Analysis of various rapid prototyping techniques for investment casting

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

Direct rapid prototyping evaluation on multijet and fused deposition modeling patterns for investment casting

The continuation from rapid prototyping into rapid tooling technologies allows speedy fabrication of sacrificial patterns for investment casting process. Direct expendable pattern fabrication with intricate features using rapid prototyping techniques significantly reduces the fabrication cost when associated with single- or low-volume production. During investment casting process, rapid prototyping patterns are subjected to high melting temperatures, high viscosities, and high thermal stress such as dewaxing and shell mold cracking. Furthermore, ceramic shell may cause crack during melting and burning out of the patterns and also incomplete collapsibility. Although rapid prototyping process can build parts with high stiffness rapidly, the part surface suffered a staircase effect and shrinkage during investment casting process solidification. This paper presents a direct approach of multijet modeling and fused deposition modeling on acrylate- and acrylonitrile–butadiene–styrene-based materials to be used as expendable patterns for the investment casting process. Thermal analyses were conducted on the rapid prototyping materials that exhibit mass loss and expansion. Quality assessment and benchmarking were performed between the rapid prototyping and the metal part on accuracy, surface roughness, and part built time. It was found that both the materials have dimensional deviation when employed in investment casting process and acrylate patterns have better surface roughness as compared to acrylonitrile–butadiene– styrene patterns. Additionally, multijet modeling recorded a significantly shorter lead time when more than a single part can be produced during the rapid prototyping process. It was observed that the shell mold after burnout experiences cracking. Results also showed that acrylate-based materials decomposed above 500°C, meanwhile acrylonitrile– butadiene–styrene was above 600°C. Acrylate material had a coefficient of thermal expansion and linear dimensional deviation as compared with acrylonitrile–butadiene–styrene. No ash was observed in the ceramic molds when the part burnout temperatures are above 500°C acrylate material and 600°C for acrylonitrile–butadiene–styrene

Measurement and analysis of water/oil multiphase flow using electrical capacitance tomography sensor

The paper investigates the capability of using a portable 16-segmented Electrical Capacitance Tomo-graphy (ECT) sensor and a new excitation technique to measure the concentration profile of water/oil multiphase flow. The concentration profile obtained from the capacitance measurements is capable of providing images of the water and oil flow in the pipeline. The visualization results deliver information regarding the flow regime and concentration distribution of the multiphase flow. The information is able to help in designing process equipment and verifying the existing computational modeling and simu-lation techniques

Evaluation of the Potential of Renewable Thermal Energy from Shingles Using Thermoelectric Generator (TEG) for Residential Use Application

A thermoelectric generator (TEG) using Seebeck effect to generate electrical energy in a residential application encompasses a case study of a test rig consisting of a concrete shingle as case study material. This paper explores its behavior and response to changes in temperature throughout the day. Four TEGs in series are mounted on the underside of a shingle. The measurement of the voltage and current response were made to determine the power generated. Using National Instruments as a data acquisition device with thermocouple probes to gather all the necessary data of which are discussed in the paper. From the experiments, the modules were able to generate up to 65.22 μW at 138Ω. This shows a considerable potential of TEG application in residential areas, as they are scalable

A study on palm fiber reinforces as a filament in portable FDM

The growth of renewable energy has been identified globally to ensure minimal environmental harm. Due to this situation, the development of green technology has enhanced the growth of renewable energy in the country. One of lignocellulosic biomass feedstock, oil palm frond was the raw material for a potential second-generation bioethanol production. Meanwhile, the sample characterizations were conducted by using the melt flow index. In addition, the 10% of oil palm fronds (OPF) was used and mixed with the HDPE which produce the composite grains. The main goals of the present work are the evaluation of the influence of several variables and test parameters on the melt flow index (MFI) of thermoplastics, and the determination of the uncertainty associated with the measurements. Hence, the capillary flow of a high-density polyethylene (HDPE) melts was studied. The shearing flow of polymeric fluids is encountered in a number of polymer processing operations. In other words, viscosity under simple shear is an important material parameter used for determining the pumping efficiency of an extruder, the pressure drop through a die, designing balanced flow runner systems in multiple cavity injection molding, computing the temperature rise due to viscous heat generation during processing. In this works, Thermagravimetric Analysis (TGA) is one of the branches under the thermal analysis, which is to determine the decomposition of the raw material that has been heat in certain temperature according the standard temperature of specific materials. Most of the thermal analysis, testing uses the weight of the sample within milligram or gram. Next, the process in the sample under DTA study is manifested by deviation of temperature difference from its background. This difference ΔT is not directly proportional to the rate of the process (dα/dt) but includes also the effect of heat inertia proportional to the slope dΔT/dt as it was derived. The filaments are inferior to the fibers for cement–matrix composites, but are superior to the fibers for polymer–matrix composites

Velocity profile measurement of solid particles using LED as a light source

Optical sensors have been widely available and used in medical applications and industries for decades. Its design comes in a wide range of varieties where each are tailored based on its type, use, size, nature of investigated materials etc. In this work, we focus on the development and investigation of an optical sensing module, which uses Light Emitting Diode (LED) as the light source and LED photosensor as detector. This sensor is to measure the velocity of a solid particle in a gas flow inside a closed pipe. Various factors such as power dissipation, wavelength of the light source, switching time and cost are considered in the design process of this sensor. The cross correlation technique is used to determine the flow rate where small particles were introduced in a natural gas flow and they went through two distanced sets of sensor module. The LED beam source in the first set of sensor will be scattered when the particle crosses it then the corresponding photodetector will collect the light signal received and generates a pulse signal. The second pulse signal is generated when the particle crosses the second set of sensor after an interval of time. The time interval measured is used to calculate the velocity of the flow. An analysis of the received pulse signals is made to determine the best configurations of the sensors. At the end of this study, we were able to develop a simple, working, and cost effective sensing module

Segmented capacitance tomography electrodes: a design and experimental verifications

A segmented capacitance tomography system for real-time imaging of multiphase flows is developed and pre-sented in this work. The earlier research shows that the electrical tomography (ECT) system is applicable in flow visualization (image reconstruction). The acquired concentration profile ob-tained from capacitance measurements able to imaged liquid and gas mixture in pipelines meanwhile the system development is designed to attach on a vessel. The electrode plates which act as the sensor previously has been assembled and fixed on the pipeline, thus it causes obscurity for the production to have any new process installation in the future. Therefore, a segmented electrode sensor offers a new design and idea on ECT system which is portable to be assembled in different diameter sizes of pipeline, and it is flexible to apply in any number due to different size of pipeline without the need of redesigning the sensing module. The new ap-proach of this sensing module contains the integration intelligent electrode sensing circuit on every each of electrode sensors. A microcontroller unit and data acquisition (DAQ) system has been integrated on the electrode sensing circuit and USB technology was applied into the data acquisition system making the sensor able to work independently. Other than that the driven guard that usually placed between adjacent measuring electrodes and earth screen has been embedded on the segmented electrode sensor plates. This eliminates the cable noise and the electrode, so the signal conditioning board can be expanded according to pipe diameter

Two parameters weibull analysis on mechanical properties of kenaf fiber under various conditions of alkali treatment

This paper present two parameters Weibull analysis result on mechanical properties of kenaf fiber under different condition of alkali treatment. The mechanical properties of kenaf fiber that as focused in this study was fiber matrix interfacial shear strength (IFSS) and fiber tensile strength (TS). Kenaf fiber were treated under various conditions alkali concentration at 2, 6 and 10 (w/v%), immersion duration at 30, 240 and 480 minute and immersion temperature at 27, 60 and 100oC. Unsaturated polyester matrix was used in this study to determine the interfacial shear strength (IFSS). The result shows that Weibull modulus of kenaf fiber interfacial shear strength (IFSS) at 30 minutes immersion duration value was 2.59 to 3.12 with characteristic strength, σo-IFSS value range was 0.29MPa to 0.37MPa. The highest Weibull modulus was at room temperature and 6% alkali concentration. For kenaf fiber tensile strength Weibull modulus, the range was 2.40 to 3.07 with characteristic strength value range from 345MPa to 597MPa. The highest Weibull modulus also was measured at room temperature and 2% alkali concentration. The characteristic strength value shows a degrading pattern with the increment on immersion temperature and alkali solution concentration

Two parameters Weibull analysis on mechanical properties of kenaf fiber under various conditions of alkali treatment

This paper present two parameters Weibull analysis result on mechanical properties of kenaf fiber under different condition of alkali treatment. The mechanical properties of kenaf fiber that as focused in this study was fiber matrix interfacial shear strength (IFSS) and fiber tensile strength (TS). Kenaf fiber were treated under various conditions alkali concentration at 2, 6 and 10 (w/v%), immersion duration at 30, 240 and 480 minute and immersion temperature at 27, 60 and 100oC. Unsaturated polyester matrix was used in this study to determine the interfacial shear strength (IFSS). The result shows that Weibull modulus of kenaf fiber interfacial shear strength (IFSS) at 30 minutes immersion duration value was 2.59 to 3.12 with characteristic strength, σo-IFSS value range was 0.29MPa to 0.37MPa. The highest Weibull modulus was at room temperature and 6% alkali concentration. For kenaf fiber tensile strength Weibull modulus, the range was 2.40 to 3.07 with characteristic strength value range from 345MPa to 597MPa. The highest Weibull modulus also was measured at room temperature and 2% alkali concentration. The characteristic strength value shows a degrading pattern with the increment on immersion temperature and alkali solution concentration

Emerging Natural Fiber-Reinforced Cement Materials and Technology for 3D Concrete Printing: A Review

Additive Manufacturing (AM) technology has been widely used in various industries like automotive, manufacturing and construction. The application of AM technology in the construction industry is a chance of significant improvement and advancement for constructing processes. AM is consist of creating layer by layer of slices to print 3-dimensional (3D) construction parts. In this regard, along with the technology and process of 3D printing in construction; many researchers worked on different materials included natural fibre reinforced cement for the 3D construction advancement. On such, the review has been done for 3D printing technology, process, latest machinery for construction, the construction flow process and emerging materials for 3D construction. For this, the most recent and critical research work since last 8-years was highlighted and argued. Different research articles and numerous latest reports from web blogs are used for furnishing this review work. Based on the review, few research gaps are discovered. Finally, the use of 3D printing in the construction industry depends on the accuracy of the printing job. Not only that, the availability of printing materials and the cost of the printing process and the time taken to print also become the factors in the technology revolution in the construction industry