Plastic Injection Moulding Research Articles

Numerical and experimental investigation on process parameters optimization in plastic injection molding for weldlines reduction and clamping force minimization

Weldlines are one of the major defects in plastic injection molding (PIM). The weldlines have an influence on not only the appearance of product but also the strength, so it is important to reduce the weldlines as much as possible. The melt plastic will be quickly solidified with the low weldline temperature that makes the weldlines long. On the other hand, clamping force also affects the product quality, but the relationship between the weldlines and the clamping force is rarely discussed in the literature. In this paper, the minimum weldline temperature is maximized for the weldlines reduction, whereas the clamping force is minimized for the high product quality. Therefore, a multi-objective design optimization of the process parameters is performed and the pareto-frontier between them is identified. Numerical simulation in PIM is generally so intensive that a sequential approximate optimization using a radial basis function network is used to identify the pareto-frontier. 3D cooling channel is used for the design optimization. Through the numerical simulation, the trade-off between the minimum weldline temperature and the clamping force is clarified. In addition, it is found that the 3D cooling channel is effective for the weldlines reduction and clamping force minimization, compared with the straight-type cooling channel. Finally, to examine the validity of the proposed approach, the experiment using the PIM machine (GL30-LP, Sodick) is carried out. It is found through the experimental result that the weldlines are reduced by the proposed approach.

Optimizing and Modeling for Plastic Injection Molding Process using Taguchi Method

The objective of this work is to study process parameters of Plastic injection molding. Taguchi method, an unconventional design of experiment, is used as an approach to optimize the process parameters to improve quality characteristic of work-piece. The two responses of experiment are volume shrinkage and total displacement. Orthogonal array (L16) is used to conduct experiments. The result shows that there are three statistically significant factors out of seven factors or process parameters. Such three factors are Melt temperature, Packing time and Cooling time. Linear equations derived from experimental results are constructed and suitable conditions can be obtained from a computer based response optimizer.

Evaluation of Wear Behaviour of Metal Injection Moulded Nickel Based Metal Matrix Composite

Metal injection moulding (MIM) is a near-net shape manufacturing technology for producing intricate parts, cost-effectively. MIM comprises combined techniques of plastic injection moulding and powder metallurgy. The present study focused on the development of the binder and fabrication of defect free MIM component. A wax-based binder system consisting of paraffin wax (PW), low density polyethylene (LDPE), polyethylene glycol (PEG-600) and stearic acid was established for MIM of NiCrSiB (70% Wt.) + Cr3C2-NiCr (30% Wt.) nickel based metal matrix composite (NMMC) powder. The feedstock was characterised through rheological properties at different temperatures. Injection temperature was determined from the rheological investigation of the feedstock having the 56% powder loading and 44% binder by volume. Sintering process was carried out with the temperature cycle in the range of 1250–1300 ∘C under hydrogen purged atmosphere. The MIM components showed good and acceptable shrinkage in linear dimensions. The mechanical properties and wear behaviour of NMMC was studied using a pin-on-disc apparatus with alumina disc.Tests were performed under dry sliding conditions at room temperature and elevated temperatures of 200 and 400 ∘C. Results shows that wear rate is maximum at 400 ∘C for 40 N and lowest at room temperature for 10 N. Further wear mechanism was analysed using scanning electron microscope (SEM).

Numerical and experimental investigation of process parameters optimization in plastic injection molding using multi-criteria decision making

In plastic injection molding (PIM), the process parameters such as packing pressure, melt temperature, and cooling time should be adjusted and optimized for high product quality and high productivity. Warpage is one of the major defects in the PIM and should be minimized for high quality. Cycle time should be minimized for the high productivity. In addition to the warpage and the cycle time, clamping force affects the product both the quality and the productivity. Therefore, for the high product quality and the high productivity, it is important to minimize the warpage, the cycle time and the clamping force simultaneously. In this paper, a multi-objective optimization of process parameters in PIM for minimizing three objectives is performed. Numerical simulation in the PIM is generally so intensive that a sequential approximate optimization using radial basis function network is adopted to determine the optimal process parameters. The radar chart is used to perform the trade-off analysis among three objective functions. In addition, the better and worse solution are newly introduced for the trade-off analysis. It is found through the trade-off analysis that all objective functions of the conformal cooling channel are well improved in comparison with the ones of the conventional cooling channel. Therefore, 43% warpage reduction, 1,7% clamping force reduction, and 47% cycle time reduction can successfully be achieved using the conformal cooling channel. Based on the numerical result, the experiment using PIM machine (GL30-LP, Sodick) is carried out. The conformal cooling channel is developed by the metal 3D printer (OPM250L, Sodick). Through the numerical and experimental result, the validity of the proposed approach is examined.

Injection moulding of plastic parts with laser textured surfaces with optical applications

The purpose of this work is to manufacture micro and nanotextured surfaces on plastic injection moulds with the aim of replicating them and obtaining plastic parts with optical applications. Different patterns are manufactured with nanosecond and femtosecond lasers in order to obtain three different optical applications: (i) homogeneous light diffusion (ii) 1D light directionality and (iii) 2D light directionality. Induction heating is used in the injections in order to improve the textures degree of replication. The steel mould and the plastic parts are analyzed with a confocal/focus variation microscope and with a surface roughness tester. A mock-up and a luminance camera are used to evaluate the homogeneity and luminance of the homogeneous light diffusion application in comparison with the current industrial solutions.

Numerical optimization of process parameters in plastic injection molding for minimizing weldlines and clamping force using conformal cooling channel

Weldlines are one of the major defects in plastic injection molding (PIM). Since the weldlines have an influence on not only the appearance of product but also the strength, it is important to reduce the weldlines as much as possible. The melt plastic will be quickly solidified with the low weldline temperature, which results in long weldlines. The weldline temperature is one of the important factors for the weldlines reduction. Clamping force also affect the product quality, but the relationship between the weldlines and the clamping force is rarely discussed in the literature. In this paper, the minimum weldline temperature is maximized for the weldlines reduction, whereas the clamping force is minimized for the high product quality. Therefore, a multi-objective design optimization is performed and the pareto-frontier between them is identified. Numerical simulation in PIM is generally so intensive that a sequential approximate optimization (SAO) using a radial basis function (RBF) network is used to identify the pareto-frontier. Through the numerical simulation, the trade-off between the minimum weldline temperature and the clamping force is clarified.

Using unique surface patterns of injection moulded plastic components as an image based Physical Unclonable Function for secure component identification

A Physical Unclonable Function uses random and inherent properties of a physical entity and can be used to uniquely identify components e.g., for anti-counterfeiting purposes. In this work we demonstrate that the surface patterns of injection moulded plastic components themselves are inherently unique and hence can be used as a PUF for reliable and secure identification. We further demonstrate that these unique surface patterns are easily accessible since they can be photographed with a simple camera set-up. This is exemplarily demonstrated for two different plastic materials on an overall of 200 injection moulded components. A set of brief experiments further examines the PUF’s robustness towards real life conditions. This approach might be useful for secure identification and authentication of components or a label-free tracking.

The Optimisation of Processing Condition for Injected Mould Polypropylene-Nanoclay-Gigantochloa Scortechinii based on Melt Flow Index

The fundamental knowledge of flow behaviour is essential in producing various plastic parts injection moulding process. Moreover, the adaptation of advanced polymer-nanocomposites such as polypropylene-nanoclay with natural fibres, for instance Gigantochloa Scortechinii may boost up the mechanical properties of the parts. Therefore, this project was proposed with the objective to optimise the processing condition of injected mould polypropylene-nanoclay-Gigantochloa Scortechini fibres based on the flow behaviour, which was melt flow index. At first, Gigantochloa Scortechinii fibres have to be preheated at temperature 120°C and then mixed with polypropylene, maleic anhydride modified polypropylene oligomers (PPgMA) and nanoclay by using Brabender Plastograph machine. Next, forms of pellets were produced from the samples by using Granulator machine for use in the injection moulding process. The design of experiments that was used in the injection moulding process was Taguchi Method Orthogonal Array -L934. Melt Flow Index (MF) was selected as the response. Based on the results, the value of MFI increased when the fiber content increase from 0% to 3%, which was 17.78 g/10min to 22.07 g/10min and decreased from 3% to 6%, which was 22.07 g/10min to 20.05 g/10min and 3%, which gives the highest value of MFI. Based on the signal to ratio analysis, the most influential parameter that affects the value of MFI was the melt temperature. The optimum parameter for 3% were 170°C melt temperature, 35% packing pressure, 30% screw speed and 3 second filling time.

Drivers of spin-off performance in industry clusters: Embodied knowledge or embedded firms?

Numerous studies attest to the distinctive performance of intra-industry spin-offs located in agglomerated regions. Besides entrepreneurs’ pre-entry experience, both superior hires and regional embeddedness have been suggested as factors contributing to this pattern. We employ linked employer-employee data to assess their relevance in the empirical context of the Portuguese plastic injection molds industry. We find that the longevity of entrants is associated with the number and quality of early employees hired from within the industry, consistent with the importance of embodied knowledge flows. Our findings do not suggest that entrants’ centrality in the regional industry network enhances their longevity.

Multi-Objective Optimization for Warpage and Cycle Time Minimization in Plastic Injection Molding Using 3D Cooling Channel

Multi-Objective Optimization for Warpage and Cycle Time Minimization in Plastic Injection Molding Using 3D Cooling Channel

Analysis of Process Parameters affecting Energy Consumption in Plastic Injection Moulding

Sustainable manufacturing has become essential amongst industries of all types due to the diminishing non-renewable sources and an ever- increasing demand for environmentally friendly products. Injection moulding is one of the most widely used processes for the production of plastic products and is a large consumer of energy. Energy efficiency has become a serious concern due to the rising energy costs and the associated environmental impacts. IEA (2007) reports that one third of the global energy consumption and 36 percent of CO2 emissions are attributed to the manufacturing sector. The aim of this study was to optimize the injection moulding process in order to reduce energy consumption whilst also ensuring no loss in part quality. This was achieved by investigating the impacts of cooling time, screw rotational speed, mould temperature and nozzle temperature. It was found that the cooling time and the nozzle temperature had the greatest impact on energy consumption. The mass and length of the part were not affected by any of the parameters within the selected processing windows, while the surface roughness was slightly influenced by the mould temperature range. Results indicated a possibility of using lower cycle times and lower nozzle temperatures to decrease energy consumption without having adverse impact on part quality. When comparing the energy consumption while using process parameters set at their minimum values compared to midpoint values, savings of 14 percent were achieved.

Fabrication of stainless steel based composite by metal injection moulding

Metal injection moulding (MIM) is large scale manufacturing method, for creation of complex shapes and miniature parts by a combination of plastic injection moulding with the flexibility in sintering of metal particulates. In current investigation binder comprised of paraffin wax, polyethylene glycol, stearic acid and low-density polyethylene are developed for moulding of composite powders of SS316L+WC-CrC-Ni, and sintered at 1200°C under hydrogen purged atmosphere. Composites are characterised with respect to rheological, thermal properties and microstructure by scanning electron microscopy, microhardness and density. Properties of sintering temperature and heating rate on the above properties have been evaluated to obtain a defect-free composite.

3D Printed Composite Keyboard Switches

This paper is a demonstration of how 3D printing can be used to create a composite (plastic and rubber) keyboard switch that is ergonomically superior to a traditional injection moulded plastic switch. The prototype switch developed in this project aims to reduce impact forces from keyboard use exerted on user’s fingers by “cushioning” the act of bottoming out the switch during a key press. This concept is significant to industry because it aims to reduce overuse injuries caused from work on computer, a portion of the $20 Billion a year owed in worker compensation in the United States. A commercial Cherry MX keyboard switch has been modified through CAD modelling and 3D printing to incorporate damping regions in the lower half of the switch housing. The switch housings were simultaneously 3D printed with plastic and rubber and their force damping properties were tested with an Arduino UNO microcontroller and force sensing resistor resting on the key tops.

DIRECT METAL LASER SINTERING, USING CONFORMAL COOLING, FOR HIGH VOLUME PRODUCTION TOOLING

Existing techniques to manufacture conventional tool steel inserts for the plastic injection moulding process are expensive and time-consuming. Complex mould inserts, difficult to manufacture with conventional processes, can be produced using Direct Metal Laser Sintering (DMLS) with Maraging tool steel (MS1). MS1 is an additive manufacturing (AM) material made available by Electro Optical Systems (EOS) GmbH. Contrary to material removal processes, DMLS can produce MS1 tool steel inserts directly from Computer-Aided Design (CAD) files suitable for high volume plastic injection moulding. Through DMLS it is possible to create conformal cooling channels inside the MS1 inserts that have advantages in reducing heat rapidly and evenly. This can result in a reduction of cycle times, cost per product as well as improving part quality by eliminating defects such as warpage and heat sinks. This paper will present a comparison between Finite Element Analysis (FEA) simulations of the injection mould inserts with actual mould trails of AM and conventional manufactured inserts. It also includes the design and manufacturing of conventional and DMLS inserts and compares the manufacturing costs and lead times. Using FEA simulations, the design of conformal cooling channels is optimised by comparing the mould temperature of different cooling channel layouts.

The Influence of Cutting Fluid Concentration on Surface Integrity of VP80 Steel and the Influence of Cutting Fluid Flow Rate on Surface Roughness of VPATLAS Steel After Grinding

The application of cutting fluid in grinding operations is crucial to control temperature levels and prevent thermal damage to the workpiece. Water-based (emulsions and solutions) coolants are used in grinding operations owing to their excellent cooling capability and relatively lower cost compared to neat oils. However, the cutting fluid efficiency is not only dependent on its type, but also on other parameters including its concentration and flow rate. In this context, this work aims to analyze the influence of the coolant concentration and flow rate on the grinding process. Two different workpiece materials for the production of plastic injection moulds were machined: VP80 and VPATLAS steel grades. Six grinding conditions (combinations of depth of cut values of 5, 15, and 25 μm with coolant concentration of 3% and 8%, respectively) were employed in the former, while two grinding conditions were used for the latter. The output parameter used to assess the influence of coolant concentration and flow rate on the grinding operation focused on the integrity of the workpiece materials (surface roughness and microhardness below the ground surface). The results showed that the surface integrity of VP80 after grinding was more sensitive to depth of cut than to cutting fluid concentration. Furthermore, the highest coolant concentration outperformed the lowest one when grinding under more severe conditions. With regard VPATLAS steel, no influence of the coolant flow rate on surface roughness was observed.

Warpage Analysis of a Plastic Spur Gear Injection Molding

The effect of various factors on the amount of warpage in an injection molded product was investigated and a plastic spur gear was used as an example. The research involved the design of a mold and die, computer-aided engineering, simulation analysis, and the determination of the plastic material and parameters. Simulation results were verified by experiment using the fabricated mold and die. Small warpage was determined using software, and the Taguchi and Response Surface Methods were used to determine the optimal parameter combinations. The optimum parameters were found to be: injection pressure, 105 MPa; packing pressure, 70 MPa; packing time, 19 s; mold temperature, 60 °C; and plastic temperature, 190 °C. The experiments were repeated, and the results were compared with the simulations to verify the reliability of the simulation results.

Wheel liner design for improved sound and structural performances

Vehicle noise is composed mainly of wheel-road noise and noise from the power unit. At low speeds power unit noise dominates while at high speeds wheel-road noise dominates as wheel-road noise level increases approximately logarithmically with speed. The wheel liner is designed as a component of the vehicle that has a multiple role. It has to prevent the dirt or water from the road surface that are engaged by the wheel to access the engine/front bay. Same time it has the important role to reduce perceived noised in the passenger’s compartment that comes from the wheel-road interaction. Progress in plastic injection moulding technology allowed for new structures to be developed – nonwoven materials in combination with a PP based carrier structure which benefits from a cell structure caused by MuCell injection moulding. The results are light parts with increased sound absorption performances. An adapted combination of materials and production processes can provide the solution for stiff yet soundproofing structures valued for modern vehicles. Sound absorption characteristics of materials used for wheel liners applications were reported in this study. Different polypropylene and polyester fibre-based thermally bonded nonwovens varying in weight and thickness were investigated. Having as a background the performances of the nonwoven material the microcellular structure was part of the analysis. Acoustical absorptive behaviour was explained by analysing the results obtained using the impedance tube and correlating with the knowledge of materials structure.

Investigation on the effects of processing parameters on shrinkage behaviour and tensile properties of injection moulded plastic gear via the Taguchi method

Controlling numerous processing parameters and sustaining the optimal performance of multiple quality characteristics give a great challenge to manufacturer to produce a high-quality product with low operating cost. It was quite tricky to find the optimal combination parameters if used unsystematic techniques such as trial and error method. In this study, the Taguchi method was adopted to identify the significant processing parameters affected the shrinkage and tensile properties of plastic gears. The effectiveness of Taguchi’s OA in reducing the number of experiment was studied and the results were analysed by ANOVA. Through the analysis, six parameters; melting temperature, mould temperature, packing pressure, packing time, cooling time and injection pressure, were carried out as significant parameters that influence dimensional stability and mechanical properties of plastic moulded gear. The findings showed that the Taguchi method is a systematic and straight forward approach that can be used in obtaining the significant processing parameters particularly in plastic gear manufacturing.

Optimisation of gate location based on weld line in plastic injection moulding using computer-aided engineering, artificial neural network, and genetic algorithm

Shock absorber is a critical element of vehicle suspension system with nonlinear characteristics. In the present work, performance of vehicle characteristics was analysed by quarter car model to study the effect of shock absorber, on the basis of linear and nonlinear damping characteristics. In addition to linear and piecewise linear, polynomial damping characteristics were considered to address the nonlinear aspect of damping characteristics. The linear and nonlinear properties of the shock absorber were incorporated in a two degree of freedom quarter car suspension system. The modelling and simulation is carried out in Adams view environment and Matlab/Simulink. A bump road profile was used to excite the quarter car suspension models. The polynomial shock absorber model was validated using experimental data taken from established literature. Simulation was undertaken to study the dynamic performance in terms of sprung mass acceleration, body displacement, suspension deflection and unsprung mass acceleration. Experimental hysteresis characteristics data, taken from established literature, were also modelled in Adams view environment and the simulated results were used for validation purpose. The suspension system response incorporating shock absorber represented by nonlinear model, hysteresis model and piece wise linear model were provided in the result section for comparison. It was observed from quantitative comparisons that the RMS values for body acceleration and body displacement of the polynomial model matched fairly well with the results of experimental hysteresis response. It was concluded that in order to study the dynamic characteristics of the vehicle accurately, nonlinear behaviour of the damper is required to be captured properly. Therefore, the proposed polynomial shock absorber model can be a better option for vehicle dynamic analysis as compared to the complex hysteresis model.

Incorporating lean thinking and life cycle assessment to reduce environmental impacts of plastic injection moulded products

In the last decades, environmental footprint of the product manufacture has emerged as an important public concern, causing manufacturers to re-assess their product's environmental impacts. Responding to global outcry on global warming, world leaders have agreed to limit global temperature rise to less than 2 °C above the temperature in pre-industrial times. As a result, governments and industrial leaders around the world have proposed a roadmap for 80% emissions reduction by 2050. The aim of this work develops a novel approach of linking Life Cycle Assessment (LCA) and Lean manufacturing to reduce the negative environmental impacts of a plastic injection moulded product. Products that use plastic as their primary source of raw materials are mainly produced by plastic injection processes. Although plastic injection moulding has many benefits such as ‘high production rates’, there is a lack of through investigation on the effects of this process has on the environment such as climate change, ozone depletion etc. This paper proposes a novel cross-functional mapping approach of linking lean-thinking and LCA. The implementation case study has been presented with the view to re-assess carbon footprint of an existing plastic product. The reported implementation work demonstrates that the adaptation of lean thinking and LCA could significantly minimise negative environmental impacts of a plastic injection product. A case study indicates that the overall environmental impact has been reduced by approximately 40% in climate change, human toxicity, photochemical oxidant formation, acidification and eco-toxicity.