Injection Mold Cavity Research Articles

An experimental analysis on thermal performance of interloping threaded cooling channels in injection mold cavity

An experimental analysis on thermal performance of interloping threaded cooling channels in injection mold cavity

Post-Molding Shrinkage, Structure and Properties of Cellular Injection-Molded Polypropylene.

Cellular injection molding is a common method of modifying polymer materials aimed at reducing the sink marks on moldings’ surfaces while reducing their weight. However, the dimensions of polypropylene (PP) samples as well as their mechanical properties after the injection molding process change as a result of re-crystallization. Knowledge of dimensional accuracy and awareness of the change in mechanical properties of products during conditioning are very important aspects in the polymer processing industry. The aim of this study was to assess the changes in the value of processing shrinkage and the size of the sink marks of porous PP moldings depending on the degree of porosity and the time since they were removed from the injection mold cavity. Studies of the structure and mechanical properties of moldings were carried out after several conditioning time intervals. The maximum conditioning time of samples was 840 h at 23 °C. Based on the analysis of the test results, it was found that the cellular injection molding process with the holding phase reduces the nucleation of gas pores, which results in a smaller reduction of sink marks than in the case of samples produced without the holding phase. However, PP moldings with a porosity degree equal to 8.9% were characterized by a higher shrinkage value after 1 h of conditioning, compared to moldings with porosity equal to 3.6%. The extension of the conditioning time also resulted in an increase in the value of linear shrinkage and the properties determined during tensile tests of solid and porous samples. Furthermore, in the case of samples with the highest porosity, the impact strength was reduced by about 30% after 840 h of conditioning compared to results obtained after 1 h.

Geometrical accuracy of injection-molded composite gears

The geometrical accuracy of injection-molded gears made of PA6, PA66 and PPA filled with glass fiber (30, 35 and 50%) were investigated. Using the AMI software, the injection mold cavity and the injection point distribution were simulated and the orientation of the glass fibers in the product was determined. The low accuracy class of injection-molded gears may indicate the need to optimize the injection process, which will be the subject of further research.

Effects of Heating and Cooling of Injection Mold Cavity Surface and Melt Flow Control on Properties of Carbon Fiber Reinforced Semi-Aromatic Polyamide Molded Products.

Fiber reinforced thermoplastics (FRTP), reinforced with glass or carbon fibers, are used to improve the mechanical strength of injection-molded products. However, FRTP has problems such as the formation of weld lines, the deterioration of appearance due to the exposure of fibers on the molded product surface, and the deterioration of the strength of molded products due to the fiber orientation in the molded products. We have designed and fabricated an injection mold capable of melt flow control and induction heating and cooling. This mold can both heat and cool the injection mold. It can also control the melt flow direction using a movable core pin. In this study, the above-mentioned mold was used for the molding of carbon fiber reinforced semi-aromatic polyamide. As a result, we found that increasing the heating temperature of the mold and increasing melt flow control volume contribute to the prevention of the generation of a weld line and the exposure of fibers on the molded product surface, as well as to the formation of a flat surface and increased bending strength. The relationships of these results with the carbon fiber orientation in the molded products and the crystallization of semi-aromatic polyamide were also examined in this study.

Polymer Based Injection Mould Cavity Inserts: An Influence on Crystallization and Thermo-Mechanical Properties of Injection Moulded Parts

Injection moulding is a major used technology in mass production of high-quality plastic and composite parts. Once the initial costs have been paid the price per produced part is extremely low and part is then created up to million times. On the other hand, the product development process is time-consuming and costly due to preparation time. Therefore, the efficiency and similarity to real production are essential. Injection moulding into polymer injection mould cavity inserts appears to be an appropriate step in the product development process in particular concerning quickly developing additive manufacturing technologies. Though polymers are thermal insulators, therefore, cooling time is longer compared to injection into fully metal moulds. The impact of different cooling conditions is a change in the crystallization of injected material causing different mechanical properties of products. Removable injection mould cavity inserts were made from PET (Polyethylene terephthalate), PEEK (Polyether ether ketone), PSU (Polysulfone) and PTFE (Polytetrafluoroethylene). The main goal was to compare crystallization and thermo‑mechanical properties of injected PP (Polypropylen) parts into polymer cavity inserts to those injected into a steel mould.

Algorithm for Micro‐Profiling from Image of the Injection Molds Complex Surfaces

AbstractNature is an excellent source of inspiration. Understanding nature can lead to new discoveries of new materials, applications, products. Scientists have found out technologies that seek to mimic some of life's unique innovations. In Germany researchers have developed a synthetic shark skin made of elastic silicone that reduces bio‐fouling. Engineers from the Massachusetts Institute of Technology have developed some “biomimicry” material out of glass and plastic that collects minute amounts of water, just like the Namib Desert beetle's back. Polymer composites are used for a very good replication of the mold cavities surface microstructures. Transformation of image to surface could be an economical solution for machining the injection mold cavities for mimic the inspiration source. In this paper an algorithm for combining the tool paths obtained on an image‐to‐surface technique with the tool paths on a complex shaped cavity is presented. The algorithm is tested by micro‐milling an injection mold surface of a cavity for a scale model stone wall and the injection molding experiments have proven the high quality of detail replication.

Assessment of Production Process Capability in the Serial Production of Components for the Automotive Industry

Abstract The article deals with the assessment of production process capability in the serial production of plastic components. The plastic component was used for analysis. Component is used in the automotive industry in car suspension shock absorbers. Assessing the capability of the product’s manufacturing process is very important. The aim of the present paper is to measure the dimensional characteristics of a thermoplastic product as a monitored quality feature. The analyzed product is manufactured in an eightfold injection mold by injection technology. The products from each injection mold cavity were considered separately. Process capability was assessed using capability indices. Process variability and centering were evaluated. Based on the analysis we can say that the production process is in excellent condition.

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines

Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. In the weld line area, the V‐shaped notch is formed and its shape and size depend on injection molding conditions and properties of processed polymer. Addition of the foaming agent to the polymer can be one of the way to improve conditions of melt streams welding due to the higher velocity of the colliding streams of unfilled polypropylene (PP) and PP filled with talc. The examinations of mechanical properties showed, however, lower tensile strength of porous parts compared to solid ones, but in the microscopic observation and measurements of the geometric structure of moldings, in the weld lines area, better surface conditions were achieved for samples made of the foamed polypropylene. The size of V‐notch, determined by the total height of the raw profile Pt, depends also on the length of polymer flow path from the gate to the weld line area. The values of Pt parameter increase with the length of the flow path, but this increase is smaller for foamed polypropylene. POLYM. ENG. SCI., 59:1710–1718 2019. © 2019 Society of Plastics Engineers

Prediction for the mechanical property of short fiber-reinforced polymer composites through process modeling method

The fiber-reinforced polymer composites are important alternative for conventional structural materials because of their excellent comprehensive performance and weight reduction. The mechanical properties of such composite materials are mainly determined by the fiber orientation induced through practical manufacturing process. In the study, a through process modeling (TPM) method coupling the microstructure evolution and the mechanical properties of fiber-reinforced composites in practical processing is presented. The numerical methodology based on the finite volume method is performed to investigate three-dimensional forming process in the injection molding of fiber-reinforced composites. The evolution of fiber orientation distribution is successfully predicted by using a reduced strain closure model. The corresponding finite volume model for TPM is detailedly derived and the pressure implicit with splitting of operators (PISO) algorithm is employed to improve computational stability. The flow-induced multilayer structure is successfully predicted according to essential flow characteristics and the fiber orientation distribution. The mechanical properties of such anisotropy composites is further calculated based on the stiffness analysis and the Tandon–Weng model. The improvement of mechanical properties in each direction of the injection molded product are evaluated by using the established mathematical model and numerical algorithm. The influences of the geometric structure of injection mold cavity, the fiber volume fractions, and the fiber aspect ratios on the mechanical properties of composite products are further discussed. The mathematical model and numerical method proposed in the study can be successfully adopted to investigate the structural response of composites in practical manufacturing process that will be helpful for optimum processing design.

The Influence of Processing Conditions on the Polypropylene Apparent Viscosity Measured Directly in the Mold Cavity

Measurements of rheological properties of polymeric materials play an increasingly important role in the polymer plastics industry. Knowledge about the plasticized material flow behavior is essential at the injection molds design stage. The polymeric viscosity curves usually are determined by a capillary rheometer tests. Nevertheless, the rheological properties determined this way differ from those observed during actual processing conditions. This paper presents a comparison of apparent viscosity measurements of polypropylene conducted by three methods. The first one was plastometer measurements made at different masses of test load. The second method evaluated the viscosity in the injection mold cavity equipped with pressure and temperature sensors. Capillary rheometer was used as the third method. It was observed that polypropylene viscosity curves, determined by different methods have a similar pattern. Comparing changes in apparent viscosity values obtained with the capillary rheometer and directly in the mold cavity, the largest differences were found for the shear rate below 1000 s −1. This proves the non‐isothermal measurement in the injection mold cavity. In the range of shear rate above 1000 s−1, the apparent viscosity determined directly in the injection mold was about 40 Pa · s greater than that measured by the rheometer, regardless of the test temperature. The results recorded by the plastometer reflect the real polypropylene viscosity curve at low shear rate values in a better way.

Monitoring of the injection and holding phases by using a modular injection mold

Abstract Introducing pressure and temperature sensors into the mold cavity allows us to determine the rheological properties of the polymeric materials being processed. Furthermore, signals registered by sensors inside the mold cavity allow us to monitor the injection and holding phases as well as the subsequent solidification of the polymer melt. The aim of this research work was to verify the operational abilities of a laboratory injection mold with pressure and temperature sensors and was designed for research purposes. Standardized test pieces to investigate the mechanical properties of polymeric materials were obtained by using a laboratory injection mold. This article presents the investigation results of the influence of microcellular foaming of polyamide on the conditions inside an injection mold cavity. Apparent viscosity fluctuations of polymer melt in subsequent processing cycles were investigated as well. Additionally, the effect of changes in the injection speed of the polypropylene melt on its rheological parameters were investigated.

Self-Assembly and Charge Transport of a Conjugated Polymer on ITO Substrates

The properties of a composite based on a high-density polyethylene Hostalen GD 7255 filled with a 10% addition of a glass powder called Mikrover were studied. The composite was obtained in the process of twin screw extrusion with cold pelletizing. The apparatus included a co-rotating twin-screw extruder with the extruder head equipped with a circular die, as well as a water cooling bath and a pelletizer. The mechanical properties of the composite were studied by producing appropriate specimens in the injection moulding process, at variable cooling times of the injection moulded parts and at variable volume rates of polymer composite flow to the injection mould cavity. The basic strength properties were determined by uniaxial tensile testing, and hardness was determined by the Shore method. It was found that injection moulding conditions influenced the mechanical properties under study. For example, an increase in cooling time was accompanied by an increase in stress at break. An increase in the volume rate of polymer composite flow to the injection mould cavity was accompanied by an increase in hardness, stress at break, tensile strength and strain at break.

The use of IR thermography to show the mold and part temperature evolution in injection molding

Abstract This study concerns the application of infrared camera for injection molding analysis by measuring temperatures of both injection molded parts and injection mold cavities in a function of injection cycles. The mold with two cavities, differing in thickness (1 and 3 mm), and a cold direct runner was used. Isotactic polypropylene homopolymer was utilized to produce parts. Mold temperature was set at 22°C and controlled by a water chiller. Five measuring points were determined: SP1, SP2 (placed in the 3 mm cavity), SP3, SP4 (located in the 1 mm cavity) and SP5 around an injection molding gate. Our investigations showed that the highest temperature is localized around SP2 point and the lowest at SP4. Also, it was proved that even after 62 injection molding cycles, temperatures of cavities were not stable, revealing their further increase with each cycle.

Supramolecular Structure of Polymers and its Effect on Surface Quality of Injection Molded Parts Using Various Surface Quality of Cavities

This article is focused on influence of finishing operations on the surface quality of polymer products. Finishing operations are the necessary part in the production of injection mold cavities. Surface quality of cavities is reflected to quality of future polymer products. Therefore, it is very important to use appropriate finishing operations and its technological conditions from the aesthetic point of view. However, it is not always necessary to use time consuming and most expensive finishing operations, because the polymeric products are not able to achieve similar surface quality as cavities. The different surface quality of injection molded parts can be also expected using various supramolecular structure of polymer (amorphous, semicrystalline). Supramolecular structure of polymer determines the future properties of product as well as the distribution of the individual macromolecules in the polymer chain. Divergent distribution may result to achievement of different surface quality of injection molded parts. This research is focused on finding an influence of supramolecular structure of chosen polymer on the surface quality of polymer product.

Impact of Viscosity on Filling the Injection Mould Cavity

Abstract The aim of this paper is to look closer at the rheological properties of plastics and their impact on technology in the plastics processing industry. The paper focuses on the influence of viscosity of the material on filling the mould cavity. Four materials were tested with the settings of process parameters with different viscosity. Using simulation software of Moldex3D, we can see the effect of change in viscosity in the material to be filled.

Sensing Uncertainty Evaluation for Product Quality

As sensing techniques continue to enhance the manufacturing industry in terms of condition monitoring, process control and decision making, understanding uncertainty involved in sensing has remained a challenging problem. Sensor readings may be affected by deterioration of the hardware and environmental perturbations. Prior studies reported in the literature assumed multiple co-located homogeneous sensors to provide redundant information for uncertainty evaluation. Such an approach is often times not applicable given space restraint and cost-effectiveness concerns. Furthermore, it is difficult to distinguish the sources that have caused the variation of sensor readings, e.g., limitation in the sensor precision or variation in the measured quantity. To address these challenges, a method for computing uncertainty of non-homogeneous sensors is developed, using on-line injection molding quality monitoring as experimental verification. The method includes two computational steps. First, measurements provided by four spatially distributed sensors (two temperature and two pressure sensors) in an injection mould cavity are fused to estimate the part quality (thickness). Second, the ground truth is approximated from the estimated part quality, through inverse process. Subsequently, the approximated ground truth is utilized to calculate the uncertainty of each sensor used in the measurement process. To quantify sensor uncertainty, a metric including accuracy, precision and trust is defined. The detection of abnormal sensors in turn provides input to improved part quality estimation. The developed technique is evaluated experimentally by measurements on a production-grade injection molding machine working under a variety of machining settings. The results demonstrate the approach's effectiveness for evaluating sensing uncertainty and improving monitoring performance.

Polymer fluidity influenced by type and amount of filler

stage of the injection molding process. This paper shows the influence of cavity surface roughness and technological parameters on the flow length of polymers into mold cavity. Application of the measurement results may have significant influence on the production of shaping parts of the injection molds especially in changing the so far used processes and substituting them by less costly production processes which might increase the competitiveness of the tool producers and shorten the time between product plan and its implementation. This research focused into the influence of technological parameters on filling of the injection mold cavity and the flow length respectively.

사출성형 금형 캐비티 내압 측정장치 개발 및 이를 이용한 새로운 복합재료의 점도 측정

본 연구진은 사출성형 공정에서 적용되는 미지 시료 및 고점도의 복합소재 점도를 추정하기 위한 새로운 방법을 제시한 바 있다. 본 논문에서는 사출성형 금형 캐비티 내압을 측정하는 장치를 개발하였다. 이는 사출성형 공정 중의 금형 내를 흐르는 용융체의 압력을 실시간으로 측정하고, 이를 CAE 해석 결과로부터 모사된 압력과 비교함으로써 CAE D/B내의 점도 데이터의 정확성을 검증할 수 있게 한다. 본 연구에서 사용한 재료는 PP(Polypropylene), PP/LGF30%(Polypropylene과 long glass fiber 50% composite), PA66/LGF50%(Polyamide 6,6와 long glass fiber 50% composite) 이다. 여기서 PP와 PP장섬유복합재료는 이미 점도 데이터가 구축되어 있으나, PA66장섬유복합재료는 새롭게 개발한 재료로써 기존의 점도 데이터가 없기에 본 시스템을 이용해서 새로운 점도 곡선을 추정하였다. 그리고, 일반 점도 측정장치로 구한 점도 곡선과도 비교하였다. 한편, 이미 점도 데이터를 갖고 있는 경우인 PP는 신뢰성을 확인할 수 있었으나, PP/LGF50%의 경우는 높은 점도와 구조의 복잡성으로 인해 기존 점도 데이터의 개선이 필요하였다. We have proposed a new method for estimating the viscosity of the composite. In this paper, we have developed a device for measuring the injection mold cavity pressure. This makes it possible to verify the accuracy of the viscosity in CAE D/B in real time by measuring the melt pressure in the mold, and comparing this with the simulated pressure from the CAE analysis. Materials used in this study is a PP(Polypropylene), PP/LGF30%(Polypropylene/long glass fiber 50% composite) and PA66/LGF50%(Polyamide 6,6/long glass fiber 50% composite). The viscosity data for PP and PP long fiber composite have already been built, but the one for PA66 long-fiber composite does not exist because it is a newly developed material. Thus we obtained the viscosity curve of PA66/LGF50% by this system. Then, the viscosity curves from conventional viscometer were also compared with the viscosity obtained by the our method. And, we proved the accuracy of the CAE data of PP. In case of PP/LGF50% which is highly viscous and complex material, we improved the existing CAE data.because there was a difference between the measuring data and the CAE data.

Online product quality monitoring through in-process measurement

Online monitoring of product quality is key to automated machine operation and process optimization. This paper demonstrates an in-process sensing technique for online product quality assessment, using injection moulding as an example. The system measures four parameters within the injection mould cavity, which are directly correlated with the part quality: melt pressure, temperature, velocity, and viscosity. Relationship between the sensor data and quality characteristics, e.g., thickness and width of the part, are established by incorporating governing physics for pressure–volume–temperature with other mechanistic models. Good agreement between sensor measurements and experimental results is confirmed from tests performed on a production-grade machine.

Suitability of Screw Plasticization for Autosterile Injection Molding

ABSTRACTSingle use medical products are subject to subsequent sterilization treatment following manufacturing processes, for example, injection molding, to obtain sterility. A new approach is developed to use the injection‐molding process to produce sterilized products without an additional sterilization procedure. To achieve the aim of an autosterile injection molding, it is necessary to evaluate the sterilization impact of screw plasticization regarding sterile polymer melts before entering the injection mold cavity. Within this study, a screw plasticization unit is fed with defined contaminated polymer granules. Geobacillus stearothermophilus spores are used as challenge organisms to determine the sterility grade of screw plasticization. The investigation includes method verification and the experimental testing of polyoxymethylene, polyethylene, and cyclo‐olefin copolymer melts at different melt temperatures of 200°C and 280°C. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2014, 33, 21403; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21403