Sheng-Hong Pong

In-line viscosity control in an extrusion process with a fuzzy gain scheduled PID controller

In the extrusion process, rapidly tracking the set point of quality factor and eliminating its variation to reduce the off-specification product is important. In this study, the fuzzy gain-scheduled proportional-integral-derivative (PID) controller is used to control the melt viscosity during extrusion processing. A second-order model related to the viscosity and the extruder screw speed is developed empirically to approximate the extrusion system. It is concluded that, in comparison to the well-known Zeigler-Nichols PID tuning control scheme, the performances of the proposed control strategy is preferable both in simulation and implementation.

In-line viscosity fuzzy control

A fuzzy control strategy on viscosity of a polymeric melt during the extruding processes is proposed to ensure producing the quality-consistent end products. Because the viscosity model in the control system varies with respect to different conditions of the system command (e.g., screw speed), we focus on using a fuzzy controller accomplished with a fuzzy modeling technique to solve the model-variant viscosity control system. Also, system stability analysis is presented. According to the simulation and the implementation results, better performances and a suitable using method are concluded.

Development of an in‐line viscometer in an extrusion molding process

In this work, an in-line viscometer to measure the viscosity of polymer melts under extrusion molding processes was developed. The in-line viscometer contains a stress sensor and a shear rate sensor which were installed between the screw and the die of an extruder. In this way, the flow line after the screw cannot be changed, unlike the present in-line capillary rheometer which can change the diameter of the pipe of the flow line and hence influence the throughput. All data acquisition is done by a computer such that the melt viscosity can be calculated automatically. The shear-thinning behavior of a low-density polyethylene (LDPE) under three different temperatures is presented in all experiments. It is concluded that the melt viscosity can be effectively monitored.

A study of photomask correction method in area‐forming rapid prototyping system

Purpose – The purpose of this paper is to present a novel photomask auto‐correction method for the area‐forming rapid prototyping (RP) system.Design/methodology/approach – A digital light processing (DLP) projector was used in this research as a light source to generate the photomask image. A set of optical lenses were mounted in front of the DLP to rescale the photomask image. The rescaled photomask image was collected into a computer via a camera. By using the technique of image processing, the actual size of the photomask was then calculated. The designed size of the photomask image was eventually achieved by adjusting the relative locations of the lenses.Findings – It was found that this proposed photomask auto‐correction method can produce a more accurate dimension of the photomask image and perform with higher efficiency than the manual calibration processes.Originality/value – The paper is believed to be the first work to use the image‐processing technique to calibrate the photomask of an area‐form...

Mechanical and thermal properties of photopolymer/CB (carbon black) nanocomposite for rapid prototyping

Purpose – The purpose of this paper is to evaluate the mechanical properties of photopolymer/CB (carbon black) nanocomposite when applied in a visible-light rapid prototyping (RP) machine. Design/methodology/approach – The mechanical properties of the samples such as hardness and tensile strength along with thermal stability were analyzed. The curing time behavior of the photopolymer/CB nanocomposites was tested by using a rigid-body pendulum rheometer. The shrinkage property and dimensional stability were also analyzed using the technique according to ASTM D2566 and ASTM D1204, respectively. Findings – The results showed that the prototype fabricated from pristine photopolymer tended to exhibit poor mechanical properties and low thermal stability. However, after adding the photopolymer with various concentrations of nano-CB and dispersant in appropriate composition, the photopolymer/CB nanocomposite prototype not only reduced its curing time but also enhanced its mechanical properties, thermal stability ...

Development of an on-line twin capillary rheometer

On-line capillary rheometers have been extensively used as a means of measuring the flow properties of polymeric melts during processing. But, none of them implemented both the Bagley and the Rabinowitsch corrections. In this work, an on-line twin capillary rheometer was developed in an attempt to measure the true viscosity for polymer characterization. The system was designed to achieve automatically rheological measurements. It was also equipped on a single screw extruder to verify its practicability. It is pronounced that using the on-line twin capillary rheometer would be more timesaving and manpower saving than use an off-line capillary rheometer.

Morphology and properties of a photopolymer/clay nanocomposite prepared by a rapid prototyping system

Abstract This study represents an in situ polymerization by preparation of tetrafunction polyester acrylate mixed with 1,6-hexanediol diacrylate/clay nanocomposite by digital light processor rapid prototyping. The morphology of nano-clay fillers and the dispersing agent in the photopolymer matrix are investigated by scanning electron microscopy (SEM). Degradation temperature, tensile strength, impact strength, and hardness are characterized by using thermogravimetric analysis, universal tensile machine, Izod impact tester, and hardness shore A tester, respectively. Results show that the effect of clay loading with an appropriate amount of dispersant tends to significantly increase not only the tensile strength and hardness but also the degradation temperature of photopolymer/clay nanocomposite; however, the impact strength is not affected. In the same conditions, as visualized on SEM images, the nanocomposite tends to form the exfoliated structure with agglomeration of clay, which is caused by uneven distribution of nano-clay in the photopolymer matrix.

Multi-objective optimization of process parameters in an area-forming rapid prototyping system using the Taguchi method and a grey relational analysis

The rapid prototyping technique has been developed over several decades. As the application becomes more widespread, the qualities of the parts produced by a rapid prototyping system must be considered. The area-forming rapid prototyping system is an emerging technology. This system has the advantage of a short build time but displays a weakness in the dimensional accuracy and surface roughness. To improve these weaknesses and simultaneously maintain a short build time, this study optimizes the process parameters using the grey relational Taguchi method. From the results, the best combinations of process parameters both for each quality and for multiple qualities are discovered. The optimization of process parameters is verified using the extra samples.

Estimation of the ends pressure drop in an online capillary rheometer—using the neural network approach

Using an online or inline capillary rheometer as a tool of rheology measurement would come into the ends pressure drop problem. In order to derive the actual pressure drop of the capillary, another capillary with the same diameter and different length is needed (according to Bagley correction) but would result in a more complex mechanism. In this study, a neural network approach is proposed to estimate the ends pressure drops in an online capillary rheometer. The back propagation learning algorithm is used for network training. The shear rate, the die pressure, and the ratio of diameters of the reservoir to the capillary are taken as the neural network inputs, and the ends pressure drop is taken as the output. Two hundred of training sets that are made from a laboratory capillary rheometer are used for network training. The trained neural network can be consequently applied to real-time assessment of the ends pressure drops in the online capillary rheometer. It is concluded that using the proposed method for calculating the ends pressure drop is effective. Besides, the simplicity of the mechanism provides good portability for both online polymer characterization and quality control in processing.

Effect of nano-BaTiO3 on thermal, mechanical, and electrical properties of HDDA/TPA photopolymer prepared by a digital light processor RP machine

Abstract The acrylate-based photopolymer consists of tetra-functional polyester acrylate (TPA), and hexanediol diacrylate (HDDA) has been successfully composited with nano barium titanate (BaTiO3) and completely cured via a digital light processor RP machine. The degradation temperature, tensile strength, hardness, resistivity, and dielectric constant of samples were characterized by Thermo Gravimetric Analyzer Hi-Res TGA2950, Universal Tensile Machine JIA701, Hardness Shore D tester, Fluke 117 multimeter, and Agilent B1500A Semiconductor Device Analyzer, respectively. The morphology changes of the samples were also investigated using the JEOL JSM-6390LV scanning electron microscopy (SEM). The results show that the improvement of degradation temperature is not obvious. Furthermore, the modulus elasticity, hardness, and dielectric constant increase as the filler loading increases up to 2 phr, but the resistivity is vice versa. Interestingly, there is an inverse correlation between dielectric constant and resistivity of photopolymer/BaTiO3 nanocomposite.