Experimental Investigation of Pattern-less Casting ... - MIT Publications

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 17Experimental Investigation of Pattern-less CastingSolution Using Additive Manufacturing TechniqueMunish ChhabraAssociate Professor, Mechanical EngineeringMIT, MoradabadDr. Rupinder SinghAssociate Professor, Mechanical EngineeringG.N.D.E.C, LudhianaAbstract- The developments in additive manufacturing(AM) have opened up new avenues for fabrication offunctional prototypes to the fabrication of tools and mouldsfor direct metal castings. Many AM techniques arecommercially available to fabricate prototypes and castingtooling directly from a computer model. Three dimensionalprinting (3DP) is one such technology which buildsprototypes, parts for end-use and for use as tooling,patterns and moulds for metal castings relatively fast and ata low cost. Rapid casting (RC) is one of the most importantapplications of 3DP, due to its ability to generate patterns,other casting tooling and direct production of pattern lessmoulds that can be used for to cast non-ferrous metals. Thispaper describes briefly the concept of additivemanufacturing, three dimensional printing and the ZCastRC solution. In addition, feasibility of ZCast RC solutionusing 3DP technique to generate Al casting has also beeninvestigated by reducing the shell wall thickness from therecommended one, 12(mm). The feasibility of RC solutionhas been assessed in terms of dimensional accuracy andsurface roughness of the castings. The castings generatedwith this process showed good process stability in thecasting of Al with the shell mould thickness from 12(mm)down to 2(mm).Keywords: Additive manufacturing, Three dimensionalprinting, Casting, IT grades.List of Abbreviations3DP Three Dimensional PrintingAl AluminiumAM Additive ManufacturingCAD Computer Aided DesignCMM Coordinate Measuring MachineIT International ToleranceRa Roughness averageRC Rapid CastingRP Rapid PrototypingRT Rapid ToolingSTL Standard Triangulation LanguageZCorp ZCorporationI. INTRODUCTIONTo reduce the product development time and reducethe cost of manufacturing, the new technology of additivemanufacturing (AM) has been developed, which offersthe potential to completely revolutionize the process ofmanufacturing [1]. In the early development of additivemanufacturing (AM) technologies, the emphasis wasdirected towards the creation of “touch-and-feel” modelsto support design [2]. Originally seen as most suitable forAM, these processes are no longer used for that purposeany longer [3]. With the advent of new materials alongwith new processes, each technology has been applied indiverse fields [4]. In particular, additive constructionapplied to the production of dies and electrodes, directlyfrom digital data, is defined as rapid tooling (RT).The RT goal is to produce complex parts quickly ofthe required accuracy and quality, so it can be used inconcurrent engineering [5]. RT is the use of AMgeneratedobjects (with or without special postprocessing)as an experimental or even regular tooling inindustrial manufacturing, particularly in metal casting[1]. The purpose of RT is not the manufacture of finalparts, but the preparation of the means to manufacturefinal parts: mass production tools such as molds, dies etc.can be ready in very short times [6]. A variety of toolingcan currently be produced using different RPtechnologies. For the purpose of classification, toolingis divided into direct or indirect tooling [7]. Pattern,cores and cavities can be obtained through rapid casting(RC) techniques [1, 8]. Many RC solutions have beendeveloped and commercialized.Great efforts have been made to develop new RCand RT technologies that combine the recently emergedAM processes with one or more subsequent processes[5]. In both cases, since the tooling phase is highly timeconsuming,great competitive advantages can beachieved. Moreover, RT and RC processes allow thesimultaneous development and validation of the productand of the manufacturing process. Technologicalprototypes can constitute a strategic means, not only forfunctional and assembly tests or to obtain the customer’sacceptance, but mainly to outline eventual critical pointsin the production process. The relevance of RCtechniques consists, above all, in a short time for partsavailability.Traditionally, in order to produce prototype a modeland eventual core have to be created, involving time andcosts that hardly match the rules of the competitivemarket. For this reason, functional tests are typicallyperformed on prototypes obtained by metal cutting,which are not effective in outlining issues related to themanufacturing process. The possibility to verify theusefulness of a technological solution, in the early stages

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 18of the product development, ensures a ‘concurrentengineering’ approach and minimize the risk of latemodifications of the definitive production tools. Theinitial increase in costs can thus be repaid through areduction of costs and time for the following phases ofdevelopment, engineering and production, as well asthrough non-monetary advantages [8]. In particular, forrelatively small and complex parts, the benefits ofadditive construction can be significant [9]. In addition,models built with the help of AM processes are used astools for casting and molding i.e. dies for an injectionmolding process and pattern for a casting process.In recent years three dimensional printing (3DP)came to the foreground as a very competitive process interms of cost and speed [10 ].The process of 3DP waspatented in 1994 under U.S. patent number 005340656[11]. It was developed at Massachusetts Institute ofTechnology (MIT) based on inkjet technology [12] andlicensed to Soligen Corporation, Extrude Hone and Z-Corporation of Burlington. It is classified as a typical“concept modeller”, a low-end system, and represents thefastest RP process [13].The 3DP prototypes may be used directly to producemoulds for casting or used as a pattern to produce mouldindirectly. In this field, innovative solutions are nowavailable based on 3DP process, which can extend RCpossibilities thanks to the lower costs with respect toprevious technologies such as selective laser sintering ofsand [14]. One such technological solution is componentprinted in starch- based powder produced on 3DP processand infiltrate with surgical wax are extensively used aspattern for investment casting [3].A second solution is the ZCast TM process, in which3D-printing technology with the use of a ceramicmaterial allows the production of complex cavities andcores, suitable for casting light alloys. Further, threecasting methods make up the ZCast TM process: directpour, the shell method, and production intent casting[15].Both the 3DP based RC solutions proved to beeffective for the production of cast technologicalprototypes, in very short time, avoiding any tooling phaseand with dimensional tolerances that are completelyconsistent with metal casting processes. Regardless of thecasting method, the foundry industry has as its centralprocess the utilization of a physical pattern to producemoulds into which to cast metal. Although, this is true forboth the design and production cycles, it is mainly thedesign stage that will benefit from rapid patterns.The use of AM technologies in the creation ofcasting patterns allows a foundry to manufacture a metalpart without the use of tooling for small quantities. It alsohelps in optimizing the casting design in terms of processand gating parameters. All of this reduces the cost andtime required to produce prototype parts [1].A key issue regarding the shell casting process is theproduction of the pattern in the case of a prototypecasting, for which the traditional die casting isuneconomical. AM techniques can meet this requirement,producing few parts in short times and without toolingcosts [16-18]. The ZCast process using 3DP techniquerepresents an innovative low-cost solution among RCtechnologies. Cast metal parts can be obtainedsignificantly faster and are less expensive than othermethods [19].The present work is an attempt to introduce the basicconcept of AM, 3DP technique and RC solution(ZCast501) and also to investigate the feasibility of theRC solution based on 3DP technique to produce nonferrous casting. Experimental studies regarding thissolution are lacking in literature, in particular thetechnological feasibility in the case of thin-walled partsneeds to be assessed.Fig.1. Additive Manufacturing (AM) concept

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 19A. AM ConceptAM is a fabrication method whereby physical objectsare constructed by depositing material layer by layerunder computer control. AM takes virtual designs (fromCAD or from animation modelling software), transformsthem into cross sections, still virtual, and then createseach cross section in physical space, one after the nextuntil the model is finished. Fig.1 shows the concept ofAM.B. The Basic Steps of Additive ManufacturingAlthough several AM techniques exist, all employ thesame basic five-steps [6]. These steps are:1. Design: Create a 3D CAD solid model of the design2. Converting: Convert the CAD model to StandardTriangulation Language (STL) format3. Pre-Process: Slice the STL file into thin crosssectionallayers (Generated by a dedicated Software)4. Building process: Construct the model one layer atopanother5. Post-Process: Clean and finish the modelA large number of AM techniques have been usedcommercially in metal casting industries such as: Stereolithography (SLA); Selective Laser Sintering (SLS);Laminated Object Manufacturing (LOM); FusedDeposition Modeling (FDM); Solid Imaging (SI) orMulti-jet Modeling and 3D printing (3DP) [20]. In thepresent research, in order to investigate the feasibility of3DP technique to produce non ferrous casting(Aluminium), the direct metal RC solution ZCast501wasused. A brief description of 3DP technique is presentedin section C.C. Three Dimensional Printing (3DP) TechniqueAs shown in Fig.2 (a) parts are built upon a platformsituated in a bin full of powder material. Powderedmaterial is distributed in form of a layer at a time andselectively hardened and joined together by depositingdrops of binder from a mechanism similar to that used forink-jet printing. Then a piston lowers the part so that thenext layer of powder can be applied. For each layer,powder hopper and roller systems distribute a thin layerof powder over the top of the work tray. Adaptedcontinuous-jet printing nozzles apply binder during araster scan of the work area, selectively hardening thepart's cross-section. The loose powder that wasn'thardened remains and acts as a support for subsequentlayers. The process is repeated to complete the part.When finished, the green part is then removed from theunbound powder, and excess unbound powder is blownoff. Finished parts can be infiltrated with wax, CA glue,or other sealants to improve durability and surface finish.Fig.2 (b) shows the complete 3DP process cycle.D. Materials for 3DPThe 3DP process is quite flexible in choice of materials.Any combination of a powdered material with a binderthat has low enough viscosity to form droplets couldpotentially be used [21]. In addition to ceramics, plastic,metal, and metal- ceramic composite parts can be made.A potential disadvantage is that the parts will always beporous because of density limitations on the distributionof dry powder. For metal-ceramic composites, the porousceramic shape is produced using 3DP and subsequentlypressure infiltrated with molten metal to form thecomposite. The main focus with ceramics, however, hasbeen on ceramic shells and cores that are used for castingmetal. Three basic material systems have been developedfor use with the 3D printers.(i) Plaster Based Material: A powder/binder systemcomprises an oxidant and a reductant (a redox couple).When the binder is applied to the powder, the oxidantand reductant react to generate an acid that catalyzescross linking. As a result, the strength of the 3D articlebuilds up. The oxidant may be in the powder, and thereductant in the binder; or the reductant may be in thepowder, and the oxidant in the binder. Plaster basedmaterials are ideal for- High strength requirements- Delicate or thin- walled parts- Accurate representation of design details- Color printing(ii) Composite Based Material: These materials are idealfor- Thin- walled enclosures- Assembly applications(iii) Starch Based Material: In this system starch-basedpolymer powders (cornstarch, dextran and gelatin etc.)are used for the 3DP process. Starch based materials areideal for- High speed printing- Large bulky parts- Patterns for investment castingE. ZCast 501 Direct Metal CastingZCast501 Direct Metal Casting is an RC solutiondeveloped by ZCorp for direct metal casting of nonferrous alloys. ZCast process creates the shell moldsdirectly from CAD data by using 3DP technology.Conventionally, metal castings are produced by usingsand casting tooling, techniques and procedures. Withrespect to traditional sand casting, limited by the patternextractability, layer by layer construction allowsobtaining complex part, without any restrictions in termsof undercuts provided only that the unconsolidatedpowder can be removed from the cavity [16]. Iteliminates the pattern creation phase of the traditionalsand casting process in a revolutionary way, resulting ina drastic reduction of the casting lead time from weeks to

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 20days [22]. ZCast provides three basic methods tofabricate moulds to produce casting rapidly [23].Reference [15] reported that the accuracy and surfacefinish are consistent with sand casting by using ZCastprocess.Feed RollerBinderCartridgeBinderComponentF. Major Features of ZCast:• ZCast501 mold is recommended for non ferrous metalswith pouring temperature below 1100 o C• The recommended shell mold wall thickness range isminimum12.5mm and maximum 25.4mm [24].• Before pouring, ZCast moulds must be baked in anoven from 180 o C to 230 o C for between 4 and 8 hours(based on volume), until it is “bone” dry.• Customers cast metal into these 3D printed molds forprototype evaluation or fully functional parts.Feed Material(Powder)PistonBuild ChamberFig.2(a) 3DP process [18]STARTLAYER OF POWDERDEPOSITED AUTOMATICALLYPRINT HEAD APPLIESRESIN TO POEDER LAYERPOWDER LAYER DRIESALMOST IMMEDIATELYADD ANOTHER LAYER?NOREMOVE COMPLETEDMODELFINISHFig. 2(b) Complete 3DP process cycleExcess MaterialChuteYESG. ZCast Methods(TM)• Direct Metal Casting (ZCast): The ZCast DirectMetal Casting consists of materials and processes thatallow designers and engineers to build moulds (copesand drags) and/or cores directly from a CAD file. Iteliminates the pattern creation phase of the traditionalsand casting process in a revolutionary way, resulting ina drastic reduction of the casting lead time from weeks todays. The process involves the design of basic partinglines and coring. A 3D mould shell approximately25(mm) thick is printed using ZCast plaster-ceramiccomposite material. If necessary, the shell is created withribbing and backfilled with traditional foundry sand togive added strength while minimizing material cost.• Loose Pattern Method (LP): The Loose Pattern (LP)method is a familiar and well-established technique inthe casting industry. The steps of this process are shownin Figure 1b. According to conventional techniques, thepatterns are usually made of wood or plastic.Implementing modern technologies, these patterns canbe produced using 3D Printing. Printed parts, havingbeen infiltrated, are aligned on a joint board. Around thepattern, a dividing surface (split line) has to be createdmanually by using resin mixed foundry sand or similarmaterials. The pattern stays loosely seated so that theprocess of creating the split line can be repeated for theother mould half, using the same pattern. The two jointboards are framed with wood which, along with the 3DPrinted pattern, constitutes the final foundry tool. Mouldhalves are then created separately by interchanging thepattern between the two core boxes.• Production Intent Casting (PIC): This method is acombination of the zp102 plaster material for creatingpatterns, and ZCast material for creating cores. It firstinvolves the creation of the foundry tooling as it wouldbe designed for the production foundry process,including core prints, offset partings, and clearances. Thepattern equipment is then printed with the zp102material, infiltrated with epoxy, and if necessarybackfilled with a rigid plastic filler for added strength. Ifcores are required, they may be produced using theZCast material.

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 21II. EXPERIMENTAIONIn the present work, the 3DP machine with ZCast directmetal casting solution was used to fabricate the shellmoulds. The 3DP printed shell model was used as thepositive pattern around which the sand is filled in amoulding box. An effort has been made throughexperiments, to study the feasibility of decreasing theshell wall thickness from the recommended one 12(mm),in order to reduce the cost of production and time as wellas to evaluate the dimensional accuracy and surfaceroughness of the Al castings obtained, for assemblypurpose. Experimental studies regarding this solution arelacking in literature. Reference [6] has conducted studiesfor two technological solutions in this field and this studyaims at evaluating the dimensional accuracy of two rapidcasting (RC) solutions based on 3D printing technology:investment casting starting from 3D-printed starchpatterns and the Z Cast process for the production ofcavities for light-alloys castings.In present work, the layer thickness, part orientationand post curing time were considered as parameters ofthe 3DP machine. The out come of the experimentalstudy will be helpful to provide data for industrialapplication of the considered technology.Objectives of the Research WorkFollowing were the main objectives of this researchwork.1. To verify the feasibility of decreasing the shellthickness from recommended one (12mm) in order toreduce the production cost and time.2. To evaluate the dimensional accuracy of the Alcastings obtained and to check the consistency of thetolerance grades of the castings (IT grades) as perallowed IS standards for casting process.3. Proof of concept, to present the concept in physicalform with minimum time by avoiding the cost ofmaking dies and other fixtures for a new concept.III. METHODOLOGYA. Identification of BenchmarkFor the investigation, an aluminum alloy casting waschosen as a benchmark, representative of the automobilefield (used in suspension system), where the applicationof RC technologies is particularly relevant. Fig.3 showsthe drawing of benchmark.B. CAD Model CreationFirstly, using the UNIGRAPHICS software CAD modelof the component was made. After making the CADmodel, the upper and lower shells of the model weremade by using the same software. The upper and lowershells of the component were made for different values ofthe thickness. The thickness values for shellswere12mm,11mm,10mm,9mm,8mm,7mm,6mm,5mm,4mm,3mm and 2mm. The upper and lower shells modelswere then converted into STL format. To establish theconsistency, the STL format has been chosen as thestandard for the AM industry .aFig.4. CAD model of (a) upper and (b) lower shell mouldbFig.3. Benchmark dimensions

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 22C. Machine PreparationsThe machine was then made ready for printing by thefollowing settings:1. Checking of the powder level.2. Preheating of the printer up to 32.2ºC.3. Prime wash- cleaning of the printer head.4. Filling of the machine bed with powder both inautomatic and manual mode.5. Toggle roller cleaning.6. Cleaning of the fast axis (FA) and slow axis (SA).Fig.7. Post heating of Shell moulds in ovenF. Shell Casting of Selected BenchmarkStarting from the CAD model of the component, shellswere modeled for different shell wall thicknesses. Fromthe analysis of geometry and volume of benchmark, singlefeeder and riser system was designed for pouring themolten metal. RP shell models are used as positivepatterns around which the sand is filled in a mouldingbox. Commercial cast aluminium alloy 333.0 was used forcasting.Fig.5. ZCorp 3DP machineD. Shell Mould PrintingAfter parameter settings of the machine (as obtainedin pilot study), the machine was set in on-line mode andthe printing of the shells for different values of thethickness was done. Fig.6 shows the 3D printing of shellmoulds.Fig.6. Printing of shell moulds using ZCast501 RC solutionE. Post processing of Shell MouldsAfter printing of shells, the shells were removedcarefully from the machine bed and de powdering of theshells was done. In the de-powdering, the extra powder(which is not glued by binder) was removed with the helpof soft brushes. After de-powdering of the shells, theshells were cured in an electric oven (see fig.7). The postcuring time for the shells was minimum 4 hours. Theupper and lower shells were placed in such a way that thecentral axis of both the shells was collinear.Fig.8. Al castings obtained with different shell mould thicknessesIII. TESTING AND ANALYSIS OF PROTOTYPE CASTINGSThe measurement paths for the internal and the externalsurfaces of the benchmark have been generated throughthe measurement software of the GEOPAK v2.4.R10CMM. These paths direct the movements of the CMMprobe along trajectories normal to the parts surface.Table1 shows variation in measured dimension ofaverage thickness castings obtained with respect to shellthickness.The results of the dimensional measurements (componentthickness) have been used to evaluate the tolerance unit(n) that derives starting from the standard tolerance factori, defined in standard UNI EN 20286-1 (1995) [25]. Thevalues of standard tolerances (also known as‘Fundamental Tolerances’) corresponding to IT5-IT18grades, for nominal sizes from 3mm to 500 mm, wereevaluated considering the standard tolerance factor i (µm)indicated by the following formula, where D is thegeometric mean of the range of nominal sizes in mm.Tolerance Factor i= 0.45 × ( D) + 0.001D ( 1)1/3

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 23S.No.TABLE IOBSERVATIONS OF FINAL EXPERIMENTATIONShell mouldthickness(mm)Componentthickness(mm)Surfaceroughness(microns)Shell mouldproductiontime(min)1 12 4.14 6.28 772 11 4.13 6.41 713 10 4.09 6.35 654 9 4.11 6.45 605 8 4.13 6.54 536 7 4.12 6.62 507 6 4.13 6.57 448 5 4.15 6.61 409 4 4.09 6.82 3910 3 3.97 6.95 3711 2 3.95 7.12 36In fact, the standard tolerances are not evaluatedseparately for each nominal size, but for a range ofnominal sizes. For a generic nominal dimension D JN , thenumber of the tolerance unit’s n is evaluated as follows:n= 1000(D JN - D JM)/ i,where D JM is measured dimension. The toleranceisexpressed as a multiple of i: for example,IT14corresponds to 400i with n= 400. Table II showsclassificatio n of different IT grades according to UNIEN20286-1. After this for each value of thick ness ofcastings, corresponding value of ‘ n’ were calcula ted, thelatter taken as a reference ind ex for evalua tion oftolerancegrade. Theresults of dimensionalmeasuremen ts (thickness of obtained castings) are shownin Fi g.9.The r esults of dimensional measurements areus ed to evaluate the tolerance gr ades. The obtainedtolerance grades are IT1 2 and IT13. The results presentedin Table II shows that the tolerance grades calculated forthe consider ed RC solution (ZCast 501) are consistentwith the values allowed for casting operations between(2)IT11 and IT18. All the obtained castings are with in therange of IT11 to IT18 and thus are completely acceptableat all shell wall thicknesses from 12(mm) down to2(mm). However, better dimensional accuracy isobtained at 5(mm) shell mould wall thickness (see TableI). It should be noted that the process of solidification atdifferent shell thickness leads to different thermalgradients, which affect the heat transfer and finallyshrinkage (thickness of component) of castings as shownin Fig.9.The roughness of the surface can be measured bycalculating the arithmetic mean value (Ra) as the bestestimate for the true value of set of experimentalmeasurements [26]. In this research, surface roughness ofthe castings obtained was measured with Mitutoyosurface roughness tester (SJ-201). The measured surfaceroughness of obtained castings is shown in Table I andFig.10. The experimental results show that the surfaceroughness increases with the decrease in shell mould wallthickness. The surface roughness obtainable by sandcasting process lies between Ra 6.3 (microns) to Ra50(microns). All castings of current experimentation arewithin this range which justifies the feasibility ofdecreasing the shell wall mould thickness from therecommended one.Fig.9. Effect of shell mould wall thickness on thickness of casting obtainedExp. No.TABLE IICLASS OF DIFFERENT IT GRADES ACCORDING TO UNI EN 20286-IShell Thickness Component thickness ToleranceTolerance Unit(mm)(mm)Factor “i”“n”(µm)D JND JMIT Grade1 12 4.2 4.14 0.73 82.19 IT 122 11 4.2 4.13 0.73 95.89IT 123 10 4.2 4.090.73 150.68 IT 134 9 4.2 4.11 0.73 123.28 IT 135 8 4.2 4.13 0.73 95.89 IT 126 7 4.2 4.12 0.73 109.58 IT 127 6 4.2 4.13 0.73 95.89 IT 138 5 4.2 4.14 0.73 82.19 IT 129 4 4.2 4.09 0.73 150.68 IT 1310 3 4.2 3.97 0.73 315.06 IT 1511 2 4.2 3.95 0.73 342.46 IT 15

MIT International Journal of Mechanical Engineering Vol. 1, No. 1, Jan 2011, pp 17-25ISSN No. 2230 – 7699 © MIT Publications 24thickness will be different. Hence there is need togenerate database of optimum shell wall thicknessesbased on dimensional accuracy, mechanical propertiesfor different volumes, weight density of materials andpouring temperature of materials.Fig.10. Effect of shell mould wall thickness on surfaceroughness of Al casting obtainedThe production time (PT) for preparing shell of differentwall thicknesses is shown in table1and Fig.11.The savingin production time for 5(mm) shell thickness as compareto 12(mm) shell thickness for Al alloy is= [PT at 12(mm) - PT at 5(mm)] / PT at 12(mm)= [(77 (min) - 40 (min)) / 77] ×100=48.05%The decrease in shell thickness reduces the volume ofZCast powder as well as the quantity of binder to beprinted by the 3DP machine. So, for the same internalgeometry, the time required to print the shell bydecreasing the wall thickness from 12mm down to 2mmwill be reduced. The saving in production time forpreparing all reduced shell wall thickness moulds ascompared to 12(mm) shell mould was also calculated andshown in Fig. 12.Fig.11. Effect of shell mould wall thickness on shellproduction timemouldThe present research work deals with the Rapid Castingof material (Al) having low melting temperature range of550- 620 o C [27], however for casting of materials havinghigh temperature range the result of optimum shellFig.12. Effect of shell mould wall thickness on shell mouldproduction timeIV. CONCLUSIONThe following conclusions are derived from the study:1. The adopted procedure is better for proof of conceptand for the new product, for which the cost ofproduction for dies and other tooling is more.2. The present study deals with finding of optimumshell thickness as per dimensional accuracy for acomponent having some definite size.3. It is feasible to reduce the shell mould wall thicknessfrom 12(mm) to 5(mm) for generating Al castingusing ZCast501 RC solution. The tolerance grades ofthe castings produced from different thicknesseswere consistent with the permissible range oftolerance grades (IT grades) as per standard UNI EN20286-I (1995).4. The dimensional accuracy (thickness of component)obtained with 5(mm) shell mould thickness wasbetter than the accuracy obtained with 12(mm)recommended shell mould thickness. However, thesurface roughness Ra values of Al castings obtainedare lie in the range of surface roughness obtainableby sand casting process.5. The experimental results indicate that at the 5mmshell thickness, the production time was reduced by48.05% less in comparison to 12(mm) recommendedshell mould thickness.ACKNOWLEDGEMENTThe authors are grateful to Management, DirectorGeneral, Director, and HOD ME of Moradabad Instituteof Technology, Moradabad for motivating us for thisinvestigation.

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