Modeling and optimization of mechanical properties for parts produced by FDM

Statistical and Empirical Modeling of Shrinkage in parts fabricated by FFM ProcessA Research Plan Presentation ByShekhar Saini801481022ME - CCR

under supervision ofDr. Vineet Srivastava & Mr. Gurpreet Singh Saini

Copyright 2013-2014Product DevelopmentMachining JoiningFormingLayer Deposition or Rapid PrototypingCopyright 2013-2014What is Rapid prototyping?A prototype is defined as An approximation of a product or system or its components in some form for a definite purpose in its implementation.

Rapid Prototyping (RP) refers to new class of manufacturing machines which quickly produce physical prototypes from 3D CAD models.

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Applications of RPDesignCAD model VerificationVisualizing ObjectProof of conceptEngineering Analysis and PlanningForm and Fit modelStress DistributionDiagnostic and Surgical Operation PlanningSurgical Preplanning

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WASHING MACHINE ROTOR

HIGH SPEED VENTILATION SYSTEMCONNECTING ROD OF ENGINECopyright 2013-2014Problem Areas of RPAccuracyStrength Surface roughness Part deposition orientation Build timeSupport structureForm FactorCopyright 2013-2014MotivationRP prototypes should have high accuracy in order to ensure proper functional requirements. The accuracy of an RP process is difficult to predict as it is a function of many factors

Accuracy of tessellation from the CAD modelSlicing algorithmPowder granulometry (in Powder based systems)Beam offset (in Laser mounted system)Shrinkage Copyright 2013-2014Shrinkage Shrinkage does not occur in a uniform manner. The shrinkage of a new layer can be constrained by the existing part substrate. In addition, areas at high temperatures tend to shrink more than those at lower temperatures and part geometries such as thick walls or sections can increase the shrinkage.

To compensate for shrinkage, a material shrinkage coefficient is calculated and a scaling factor is applied in each direction to the STL file

The resulting geometry can be slightly oversized compared with the nominal geometry, depending on the scaling factor used. Therefore, the present work aims on finding out the effect of process parameters on shrinkage for better accuracy. Statistical models of shrinkage along X, Y and Z-axes will be developed to scale up the STL file for better accuracy.Copyright 2013-2014Literature ReviewWang et al. (1996)Acrylic based polymer, SL (Stereo lithography).

Derive relationship between post curing shrinkage and process parameters(post curing duration, laser power, layer pitch)Using least square method relationship between post curing shrinkage and process parameters were derived.Cross-Sectional Profile of multi-layer structure

Rapid prototype manufacturing using the Stereolithography techniqueCopyright 2013-2014Dao et al. (1999)

ABS plastic, FDM (Fused Deposition Modeling)To Improve dimensional accuracy.It was found that an SCF of 1.010 will produce a 53%reduction in mean error of the dimensions.

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Copyright 2013-2014Xiangwei Wang (1999)Polystyrene in powder state, Selective laser sintering(SLS).To derive basic formula for shrinkage and beam offset.For good accuracy different parts should be applied different beam offset depending on weight of the part as shrinkage is not very critical.Beam offset and shrinkage calibration procedure

Scaling factor k and beam offset b/2 with part weightCopyright 2013-2014R. Nosouhi and S. Rahmati (2010)

Acrylic based photopolymer, SL (Stereo lithography).To reduce shrinkage by FE Analysis and Star weave hatching method.Parts produced using Circular Star weave hatching method are more accurate than those produced by Star weave.

MethodologyChoosing the machine, laser and resin parametersDetermination of curing curves in different directionsDrawing of new solid partDrawing the liquid parts using Boolean OperationsAssembly of the solid and liquid partsSaving the drawn model with a format which is recognizable by PE softwareImporting the assembly in the PE softwareDetermination of the mechanical propertiesAssembly of solid and liquid parts, applying the loads and boundary conditions, meshing, etc.Obtaining the resultsCopyright 2013-2014D. Karalekas and A. Aggelopoulos (2002)Acrylic based photopolymer, SL (Stereo lithography).To calculate magnitude of the resulting shrinkage strains.Specimens post-cured under intense UV light exhibited a uniform shrinkage while thermal post curing results in higher shrinkage.Schematic diagram of two-layer resin laminate before and after deformation.

Schematic representation of experimental setup for measuring out-of-plane deflections.Copyright 2013-2014Wang et al. (2006)Polystyrene in powder state, Selective laser sintering(SLS)Minimize the shrinkage using neural network to define relationship between process parameters and shrinkage.By lowering scanning speed, higher laser power and highest allowable temperature of working environment improves accuracy.

Trained result of the training sets using different numbers of hidden neuronsCopyright 2013-201413Research Gaps From literature survey it has been observed that maximum work regarding part strength is concerned on FDM, SLS, SL technologies.

It has been observed that there is no work related to parts related to 3D printing technology in relation to the accuracy of the parts developed.Copyright 2013-2014Research Objective Based on the literature survey presented, following objectives are being proposed.

To Develop a Statistical model based on the effect of various process parameters on shrinkage of parts fabricated by FFM method.

To Validate the developed model and optimize the shrinkage.

To Develop an empirical relationship between process parameters and shrinkage.

Copyright 2013-2014Research Objective To fulfill these objectives the process parameters selected for fabrication are as follows:Low levelMedium levelHigh levelNozzle diameter (mm)0.20.30.4Layer Thickness (mm)0.10.20.3Part bed Temperature ( c)108110112Length of part(mm)103050Copyright 2013-2014MethodologySolid modelling of specimen according to standards.Selection of process parameters and there ranges based on the machine limitations.Creation of design of experiment plans to establish testing conditions.Fabrication of specimen based on test condition.Experimental testing to generate data for statistical modelling(based on doe plan).Estimation of error and validation of statistical models.Optimization of responses based on the limitation of the process parameters.Empirical Modeling of shrinkage.Thesis writing.Copyright 2013-2014Work plan2014-152015-162015-16II SemI SemII SemLiterature survey.To prepare CAD model of parts in CAD package.To prepare design of experiment (DOE) according to process parametersTo fabricate the parts according to DOE plans.To study the effect of process parameters on pre-selected mechanical properties.Validation and optimization of process parameters for mechanical properties.Empirical Modeling of shrinkage.Thesis writing.Copyright 2013-201418Parts to be fabricated

Copyright 2013-2014ReferencesW. L. Wang, C. M. Cheah, J. Y. H. Fuh and L. Lu. Influence of process parameters on stereolithography part shrinkage, Materials & Design. Vol. 17, No. 4, pp. 205-213, 1996.Quang Dao, Jane C. Frimodig, Hung N. Le, Xiao Zhe Li and Boris Fritz. Calculation of Shrinkage Compensation Factors for Rapid Prototyping (FDM 1650), Computer Applications in Engineering Education. vol. 7, no. 3, pp. 186-195, 1999.Xiangwei Wang, "Calibration of shrinkage and beam offset in SLS process", Rapid Prototyping Journal, Vol. 5, Iss 3, 1999.R. Nosouhi and S. Rahmati, Finite Element Analysis of Shrinkage Phenomena in Stereolithography and Development of a New Hatching Method, 10th Iranian Conference on Manufacturing Engineering, ICME 2010.D. Karalekas and A. Aggelopoulos, Study of shrinkage strains in a stereolithography cured acrylic photopolymer resin, Journal of Materials Processing Technology, 136, 146150, 2003.

Copyright 2013-2014Rong-Ji Wang, Lingling Wang, Lihua Zhao and Zijian Liu, Influence of process parameters on part shrinkage in SLS, Int J Adv Manuf Technol, 33, 498504, 2007.Lecture Slides by Dr. Vineet Srivastava, Introduction to RP, dated on 12/01/2015.Lecture Slides by Dr. Vineet Srivastava, Principle, Steps, Process Chain of RP, dated on 12/01/2015.Lecture Slides by Dr. Vineet Srivastava, Classification of RP, dated on 19/01/2015.

Copyright 2013-2014Thank YouCopyright 2013-2014How presentation will benefit audience: Adult learners are more interested in a subject if they know how or why it is important to them.Presenters level of expertise in the subject: Briefly state your credentials in this area, or explain why participants should listen to you.22