VERIFICATION OF MECHANICAL PROPERTIES OF ABS MATERIALS USED IN FDM RAPID PROTOTYPING TECHNOLOGY

Proceedigs i Maufacturig Systems, Volume 8, Issue 2, 2013 ISSN 2067-9238 VERIFICATION OF MECHANICAL PROPERTIES OF ABS MATERIALS USED IN FDM RAPID PROTOTYPING TECHNOLOGY Ludmila NOVAKOVA-MARCINCINOVA 1,*, Jozef NOVAK-MARCINCIN 2 1) Eg., scietific worker, Faculty of Maufacturig Techologies, Techical Uiversity of Kosice, Presov, Slovakia 2) PhD, Prof., Faculty of Maufacturig Techologies, Techical Uiversity of Kosice, Presov, Slovakia Abstract: I this paper, iformatio about commo ad advaced materials used for maufacturig of products by Fused Depositio Modellig (FDM) rapid prototypig techology is preseted. I differet rapid prototypig techologies the iitial state of material ca come i either solid, liquid or powder state. The curret rage materials iclude paper, ylo, wax, resis, metals ad ceramics. I FDM as basic materials ABS - Acryloitrile Butadiee Styree, polyamide, polycarboate, polyethylee ad polypropylee are maily used. Mai part of the paper is focused o experimetal testig of rapid prototypig materials realized by differet research teams ad presets outputs of testig of ABS material i FDM techology realized by authors. Key words: fused depositio modelig, Acryloitrile Butadiee Styree, mechaical properties. 1. INTRODUCTION 1 Rapid Prototypig (RP) ca be defied as a group of techiques used to quickly fabricate a scale model of a part or assembly usig three-dimesioal computer aided desig (CAD) data. What is commoly cosidered to be the first RP techique, Stereolithography, was developed by 3D Systems of Valecia, CA, USA. The compay was fouded i 1986, ad sice the, a umber of differet RP techiques have become available. Rapid Prototypig has also bee referred to as solid free-form maufacturig, computer automated maufacturig, ad layered maufacturig. RP has obvious use as a vehicle for visualizatio. I additio, RP models ca be used for testig, such as whe a airfoil shape is put ito a wid tuel. RP models ca be used to create male models for toolig, such as silicoe rubber moulds ad ivestmet casts. I some cases, the RP part ca be the fial part, but typically the RP material is ot strog or accurate eough. Whe the RP material is suitable, highly covoluted shapes (icludig parts ested withi parts) ca be produced because of the ature of RP. There is a multitude of experimetal RP methodologies either i developmet or used by small groups of idividuals. Next sectios will focused o RP materials ad materials experimets i Fused Depositio Modellig (FDM) techology [1, 2]. traces the part's cross sectioal geometry layer by layer. The build material is usually supplied i filamet form, but some setups utilize plastic pellets fed from a hopper istead. The ozzle cotais resistive heaters that keep the plastic at a temperature just above its meltig poit so that it flows easily through the ozzle ad forms the layer. The plastic hardes immediately after flowig from the ozzle ad bods to the layer below. Oce a layer is built, the platform lowers, ad the extrusio ozzle deposits aother layer. The layer thickess ad vertical dimesioal accuracy is determied by the extruder die diameter, which rages from 0.013 to 0.005 iches. I the X Y plae, 0.001 ich resolutio is achievable. A rage of materials are available icludig ABS, polyamide, polycarboate, polyethylee, polypropylee, ad ivestmet castig wax [3, 4]. For better orietatio of user i process of settig of suitable parameters durig the preparatio of pritig there was algorithm elaborated which accumulates all 2. FUSED DEPOSITION MODELING METHOD Fused Depositio Modellig (FDM) was developed by Stratasys i Ede Prairie, Miesota. I this process, a plastic or wax material is extruded through a ozzle that * Correspodig author: Bayerova 1, 08001 Presov, Slovakia Tel.: 00421-51-7723012 Fax: 00421-51-7733453 E-mail addresses: ludmila.marciciova@tuke.sk (L. Novakova- Marciciova), jozef.marcici@tuke.sk (J. Novak-Marcici) Fig. 1. Fused Depositio Modellig techology.

88 L. Novakova-Marciciova ad J. Novak-Marcici / Proceedigs i Maufacturig Systems, Vol. 8, Iss. 2, 2013 / 87 92 separated without ay problems, as because of reducig temperature it is particularly fragile. However, for complex parts with cavities there is eed to use the washer to remove support material from places that are ot accessible for ay istrumet. The last step is gear assembly, which cosists of forty parts ad testig of prototype fuctioality. Durig the fuctioal testig, we used a electric motor with a speed regulator coected to the iput shaft. The test showed flawless shiftig ad fixig of rates i the desired positio [7]. Fig. 2. FDM device UPrit from Dimesio. factors ad steps that lead to selectio of most suitable variat. All the attempts were realized as a part of preparatio stage for pritig o UPrit machie that utilize FDM techology to build the prototype. This techology, developed by Stratasys, uses the software program to oriet the model ad geerate buildig slices. Priter dispeses with basic buildig material ad support material which is used if ecessary for creatio of holes, cavities, drafts, etc. Each material has its ow ozzle. Creatio of particular prototype layers with use FDM method is show i Fig. 1. O the Departmet of Maufacturig Techologies of the Faculty of Maufacturig Techologies of TU Košice with a seat i Prešov there is UPrit 3D FDM priter from Dimesio available (Fig. 2). It is a small 3D priter with 635 660 787 mm dimesios suitable for office eviromet which uses the pritig priciple of Fused Depositio Modelig. Maximum dimesios of prited prototype are 203 152 152 mm. This priter prits oly oe layer of costat thickess 0.254 mm which is as the accuracy of the prit i the Z axis very acceptable [5]. These priter used as buildig material thermoplastic ABCplus Ivory which comes i stadardized packages as fiber with a diameter of 1.6 mm rolled oto a reel. Each spool cotais 500 cubic cetimeters of material. The support material used is resi Soluble SR-P400 which comes i the same package as a buildig material. After pritig the prototype it is ecessary to clea the prototype of the auxiliary material. For this priter we use Catalyst program which serves to complete pritig settigs such as dispositio of compoets o workig desktop or set-savig modes where savigs ca be achieved by buildig ad supportig material to 40% depedig o the shape ad parts at the expese of stregth of the prototype. I a first step we geerated STL data i the CAD system that ca be loaded to the Catalyst program for layered rederig of the model. After startig of prit cycle the system warms up pritig jet ad whole work area for workig temperature. This lasts about 15 miutes, durig which the ozzle ad purifyig device are calibrated. Followed by the prit itself, the ozzle is movig over X Y pad ad workig i the Z axis. After pritig it is ecessary to separate the support material from the buildig oe. I the semi-simple compoets the support material ca be 3. ACRYLONITRILE BUTADIENE STYRENE Fused Depositio Modelig is oe of the typical RP processes that provide fuctioal prototypes of ABS plastic. FDM produces the highest-quality parts i Acryloitrile Butadiee Styree (ABS) which is a commo ed-use egieerig material that allows you to perform fuctioal tests o sample parts. FDM process is a filamet based system which feeds the material ito the heated extrusio head ad extrudig molte plastic that hardes layer-by-layer to form a solid part. FDM parts are tougher ad more durable tha those produced by SLA. ABS parts are sufficietly resistat to heat, chemicals, ad moisture that allows FDM parts to be used for limited to extesive fuctioal testig, depedig upo the applicatio. FDM materials allow you to maufacture real parts that are tough eough for prototypig, fuctioal testig, istallatio, ad most importatly for ed use. Real productio thermoplastics are stable ad have o appreciable warpage, shrikage, or moisture absorptio, like the resis (ad powders) i competitive processes. Because thermoplastics are evirometally stable, part accuracy (or tolerace) does ot chage with ambiet coditios or time. This eables FDM parts to be amog the most dimesioally accurate. Basic FDM materials [8, 9]: 1. ABS - A ABS prototype has up to 80% of the stregth of ijectio moulded ABS meaig that it is extremely suitable for fuctioal applicatios. 2. ABSi - ABSi is a ABS type with high impact stregth. The semi-traslucet material used to build the FDM parts is USP Class VI approved. 3. ABS-M30 - ABS-M30 is 25 75% stroger tha the stadard ABS material ad provides realistic fuctioal test results alog with smoother parts with fier feature details. 4. ABS-ESD7 ABS-ESD7 is a durable ad electrostatic dissipative material suited for Ed-use compoets, Electroic products, Idustrial equipmet ad Jigs ad fixtures for assembly of electroic compoets. 5. PC-ABS PC-ABS is a bled of polycarboate ad ABS plastic which combies the stregth of PC with the flexibility of ABS. 6. PC-ISO PC-ISO bleds are widely used throughout packagig ad medical device maufactures. The PC- ISO material used to build the FDM parts is USP Class VI approved ad also ISO 10993-1 rated. 7. ULTEM 9085 ULTEM 9085 is a pioeerig thermoplastic that is strog, lightweight ad flame retardat (UL 94-V0 rated). The ULTEM 9085 material

L. Novakova-Marciciova ad J. Novak-Marcici / Proceedigs i Maufacturig Systems, Vol. 8, Iss. 2, 2013 / 87 92 89 opes up ew opportuities for the direct additive costructio of productio grade compoets. 4. MECHANICAL PROPERTIES OF PLASTICS Plastics have the characteristics of both a viscous liquid ad a sprig-like elastomer, traits kow as a viscoelasticity. These characteristics are resposible for may of the characteristic material properties displayed by plastics. Uder mild loadig coditios, such as shortterm loadig with low deflectio ad small loads at room temperature, plastics usually react like sprigs, returig to their origial shape after the load is removed. Uder log-term heavy loads or elevated temperatures may plastics deform ad flow similar to high viscous liquids, although still solid. Creep is the deformatio that occurs over time whe a material is subjected to costat stress at costat temperature. This is the result of the viscoelastic behavior of plastics. Stress relaxatio is aother viscoelastic pheomeo. It is defied as a gradual decrease i stress at costat temperature. Recovery is the degree to which a plastic returs to its origial shape after a load is removed. Specific gravity is the ratio of the weight of ay volume to the weight of a equal volume of some other substace take as the stadard at a stated temperature. For plastics, the stadard is water. Water absorptio is the ratio of the weight of water absorbed by a material to the weight of the dry material. May plastics are hygroscopic, meaig that over time they absorb water. Tesile stregth at break is a measure of the stress required to deform a material prior to breakage. It is calculated by dividig the maximum load applied to the material before its breakig poit by the origial crosssectioal area of the test piece. Tesile modulus (modulus of elasticity) is the slope of the lie that represets the elastic portio of the stressstrai graph. Elogatio at break is the icrease i the legth of a tesio specime, usually expressed as a percetage of the origial legth of the specime. Compressive stregth is the maximum compressive stress a material is capable of sustaiig. For materials that do ot fail by a shatterig fracture, the value depeds o the maximum allowed distortio. Flexural stregth is the stregth of a material i bedig expressed as the tesile stress of the outermost fibers of a bet test sample at the istat of failure. Flexural modulus is the ratio, withi the elastic limit, of stress to the correspodig strai. Izod Impact is oe of the most commo ASTM tests for testig the impact stregth of plastic materials. It gives data to compare the relative ability of materials to resist brittle fracture as the service temperature decreases. For fidig hardess, Rockwell Number is the et icrease i depth of impressio as the load o a peetrator is icreased from a fixed miimum load to a high load ad the retured to a miimum load. Thermal coductivity is the ability of a material to coduct heat; a physical costat for the quatity of heat that passes through a uit cube of a material i a uit of time whe the differece i temperature of two faces is 1 C. Limitig oxyge idex is a measure of the miimum oxyge level required to support combustio of the polymer. Absorptio. Polymers have a potetial to absorb various corrodets the come to cotact with, particularly orgaic liquids. This ca result i swellig, crackig ad peetratio to the substrate of the compoet. From these mechaical properties of plastic materials is very importat tesile stregth at break ad will researched for ABS material used i Fused Depositio Modelig rapid prototypig techology. 5. TENSILE STRENGTH OF ABS MATERIAL Experimetal testig tesile stregth of ABS plastics must be realized accordig to iteratioal stadard EN ISO 527-1 Plastics - Determiatio of tesile properties - Part 1: Geeral Priciples ad iteratioal stadard EN ISO 527-2 Plastics - Determiatio of tesile properties; test coditios for mouldig ad extrusio plastics. The test methods are selectively suitable for use with the followig rage of materials: rigid ad semirigid thermoplastics mouldig, extrusio ad cast materials, icludig compouds filled ad reiforced by e.g. short fibres, small rods, plates or graules but excludig textile fibres (see ISO 527-4 ad ISO 527-5) i additio to ufilled types; rigid ad semirigid thermosettig mouldig ad cast materials, icludig filled ad reiforced compouds but excludig textile fibres as reiforcemet (see ISO 527-4 ad ISO 527-5); thermotropic liquid crystal polymers. The methods are ot suitable for use with materials reiforced by textile fibres (see ISO 527-4 ad ISO 527-5), with rigid cellular materials or sadwich structures cotaiig cellular material. The methods are applied usig specimes which may be either moulded to the chose dimesios or machied, cut or puched from ijectio- or compressiomoulded plates. The multipurpose test specime is preferred (see ISO 3167:1993 Plastics Multipurpose test specimes). 5.1. Test specimes Wherever possible, the test specimes shall be dumb-bell-shaped types 1A ad 1B as show i Fig. 3. Type 1A is preferred for directly-moulded multipurpose test specimes, type 1B for machied specimes. Types 1A ad 1B test specimes havig 4 mm thickess are idetical to the multipurpose test specimes accordig to ISO 3167, types A ad B, respectively. Test specimes shall be prepared i accordace with the relevat material specificatio. Whe oe exists, or uless otherwise specified, specimes shall be either directly compressio- or ijectio moulded from the material i accordace with ISO 293, ISO 294 or ISO 295, as appropriate, or machied i accordace with ISO 2818 from plates that have bee compressio- or ijectio-moulded from the compoud.

90 L. Novakova-Marciciova ad J. Novak-Marcici / Proceedigs i Maufacturig Systems, Vol. 8, Iss. 2, 2013 / 87 92 Fig. 3. Test specimes type 1A ad 1B. All surfaces of the test specimes shall be free from visible flaws, scratches or other imperfectios. From moulded specimes all flash, if preset, shall be removed, takig care ot to damage the moulded surface. Test specimes from fiished goods shall be take from flat areas or zoes havig miimum curvature. For reiforced plastics, test specimes should ot be machied to reduce their thickess uless absolutely ecessary. Test specimes with machied surfaces will ot give results comparable to specimes havig omachied surfaces. 5.2. Productio of test specimes by FDM method To prototype successfully, first select a appropriate rapid prototypig tool. There are hudreds of rapid prototypig tools available. They rage from simple graphics packages that allow you to draw screes to complex systems that allow you to create aimatio. Each tool is better for some fuctios tha for others. Although several rapid prototypig techiques exist, all employ the same basic five-step process. The steps are [6]: 1. Creatio of CAD models of the product parts. 2. Coversio of CAD models ito STL formats. 3. Use of STL files i Rapid Prototypig devices. 4. Productio of the parts by oe layer atop aother. 5. Cleaig of parts ad assembly of the product. Model of selected part was created ad subsequetly modified i CAD/CAM/CAE system Pro/ENGINEER. Trasfer of models betwee Pro/ENGINEER ad aother CA systems was implemeted usig the exchage format IGES where they were treated. O Fig. 4 is example of CAD model of parts i Pro/ENGINEER. O the start of Fig. 5. Layered model of specime i Catalyst software. the productio process are geerated STL data i the Pro/ENGINEER system ad these STL data are ext loaded to the Catalyst program for layered rederig of the model (Fig. 5). For RP methods there are specific productio devices (3D priters) that use their ow software based o priciple of readig ad processig of iput STL data. I spite of differet maufacturers, such programs have the same characteristic features: settigs for sigle layer resolutio, settigs for desity of model material, settigs for desity of support material, STL processig to layer mode. All these software solutios allow their user to chage large umber of differet settigs. Chages are made by user himself. Programs for preparatio of FDM productio make may actios easier ad more automatic, but decidig process about particular parameters is still up to user. I case of usig the automatic mode these decisios are made by program without explaatio, so there is space for optimizatio of settig cotrary to user criteria. Solutio could be realized i implemetatio of decidig steps or automatic decisio with actual iformatio about reasos ruig o backgroud, evetually together with iformatio about parts already produced. First step is to defie the surfaces ad costructioal poits that represet fuctioal features of part ad thus they should coditio requiremets o quality. Higher parameters of quality meas loger pritig times ad higher eergy cosumptio, but utilizatio possibility of such models is much higher as they ca be used istead of real fuctioal parts. Next step i 3D pritig preparatio process is to defie the locatio of the model o Fig. 4. CAD model of specime realized i Pro/ENGINEER. Fig. 6. Produced prototype of 3D specime by FDM method.

L. Novakova-Marciciova ad J. Novak-Marcici / Proceedigs i Maufacturig Systems, Vol. 8, Iss. 2, 2013 / 87 92 91 Fig. 7. Specimes prepared for realizatio of experimet. Fig. 9. Readigs for tesile testig of test specimes of ABS plastic. Fig. 10. Test specimes after realized experimet. Fig. 8. Test machie TIRA-test 2300. workig board of priter. O Fig. 6 is view of workplace of 3D FDM priter UPrit with prited part ad o Fig. 7 are specimes prepared for realizatio of tesile stregth experimets [8]. 5.3. Realizatio of ABS tesile stregth experimets Experimetal tests for defiitio of tesile stregth of ABS material was realized i Laboratory of mechaical ad techological experimets of Departmet of techologies ad materials of Techical Uiversity of Kosice with use of test machie TIRA-test 2300 (Fig. 8). Readigs for tesile testig of test specimes of ABS plastic are preseted by Fig. 9. 5.4. Statistical treatmet of test results Statistical iterpretatio of test results-estimatio of the mea ad cofidece iterval is defied by ISO 2602 stadard. The scope of this Iteratioal Stadard is limited to a special questio. It cocers oly the estimatio of the mea of a ormal populatio o the basis of a series of tests applied to a radom sample of idividuals draw from this populatio, ad deals oly with the case where the variace of the populatio is ukow. It is ot cocered with the calculatio of a iterval cotaiig, with a fixed probability, at least a give fractio of the populatio (statistical tolerace limits). It is recalled that ISO 2854 relates to the followig collectio of problems (icludig the problem treated i this Iteratioal Stadard): - estimatio of a mea ad of the differece betwee two meas (the variaces beig either kow or ukow); - compariso of a mea with a give value ad of two meas with oe aother (the variaces beig either kow or ukow, but equal); - estimatio of a variace ad the ratio of two variaces; - compariso of a variace with a give value ad of two variaces with oe aother. The statistical treatmet of the results allows the calculatio of a iterval which cotais, with a give probability, the mea of the populatio of results that would be obtaied from a very large umber of determiatios, carried out uder the same coditios. I the case of items with a variability, this Iteratioal Stadard assumes that the idividuals o which the determiatios are carried out costitute a radom sample from the origial populatio ad may be cosidered as idepedet. The iterval so calculated is called the cofidece iterval for the mea. Associated with it is a cofidece level (sometimes termed a cofidece coefficiet), which is the probability, usually expressed as a percetage, that

92 L. Novakova-Marciciova ad J. Novak-Marcici / Proceedigs i Maufacturig Systems, Vol. 8, Iss. 2, 2013 / 87 92 the iterval does cotai the mea of the populatio. Oly the 95 % ad 99 % levels are provided for i this Iteratioal Stadard. Estimatio of the mea of the measured values of ultimate tesile stregth σ M [MPa] test specimes of ABS plastic is implemeted through ugrouped results. Case results grouped ito classes are cosidered at a sufficietly high umber of measuremets, for example over 50. After the elimiatio of ay problem of measuremet data icludes the measured series = 10 measuremets x i (where i = 1, 2, 3,..., ), some of which have the same value. The mea m of the uderlyig ormal distributio is estimated by the arithmetic mea z of the results: geeratio of database that would process ad archive all output data after productio of part models. Relatios would be observed betwee chose parameters of basic ad support material, times of productio ad quality, all icludig ecoomical aspects. This supportive database system would together with software philosophy based o described steps for selectio of suitable parameters assure maximal ecoomy while keepig comfort ad effective way of selectio. ACKNOWLEDGEMENTS: Miistry of Educatio, Sciece, Research ad Sport of SR supported this work, cotract VEGA No. 1/0032/12, KEGA No. 002TUKE- 4/2012 ad ITMS project 26220220125. 1 1 σ ( 26 29 28 28 28 29 28 29 28 28) = σ Mi = + + + + + + + + +, i = 1 10 σ =28.1 Mpa. (1) Cofidece iterval for the average file is calculated from the estimated mea ad stadard deviatio. The estimate of the stadard deviatio σ is calculated set of squares of deviatios from the arithmetic mea by the formula (2): s 1 = 1 1 2 ( σ σ ) i i = 1 s 1 = 0.8756 Mpa. (2) Two-sided cofidece iterval for the average file is for a cofidece level of 95% determied by the followig two-sided iequality: t t 0.975 0.975 σ. s < m < σ +. s (3) 1 1 28.1 MPa 0.715. 0.8756 MPa < m < 28.1 MPa + 0,715. 0.8756 Mpa; 27.473946 MPa < m < 28.726054 Mpa. (4) The actual value of ultimate tesile stregth of test specimes of ABS plastic is σ M1 = (28.1 ± 0.626) MPa with a probability of 95%. 7. CONCLUSIONS This paper was focused o optimizatio of FDM samples preparatio processes. It described the steps that lead to selectio of suitable settigs. Output values obtaied from productio software are preseted. Assets for the future could lie i possibility of havig all the ecessary iformatio at oce ad thus to make the right decisio o proper settigs variat based o real facts. Realizatio of such iovatio ca be achieved through ; REFERENCES [1] C.K.Chua, K.F. Leog, C.S. Lim, Rapid Prototypig: Priciples ad Applicatios, World Scietific Publishig, Sigapore, 2003. [2] R.Noorai, Rapid Prototypig: Priciples ad Applicatios, Joh Wiley&Sos, New Jersey, 2005. [3] J. Novak-Marcici, J. Bara, L. Novakova-Marciciova, V. Fecova, Aalyses ad Solutios o Techical ad Ecoomical Aspects of Rapid Prototypig Techology, Tehicki Vjesik - Techical Gazette, Vol. 18, No. 4, 2011, pp. 657 661. [4] Novak-Marcici, J., Novakova-Marciciova, L., Bara J., Jaak, M.: Applicatio of FDM rapid prototypig techology i experimetal gearbox developmet process. Tehicki Vjesik, Vol. 19, No. 3, 2012, pp. 689 694. [5] J. Novak-Marcici, M. Jaak, L. Novakova- Marciciova, Icreasig of product quality produced by rapid prototypig techology, Maufacturig Techology, Vol. 12, No. 12, 2012, pp. 71 75. [6] L.N. Novakova-Marciciova, Advatages of rapid prototypig for iovatio of products, Proceedigs of the 1st iteratioal coferece Quality ad Iovatio i Egieerig ad Maagemet, Cluj-Napoca, 2011, pp. 333 336. [7] L.N. Novakova-Marciciova, V. Fecova, Special applicatios of rapid prototypig techologies, AEI 2011, Iteratioal coferece o applied electrical egieerig ad iformatics, Italy TU Košice, 2011, pp. 95 99. [8] L. Novakova-Marciciova, M. Jaak, Applicatio of progressive materials for RP techology, Maufacturig Techology, Vol. 12, No. 12, 2012, pp. 76 79. [9] FDM: Materials & datasheets (2012): http://www.materialise.com/fdm-materials.