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Molded Parts (molded + part)

Distribution by Scientific Domains

Polymers and Materials Science	62%

Selected Abstracts

Effects of nano- and micro-fillers and processing parameters on injection-molded microcellular composites

POLYMER ENGINEERING & SCIENCE, Issue 6 2005
Mingjun Yuan
The effects of submicron core-shell rubber (CSR) particles, nanoclay fillers, and molding parameters on the mechanical properties and cell structure of injection-molded microcellular polyamide-6 (PA6) composites were studied. The experimental results of PA6 nanocomposites with 5.0 and 7.5 wt% nanoclay loadings and of CSR-modified PA6 composites with 0.5 and 3.1 wt% CSR loadings were compared to their neat resin counterparts. This study found that nanoclay was more efficient in promoting a smaller cell size, larger cell density, and higher tensile strength for microcellular injection molding parts. A higher nanoclay loading led to more brittle behavior for microcellular parts. It was found that a proper amount of CSR particles could be added to the microcellular injection-molded PA6 to reduce the cell size, increase the cell density, and enhance the toughness of the molded part. However, CSR particles were less effective cell nucleation agents as compared to nanoclay for producing desirable cell structures, and a higher CSR loading was found to have diminishing effects on the process and on the properties of the parts. POLYM. ENG. SCI., 45:773,788, 2005. © 2005 Society of Plastics Engineers [source]

Real-time monitoring of injection molding for microfluidic devices using ultrasound

POLYMER ENGINEERING & SCIENCE, Issue 4 2005
Y. Ono
Real-time process monitoring of the fabrication process of microfluidic devices using a polymer injection molding machine was carried out using miniature ultrasonic probes. A thick piezoelectric lead-zirconate-titanate film as an ultrasonic transducer (UT) was fabricated onto one end of a 4-mm diameter and 12-mm long steel buffer rods using a sol gel spray technique. The center frequency and 6 dB bandwidth of this UT were 17 MHz and 14 MHz, respectively. A signal-to-noise ratio of more than 30 dB for ultrasonic signals reflected at the probing end was achieved. The probe can operate continuously at 200°C without ultrasonic couplant and cooling. Clear ultrasonic signals were obtained during injection molding of a 1-mm-thick part having test patterns on its surface. Shrinkage of the molded part and part detachment from the mold were successfully monitored. Surface imperfections of the molded parts due to a lack of the sufficient holding pressure is discussed with regard to the ultrasonic velocity obtained. The presented ultrasonic probes and technique enable on-line quality control of the molded part by optimizing the holding pressure and improvement of process efficiency by reducing the cycle time. POLYM. ENG. SCI., 45:606,612, 2005. © 2005 Society of Plastics Engineers [source]

Design and implementation of a process optimizer: a case study on monitoring molding operations

EXPERT SYSTEMS, Issue 1 2005
H.C.W. Lau
Abstract: To cope with the requirements of high dimensional accuracy for injection molding components, it is important to optimize the process parameters in order to sustain the high level dimensional quality of the molded parts. In this respect, a study in the domain of process optimization is of paramount importance in terms of determining the optimal set of injection molding parameters. To this end, a methodology to establish an integrated model which consists of both fuzzy logic reasoning and a genetic algorithm is proposed. These two artificial intelligence techniques can complement each other to form an integrated model which capitalizes on the merits and at the same time offsets the pitfalls of the involved technologies. To validate the feasibility of the proposed model, a case study related to injection molding optimization is also covered in this paper. [source]

Online control of the injection molding process based on process variables

ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2009
Walter Michaeli
Abstract The conventional control of the injection molding process is based on machine variables, which cannot sufficiently characterize the course of the process. Hence, a system that controls the injection molding process based on process variables has been developed at the Institute of Plastics Processing at RWTH Aachen University during the last years. It controls the quality determining process variable cavity pressure directly and realizes a desired course of cavity pressure in the injection and holding pressure phases. The cavity pressure course in the holding pressure phase is controlled online on the basis of pvT behavior of the processed plastic material. Thus, an optimal course of the process in the pvT diagram can be guaranteed and the quality constancy of the molded parts can be clearly increased. Using the pvT-based process control, the effect of varying mold and melt temperatures on the molded part weight can be decreased by about 90% compared with the conventional process control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:65,76, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20153 [source]

Minimizing the sinkmarks in injection-molded thermoplastics

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2001
Shih-Jung Liu
Injection molding is one of the most important methods for the manufacture of plastic products; however, there are several unresolved problems that confound the overall success of this technique. Sinkmarks occurring on the surface of molded parts caused by inappropriate mold design and processing conditions is one problem. In this report, an L'18 orthogonal array design based on the Taguchi method was conducted to minimize the sinkmarks of injection-molded thermoplastic parts. The polymeric materials used were general-purpose polystyrene and low-density polyethylene. A plate cavity with various ribs was used for molding. Experiments were carried out on an 80-ton reciprocating injection-molding machine. After molding, the sinkmarks on the surface of molded parts were characterized by a profile meter. For the factors selected in the main experiments, the corner geometry and the width of the rib were found to be the principal factors affecting sinkmark formation in injection-molded thermoplastics. A rib of an undercut geometry and a small width produces parts with the least sinkmark. Experimental investigation of an injection-molding problem can help illuminate the formation mechanism of sinkmarks so that steps can be taken to optimize the surface quality of molded parts. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 202,215, 2001 [source]

The occurrence of surface roughness in gas assist injection molded nylon composites

POLYMER COMPOSITES, Issue 2 2000
Shih-Jung Liu
Gas assist injection molding has increasingly become an important industrial process because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that limit the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composities. The materials used were 15 % and 35% glass-fiber filled nylon-6 composites. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. Two "float-shape" axisymmetric cavities were used. After molding, the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature, mold temperature, melt filling speed, short-shot size, gas pressure, and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness results mainly from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure. [source]

Spatial orientation of nanoclay and crystallite in microcellular injection molded polyamide-6 nanocomposites

POLYMER ENGINEERING & SCIENCE, Issue 6 2007
Mingjun Yuan
Three different types of characteristic structures-microcells, nanoclay, and crystallite lamella-exist in injection molded polyamide-6 microcellular nanocomposites. These structures are in completely different scales. The spatial orientation of these microscale structures crucially determines the material's bulk properties. Based on scanning electron microscopy, transmission electron microscopy, and two-dimensional X-ray diffractometry measurements, it was found that the nanoclay and the crystallite formed special geometric structures around the microcells and near the part skins. The nanoclay platelets lay almost parallel to the surfaces of the molded parts. Preferred orientation of the crystallites was induced by the presence of the nanoclay. A molecular-based model is proposed to describe the structural hierarchy and correlations among the microcells, nanoclay, and crystallite lamella. From the small-angle X-ray scattering experiments, it was found that microcellular injection molding produces relatively smaller crystallite lamella than that of conventional injection molding, and that for both solid and microcellular neat resin parts the crystallite lamella thickness at the part skin is smaller than that at the core. Polarized optical microscopy results also indicated that the size of crystallites in the microcellular neat resin and nanocomposite parts is smaller than that in the corresponding solid parts. POLYM. ENG. SCI., 47:765,779, 2007. © 2007 Society of Plastics Engineers [source]