Packing Stage Research Articles

Fabrication of nanopillar arrays by combining electroforming and injection molding

Injection molding is regarded as one of the cost-effective molding technologies to produce polymer items in large numbers. In this paper, a fabrication method for nanopillar arrays by combining electroforming and injection molding has been proposed. Mold inserts with satisfactory replication and high homogeneity have been electroformed by a self-designed micro-electroforming equipment. A variotherm injection molding technique with electrical heating and oil cooling has been realized for precise temperature control on mold cavity. It is shown that the mold cavity temperature can be represented by the measured temperature of the thermocouple installed in the mold. Nanopillars are found to be almost filled during the packing stage. Circular structures at the top of nanopillars have been observed under a lower packing pressure. As a key processing parameter, mold temperature is recommended as 25 °C higher than the polymer glass transition temperature. To ensure better replication quality of nano-patterns, the demolding temperature should be around 10 °C lower than the polymer glass transition temperature.

The Elastic Mold Deformation During the Filling and Packing Stage of the Injection Molding Process

The accurate numerical prediction of the mold filling process of long and thin walled parts is dependent on numerous factors. This paper investigates the effect of various influencing variables on the filling pattern by means of simulation and experimental validation. It was found that mold temperature, process settings and venting conditions have little effect on the predicted filling pattern. However, in the actual case study, the filling behavior observed during the experiments was significantly different compared to the numerical prediction. A structural finite element analysis of the moving mold half showed an unacceptable large deformation of the mold plates under injection pressure. A very good correlation between simulation and experiment was attained after improving the stiffness of the mold. Therefore it can be concluded, that the elasticity of the mold may have a significant influence on the filling pattern when long and thin walled products are considered. Furthermore, it was shown, that even an apparently stiff mold can exhibit a distinct deformation during filling and packing stage.

Quantifying food waste in Hawaii's food supply chain.

Food waste highlights a considerable loss of resources invested in the food supply chain. While it receives a lot of attention in the global context, the assessment of food waste is deficient at the sub-national level, owing primarily to an absence of quality data. This article serves to explore that gap and aims to quantify the edible weight, economic value, and calorie equivalent of food waste in Hawaii. The estimates are based on available food supply data for Hawaii and the US Department of Agriculture's (USDA's) loss-adjusted food availability data for defined food groups at three stages of the food supply chain. At its highest aggregated level, we estimate Hawaii's food waste generation at 237,122 t or 26% of available food supply in 2010. This is equivalent to food waste of 161.5 kg per person, per annum. Additionally, this food waste is valued at US$1.025 billion annually or the equivalent of 502.6 billion calories. It is further evident that the occurrence of food waste by all three measures is highest at the consumer stage, followed by the distribution and retail stage, and is lowest at the post-harvest and packing stage. The findings suggest that any meaningful intervention to reduce food waste in Hawaii should target the consumer, and distribution and retail stages of the food supply chain. Interventions at the consumer stage should focus on the two protein groups, as well as fresh fruits and fresh vegetables.

Property enhancement of PP-EPDM thermoplastic vulcanizates via shear-induced break-up of nano-rubber aggregates and molecular orientation of the matrix

In this study, in order to investigate the influence of melt shearing on the phase morphology and mechanical performance of PP/EPDM thermoplastic vulcanizates (TPVs), the oscillatory melt shear was successively applied on the TPV melt in the mold cavity during the packing stage of injection molding by a modified facility, called dynamic-packing injection molding. For a clear comparison, conventional injection molding was also used. It is shown that conventional injection-molding results in large EPDM rubber aggregates with dimensions of ∼1.5 μm dispersed in the PP matrix. To our surprise, well-dispersed nanoscale EPDM particles with dimensions of ∼40 nm have been achieved for the first time when introducing oscillatory melt shearing, in additional to a largely enhanced molecular orientation for PP matrix. As a result, a simultaneous improvement of tensile strength and elongation has been achieved for dynamic packing injection molded samples. In addition, step cycle tests showed typical “Mullins effect” for both conventional injection-molded samples and dynamic packing injection molded samples but improved fatigue resistance for dynamic packing injection molded ones. To isolate the contribution of PP matrix orientation and nanoscale EPDM particle on the tensile behavior of PP/EPDM TPVs, thermal annealing of injection molded samples were carried out to eliminate the orientation of PP matrix. It was found that the tensile strength is decreased but the elongation at break is maintained after annealing of dynamic packing injection molded samples. By comparing the property change before and after annealing, it is concluded that the orientation of PP matrix is in great favor of Young's modulus and tensile strength while the enhanced elongation at break is directly corresponding to the decreased rubber size and improved dispersion in TPVs. Our work demonstrates the strong effect of melt shearing on the breakup of rubber particles and matrix orientation of TPVs as well. The isolation of the contribution of PP matrix orientation and rubber particle size on the tensile behavior of TPVs provides guidance for the preparation of new TPVs with high performance.

A GENETIC ALGORITHM FOR THE ECONOMIC MANPOWER SHIFT PLANNING PROBLEM

A modified genetic algorithm (GA) is presented for the solution of the economic manpower shift planning (EMSP) problem. This is an NP-hard capacity planning problem arising in various industrial settings including the packing stage of production in process industries and maintenance operations. Given a set of independent jobs, their production targets, and a planning horizon, EMSP seeks the manpower to be planned for each workday shift in order to complete all the jobs within the specified time horizon at minimum cost. These are the key innovative aspects of the developed GA: (1) it uses a problem-specific encoding of the solution structure at the genotypic level; (2) it adopts a special greedy algorithm for mapping genotypes to phenotypes (i.e., to actual EMSP solutions); (3) it employs an adaptive parameter control scheme to adjust the mutation rate during its run. Extensive experiments over various industrial simulated environments and comparisons with the best existing EMSP heuristic (namely the block planning greedy algorithm) show the superiority of the proposed solution approach in terms of solution quality. Furthermore, comparisons to the results obtained by the standard CPLEX optimizer showed the proposed solution's performance to be very satisfactory.

The Mitochondrial Intermembrane Space Oxireductase Mia40 Funnels the Oxidative Folding Pathway of the Cytochrome c Oxidase Assembly Protein Cox19

Mia40-catalyzed disulfide formation drives the import of many proteins into the mitochondria. Here we characterize the oxidative folding of Cox19, a twin CX9C Mia40 substrate. Cox19 oxidation is extremely slow, explaining the persistence of import-competent reduced species in the cytosol. Mia40 accelerates Cox19 folding through the specific recognition of the third Cys in the second helical CX9C motif and the subsequent oxidation of the inner disulfide bond. This renders a native-like intermediate that oxidizes in a slow uncatalyzed reaction into native Cox19. The same intermediate dominates the pathway in the absence of Mia40, and chemical induction of an α-helical structure by trifluoroethanol suffices to accelerate productive folding and mimic the Mia40 folding template mechanism. The Mia40 role is to funnel a rough folding landscape, skipping the accumulation of kinetic traps, providing a rationale for the promiscuity of Mia40.

On the role of colloidal crystal-like domains in the film forming process of a carboxylated styrene-butadiene latex copolymer

Abstract Environmental scanning electron microscopy (ESEM) was employed to study the mechanism of film formation of a carboxylated styrene-butadiene latex copolymer with a glass transition temperature ( T g ) of 6 °C. ESEM allows the investigation of wet samples in their native state which is required to study the drying process of latex dispersions. The film forming process was tracked by time-dependent ESEM monitoring of the latex particle morphology and by observing the different stages occurring during the drying process. The focus of our study was an analysis of the three-dimensional (3D) arrangement of the latex particles and a comparison of their appearance on the surface and in the center of the coalesced film. It was found that in the course of film formation, the latex particles arrange in domains which are similar to colloidal crystals. Such domains occur at the stage of dense particle packing. Particle coalescence appears to begin first in these domains before a continuous and homogeneous film is formed which then spreads across the entire substrate. The results suggest that for our carboxylated styrene-butadiene copolymer the current model known for the film forming mechanism which includes four main steps should be complemented by two additional ones, namely the arrangement of particles in crystal-like domains and the beginning of coalescence within these domains. This specific behavior only occurs for monodisperse latices.

Efficient greedy algorithms for economic manpower shift planning

Consideration is given to the economic manpower shift planning (EMSP) problem, an NP-hard capacity planning problem appearing in various industrial settings including the packing stage of production in process industries and maintenance operations. EMSP aims to determine the manpower needed in each available workday shift of a given planning horizon so as to complete a set of independent jobs at minimum cost. Three greedy heuristics are presented for the EMSP solution. These practically constitute adaptations of an existing algorithm for a simplified version of EMSP which had shown excellent performance in terms of solution quality and speed. Experimentation shows that the new algorithms perform very well in comparison to the results obtained by both the CPLEX optimizer and an existing metaheuristic. Statistical analysis is deployed to rank the algorithms in terms of their solution quality and to identify the effects that critical planning factors may have on their relative efficiency.

The Elastic Mold Deformation During the Filling and Packing Stage of the Injection Molding Process

The accurate numerical prediction of the mold filling process of long and thin walled parts is dependent on numerous factors. This paper investigates the effect of various influencing variables on the filling pattern by means of simulation and experimental validation. It was found that mold temperature, process settings and venting conditions have little effect on the predicted filling pattern. However, in the actual case study, the filling behavior observed during the experiments was significantly different compared to the numerical prediction. A structural finite element analysis of the moving mold half showed an unacceptable large deformation of the mold plates under injection pressure. A very good correlation between simulation and experiment was attained after improving the stiffness of the mold. Therefore it can be concluded, that the elasticity of the mold may have a significant influence on the filling pattern when long and thin walled products are considered. Furthermore, it was shown, that even an apparently stiff mold can exhibit a distinct deformation during filling and packing stage.

Integrating Design for Assembly Guidelines in Packaging Design with a Context-based Approach

In the product lifecycle, the packaging, as an object, has been on the back burner with respect to product and production systems design and some authors stated that its influence starts at the packing stage and ends when the customer obtains the product.Only a few years ago, its strategic role, protecting, containing and preserving the product, has been recognized, both in theory and in practice [1]. In this way, the packaging design has been focused in the accomplishment of some specific objectives, such as cost and space saving, material reduction, and quality problems avoidance. These approaches are object-related, but the design process is not considering that the packaging is also utilized to handle, transport, distribute, retail and promote the product. Therefore, even if mathematical solutions could be obtained for space optimization problems, these could not be relevant at industrial level since they are unfeasible throughout the packaging lifecycle, from either logistics or quality standpoints; and new restrictions should be considered.An approach proposed by Lee & Lye [2], called “Design for manual Packaging (DFPkg)”, is based on Design for the Environment (DFEnv) and Design for Assembly (DFA) guidelines, since the activities related with packaging could be considered as assembly activities seeing that all the packed pieces are part of a unique system. Nevertheless, some guidelines from DFA are omitted or decontextualized and they are not connected to restrictions in the mathematical models.This paper presents an integral approach for packaging design, complementing the guidelines proposed by Lee & Lye [2] in key contexts of the packaging lifecycle, in order to generate restrictions for an optimization model. Besides, this approach has been validated with a real industrial case study where the obtained solution is compared with the current one.

Gender Distribution of Amalgam Restoration and Treatment Pattern in Regular Attendees of a Teaching Hospital in Nigeria

ABSTRACT Background Amalgam restoration has been the main procedure carried out over the last two centuries in spite of going through 2 major wars by those opposed to amalgam; however, it has been known that several factors affect it from the stage of titration, packing and finishing of the material but studies on the effect of gender on the treatment and distribution pattern are very scarce. Materials and methods This is a 12 years cross-sectional longitudinal retrospective study of dental records of patients who had attended the Dental Centre of University College Hospital, Ibadan, a Teaching Hospital located in the South West of Nigeria, regularly for a minimum period of 5 years. Results A total of 2,094 restorations were found to meet the criteria with males accounting for 691 (33%) and females 1403 (67%). When distributed into classes of restoration, females had more class I, II and V restorations placed (69.8%, 62.7%, 63.6%) more than males (30.2%, 37.3%, 36.4%) respectively. Females also had more primary placements and replacement done for all the classes of restorations. Conclusion More female patients attended the conservative dentistry clinic regularly more than their male counterparts and more females had higher number of restorations placed, however, there is a reduced female:male ratio in the subgroup of class II amalgam restorations. It was observed that the most frequent reason given in replacement of restorations was fractured amalgam restorations. How to cite this article Olaleye AO. Gender Distribution of Amalgam Restoration and Treatment Pattern in Regular Attendees of a Teaching Hospital in Nigeria. World J Dent 2014; 5(2):109-112.

Natural occurrence of fumonisins and ochratoxin A in some herbs and spices commercialized in Poland analyzed by UPLC–MS/MS method

Unsanitary conditions during harvesting, drying, packing and storage stages in production and processing of spices and herbs could introduce mycotoxin contamination. The occurrence of ochratoxin A and fumonisins in popular spices and herbs was studied, using liquid chromatography-electrospray-mass spectrometry. Apart from mycotoxins, ergosterol as a factor indicating fungal development was also analysed. A total of 79 different samples commercialized in Poland were randomly purchased from popular markets were tested for mycotoxins. The frequency of samples with fumonisins was lower (31%) than ochratoxin A (49%). Free from mycotoxins were samples of bay leaf and white mustard. ERG content – in spice samples with high concentration level of mycotoxins – was also significantly higher than in samples with little to no mycotoxins.

Numerical Simulation Research of Precision Injection Molding Control Method Based on P-V-T Properties of Polymers

Nowadays, with the rapid development of aerospace, auto, communication, consumer electronics and other fields, precision injection molding has been widespread concerned. P-V-T (Pressure-Specific-volume-Temperature) properties are inherent characteristics of polymers. In this paper, P-T parameters were set up in packing stage to achieve constant specific-volume control. Numerical simulation of P-V-T control strategy with Moldflow was carried out. Compared with conventional control strategy, the results showed that P-V-T control of precision injection molding could bring out more uniform density distribution, reduction in volume shrinkage and warpage of molded parts. It was concluded that the P-V-T control method could effectively improve the molding quality of the plastic product.

Formation of Interlinked Shish-Kebabs in Injection-Molded Polyethylene under the Coexistence of Lightly Cross-Linked Chain Network and Oscillation Shear Flow

It has been well established that the entangled molecular network facilitates the formation of shish-kebabs under flow field, however, the entangled network, usually formed by long chains, tends to disentangle due to molecular relaxation. In the present work, a small amount of lightly cross-linked polyethylene (LCPE), which can be considered as stable molecular chain networks, was added to short-chain polyethylene and then injection-molded using a modified injection molding technology-oscillation shear injection molding (OSIM), which can exert a successive shear field on the melt in the mold cavity during packing stage. The hierarchic structure of the OSIM samples was characterized through differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). It was found that the oscillation flow field promoted the formation of interlinked shish-kebabs in the intermediate layer of OSIM samples, while there are still typical spherulites in the core layer of OS...

Morphology and Crystallization Behavior of Compatibilized Isotactic Polypropylene/Poly(butylene terephthalate) Blends under Shear Flow

The blends of isotactic polypropylene (iPP) and poly(butylene terephthalate) (PBT) were prepared by using a special injection molding process named oscillation shear injection molding (OSIM). Morphology, crystallization behavior and molecular orientation were investigated systematically. The Scanning Electronic Microscopy (SEM) results showed that the dispersed PBT phase changed from sphere to fibril-like morphology in shear layer, due to the shear stress imposed during the packing stage. The interfacial adhesion of two phases could be enhanced by applying shear stress and could be further strengthened by the addition of compatibilizer. The crystallization behavior was investigated by the Differential Scanning Calorimetry (DSC). iPP/PBT blends showed higher onset crystallization temperature (To) and peak crystallization temperature (TP) than neat iPP, indicating that PBT phase can serve as a good heterogeneous nucleation agent for iPP crystallization. Moreover, the two-dimensional wide angle X-ray diffraction (2D-WAXD) revealed that the deformed PBT phase could cause iPP molecules around them to retain the orientation or to slow down the relaxation of iPP chains, and PBT phase facilitated the formation of α-iPP.

An experimental study on the effects of injection-molding types for the birefringence distribution in polycarbonate discs

Even though injection molding technology has been developed for many years, it is still needed to study the effect of processing conditions on the final properties of injection-molded parts for producing precision products in optical field. The optical anisotropy, i.e., birefringence, is a significant factor which affects the function of many optical components. In the present study, we have focused on the effects of packing and compression processes on the birefringence structure remaining in the disc by examining the gap-wise distribution of birefringence and extinction angle. As a result, two extra birefringence and extinction peaks near the center in thickness direction showed the effect of packing pressure, which came from the extra flow during packing stage. Furthermore, more uniform birefringence distribution was found in injection/compression case than in conventional injection-molded case. Depending on the process condition, even the reversal flow was found from the distribution of extinction angle in injection/compression case. Finally, graphical representation technique of optical refractive indicatrix was suggested to show the difference of final birefringence structure for different process types.

Internal characterization of denture base by using acrylic stains and tissue paper.

Characterization of an artificial denture is required to give the denture a more natural appearance. This article describes the laboratory procedures for internal characterization of denture base in a removable prosthesis using acrylic stains and absorbent tissue paper incorporated in the heat cure polymerizing denture base resin at the stage of packing.

Formation of Particle Layer Within Coated Slurry Characterized by Thickness Variation

An understanding of the conversion process from slurry to particle layer on a substrate is required for the precise control of the particle alignment and the material distribution in the coated slurry. In this work, variation of coated slurry thickness during drying was applied to evaluate drying and particle layer formation simultaneously. The slurry used consisted of micron-sized silica or poly (methyl methacrylate) particles and an aqueous solution of poly-vinyl alcohol (PVA) possessing differing degrees of hydrolysis. During the drying process, initially the thickness of the coated slurry was observed to decrease at a constant rate in the concentration stage, and subsequently it began to show large fluctuations due to the emergence of particles on the drying surface in the packing stage. In the final fixing stage, the fluctuation of film thickness was restricted because particles were immobilized by highly viscous concentrated PVA or by PVA molecule bridging. Based on the variation and fluctuation of film thickness, we introduced two characteristic dimensionless time ratios: (a) void fraction in a packed particle layer at the end of concentration stage; and (b) the time required to fix particle position after the end of the packing stage. We concluded that the dispersed state and settling velocity of the particle determines the space between particles in a loose packing layer, and we found that the distribution of polymers in a particle layer has a strong influence on the mobility of particles in a tightly packed layer.

Resource-constrained production planning in semicontinuous food industries

The resource-constrained production planning problem in semicontinuous multiproduct food industries is addressed. In particular, the case of yogurt production, a representative food process, in a real-life dairy facility is studied in detail. The problem in question is mainly focused on the packing stage, whereas timing and capacity constraints are imposed with respect to the batch stage to ensure the generation of feasible production plans. A novel mixed discrete/continuous-time mixed-integer linear programming model, based on the definition of families of products, is proposed. Timing and sequencing decisions are taken for product families rather than for products; thus, reducing significantly the model size. Additionally, material balances are realized for every particular product, permitting the detailed optimization of inventory and operating costs. Packing units operate in parallel and share resources. Qualitative as well as quantitative objectives are considered. Several industrial case studies, including also some unexpected events scenarios, have been solved to optimality.

A New Technique for Investigating the Process of Tablet Compression: A Preliminary Report

Abstract This preliminary report covers static tests involving the incorporation of an electrical conducting material in a tablet formula and subsequent recording during compression of the change in electrical resistance of the compact. An assessment of the experimental variables has indicated optimum conditions for making dynamic tests on an instrumented tablet machine and suggested more refined adaptations of the technique. Comparisons between this electrical property of the material and other properties such as relative volume, initial granule size, moisture content of the granules and crushing strength of the compact are presented. The resistance plots show evidence of change in the physical condition of the material under pressure; that is an initial packing stage followed by a brief period during which the granular structure is capable of supporting the imposed load without breakdown and finally gradual failure of the granules to give a compact mass.