摘要:

AbstractThe placement of a gate in an injection mold is one of the most important variables of the total mold design. The quality of the molded part is greatly affected by the gate location, because it influences the manner in which the plastic flows into the mold cavity. Some defects, such as weldline and overpack, can be effectively controlled only by the gate location. Therefore, the product quality can be greatly improved by determining the optimum gate location. In this paper, we develop a general methodology for gate location optimization. We first quantify quality in terms of flow simulation outputs. We can thus assess detrimental effects such as warpage and dimensional instability as a function of the independent variable, which is in this case the gate location. Next we develop methods to search for the optimum gate location. The search method introduced in this paper is a method that combines a deterministic hill climbing search with a stochastic annealing search method. The method is appropriately called simulated annealing and hill climbing (SANHIL). The criteria used for evaluation during the search process are a function of the flow simulation outputs. We demonstrate the success of the method for a complex industrial mold. The approach is applicable to any complex mold geometry and any plastic.

ISSN:0032-3888    

DOI:10.1002/pen.760301502

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe quality of an injection molded part is affected by many factors. These include geometric parameters associated with the mold design and the cooling system design as well as process parameters such as the molding conditions during the filling phase. In the companion paper, the problem of automatic optimization of gate location was addressed. In this paper, a methodology for molding condition optimization is presented. The optimization problem can be broken into three parts. An approximate feasible molding space (AFMS) is first determined to constrain the search space for the optimization algorithm. Quality is quantified as a function of flow simulation outputs and constitutes the objective function that must be minimized. The resulting optimization is solved by iterative search in the constrained space based on numerical optimization algorithms. The proposed methodology is not dependent on any particular simulation package and may be applied for any thermoplastic material and any complex mold geometry.

ISSN:0032-3888    

DOI:10.1002/pen.760301503

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Buss cokneader is a single‐screw extruder with interrupted flights. Pins from the barrel are inserted into the screw channel. The screw is both rotating and oscillating. Due to this action, screw flights are continuously wiped by the pins. During one passage of the pin, the material is not only subjected to high shear stress, but it is reoriented as well, thus promoting the distributive mixing process by the local weaving action of the pins and screw flights. Attempts to model the cokneader tend to focus on a single pin passing through the hole in a screw flight (1, 2). However, a more comprehensive model can start with the same equations that apply to the corotating twin‐screw extruder (3). Because the effect of leakage flows on the local pressure gradient has to be considered along with the effect of the local dragging action of the pins (neglecting the oscillatory action), experiments with model liquids have been performed to evaluate the comprehensive model. Additional experiments with a Plexiglas‐wailed cokneader support the calculations concerning filled lengths in various screw geometries. These results, and those of model calculations, which are extended to the nonisothermal, non‐Newtonian situation, are pr

ISSN:0032-3888    

DOI:10.1002/pen.760301504

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA methodological survey of coacervation/phase separation techniques employed for the preparation of microspheres and microcapsules is presented. Basic features of macromolecular coacervation are discussed, and a classification of different coacervation procedures (i.e., simple, complex, aqueous, and nonaqueous) is provided. Microsphere formation and microencapsulation techniques based on coacervation/phase separation of gelatin, gelatin‐acacia, and ethylcellulose are described, and those of a wide range of other polysaccharide derivatives and synthetic polymers are tabulated. The dependence of microsphere/microcapsule characteristics on manufacturing parameters and performance evaluation of microspherical/microcapsular products are also discusse

ISSN:0032-3888    

DOI:10.1002/pen.760301505

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA methodological survey of microsphere formation and microencapsulation techniques based on solvent extraction/evaporation techniques is presented. Thus, basic features of solvent extraction and solvent evaporation processes, including droplet formation, droplet/particle stabilization, and solvent removal, are outlined. Preparation of a wide range of microspherical and microcapsular products based on biodegradable polyesters, polysaccharides, and nonbiodegradable polymers are discussed. Dependence of microcapsule characteristics on manufacturing parameters, as well as performance evaluation of microspherical and microcapsular products, are also briefly covered.

ISSN:0032-3888    

DOI:10.1002/pen.760301506

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractAssumed is that there is no mass transfer among the droplets of reacting organic phase in a continuous vinyl chloride (VCM) suspension polymerization reactor. A mathematical model is thus developed to allow the calculation of steady states and the analysis of their dynamic stability. The results obtained are compared with those obtained with the hypothesis of perfect micromixing. It Is shown that both assumptions lead to similar dynamic structures, which confirms the complex behavior of these reactors. There are major differences, however, that can be exploited in future experimental work.

ISSN:0032-3888    

DOI:10.1002/pen.760301507

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA major factor that weakens the weld line in injection moldings is the V‐notch structure. Though the existence of a V‐notch is well known, its depth variation with molding conditions has not been detailed. The aim of this paper is to clarify the V‐notch structure and its effect on the strength of general purpose polystyrene injection moldings. A dog bone type tensile specimen with a weld line was molded under several molding conditions. The surface of the weld line was partially eliminated by cutting with a milling machine to seven levels of cut depth (Dc). As a result, the weld strength increased withDcto about 50%. The relationship between the weld strength andDcmade it possible to determine the V‐notch depth, which vas defined as the “depth of the weld line.” From these results, a hypothesis is proposed that the V‐notch has a structure with a fine groove on the surface and a poorly bonded inner layer. This study considered the relationships among the weld strength, the depth of the weld line, and moldi

ISSN:0032-3888    

DOI:10.1002/pen.760301508

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760301501

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY