Analysis of various rapid prototyping techniques for investment casting

• Main Author: Marwah, Omar Mohd Faizan
• Format: Thesis
• Language: English; English
• Published: 2016
• Subjects: TS155-194 Production management. Operations management
• Online Access: http://eprints.uthm.edu.my/889/1/24p%20OMAR%20MOHD%20FAIZAN%20MARWAH.pdf; http://eprints.uthm.edu.my/889/2/OMAR%20MOHD%20FAIZAN%20MARWAH%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/889/

Rapid prototyping (RP) technology is currently receiving huge attention as a prospective alternative to replace the conventional wax material as a master pattern in the investment casting (IC) process. This is because the RP technology allows simple to complex patterns to be fabricated directly from a computer model in a shorter time without using any hard tooling. However, quality of the RP patterns remains to be solved due to the staircase effect caused by the layered building method. Additionally, inappropriate settings of the RP parameters and the IC process variables such as pattern structure designs, shell preparation and burnout temperature may cause serious defects in the ceramic mould. This study was undertaken to investigate the use of RP patterns from three RP technologies in the IC process. These RP technologies include fused deposition modeling (FDM), multijet modeling (MJM) and 3D Printer (3DP) using acrylonitrile butadine styrene (ABS), SR200 acrylate and ZP150 powder based materials respectively. Experiments were conducted to assess the influence of the process parameters on the quality of RP patterns using design of experiment (DOE) method in order to obtain the best RP process parameters in minimizing the RP responses such as dimensional accuracy (DA), surface roughness (SR) and build time (BT). In addition, the effects of the internal pattern structures on the quality of the ceramic shell moulds that are suitable for the IC process were also evaluated and analysed. Based on the results of analysis of variance (ANOVA), it was found that layer thickness (LT) and road width (RW) for FDM, LT and shell value core (SVC) for 3DP and part orientation (PO) for MJM were significant parameters affecting the DA. Findings also showed that LT, PO, air gap (AG) and RW for FDM, PO and part position (PP) for MJM, LT and SVC for 3DP significantly affect the part SR. It was observed that LT, raster angle (RA), PO and interaction of LT and PO for FDM, LT and PO for 3DP, PO and PP for MJM were significant parameters influencing the part BT. Results from the main effects plot indicated that all significant parameters should be set at low level in order to obtain better DA and SR. In addition, all significant parameters for FDM and 3DP should be set at high level and MJM at low level to achieve faster part BT. Empirical models for the RP responses were established based on the experimental data using the regression equation and can be readily applied to predict the respective responses. Comparing the results of different RP part internal structures and the casting parts, it was observed that the part with internal structure produces the lowest deviation of 0.006mm on DA compared to hollow structure of 0.013mm. However internal structure had no significant effect on part SR and at the same time also resulted in longer process time. It was also found that the optimum shell thickness of ST3, ST2 and ST1 for ABS, acrylate SR200 and ZP150 powder based materials can minimise the occurrence of shell cracking of the IC ceramic mould.