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During an injection molding of composite materials, fiber attrition occurs and the average fiber length is reduced. In order to control the breakage of fibers and degradation of mechanical properties during processing, Flat glass Fiber (FF), that has oval cross-section shape, has been developed to use for glass fiber reinforced thermoplastic (GFRTP). Using FF as reinforcement of GFRTP has advantages as following: (1) Fluidity of FF is better than conventional Normal glass Fiber (NF) with 'circular' cross-section; (2) Fiber breakage during the injection molding process using FF is smaller than that using NF. In this study, the mechanical properties of FF and NF were compared for reinforcement of long fiber thermoplastics pellets (LFT pellets). We have also investigated the effect of screw design on fiber damage and the mechanical properties. The mechanical properties of specimens molded by FF reinforcement LFT (FF-LFT) pellets were superior to these of NF reinforcement LFT (NF-LFT) pellets. The former could give composites with higher fluidity and longer residual fiber length. Moreover, FF was able to strengthen injection-molded samples with higher fiber content than NF. Low shear type screw was effective to prevent the fiber attrition during plasticization process, hence leads to better mechanical properties of GFRTP

In recent years, from an environmental perspective, there has been increasing interest in the change to a sustainable society. The use of natural-fiber-reinforced biodegradable composites has been proposed as one solution. Bamboo is an often used renewable bio-resource; it has an inherent advantage of rapid growth. Polybutylene succinate (PBS), used as matrix resin, has biodegradable characteristics. This paper describes flexural properties of bamboo/PBS composites prepared by injection molding. The following results were obtained. The flexural modulus was improved with increasing bamboo powder contents when the cylinder temperature of the injection molder was 140°C. However, the flexural strength showed the opposite tendency to be decreased with increasing bamboo powder contents. An SEM photomicrograph of the fracture surface for bamboo/PBS composites showed typical fracture behavior of pull-out fibers without fiber fracture. Furthermore, there was no adhesion of PBS resin on the bamboo fiber surface. Processing conditions affected mechanical properties of bamboo/PBS composites, imparting higher flexural strength and flexural modulus at high cylinder temperatures such as 180°C and 200°C.

The application of additive manufacturing (AM) has increased exponentially in recent years. Industries are keen to explore this innovative technology but are apprehensive about the high processing cost of the process. Hence, it is crucial to carry out a cost analysis of the process. This paper presents an approach to compare the costs of an AM process (selective laser sintering (SLS)) and a traditional manufacturing process (injection molding (IM)) in the presence of uncertainties. Initially, the deterministic cost models comprising necessary cost variables for SLS and IM are described. The deterministic models are converted to fuzzy set-based models for tackling uncertainties. For this purpose, important uncertain variables are treated as fuzzy members and fuzzy arithmetic is employed. Only linear triangular fuzzy numbers are used in this work. Fuzzy cost estimates produce three values (low, most likely and high estimates) of cost corresponding to membership grades. A methodology to compare two fuzzy costs of the processes is proposed for a variable demand scenario. Concept of fuzzy reliability is suitably utilized and variability in demand is tackled from probability theory. Variable demand is assumed to follow uniform as well as normal probability distributions. The methodology is illustrated with the help of two examples.

The manufactured products that rely on molten Acrylonitrile Butadiene Styrene (ABS) via Tederic machine (450t) suffer from some types of defects such as black dots, shrinkage, and bubbles, which weaken the competitiveness. Therefore, this work proposes the Jidoka recruit’s network system (JRNS) to set optimal operating parameters to reduce the processes’ output variations and cut down on total process wastage autonomously. The suggested JRNS consists of two sequential stages. The first stage in front propagation relies on response surface methodology (RSM) in classifying the significant operating parameters from 15 candidates experimentally (DOE) to identify the most crucial one. The second stage predicts the processes’ deviation by integrating two meta-heuristic methods called harmony search (HS) and weighted superposition attraction (WSPA) in the backpropagation to automatically reset the operating parameters to keep the product within the standard specification to avoid 11 defect chances. JRNS is innovative and has been used to upgrade autonomous control for enhancing the Tederic machine (450t) process to reduce 70.98% of molding defects. The JRNS (RSM, $\mathrm{\text{WSPA}}+\mathrm{\text{HS}}$) increases the operation efficiency from 94% to 100% and reduces the defects per million opportunity to the six sigma scale.

A novel category of polyphenylene oxide/high-impact polystyrene (PPO/HIPS) alloy was used as the polymer matrix (abbreviated as mPPO) and loaded with different volume fractions (0, 10, 20, 30, 40, 50 vol.%) of MgTiO₃–Ca${}_{0.7}$La${}_{0.2}$TiO₃ (abbreviated as MTCLT) ceramics to prepare composites by injection molding. Its micromorphology, density, dielectric, thermal and mechanical properties were analyzed in detail. The experimental results show that the composites possess a compact microstructure because HIPS increases the fluidity of PPO. Due to the excellent dielectric properties of both mPPO and MTCLT, the composites have an extremely low dielectric loss. The realization of the high ceramic filler fraction greatly limits the thermal expansion of the polymer chain by introducing the interphase, so that the coefficient of thermal expansion of the composite material could be as low as 21.8 ppm/${}^{\circ }$C. At the same time, the presence of ceramic particles could reinforce the mechanical property of the composites. When the ceramic filler fraction is higher than 20 vol.%, the bending strength of the composite material is around 110 MPa. When the ceramic filler fraction is 40 vol.%, the composite possesses the best comprehensive performance. The dielectric constant is 6.81, the dielectric loss is 0.00104, the thermal expansion coefficient is as low as 25.3 ppm/${}^{\circ }$C, and the bending strength is 110.4 MPa. Due to its excellent properties, this material can be a good candidate in the field of microwave communication.

Injection compression molding (ICM) with high aspect ratio surface features was performed to clarify the effect of molding conditions on replication characteristics and molecular orientation distribution. Short-shot defects and surface replication were better when using ICM than when using conventional injection molding. A long compression stroke and short delay time condition were optimum conditions to used to achieve uniform surface replication. Molecular orientation was also reduced by the long compression stroke. To reduce molecular orientation, the compression motion should be carried out immediately after injection motion in the case of 0.2 mm thickness. For 0.6 mm thickness, the compression motion was conducted after the shear stress relaxation to reduce the molecular orientation. Short-shot tests revealed distinctive replication behavior in ICM. Results show that replication behavior and local molecular orientation are generated by a slightly frozen layer at the filling area before compression.

Microfluidics is a multidisciplinary technology which enables the face-lift crossing a wide range of applications such as life science research, point-of-care diagnostics and personal medicine. Polymer materials, especially thermoplastics, are dominating this emerging market due to the low material cost and the ease of mass production. This paper reviews the major fabrication technologies for making polymer, especially thermoplastic microfluidic chips, such as micro tooling, injection molding, bonding and surface treatment. The paper also summarizes the key challenges in fulfilling the needs of next generation microfluidic products.

In recent years, increased attention has been shifted to the design of cooling systems in the injection molding process, as it becomes clear that the cooling systems affect significantly both productivity and the part quality. In order to systematically improve the performance of a cooling system the mold designer may need a computer aided optimal design system for designing the injection mold cooling systems and determining the process conditions during the cooling stage. In this chapter, an efficient optimization procedure for this problem is proposed utilizing (i) the special boundary element analysis, (ii) the corresponding design sensitivity analysis using the direct differentiation approach, and (iii) the optimization algorithm. For this optimal design, an objective function is proposed to minimize a weighted combination of the cooling time and the temperature nonuniformity over the part surface. The former has to do with the warpage in the final part, while the latter is directly related to the overall productivity of the injection molding process. In this optimization program, various design variables are considered as follows: (i) (design variables related to processing conditions) the inlet coolant bulk temperature and inlet coolant volumetric flow rate of each cooling channel and (ii) (design variables related to mold cooling system design) the radius and location of each cooling channel. Each step of the proposed optimization procedure will be briefly explained below. First, in thermal analysis, mold heat transfer is considered as a cyclic-steady, three-dimensional conduction; heat transfer within the melt region is treated as a transient, one-dimensional conduction; heat exchange between the cooling channel surfaces and the coolant is considered to be steady; heat exchange between ambient air and mold exterior surfaces is also considered steady. Numerical implementation includes the application of a hybrid scheme consisting of a modified three-dimensional boundary element method for the mold region and a finite difference method with a variable mesh for the melt region. However, it was found that seemingly negligible inaccuracy in the thermal analysis result sometimes lead to a meaningless sensitivity analysis result. In this study, the thermal analysis system based on the above-mentioned modified boundary element method has been improved and rigorous treatments of boundary conditions appropriate for sensitivity analysis have been developed by considering the following issues: (i) numerical convergency, (ii) the series solution in part thermal analysis, (iii) the treatment of tip surface of line elements, (iv) the treatment of coolant, and (v) the treatment of mold exterior surface. Using an example, the importance of these issue is amply demonstrated. Next, the sensitivity analysis program developed in the present studies utilizes the implicit differentiation of the boundary integral equations and the boundary conditions presented in thermal analysis with respect to all design variables to obtain the sensitivity equations. A sample problem is solved to demonstrate the accuracy and the efficiency of the present sensitivity analysis formulation as well as to discuss the characteristics of each design variable. Finally, the CONMIN algorithm is applied for the optimization program with the help of the above thermal analysis and corresponding design sensitivity analysis. In this optimization program, the proper constraints imposed upon the design variables are considered to maintain design reality. The CONMIN algorithm employs the augmented Lagrangian multiplier method to deal with the equality constraints and the Davidon–Fletcher–Powell method for the unconstrained minimization during the successive unconstrained minimization procedure. Two sample problems were solved to demonstrate the efficiency and the usefulness of the objective function. The developed computer aided optimal design system would be very useful for injection mold designers in obtaining an optimal configuration of an injection mold cooling system in terms of radii and locations of cooling channels, as well as determining the optimal processing conditions of the cooling stage in terms of the inlet coolant bulk temperature and the inlet coolant volumetric flow rate of each cooling channel by minimizing certain objective functions related to the part quality and/or the productivity in the injection molding processes.

Mold temperature plays an important role in injection molding technology. The heating process for electric hating and steam heating methods are numerically compared. The results suggest that the steam heating technique provides much higher short-term heating efficiency, while the electric heating method supplies higher long-term temperature. The steam heating method presents higher effectiveness than the electric heating method.