SUMMARY OF PHD. THESIS RESEARCH ON ALUMINUM VACUUM CASTING OF COMPLEX PARTS

Transcription

1 Investeşte în oameni! FONDUL SOCIAL EUROPEAN Programul Operational Sectorial pentru Dezvoltarea Resurselor Umane Eng. Alina Ioana LUCA SUMMARY OF PHD. THESIS RESEARCH ON ALUMINUM VACUUM CASTING OF COMPLEX PARTS PhD. Supervisor, Prof.Dr.Eng. Nicolae BÂLC TECHNICAL UNIVERSITY OF CLUJ-NAPOCA FACULTY OF MACHINE BUILDING 2011

2 Investeşte în oameni! FONDUL SOCIAL EUROPEAN Programul Operaţional Sectorial Dezvoltarea Resurselor Umane Axa prioritară: 1 Educaţia şi formarea profesională în sprijinul creşterii economice şi dezvoltării societăţii bazate pe cunoaştere Domeniul major de intervenţie: 1.5 Programe doctorale si postdoctorale în sprijinul cercetării Titlul proiectului: Proiect de dezvoltare a studiilor de doctorat în tehnologii avansate- PRODOC Cod Contract: POSDRU 6/1.5/S/5 Beneficiar: Universitatea Tehnică din Cluj-Napoca FACULTY OF MACHINE BUILDING Eng. Alina Ioana LUCA SUMMARY OF PHD. THESIS RESEARCH ON ALUMINUM VACUUM CASTING OF COMPLEX PARTS PhD. Supervisor Prof.Dr.Eng. Nicolae BȂLC Committee for public upholding: PRESIDENT: MEMBERS: -Prof.Dr.Eng. Danuţ JULEAN - Vice Dean, Technical University of Cluj-Napoca; -Prof.Dr.Eng. Nicolae BÂLC - PhD. Supervisor, Technical University of Cluj- Napoca; -Prof.Dr.Eng. Nicolae V. IVAN - Reviewer, Transilvania University of Brasov; -Prof.Dr.Eng. Laurenţiu SLĂTINEANU - Reviewer, Gh. Asachi University of Iasi; -Prof.Dr.Eng. Petru BERCE - Reviewer, Technical University of Cluj-Napoca.

3 CONTENTS Contents... 1 List of abbreviations... 4 Introduction. 5 CHAPTER 1 THE ANALYSIS OF THE CASTING TECHNOLOGIES OF METAL PARTS WITH COMPLEX SHAPES 1.1. Introduction Casting technology of metal parts with complex surfaces Permanent mold casting technologies Expandable mold casting technologies Comparative studies. Conclusions.. 31 CHAPTER 2 THE CURRENT STAGE OF THE VACUUM CASTING TECHNOLOGY 2.1. Introduction The main steps for vacuum casting technology The current stage of aluminum vacuum casting technology using wax 48 patterns The current stage of casting process simulation Conclusions.. 57 CHAPTER 3 RESEARCH OBJECTIVES Eng. Alina-Ioana LUCA 3

4 CHAPTER 4 CONTRIBUTIONS REGARDING THE MODELING AND OPTIMIZATION OF THE VACUUM CASTING PROCESS 4.1. Modeling and optimization of wax casting in the silicone rubber mold Stages of the mathematical model development Planning the experiments Experimental research Mathematical modeling of wax casting process Analysis of wax casting process parameters Modeling and optimization of aluminum vacuum casting process Experimental research Comparative study between gravity wax casting and vacuum wax casting Analysis of the aluminum shrinkage coefficient in vacuum casting 97 process Mathematical modeling of aluminum vacuum casting process Roughness variation in the vacuum casting process Conclusions CHAPTER 5 CONTRIBUTIONS REGARDING THE CASTING DESIGN 5.1. Contributions regarding the wax gating system design in aluminum vacuum casting process Determination of sprue design for aluminum alloy casting Determination of feeder sizes for aluminum alloy casting Economical aspects of aluminum vacuum casting process Conclusions Eng. Alina-Ioana LUCA 4

5 CHAPTER 6 CONTRIBUTIONS REGARDING THE SIMULATION AND ANALYSIS OF THE INVESTMENT CASTING PROCESS 6.1. The usefulness of casting simulation software The main steps for casting simulation using dedicated software Investment casting process simulation Process Simulation Simulation of solidification process Simulation results and analysis of casting design Conclusions CHAPTER 7 EXPERIMENTAL RESEARCH FOR TESTING AND VALIDATING THE THEORETICAL CONTRIBUTIONS 7.1. Experimental research Measurements achievement Results validation Conclusions CHAPTER 8 FINAL CONCLUSIONS AND ORIGINAL CONTRIBUTIONS 154 REFERENCES Eng. Alina-Ioana LUCA 5

6 Abstract of the PhD. Thesis Vacuum casting (VC) is one of the most important technology in manufacturing metal parts with complex geometries and intricate details. The cast parts are used on a large scale in the auto industry, aeronautics industry, machine building, jewelry manufacturing and medicine. Current trends on the market refer to the decrease in life cycle of products, due to the fact that new or improved products appear on the market and replace the old ones to satisfy the customers needs. The trends, based on the need to lower the life cycle of products can score some current market trends: reducing product design time, reduce time to achieve the prototypes, reducing the manufacturing time, increase dimensional accuracy and improving the quality of parts, increasing complexity and decreasing production costs. Vacuum casting steps ahead of other technologies, with several features such as high complexity of parts that can be cast, precision and good quality of parts, relatively short manufacturing time and not least low cost. Due to numerous advantages that it offers, vacuum casting is a viable solution for manufacturing complex shapes metal parts in small series or prototype manufacturing. This thesis entitled, RESEARCH ON ALUMINUM VACUUM CASTING OF COMPLEX PARTS, is structured in 8 chapters and includes studies and research regarding investment casting of complex shapes metal parts, whose content is presented in the following. The 1st chapter of this PhD thesis, entitled The analysis of the casting technologies of metal parts with complex shapes, shortly presents the significant casting technologies of complex metal parts used in the industry. The most used metal casting technologies are: pressure casting, gravity casting, centrifugal casting, sand casting, shell mold casting and investment casting. Also, in this chapter a comparative analysis is done between the most used casting technologies. Within this comparison several parameters are analyzed, like: the type of metal that can be cast, the complexity of the parts, the accuracy, the quality of the parts, productivity, manufacturing time. There are also presented the advantages and disadvantages Eng. Alina-Ioana LUCA 6

7 of the casting technologies, special attention being accorded to metal vacuum casting technology, that is actually the main subject of this PhD paper. The 2nd Chapter of the thesis, entitled The current stage of the vacuum casting technology, presents the actual stage of the research in the field of vacuum casting using wax patterns. The 3rd Chapter of the thesis highlights the main objectives of the paper. In Chapter 4 of this paper, entitled Contributions regarding the modeling and optimization of the vacuum casting process, an innovative method has been proposed of mathematical modeling of wax casting process and also for aluminum casting process. In the first part of the chapter a method is proposed to solve one of the most important problems encountered in the wax casting process and that is the mathematical modeling of the process. In this chapter is presented the methodology to develop a mathematical model that describes the connection between the shrinkage of the wax patterns and the process parameters (wax temperature, silicone rubber mold temperature). By using the response surface methodology several types of mathematical models have been analyzed and it has been established a model that best describes the connection between the shrinkage of the wax patterns and the process variables. After establishing the mathematical model, the meaning of every symbol within the mathematical model has been verified. The mathematical model has been tested and validated by a graphic comparison with the experimental results, noticing a good connection and obtaining a difference of less than 10%. Beginning from the experimental research an analysis has been made, regarding the influence of the process parameters on the wax patterns shrinkage coefficient. In this PhD thesis experimental studies have been made in order to analyze the wax casting parts, respectively wax patterns made using the vacuum casting technology and gravity casting technology. Starting from the mathematical modeling for prediction of the wax patterns shrinkage and taking into account the aluminum shrinkage coefficient, a mathematical model has been developed to predict the shrinkage coefficient of the aluminum parts obtained through vacuum casting process. To obtain accurate parts it is necessary to increase the dimensions of the master model by adjusting the nominal casting dimensions with the shrinkage factor. Eng. Alina-Ioana LUCA 7

8 The surface quality of the cast metal parts through vacuum casting technology is a topic which is given a special attention. Thus, a study was undertaken to analyze the surface roughness variation of aluminum parts, depending on the roughness of the master model. Chapter 5, entitled "Contributions regarding the casting design" presents a method to solve one of the most important problems encountered in the lost-wax casting process, the optimization of the wax gating system by determining the optimal dimensions of the gate, sprue and feeders. In this chapter, starting from the classic metal casting process, is proposed a method to calculate the optimal dimensions of the gating system, proposing mathematical relations for the gate, sprue and feeders. At the end of this chapter is proposed an algorithm for calculating the cost of parts manufactured through vacuum casting technology. In Chapter 6, entitled "Contributions regarding the simulation and analysis of the investment casting process", is presented the analysis and simulation of the Investment Casting process using dedicated software applications, in order to improve the process. Chapter 7 entitled "Experimental research for testing and validating the theoretical contributions" presents the experimental study undertaken for testing and validating the new mathematical model for calculating the shrinkage of cast aluminum parts and the calculating relations for the optimal dimensions of the feeding system. Thus calculating the optimal value of the feeding system dimensions and increasing the master model with the calculated value of the shrinkage, using the developed model, aluminum parts with complex shapes have been manufactured obtaining a high dimensional accuracy and a good surface quality. The last chapter of this thesis, Chapter 8, entitled "Final conclusions and original contributions" is dedicated to establish some conclusions, highlighting the main theoretical and experimental contributions of the author and also proposes directions for further research. Cluj-Napoca, September 2011 Author: Eng. Alina Ioana LUCA Eng. Alina-Ioana LUCA 8