Theoretical and Experimental Contributions Regarding the Optimization of Rapid Prototyping Technologies

Transcription

1 TECHNICAL UNIVERSITY OF CLUJ-NAPOCA FACULTY OF MACHINE BUILDING Theoretical and Experimental Contributions Regarding the Optimization of Rapid Prototyping Technologies Doctoral thesis ABSTRACT Scientific Author: Eng. Sorin-Daniel BRĂTIAN Scientific Coordinator: Proff. Dr. Eng. Petru BERCE

2 Content Introduction 6 1 Actualities and perspectives regarding Rapid Prototyping technologies Present stage of the technologies for manufacturing rapid prototypes Classification of the technologies of rapid prototyping Suppliers of RP systems Laminated Object Manufacturing method (LOM) LOM technologies Materials used in the process of manufacturing by LOM Post processing and treating Fused Deposition Modelling method (FDM) FDM technologies Materials used in the process of manufacturing by FDM Post-processing of the models D Printing method (3DP) D Printing technologies Materials used in 3D Printing process Post treating Selective Laser Sintering (SLS) method Working principle of the selective laser sintering system (SLS) Materials used in selective laser sintering process Post processing and treating Direct manufacturing of metallic parts Direct metal laser sintering (DMLS) Selective laser sintering melting (SLM) Conclusions 49 2 Thesis objectives Present tendencies of the research Research objectives CAD resources necessary for manufacturing rapid prototypes D modelling by the help of specialized softwares Geometric model transfer between CAD model and RP system STL. file content 57 2

3 3.2.2 vertex-to-vertex rule Conclusions 62 4 Development of some mathematical models for optimisation of LOM parts General considerations Flow charts Processing of a mathematical model for determining the angles of rotation on OX and OY so that the manufacturing time to be minimum in case of FDM (Fused Deposition Modelling) process Description of the tminfdm program for determining the angles of rotation so that the working time to be minimum. Flow chart. Experimental results Determining the angles of rotation on Ox and OY so that the average roughness to be minimum in case of manufacturing on FDM (Fused Deposition Modelling) process Description of the t_rmediu_fdm programme for determining the angles of rotation so that the average roughness should be under certain limit. Flow chart. Experimental results Processing of a mathematical model for determining the angles of rotation of the part so that the manufacturing time should be minimum on manufacturing by SLS (Selective Laser Sintering) system Description of tminsls programme for determining the angles of rotation so that the manufacturing time of the part to be minimum on SLS system. Flow chart. Experimental results Determining the angles of rotation so that the average roughness should be minimum on manufacturing by SLS (Selective Laser Sintering) Description of t_rmediu_sls programme for determining the angles of rotation on OX and OY axis so that the average roughness should be reduced on manufacturing by SLS. Flow chart. Experimental results Conclusions Final conclusions, personal contributions and future perspectives on the development of the research General considerations Personal contributions regarding optimising the Rapid Prototyping technologies Future research 162 Bibliography 164 Appendix

4 Appendix Appendix Appendix Appendix Appendix Appendix Appendix Chapter 1 These new technologies of Rapid Prototyping have a great impact in many areas, from the industrial production to medicine, giving in this way to this technology a strategic importance inside companies that use RP technologies. RP models obtained by these methods (LOM, SLS, FDM, SLA etc) are successfully used in automobile industry, in medicine, architecture exactly for the reason to study the shape, the assembly conditions and sometimes the functionality. Many prestigious companies, and not only them, are using these methods to get out to the market products of good quality, on a short time. These RP models are used for different functional tests, simulation tests or manufacture tests. The tests made directly on these RP models are very dependent on the materials used in present by these technologies. Therefore, the material for the model and the method used should be chosen accordingly to the followed goal of the test. Optimum usage of RP technologies is when the designers are completely using these technologies for checking the shape, manner of fastening and functionality. In this way it would be possible for them to test and to completely evaluate different ideas before the final product, resulting thereby high integrated products that fulfil the customer needs. On the other hand, these technologies will allow other technologies to consistent reduce the time of assimilation of new products, execution of new tooling at much more reduced costs than classic technologies. Chapter 2 Thesis objectives are the following: v Elaboration of a mathematical model for determining angles of rotation on OX and OY so that the volume of the support should be minimum for FDM (Fused Deposition Modelling) method and also the elaboration of a programme for optimisation. 4

5 v Determining the angles of rotation on OX and OY so that the general roughness to be minimum on the case of manufacturing on FDM (Fused Deposition Modelling) system and also elaboration of flow chart and of the appropriate programme. v Elaboration of a mathematical model for determining the angles of rotation of the part so that time of manufacturing on SLS (Selective Laser Sintering) system should be reduced at minimum and also getting out the flow chart and the programme for optimisation. v Determining the angles of rotation so that the general roughness should be minimum at manufacturing on SLS (Selective Laser Sintering) system and also elaboration of programme for optimisation. Chapter 3 The accuracy and the triangulation of 3D model influence the accuracy and quality of the physical model manufactured on each of the RP systems. A correct STL file must have an appropriate number of facets to clearly show the details of the object, but in the same time the number of triangles should not be too high in order to be easily workable with this file. Optimised files are playing and loading up to 10 times faster than the files that are not optimised, these remaining valid and editable by any application that accepts STL files. A too small number of approximation facets makes that smooth surfaces of the initial model to be materialise as clear polyhedral surfaces, and in certain cases the surfaces may be completely degenerated resulting in loosing the details of the model. The recommendation is that in case there are any doubts regarding choosing the number of triangles for faceting is better to choose a higher value even if this thing implies larger space on disk for STL file and larger processing time. Therefore a correct orientation will determine increasing the accuracy of the part and reducing the necessary time of manufacturing the model. Also, it will drive to minimization of costs for manufacturing complex prototypes. Continuous development of CAD softwares determine many companies to make that jump from drawing board to computer-aided-design, in order to use completely the advantages of CAD systems in the design phases. In present, CAD softwares are in a continuous modernisation and development; every year prestigious companies that develop such softwares (e.g. SolidWorks, Pro-E, Catia, AutoCAD) improve and deliver on to the market new versions of CAD softwares. To make possible an efficient usage of all RP systems, CAD softwares adopted by the users have to keep an essential condition and in the same time very important: to automatically generate STL files and to give a simple and efficient control of the quality of the STL approximation of the geometric model. 5

6 Chapter 4 Below are presented four mathematical models in order to optimize the manufacturing time and to reduce the average roughness for each of the following studied systems: first one, Selective Laser Sintering (SLS) and second Fused Deposition Modelling (FDM). It was chosen two possibilities, first one was optimisation of the position of the part on working area of the system so that the manufacturing time of the part should be reduced, and the second possibility was optimisation of the position of the part on working area of the system so that the average roughness of the part should be as much as possible reduced (minimum). The objective was to determine the couple of angles for OX axis and respectively, OY axis, so that the manufacturing time to be minimized or the average roughness to be reduced to minimum. In case of Selective Laser Sintering (SLS) the minimization of time was accomplish through positioning of the part on working are in such a manner that the height of the part on Z axis to be reduced at minimum. In case of Fused Deposition Modelling (FDM) reducing the manufacturing time was accomplished through minimisation of the volume of existing support material. For optimal positioning of the part so that the average roughness to be minimum was determined for each of the studied system a relation between roughness and the layer profile. The forth programmes made by the help of C++ programming language confirm the opportunity of these optimisations and their immediately practical application. In order to determine minimum time for manufacture of a part by Fused Deposition Modelling (FDM) was used the idea of minimizing the support. Therefore, the conclusion was that as less support system builds, less is the time of manufacturing the part. In case of Selective Laser Sintering the time for manufacture a part decreases according to minimizing the height on Z axis. For optimization of the minimum roughness was developed two programmes, one for Fused Deposition Modelling (FDM) and the other for Selective Laser Sintering (SLS), that on the basis of formulae determined in Chapter 4 was calculated for each couple of angles, the theoretical average roughness from were the programme indicate and show only the lower value together with afferent couple of angles. Chapter 5 Certainly the research on RP area in optimizing the technological parameters of these methods will continue and surely develop. We suppose that future research will increase the performance of RP technologies and will extend the application and usage area. The research can be oriented towards: 6

7 v Optimization of the technological parameters on the basis of certain objectives (appointed aim) initially decided; v Improvement of the physical and mechanical properties of the manufactured parts (prototypes); v Research and developing new materials treatable through these technologies; v Enlarging the research towards manufacturing technologies from metallic powders especially SLS and SLM; 7