Plastic Injection Research Articles

Robotized cell design for part assembly in the automotive industry

Today, the automotive industry faces its biggest challenge, which is keeping a constant evolution, accounting for the market needs in what comes to the enormous quantity of parts and systems that go hand in hand with the production of the vehicle, and at the same time, keep up with the quality requirements and deadlines. Throughout time, automation and robotics became the best way to achieve the goals required by the market. In the automotive industry, automation presents itself at a continuous evolution, constantly presenting new solutions, and the production and assembly lines increasingly resort to completely automated processes. This work is based on the needs of an automotive parts’ supplier. In which regards to the injection of plastic, the production is fluent and quick, and to take advantage of such production speed, it is desirable to execute the assembly steps immediately after the removal of the parts from the injection moulds. The proposed work consists of the design of a robotized cell with the goal of inserting metal clips in two different automotive parts after the injection process. The idea is to conceptualize and conceive a completely automated equipment, capable of executing this task using a six-axis robot. To secure the part for clip assembly, the equipment must be ready to ensure the positioning and locking of the part in all axes and, to lighten the robot’s job, it must also be capable of using a feeding system to load the robot’s tool. The results of this project were positive, the equipment was successfully concluded and delivered to the customer, meeting the construction requirements, and, most importantly, the cycle time.

Investigation of the Warpage of a High-Density Polyethylene Pallet by Plastic Injection Compression Molding: Part I-Numerical Approach.

Many challenges are associated with the injection compression molding process for producing a half-pallet (1320 mm × 1110 mm × 75 mm, length × width × height), which is butt-welded to another one for enhancing its strength. This pooled high-density polyethylene (HDPE) pallet is able to endure the impacts of a heavy load and a low ambient temperature. Reducing the warpage of a half-pallet is, therefore, essential for reducing the residual internal stress within the welded portions. An advanced Moldex3D package helps to detail the temperature distribution and warpage of a half-pallet. The pre-setting molding parameters from a mass-production factory produce half-pallets with worse flatness. In this investigation on using appropriate cooling water temperatures within the core and cavity plates of the mold, the numerical results show that the warpage of the top surface of the half-pallet was 11.549 mm, low warpage with respect to this large-scale pallet. Furthermore, the compression speed of 50–60 mm/s may have produced a low flatness of the half-pallet in this study.

Bonding integrity of hybrid 18Ni300-17-4 PH steel using the laser powder bed fusion process for the fabrication of plastic injection mould inserts

Laser powder bed fusion (LPBF) is a metal additive manufacturing (AM) process for fabricating high-performance functional parts and tools in various metallic alloys, such as titanium, aluminium and tool steels. One specific AM application is fabricating conformal cooling channels (CCC) in plastic injection moulding tool inserts to improve cooling efficiency. This article reports the development of a novel hybrid powder-wrought alloy steel combination intended for injection mould inserts use. In this investigation, cylindrical parts made of 18Ni300 steel powder and wrought 17-4 PH steel were additively fabricated using a hybrid-build LPBF AM technique, followed by various post-build heat treatments. Standard mechanical and microstructural techniques were employed to examine the bonded powder-substrate interface. Microstructure analysis revealed defect-free, fully dense, homogenous powder-substrate fusion across a 280-µm-thick region. Tensile tests confirmed strong powder-substrate bonding due to solid solution strengthening within the region. All tensile fractures were ductile under all heat treatment conditions and occurred about 8 mm from the interface, at the side where the materials were of lower strength. The hybrid-built parts exhibited an ultimate tensile strength of 1009–1329 MPa, with 16.1–17.4% elongation at fracture. Hardness values on the AM-deposited and substrate sides were 31–55 HRC and 32–43 HRC, respectively. A direct post-build 490 °C/1 h age-hardening treatment achieved the best combination of hardness, tensile strength and ductility. The overall result demonstrates that hybrid-built powder 18Ni300-wrought 17-4 PH steel can be a material choice for manufacturing durable and high-performance injection mould inserts for high-volume production.

COMPUTER ANALYSIS OF THE TECHNOLOGICAL PROCESS OF A SELECTED COMPONENT'S PLASTIC INJECTION

The article describes an optimization methods analysis in the technological process of plastic injection using the simulation tool Autodesk Moldflow Adviser. The Polyethylene 120J was the material used in production of the plastic part analyzed. Following the simulations, deficiencies affecting the quality of the final part were identified. Modifications were gradually made both in the cover's design and as changes in the process parameters so as to eliminate the deficiencies identified. In the first step, the value of the injection time was modified based on the results of the analysis of the determination of the ratio of solidified layers at the end of the process of filling the mold cavity. The second type of adjustment required a change in the molding's design. Based on the result of the simulation of forecasting cooling quality, we proposed a change in the wall thickness of selected model elements, specifically the adjustment of the wall thickness of the bolted joint column from 3 to 4 mm. The last adjustment consisted of adjusting the additional pressure profile.

Prediction of Gloss in Plastic Injection Parts Based on 3D Surface Roughness from Virtual Machining with Artificial Neural Networks

The gloss is one of the most important characteristics of plastic injection molding parts, whereby the molding process needs to consider the influence of the three main factors such as the surface roughness of the cavity, chemical properties of the plastic, and injection parameters. The surface roughness of the plastic injection mold was considered for the gloss that occurs with the parts of the plastic injection processes. Therefore, the objective of this research is to predict the gloss for plastic injection parts based on the artificial neural network method from the input parameters of 3D surface roughness from virtual machining on a 3-axis CNC machining center, and plastic injection parameters. The shape generation motions were mathematically described by combining 4 × 4 transformation matrices including the kinematic motion deviations, machining parameters, end milling ball nose geometries, and cutting force. The results of the research showed the prediction of gloss in plastic injection parts from a neural network model compared to the gloss value of the actually measured workpiece and response surface methodology combined with central composite design. It was found that the average error of the gloss was 2.36%. The proposed method provides us with a systematic method to estimate the gloss for plastic injection parts before producing the actual cavity mold, which leads to increased accuracy as well as efficiency in manufacturing plastic injection parts.

Thermoplastic natural rubber based on linear-low-density polyethylene

Thermoplastic natural rubber (TPNR) is one of the alternative natural rubber (NR) products obtained by blending NR with any compatible thermoplastics, e.g., high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear-low-density polyethylene (LLDPE), polystyrene (PS), polylactic acid (PLA) at the temperature above the melting point of plastics, which is always above the softening point of NR. Unlike vulcanized NR, TPNR is recyclable and convertible to the final articles using the existing plastic technologies, including extrusion and injection molding. TPNR materials based on NR/LLDPE blends filled with two types of inorganic fillers, i.e., titanium dioxide and silica, were prepared and their properties were discussed in the current work. Silica provided a better reinforcing effect to the NR/LLDPE blends, whereas the blends filled with titanium dioxide exhibited excellent UVA and weather resistance. The resulting NR/LLDPE blends filled with inorganic fillers can be injection molded to form the products with desired shapes.

Methodology to implement CAE validation in repair & redesign parts process of plastic injection molds

Repairs and redesigns for plastic injection molding parts generally is a short and straightforward process consisting of inspection, modeling, and evaluation. The present paper implements a methodology for redesigning and repairing injection molding parts based on the frontal process for developing concepts. The proposed methodology helps in the validation through Computer-Aided Engineering (CAE) in the designing stage using CAD software, ensuring the quality of the repair. Furthermore, the redesigned development has been carried out in the best way to obtain a better cooling, robustness, or plastic flow. In this research is implemented the proposed methodology in a Hot Runner System. Furthermore, a numerical simulation for three cases to evaluate the heat transfer and cooling times performed, finding the main differences in heat transfer due to drilled or milled rectangular channels, minimizing the time to reach ejection temperature and mold/part temperatures.

Recent progress in minimizing the warpage and shrinkage deformations by the optimization of process parameters in plastic injection molding: a review.

The quality control of plastic products is an essential aspect of the plastic injection molding (PIM) process. However, the warpage and shrinkage deformations continue to exist because the PIM process is easily interfered with by several related or independent process parameters. Thus, great efforts have been devoted to optimizing process parameters to minimize the warpage and shrinkage deformations of products during the last decades. In this review, we begin by introducing the manufacturing process in PIM and the cause of warpage and shrinkage deformations, followed by the mechanism about how process parameters, like mold temperature, melt temperature, injection rate, injection pressure, holding pressure, holding and cooling duration, affect those defects. Then, we summarize the recent progress of the design of experiments and four advanced methods (artificial neural networks, genetic algorithm, response surface methodology, and Kriging model) on optimizing process parameters to minimize the warpage and shrinkage deformations. In the end, future perspectives of quality control in injection molding machines are discussed.

Feasibility Study of the Flatness of a Plastic Injection Molded Pallet by a Newly Proposed Sequential Valve Gate System.

The investigation of plastic pallet molding, assisted by a sequential valve gate system, has not yet been performed due to the limitations of the pallet scale. Furthermore, at present, the application of recycled plastics by chemical industries has become extremely popular around the world. This study aimed to determine pallet flatness experimentally and numerically using recycled polypropylene with a large-scale pallet. Short-shot testing on injection molding was performed to obtain short-shot samples for confirmation of the flow front during simulated filling. The real injected pallet profile, which was measured by an ATOS, was compared after confirmation to the numerical profile of the pallet. The pallet’s flatness was accurately compared to the real experimental and numerical results. By adjusting the temperature of the cooling channel within the cavity plate to 55 °C, the flatness of the pallet achieved by the newly proposed sequential valve gate-opening scheme was about 7 mm, which meets the height directional warpage standard determined by the pre-set sequential scheme. The numerical flatness is in line with existing flatness values for pallets. Furthermore, the proposed cooling temperature gives the highest yield in terms of pallet molding from the perspective of the stakeholders.

Using the Area of Contact between Layers as a Predictor for the Anisotropic Strength of Parts Produced by FDM

Abstract: Fused Filament Fabrication (FFF), better known as FDM© (Fused Deposition Modeling) is an additive manufacturing process (AM) by which a physical object can be created from a 3D model generated in the computer, through layer-by-layer deposition of semi-melted plastic filaments. However, parts produced by the FDM process have different characteristics compared to parts produced by traditional methods such as plastic injection, especially with regard to mechanical properties related to stresses (tensile, compression, torsion and shear), due to the anisotropic nature of the process deposition. Many works have been carried out in order to determine the influence between the FDM process parameters and the mechanical characteristics of parts produced by this technology. Traditionally, the studied parameters comprise those that are adjusted in slicing software, which does not satisfactorily reflect the bond between the layers. This work uses the area of contact between the layers as the determining factor of the transverse tensile strength to bedding and suggests a methodology for the determination of this parameter. Using analysis of variance (ANOVA) and the Taguchi analysis method, we identified the contact area between the layers as the most relevant parameter for tensile strength in the transverse direction of the printed layers with a relevance of more than 95% over the others investigated parameters. From the survey of relevant properties, new tests were carried out to determine a mathematical model to predict the minimum slicing parameters that should be used to obtain the required strength. Keywords: Fused Deposition Modeling, Mechanical Strength, AM Anisotropic Property, Layer Bond Properties, PLA.

Metal Additive Manufacturing of Plastic Injection Molds with Conformal Cooling Channels.

Conformal cooling channels (CCCs) are widely used in the plastic injection molding process to improve the product quality and operational performance. Tooling that incorporates CCCs can be fabricated through metal additive manufacturing (MAM). The present work focuses on the MAM of a plastic injection mold insert with different CCC types that are circular, serpentine, and tapered channels with/without body-centered cubic (BCC) lattices. The entire manufacturing process of the mold insert is explained from the design step to the final printing step including the computational thermal & mechanical simulations, performance assessments, and multiobjective optimization. Compared to the traditional channels, conformal cooling channels achieved up to 62.9% better cooling performance with a better thermal uniformity on the mold surface. The optimum mold geometry is decided using the multiobjective optimization procedure according to the multiple objectives of cooling time, temperature non-uniformity, and pressure drop in the channel. Direct Metal Laser Sintering (DMLS) method is used for manufacturing the molds and the quality of the printed molds are analyzed with the X-ray Computed Tomography (X-ray CT) technique. The errors between the design and the printed parameters are less than 5% for the circular and tapered channels while the maximum deviation of the strut diameters of the BCC is 0.06 mm.

Coaxiality Optimization Analysis of Plastic Injection Molded Barrel of Bilateral Telecentric Lens

Plastic optical components are light in weight, easy to manufacture, and amenable to mass production. However, plastic injection molded parts are liable to shrinkage and warpage as a result of the pressure and temperature variations induced during the molding process. Consequently, controlling the process parameters in such a way as to minimize the geometric deformation of the molded part and improve the performance of the optical component as a result remains an important concern. The present study considered the problem of optimizing the injection molding parameters for the plastic lens barrel of a bilateral telecentric lens (BTL) containing four lens assemblies. The study commenced by using CODE V optical software to design the lens assemblies and determine their optimal positions within the barrel. Taguchi experiments based on Moldex3D simulations were then performed to determine the processing conditions (i.e., maximum injection pressure, maximum packing pressure, melt temperature, mold temperature, and cooling time) which minimize the coaxiality of the plastic barrel. Finally, CODE V and grayscale analyses were performed to confirm the optical performance of the optimized BTL. The Taguchi results show that the coaxiality of the plastic lens barrel is determined mainly by the maximum packing pressure and melt temperature. In addition, the CODE V and grayscale analysis results confirm that the optimized BTL yields a better modulus transfer function, spot diagram performance, and image quality than a BTL produced using the general injection molding parameters.

Effect of Temperature Ageing on Injection Molded High-Density Polyethylene Parts Modified by Accelerated Electrons

The temperature ageing of high-density polyethylene (HDPE) modified by accelerated electrons was studied. Commodity plastic HDPE was used as a basic polymer material which was modified by radiation cross-linking. This polymer was used because of its excellent processability and chemical resistance. Plastic injection molding technology was used for the production of test specimens. These specimens were modified with the dose of radiation 33, 66, 99, 132, 165, and 198 kGy. The prepared specimens were tested to determine: gel content, degree of swelling, temperature stability, and changes in mechanical properties after temperature ageing. The results were determined by scanning electron microscopy (SEM) analysis on the fracture surfaces. The results of this study confirm that modification of HDPE by radiation cross-linking has a significant effect on increasing temperature stability. It has been shown that HDPE modified by radiation cross-linking can withstand temperatures exceeding the melting point of the original HDPE for a short-term.

Heat Control simulation for variothermal injection moulding moulds using infrared radiation

Mould temperature control has a significant influence on component quality and costs in the plastic injection moulding process. In the case of standard applications isothermal temperature control, in which the mould temperature is maintained at one level, is sufficient. For special applications (e.g. plastic optics; long, thin components; moulding of microstructures) variothermal temperature control using cyclically changing temperatures is beneficial. Therefore, the use of infrared radiators offers advantages in terms of achievable temperatures and investment costs but at low heating rates and efficiency. This paper therefore investigates the possibility of increasing the efficiency of energy input by infrared radiation into metals in particular into aluminium. For this purpose, a simulation model is developed. The numeric models used are validated by means of experiments. A short-wave infrared radiator is investigated, consisting of a tungsten filament in a quartz glass tube. The emitter power is varied from 1200 to 400 W. An aluminium sample with a thickness of 10 mm and a square base with an edge length of 60 mm is investigated. The temperature is measured on the non-irradiated side in the centre of the sample surface and at a distance of 20 mm from it while being irradiated. For the numerical model, a ray tracing simulation is carried out in a first step, the result of which is used as a Neumann boundary condition for a thermal simulation in second step. The model created can serve as a basis for the thermal design of more complex geometries.

Optimization of the Cooling of a Thermoplastic Injection Mold

In injection molding processes for thermoplastic parts, the polymer solidification phase in the molding cavity has a strong influence on the quality of the shaped parts and also on the process cycle time. Reducing cycle time is one of the major concerns for plastic injection industries. As cooling phase presents the most critical phase to get quality and cycle time of the part, the application of additive manufacturing (AM) technologies has been overcoming the limitations of traditional cooling system design. AM enables the construction of conformal cooling channels for higher cooling uniformity due to its almost unlimited freedom of design that can fulfil the desired functions in injection molding process equipment. The analysis of the heat transfer during the phase of cooling allows the investigation of the optimal positioning of the cold sources and their intensities. In this paper, a systematic approach is used to replace conventional channels in an injection molding tool with conformal cooling channels. A simulation is used to develop a numerical model that describes the heat transfer and predicts the cycle time of both the optimal and conventional designs. Finally, a numerical comparison is made between traditional and conformal cooling to demonstrate the beneficial effect on reducing the manufacturing cycle and enhancing part quality.

Two Phases Anomaly Detection Based on Clustering and Visualization for Plastic Injection Molding Data

The importance of smart factory is increasing. Among them, the importance of sensor data-based anomaly detection research is increasing. Accordingly, this paper presents a framework by using sensor data of plastic injection machine and deep learning models to perform anomaly detection and cluster secured outliers. This study aimed to be a practical solution and proposal for factories that want to introduce smartfactory system. According to this goal, three main contributions are assumed. The three main contributions are as follows. First, assuming a situation suitable for the manufacturing site, and appropriate approach was used. Second, it is possible to secure outliers by applying Auto Label using with pseudo labeling technique. Third, the decision maker can identify the potential cause of the defect. These three advantages can be found in the Two Phases Anomaly Detection system architecture. The artificial intelligence model used as a classifier in the pseudo labeling technique was LSTM and Accuracy showed high reliability of more than 90%. And through the SOM algorithm, clustering visualization of defective data is shown.

Metal additive manufacturing of conformal cooling channels in plastic injection molds with high number of design variables

Metal additive manufacturing (MAM) is an effective way to fabricate conformal cooling channels (CCCs), which follow the curves of the plastic product in the mold body of the plastic injection. CCCs have free-curved pathways thanks to the design & manufacturing flexibilities of the MAM process so that they can achieve better cooling performance with shorter cooling time and smaller temperature non-uniformity. On the other hand, the flexibilities of the MAM process bring multiple options for design variables and the high number of design variables make the final design of CCCs complex, high-cost, and time-consuming. Considering this challenge, this study presents the entire process of MAM of CCCs for a target product with eight different design variables, which makes it a product with a high number of design variables, from the initial design to the on-site manufacturing including the steps of computer-aided design & simulations, metamodel, multiobjective optimization, and the printing quality monitoring. The target product has three main objectives that are i) the temperature difference between the maximum and minimum values at the internal wall of the mold, ii) maximum temperature in the mold body, and iii) pressure drop. The optimized product is then printed via direct metal laser sintering (DMLS) machine and the quality check is done via X-ray computed tomography.

A Fuzzy Rule-based Network Model for Optimization of Process Parameters in Plastic Injection Molding

A Fuzzy Rule-based Network Model for Optimization of Process Parameters in Plastic Injection Molding

Multi-objective optimisation of plastic injection moulding process using mould flow analysis and response surface methodology

Multi-objective optimisation of plastic injection moulding process using mould flow analysis and response surface methodology

The influence of surface finishing on laser heat treatments of a tool steel

Laser heat treatments (LHT) has received growing attention in the last years because of highly localized precision and manufacturing efficiency related to laser processing of moulds steel. Due of its strong resistance and ability to maintain hardness and strength at high temperatures, AISI P20 steel is one of the most widely used tool steel in the plastics injection mould industry.This work presents an experimental investigation on LHT using P20 mod. steel produced with different surface finishes. After mechanical surface finishing, the diode laser beam with 15 mm width was applied to the P20 specimens at 1060 ⁰C using a feed rate of 8.8 mm·s-1in an air and argon ambient. The influence of different LHT atmosphere conditions and specimen initial surface finishing on characteristics such as final roughness, microhardness and microstructure were comprehensively analyzed. The use of a controlled atmosphere during processing showed an increment in depth and hardness values of samples. Through 3D profilometer, it was possible to determine the samples roughness. Results showed that lower average roughness leads to higher hardness values close to the surface, while higher average roughness lead to a deeper heat-treated zone. Macroscopical analysis revealed the depth and width afftected by LHT. The microhardness results showed an increment from 300 HV to around 750 HV on laser heat-treated zone using a controlled environment. Optical microscopy analysed the microstructural changes into martensite between LHT and non LHT zones for all samples.