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It is well known that gas permeability of packaging is a key element for improving food shelf life [1]. In order to achieve desired gas barrier for specific gas species as well as maintain other physical properties and being cost efficient, multilayer structures are widely used in packaging industry to meet different requirements. It is a trend that the industry is transforming from monolayer structure and 3-layer structure to 5-layer structure, 9-layer structure and even 11-layer structure [2]. Multilayer structures not only provide flexibility for manufacturers to apply various functionalities, but also potentially reduces the cost of complex packaging systems. However, multilayer co-extrusion process itself is sometimes a challenge for many producers. In this study, an alternative technique, which produces materials with layer-like morphology is reported. These materials are innovatively formulated and engineered so that multilayer-like morphology arises after they are simply extruded through a single extruder. These materials can be used as monolayer films or co-extruded with other polymers. Good gas barrier (both OTR and WVTR) properties are discovered for these materials. Nevertheless, these materials depending on the specific grade can be used for cast film, blown film and biaxially-orientation film.
Accurate understanding of changeover time (i.e., the time it takes to change formulations) in a blown film line can minimize waste and maximize production. Previous work examined changeover time in extruders, and residence time distribution for blown film [Wang et. al., ANTEC Tech. Papers, 2015, Wang et. al., ANTEC Tech. Papers, 2017]. This work uses transmission UV-Vis spectroscopy with a copper phthalocyanine tracer to examine the factors affecting changeover time for a blown film line. Our results show that throughput is the strongest factor influencing changeover time, and material rheology is a weaker but potentially important factor.
Much of transparent, flexible high-barrier packaging film is based on biaxially oriented polypropylene (BOPP). The biaxial orientation process improves the barrier to both oxygen and water vapor; yet this must be combined with other layers or an organic coating to satisfy the product requirements. This paper reports on further improvements of 40% in barrier to both oxygen and water vapor in BOPP-NC over BOPP after incorporating a masterbatch additive based on nanoclay into the polypropylene. The biaxial orientation was carried out on extruded sheets of 300 micron thickness with a Karo IV apparatus. The maximum area stretch ratio achieved during biaxial stretching of the resulting compound was equal to that obtained with the base polypropylene. TEM showed that the dispersion of nanoclay was maintained after the biaxial stretching while XRD studies revealed that the crystalline lamellar width in the BOPP-NC was larger than in BOPP.
A novel polyethylene product was developed for making biaxially oriented polyethylene (BOPE) films via a commercial scale tenter frame line. As compared to the conventional polyethylene grade with a similar density and a similar melt index, the novel polyethylene could be stretched to 5x in the machine direction and 9x in the transverse direction in a wide temperature window. The BOPE film exhibited higher modulus, higher dart and puncture impact strength, easier tear, and better optical properties than the incumbent blown film used in lamination film applications. A laminated film with a BOPE layer was also evaluated and compared to the incumbent film that had a biaxially oriented polyamide layer. The BOPE laminated film showed equivalent performance at a lower film cost.
A method to measure oxygen permeance in a sealed flexible packaging, based on ASTM F2714 – 08 (standard test for oxygen headspace analysis of packages using fluorescent decay) is proposed. This method allows to consider the effect on the barrier properties of the sealing integrity, the packaging geometry and the defects due to handle or quality issues (pinholes, wrinkles, among others). This kind of measurements are relevant for the adequate design of packaging, a better estimation of the shelf life and the evaluation of quality problems. Traditionally, the oxygen permeance and oxygen transmission rate (OTR) in packaging films are measured using the standard coulometric method (ASTM D3985). In this method, the samples are taken from the roll or cut from a complete package. In this case, oxygen permeance is measured under ideal conditions, without considering the real packaging application scenario. Oxygen permeance measurements on four different barrier-level packages were carried out with the proposed method and with the standard coulometric method. Results are compared and the advantages and disadvantages of the proposed method are described.
Recently, many automation technologies and equipment are applied for new injection molding systems to execute automation for Industry 4.0. However, there are also a huge numbers of the existed injection machines or systems which are not ready for automation yet. Indeed, before automatic manufacturing, how to retain good quality is one of the crucial factors in injection molding. In this study, we have focused on how to discover the under-performance problem of some existed injection machine to face the automation challenge using CAE technology. In the real testing case, we have demonstrated that CAE simulation prediction can be regarded as the ideal target for manufacturing. Furthermore, it is also estimated the difference between simulation prediction and real experimental result quantitatively. However, after careful comparison on the amount of the driving force to generate deviation from the target, the real experimental result presents almost the same trend and the same amount as numerical prediction did. Moreover, we also tried to compensate the under-performance of the real experiment using a series of packing pressure settings suggested by numerical simulation. Results showed that quality can be improved significantly.
Plastic injection molding has become an important technique in traditional industry in recent years. In the process of injection molding, many manufacturers rely on the experiences of skilled workers, rather than utilizing an efficient method to eliminate processing defects, resulting in difficulties in quality control and increased total cost. To solve the problem of defect removal effectiveness, computer-aided engineering (CAE) is often employed, which can eliminate molding defects, through simulation analysis, before manufacturing. However, some unpredictable problems remain during the actual molding, which require the assistance of field technicians.The outcomes of injection molding, which involve injection pressure, cooling time, and warping deformation, have an intricate connection with control factors, which cannot be classified by regular linear programming. Back Propagation Neural Network (BPNN) has excellent predictive ability in solving non-linear problems. It can accurately predict the results after executing a series of training data. This study combined the orthogonal Taguchi Method and BPNN to construct a computing system for predicting the analysis result of CAE, and analyze the influence of multi-layer structure on prediction accuracy. The results showed that using the Taguchi Method to optimize the parameters of BPNN can increase the accuracy of prediction. Using the optimized network parameters can reduce the prediction error of the maximum injection pressure and maximum cooling time to less than 1%. However, there is still an error of 7.26% for the prediction on warping deformation, which demands further investingation of training data.
Thin polymeric microfluidic chip design (chip thickness 0.6mm or less) is desired for lab-on-chip device due to rapid heat transfer across thickness direction. This feature results in better bonding property and temperature control during diagnostic analysis. It also offers good optical properties for the observation of fluidic mixing, filtering and reaction in the multi-layer and multi-functional chip design. However, polymer melt filling for thin chip poses great challenges as the frozen layer along melt flow path is built up rapidly for conventional injection moulding process. Some moulding defects may associate with thin chip design such as short shot, warpage, thickness variation and birefringence etc. In this paper, a series of Moldflow simulation studies were conducted to virtually investigate the effects of thin chip melt filling characteristics for both conventional injection moulding (CIM) and injection compression moulding (ICM) processes. The simulation results show that injection compression process is an enabling moulding technique for a polycarbonate (PC) based 0.6mm polymeric micro reactor chip design. Compared to CIM process, there is more than 30% improvement on chip micro feature replication accuracy and chip deflection.
This is an invited paper for the Join IMD-PD3 Session.For a plastic part or assembly to perform as expected, proper consideration must be given to material selection, part design, tooling, and processing. In many instances, design errors are misclassified as tooling, processing or material issues. It is also not uncommon to attribute design related failures to customer abuse! As an example, a sharp transition in the wall thickness can cause:- Flow marksMisclassified as poor gate design or location, inadequate cooling, too little or too much holding pressure, high injection speed causing chain breakdown or pigment degradation, contamination, etc.- Poor chemical resistance and cracks Misclassified as the chemical resistance of the material- Failure in dropMisclassified as processing issues causing high molded stresses, material weakness, customer abuse, etc.- WarpageMisclassified as uneven packing pressures, poor cooling, etc.Numerous actual parts will be shown to illustrate the foregoing.
In a magneto-Archimedes levitation device, a three-dimensional (3D) injection molded part can be levitated with a posture that is closely related to its shape and internal defect. Here, a novel, non-invasive characterization method for 3D injection molded parts via magneto-Archimedes levitation is proposed. FLUENT-EDEM multiphase software was used to simulate the levitation process of the 3D part. Through the results of the EDEM software, the curves of the levitation height, equilibrium posture, and potential energy versus simulation time were obtained. The final levitation height and the equilibrium posture of the part were determined by the principle of minimum potential energy. Several experiments with vari¬ous 3D parts and different internal defects were carried out to verify the proposed method. Experimental results showed that the proposed method had high accuracy in measuring equilibrium posture and levitation height. For defective parts with small voids (2 mm3), the maximum deviation between the calculated tilt angles and the exper¬imental results was less than 4.7°. In general, the proposed method has the potential of broad application in the non-invasive characterization of injection molded parts.
In the article, we discuss a new fiber orientation model (Ci-D3) for prediction of fiber orientation in plastic composites during injection molding. We also compare fiber orientation predictions of the new model with: Folgar-Tucker (FT) and Reduced Strain Closure (RSC) with two different closure approximations (Hybrid and Orthotropic). Ci-D3 with Orthotropic closure approximation has shown predictions closest to the experiment followed by RSC with Orthotropic closure. Using Ci-D3 with Orthotropic instead of FT with Hybrid closure allows to halve average discrepancies between experimental measurements of fiber orientation and computer predictions.
In many industrial applications such as automobiles,aircraft and home appliances, it is essential to meet tight dimensional tolerances after injection molded components are mounted into the designed position. The prediction of the final deformation and stress of the components after the assembly normally requires a combination of warpage analysis, an interface between warpage analysis and structural analysis and a separate structural analysis, as the process-induced and assembly-induced deformation are calculated sequentially. A much simpler approach is developed for predicting the final deformation and residual stress, which only requires a warpage analysis with specially calculated boundary constraints. It has been implemented in three widely-used modelling methods in injection molding simulation: the midplane shell model, dual-domain shell model and three-dimensional tetrahedral model. Two numerical examples are given to illustrate the effectiveness of the approach. This proposed approach provides an easy and valuable tool for predicting the amount of geometric deviation between the final mounted component and the original design.
The temperature control of molding tools, in this case injection molding, plays a critical role in the quality of manufactured plastic articles. Key parameters such as shrinkage, warpage, crystallinity, etc. can be significantly influenced by the temperature control concept. Variothermal process control in particular delivers good results in terms of flow path length and part quality. For tools in the small to medium size range, these structures can be additively generated by methods such as selective laser sintering. For large workpieces however, such as automobile bumpers or containers, the currently available manufacturing technologies reach the limits of their geometry. Up to now, it has not been possible to additively manufacture such large-format tools while generating temperature control channels at the same time. This paper presents a method of manufacturing large-scale mold tools with temperature control channels by combining the additive manufacturing techniques of arc welding and diffusion bonding with conventional processes.
The demand for innovation within the plastics industry has led to a large variety of specially adapted production processes. Meeting the requirements for lightweight and complex shaped part geometries the special injection molding process GITBlow was invented by the Kunststofftechnik Paderborn a few years ago. The process consists of the production of a preform via gas-assisted injection molding (GAIM) and a secondary gas injection for a further inflation of this preform within a larger cavity. In this paper the focus is set on the second gas injection and the inflation behavior of the preform. Despite the similarities between this step and conventional injection blow molding, there are some distinctive differences concerning the temperature level and temperature distribution prior to the inflation. In a systematic approach with several materials and process settings, a process characteristic strain rate profile is determined using a specially adapted mold. Using the laws of fluid dynamics, the measured profiles are analyzed in more detail.
Microstructured surfaces offer a high potential for use in the injection molding process. On the one hand, structures can be utilized to functionalize molded parts during the molding process and on the other hand, to manipulate the flow properties of the plastic melt in the mold. The following work addresses the development of an integrative simulation methodology, which will allow for predicting the replication quality of structures from steel to plastic part, thus enabling the efficient development of customized microstructures.The selected model approach achieved a good representation of the structure replication in plastics based on process settings and structure geometry. Furthermore, the main influencing factors on the structure replication were determined and statistically evaluated. Using this model and an integrative link to a commercial injection molding simulation software, it is already possible to predict the local degree of replication of microstructured surfaces.
The achievement of an adequate accuracy of the micro injection molding (μIM) process applied to the replication of micro-features is a complex task. The selection of parameters influences the filling performance as well as the replicated quality of micro-features and local mechanical property. In this paper, the relationship between process parameters, filling morphology of micro-features and mechanical property were investigated based on DOE method. It was found that the biggest contribution of process parameter to replicated quality for micro feature parallel to flow direction was hold pressure, while mold temperature had the most influence on replicated ability for micro feature perpendicular to flow direction. Local mechanical properties were also different between two arrangements of micro features and substrate in the same micro part. The micro feature with high filling height had a smaller modulus than that with low filling height. The modulus on substrate were bigger than that on micro features. Meanwhile, mechanical property on substrate had no relationship with the arrangement of micro features.
Warpage is an important indicator when evaluating the quality of an injection molding product. How to control the warp within tolerance is a critical issue concerned by designer and molder. Accurate computer aided engineering (CAE) warpage prediction helps designer to find the best design from different prototypes quickly at the beginning of development, decreasing the cost. However, the warpage is the final result affected by several factors during injection molding, for instance material, injection machine, part and mold design. Hence, an accurate warpage prediction must take these factors into consideration comprehensively. The real machine response is compared with filling pressure to verify whether the flow simulation is accurate enough as input parameter of following warpage prediction. Unlike linear warpage calculation simply based on material PVT property, Moldex3D solver considers material viscoelasticity to simulate the significant modulus change when polymer transits from rubbery phase to glassy phase. Together with in-mold constraint and free deformation after ejection in warpage calculation, the warpage prediction shows high agreement with real box product on three different materials, PS, PC and PP.
The microcellular injection molding process is widely used in the automotive, packaging, sporting goods, and electrical parts industries. The Mucell® process offers many advantages such as material and energy savings, low cycle time, cost effectiveness, and dimensional stability of products. Thermoplastic Polyurethane (TPU) is a common material for molding the outsole of shoes because of its outstanding properties such as hardness, abrasion resistance, and elasticity.Though many shoe manufacturers have begun applying Mucell® processes to TPU midsoles manufacturing, in moving to mass production, problems remain. The main problem is the uniformity of the cell size in the midsole. The cell size is affected by injection process induced pressure drops which lower the cell size uniformity in different regions and reduce the bouncing properties of the material. To address this problem, gas counter pressure technology was used to achieve a uniform cell size distribution midsole in the Mucell® process in this study.
Quality optimization is a common concern in injection-molded products. The relation between pressure, specific volume and temperature is a key property in polymer processing. Because of the unpredictability of this relationship, it is difficult to mold products while maintaining quality in volume production. Traditionally, the most common approach to troubleshooting is for an experienced operator to adjust parameters repeatedly. Based on the PVT theory, this study created a practical PVT control technology using an infrared temperature sensor with pressure sensor in the mold. This method was then used to investigate the effect of molding parameters on the controllability and optimization of product quality.Results show that the PVT curves are constant under consecutive molding cycles and reveal the effect of molding parameters on quality controllability. Specific volume is directly related to product properties such as shrinkage, weight, and warpage. Three control methods for optimizing product quality were also investigated. The dynamic PVT control method molds parts with the smallest total shrinkage, heaviest weight, and least warpage. For molding stability, the PVT control method maintains constant product weight, shrinkage, and warpage.
As industries transition, the application of composite materials has expanded. Composite materials manufacturing processes and technologies have become a focus of technology research and development. For fiber composite materials, since the fibers affect product properties, controlling them is a key to improving product performance. In this study, conductive paths were formed by adding nickel-coated carbon fiber to give the products electrical conductivity. In combination with a permanent magnet mold, experiments were conducted to verify whether the external magnetic field had an effect on the fiber orientation during filling. In the experimental part, the external magnetic field was ineffective due to cooling. Therefore, injection molding parameters such as temperature (melt temperature, mold temperature) as discussed herein. To understand whether there is an external magnetic field for the fiber orientation tensor, the influence of different parameters on the fiber orientation tensor and the through-plane conductivity under the condition of external magnetic field are explored.
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