (LT-RP) and green manufacturingrdquo ManufacturingTechnology amp Machine Tool no 4 pp 71ndash75 2008

[11] C Zhizhong L Dichen and L Jishun ldquoResearch on a newtechnology of complex shape of the silicon carbide ceramicrdquoChinese Journal of Mechanical Engineering vol 19 no 2 pp236ndash238 2008

[12] H A K Toprakci S K Kalanadhabhatla R J Spontak andT K Ghosh ldquoPolymer nanocomposites containing carbonnanofibers as soft printable sensors exhibiting strain-reversiblepiezoresistivityrdquo Advanced Functional Materials vol 23 no 44pp 5536ndash5542 2013

[13] J Lan Design and Fabrication of a Modular Multi-Material3D Printer Massachusetts Institute of Technology CambridgeMass USA 2013

[14] L Na Y Jiquan C Jihong and Q Weixing ldquoDigital printing ofthe thin film sensor with sharp edge based on electrodynamics3DPrdquoThe Open Electrical amp Electronic Engineering Journal vol8 no 1 pp 573ndash579 2014

[15] R Chumnanklang T Panyathanmaporn K Sitthiseripratipand J Suwanprateeb ldquo3D printing of hydroxyapatite effect ofbinder concentration in pre-coated particle on part strengthrdquoMaterials Science and Engineering C vol 27 no 4 pp 914ndash9212007

[16] Z Fan J C Ho T Takahashi et al ldquoToward the development ofprintable Nanowire electronics and sensorsrdquo Advanced Materi-als vol 21 no 37 pp 3730ndash3743 2009

[17] J-S Lee S-Y Kim Y-J Kim et al ldquoDesign and evaluationof a silicon based multi-nozzle for addressable jetting usinga controlled flow rate in electrohydrodynamic jet printingrdquoApplied Physics Letters vol 93 Article ID 243114 2008

[18] S Logothetidis ldquoFlexible organic electronic devices materialsprocess and applicationsrdquoMaterials Science and Engineering BSolid-State Materials for Advanced Technology vol 152 no 1ndash3pp 96ndash104 2008

[19] A A Goghari and S Chandra ldquoProducing droplets smallerthan the nozzle diameter by using a pneumatic drop-on-demand droplet generatorrdquo Experiments in Fluids vol 44 no1 pp 105ndash114 2008

[20] Y D Zhang S H Wang G L Ji and Z Dong ldquoExponentialwavelet iterative shrinkage thresholding algorithm with ran-dom shift for compressed sensing magnetic resonance imag-ingrdquo IEEJ Transactions on Electrical and Electronic Engineeringvol 10 no 1 pp 116ndash117 2015

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Zhang et al studied multibranch multilayer structure andthe artificial bone bracket containing heterogeneous porousstructure with gradient function of the bioengineering orga-nization [10] Zhizhong et al study the forming process ofcomplex shapes silicon carbide ceramic components based onstereolithography technology manufacturing [11ndash15]

Some molding material was applied in these moldingmethods which is very limited and some lower moldingprecision and the molding efficiency are low and formedcertain limitations for controlling the multiphase material inthe space within heterogeneous objects precisely Althoughthis molding method or system is not yet mature or perfectit gave a basis for the rapid manufacturing of heterogeneousobjects

The RP-based manufacturing method for heterogeneousobjects due to the discrete-accumulation principle makessimultaneous molding in geometry and material distributionpossible and occupies an important position in terms offorming heterogeneous objects in recent years [12 16 17]Domestic and foreign research institutions and departmentsare committed to the RP molding of heterogeneous objectsand have achieved preliminary results [18 19] This paperpresents a digital microdroplet ejection technology of manu-facturing methods for heterogeneous objects and a designedprototyping system A good and effective heterogeneousmaterial injection shaping models were given for 3D digitalmanufacturing

The structure of this paper is as follows the instructionwas given in Section 1 The art of manufacturing was givenin Section 2 The CAD model of heterogeneous objects waspresent in Section 3 The CAD model data processing forheterogeneous objects was given in Section 4 The dropletsinjection molding of multiphase material parts was given inSection 5 And the conclusion was given in Section 6

2 Design and Manufacture Processes ofHeterogeneous Objects

Heterogeneous objects especially themanufacturing of func-tionally graded materials must be formed in a single man-ufacturing which is difficult for traditional manufacturingmethod to cope with due to the materials and structuresThecharacteristics of accurate injecting and accumulation pro-cess point-by-point of the 3D printing in rapid prototypingprovide a possible means of production for heterogeneousobjects and are capable of unifying the preparation of mate-rials and manufacturing of parts The system structure is inFigure 1

A molding method for heterogeneous objects combinesthe designingCADmodel [20] of themultimaterial 3Dprint-ing technology compositematerials preparation process anddesign and manufacturing process is shown in Figure 1 Thisprocess includes three parts CAD model of heterogeneousobjects designing the molding data processing and formingequipmentThe object was first described in point clouds andtransformed into STL file with the points which store the keyinformation of material and structure of object The slicingcodes were translated to print road of the forming equipment

Table 1 The material distribution definition for nodes

Nodes Node material values indicate1198751 (1 0 0 075 0 0 1 +infin 0 0 minus1 0 0 0 0)1198752 (075 025 0 067 minus133 0 minus1 2 0 0 minus1 0 0 0 0)1198753 (05 05 0 05 minus15 0 minus1 15 minus05 0 minus1 0 0 0 0)1198754 (025 075 0 0 minus2 0 minus1 133 minus067 0 minus1 0 0 0 0)1198755 (0 1 0 0 minusinfin 0 minus1 0 minus075 0 minus1 0 0 0 0)1198756 (05 05 0 05 minus15 1 minus067 15 minus05 1 minus067 0 0 0 minusinfin)1198757 (033 033 033 1 minus1 15 minus05 1 minus1 15 minus05 1 minus1 0 minus2)1198758 (016 016 067 1 minus1 2 0 1 minus1 2 0 1 minus1 05 minus15)1198759 (0 0 1 0 0 +infin 0 0 0 +infin 0 1 minus1 067 0)

The forming equipment is called three-dimensional printing(3DP) which is used for fabricating prototypes directly fromCAD models in a layer-by-layer manner There was a largevariety of 3DP processes introduced in the past decadeSuccessive layers of prototype are printed using digital modeluntil the whole prototype is fabricated

3 The CAD Model of Heterogeneous Objects

31 Design Process of Heterogeneous Objects CAD modelof heterogeneous objects includes structural model andmaterials model and materials model design is based onthe structure model and the design process is as shown inFigure 2

Firstly from CAD STL model of heterogeneous objectswhich aim for the contour surface geometry the vertexof each STL triangular facets could be gained that is thenode data Then subdivide the model node grid basedon the design requirements and functional requirementsof heterogeneous objects Before the process of assigningthe material for nodes material definition of the featurenodes should be decided and the subsequent interpolationoperation is carried out on thematerial interpolation betweenthe nodes

32 Node Material Assignment The functionally gradientmaterial planemodel is shown in Figure 3 for example whichis composed of three metallic materials Zn Al and Cu Theouter feature points 1198751 1198755 11987511 11987510 constitute the outlineframe and the device feature points 1198752 1198753 1198754 1198756 1198757 1198758and 1198759 constitute the subdivision feature nodes and could beappropriately subdivided as in Figure 3(a)

The definition of the feature nodes in the CAD model ofthe heterogeneous objects is according to (1) and Table 1 forthe feature node material assignment

119875119894 = (1199041 1199042 119904119897 1199091 11990910158401 1199101 119910

10158401 119909119895 119909

1015840119895 119910119895 119910

1015840119895)

119896

sum119897=1

119904119897 = 1 119904119897 isin [0 1]

119909119905 =119872119875119905+1 (119904119905 119909)119872119875119905 (119904119905 119909)



Monochrome STL

model

Color heterogeneous

objects model

Model

orientation


Support

generation

Nozzle

control

system

Material

control

system

Detection

system

Energy

control

system

CAD

model

design

3D CAD models

Point clouds

Mesh refinement and

optimization

Forming

equipment

Molding

data

processing

Color conversion

Halftone conversion

Machinery

Model

slices

Process

parameter

settings

Processing

file

generationMachining

simulation







Design requirements


1199091015840119905 =119872119875119905minus1 (119904119894 119909)119872119875119905 (119904119905 119909)

119910119905 =119872119875119905+1 (119904119905 119910)119872119875119905 (119904119905 119910)

1199101015840119905 =119872119875119905minus1 (119904119905 119910)119872119875119905 (119904119905 119910)

(1)


Geometric

representation

of the outer

contour

Contour node

extract

Node mesh


for feature nodes

Node

material

interpolation

Material

interpolation

between nodes





control point


P1 P5

P11P10

P2 P3 P4

P6P

P7

P8

P9

Cu Al

Zn

x

y

x998400

y998400









119872119875119895(119909120572119894) = (1 minus 120572119894 (119909))119872119875119894(119909) + 120572119894 (119909)119872119875119894+1(119909)

119872119875119895(119910120572119894) = (1 minus 120572119894 (119910))119872119875119894(119910) + 120572119894 (119910)119872119875119894+1(119910)

120572119894 (119909) =119889 (119875119895 (119909) 119875119894+1 (119909))119889 (119875119894 (119909) 119875119894+1 (119909))

120572119894 (119910) =119889 (119875119895 (119910) 119875119894+1 (119910))119889 (119875119894 (119910) 119875119894+1 (119910))

0 le 120572119894 (119909) le 1 0 le 120572119894 (119910) le 1

(2)






188

442

228

142

P

C 37

M 87

Y 45

K 28

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩


⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

C = 00100101

M = 01010111

Y = 00101101

K = 00011100

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

m1 = 00010011

m2 = 00101100

m3 = 00010111

m4 = 00001110


h1

h2

h3

h4






119875119911 (119896 119894 119895 119898119897) (3)



4

sum119897=1

119898119897 = 1 (4)
























6 Conclusions





Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Monochrome STL

model

Color heterogeneous

objects model

Model

orientation


Support

generation

Nozzle

control

system

Material

control

system

Detection

system

Energy

control

system

CAD

model

design

3D CAD models

Point clouds

Mesh refinement and

optimization

Forming

equipment

Molding

data

processing

Color conversion

Halftone conversion

Machinery

Model

slices

Process

parameter

settings

Processing

file

generationMachining

simulation







Design requirements


1199091015840119905 =119872119875119905minus1 (119904119894 119909)119872119875119905 (119904119905 119909)

119910119905 =119872119875119905+1 (119904119905 119910)119872119875119905 (119904119905 119910)

1199101015840119905 =119872119875119905minus1 (119904119905 119910)119872119875119905 (119904119905 119910)

(1)


Geometric

representation

of the outer

contour

Contour node

extract

Node mesh


for feature nodes

Node

material

interpolation

Material

interpolation

between nodes





control point


P1 P5

P11P10

P2 P3 P4

P6P

P7

P8

P9

Cu Al

Zn

x

y

x998400

y998400









119872119875119895(119909120572119894) = (1 minus 120572119894 (119909))119872119875119894(119909) + 120572119894 (119909)119872119875119894+1(119909)

119872119875119895(119910120572119894) = (1 minus 120572119894 (119910))119872119875119894(119910) + 120572119894 (119910)119872119875119894+1(119910)

120572119894 (119909) =119889 (119875119895 (119909) 119875119894+1 (119909))119889 (119875119894 (119909) 119875119894+1 (119909))

120572119894 (119910) =119889 (119875119895 (119910) 119875119894+1 (119910))119889 (119875119894 (119910) 119875119894+1 (119910))

0 le 120572119894 (119909) le 1 0 le 120572119894 (119910) le 1

(2)






188

442

228

142

P

C 37

M 87

Y 45

K 28

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩


⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

C = 00100101

M = 01010111

Y = 00101101

K = 00011100

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

m1 = 00010011

m2 = 00101100

m3 = 00010111

m4 = 00001110


h1

h2

h3

h4






119875119911 (119896 119894 119895 119898119897) (3)



4

sum119897=1

119898119897 = 1 (4)
























6 Conclusions





Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










control point


P1 P5

P11P10

P2 P3 P4

P6P

P7

P8

P9

Cu Al

Zn

x

y

x998400

y998400









119872119875119895(119909120572119894) = (1 minus 120572119894 (119909))119872119875119894(119909) + 120572119894 (119909)119872119875119894+1(119909)

119872119875119895(119910120572119894) = (1 minus 120572119894 (119910))119872119875119894(119910) + 120572119894 (119910)119872119875119894+1(119910)

120572119894 (119909) =119889 (119875119895 (119909) 119875119894+1 (119909))119889 (119875119894 (119909) 119875119894+1 (119909))

120572119894 (119910) =119889 (119875119895 (119910) 119875119894+1 (119910))119889 (119875119894 (119910) 119875119894+1 (119910))

0 le 120572119894 (119909) le 1 0 le 120572119894 (119910) le 1

(2)






188

442

228

142

P

C 37

M 87

Y 45

K 28

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩


⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

C = 00100101

M = 01010111

Y = 00101101

K = 00011100

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

m1 = 00010011

m2 = 00101100

m3 = 00010111

m4 = 00001110


h1

h2

h3

h4






119875119911 (119896 119894 119895 119898119897) (3)



4

sum119897=1

119898119897 = 1 (4)
























6 Conclusions





Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










188

442

228

142

P

C 37

M 87

Y 45

K 28

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩


⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

C = 00100101

M = 01010111

Y = 00101101

K = 00011100

⎧⎪⎪

⎪⎪⎪

⎪⎨

⎩

m1 = 00010011

m2 = 00101100

m3 = 00010111

m4 = 00001110


h1

h2

h3

h4






119875119911 (119896 119894 119895 119898119897) (3)



4

sum119897=1

119898119897 = 1 (4)
























6 Conclusions





Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation


























6 Conclusions





Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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