Papers by Keyword: Injection Moulding

Abstract: Efficient thermal management is a key factor in improving the sustainability and productivity of injection moulding processes, particularly at the micro-scale where thermal transients strongly affect part quality and cycle stability. This work investigates the thermal behaviour of hybrid moulds composed of polymeric support plates manufactured in Precision Resin V01 and stainless-steel inserts manufactured by additive manufacturing. An experimental campaign was carried out on a micro-injection moulding machine to characterize the intrinsic thermal response of the mould under uncooled conditions. Temperatures were monitored through embedded thermocouples and used to develop and calibrate a three-dimensional transient numerical model in COMSOL Multiphysics. Particular attention was devoted to the identification and calibration of heat transfer coefficients at the injection and extraction interfaces, which were found to play a dominant role in governing insert temperature evolution. The calibrated model accurately reproduces the experimental thermal transients, with deviations below 10%, demonstrating its reliability as a predictive tool for analysing mould thermal behaviour and supporting early-stage design and process optimization. The results highlight the advantages of hybrid architectures in promoting thermal stability and provide a robust methodology for modelling heat exchange in unconventional mould configurations.

Abstract: Warpage in injection-molded thin-walled box-shaped parts is primarily caused by non-uniform cooling and differential shrinkage. This study proposes a two-step, multi-objective optimization strategy to reduce part warpage by addressing both thermal and geometric factors. In the first step, the mold cooling system is optimized through a bi-objective formulation that simultaneously minimizes (i) the temperature standard deviation within the part and (ii) the total cooling channel length. The optimization is carried out using a coupled workflow involving parametric CAD modeling, Autodesk Moldflow simulations, and a genetic algorithm. The optimized cooling design reduces temperature non-uniformity by 44% compared to a conventional cooling layout. In the second step, a geometric optimization is performed through the addition of a reinforcing border, where maximum deflection and total part volume are minimized simultaneously. The combined optimization leads to a reduction in maximum warpage from 14.5 mm in the reference configuration to 2.06 mm in the final design. The results demonstrate the effectiveness of a sequential optimization approach in achieving significant warpage reduction while maintaining material and manufacturing efficiency.

Abstract: Novel injection moulding tools have been developed using metal additive manufacturing, particularly Selective Laser Melting (SLM). These technique enables the fabrication of new complex geometries, including the integration of lattice structures within components. These structures are renowned for their lightweight and high-strength characteristics. When designed with enhanced thermal properties, lattice structures have the potential to significantly improve the performance of injection moulding tools, where efficient thermal management is of importance. To realise these innovative thermal capabilities, a comprehensive investigation of the thermal behaviour and conductivity of the structures is essential. To this end, a cost-effective experimental setup has been designed and constructed. The system employs a comparative method, whereby heat flow through a 3D-printed sample is measured in series with a reference material. By analysing the temperature gradients across both bodies, the thermal conductivity of the printed structure can be accurately determined. BK7 glass is utilised as the reference material, due to its well-characterised and stable thermal conductivity. A key factor affecting measurement accuracy is interfacial thermal resistance, which arises at the contact interface between two materials and can hinder heat transfer. This resistance is influenced b the material properties, surface finish and contact pressure. To minimize the effect of interfacial resistance and ensure more reliable conductivity measurements, multiple tests are conducted on the same structure under varying temperature conditions. This approach facilitates the identification and compensation of thermal contact resistances.

Abstract: Injection moulding is the most diverse and dynamically developing polymer processing technology. Conventional injection moulding is economically viable only in large-volume part production. However, there is an ever-growing demand for more customised, low-volume plastic products, which is called mass customization. This need can be served by the hybridisation of injection moulding with additively manufactured, low-volume injection moulds (produced for example from thermoset resins by PolyJet technology). In our work, we elaborated a novel state-monitoring and modelling method to analyse the mechanical and thermal characteristics (strains and temperature distribution) of these polymeric injection mould inserts during operation. The results of the modelling method were successfully validated by the actual injection moulding experiments, proving the adequacy of the modelling method.

Abstract: This study explored the effects of glass fiber and granite powder reinforcements on the mechanical properties of Acrylonitrile Butadiene Styrene (ABS) polymer composites produced via injection molding. Four formulations were tested: pure ABS (Batch A), ABS with 10% glass fiber (Batch B), ABS with 10% granite powder (Batch C), and a hybrid of 10% glass fiber and 10% granite powder (Batch D). Mechanical testing included tensile, flexural, compressive, impact strength, and hardness tests. Batch B showed the highest tensile strength (45.76 MPa), outperforming pure ABS (41.6 MPa), whereas the granite powder in Batch C reduced the tensile strength (36.9 MPa). Hybrid Batch D moderately improved the tensile strength (42.54 MPa) but was less effective than glass fiber alone. Batch B exhibited the highest flexural strength, whereas Batch D exhibited the highest compressive strength. The impact resistance decreased for all filled composites, particularly Batch D. Hardness was the highest in Batch D, reflecting greater material rigidity. Morphological analysis confirmed the good filler dispersion, which influenced the observed mechanical properties. Glass fiber proved to be highly effective for tensile, flexural, and hardness improvements, whereas the combination of fillers enhanced the compressive strength and hardness, offering tailored property enhancements for specific applications.

Abstract: The injection moulding industry is dynamically developing. The growing demand for more customizable products can be served by low or middle volume production using prototype moulds and inserts. The conventional material of prototype moulds is aluminum because of its excellent machinability, acceptable strength and stiffness and outstanding thermal conductivity. Prototype moulds are gaining ground in the injection moulding industry, yet their operational behavior (including exact mechanical and thermal process parameters) is largely unknown. We created a comprehensive state monitoring system that measures the operational strain, cavity pressure and temperature of different prototype injection moulds. This way, all important process parameters can be measured and the relations between the moulding parameters and the operational pressure loads, deformations and temperatures can be quantified and analysed.

Abstract: Since conventional cooling systems with channels are not adequate to achieve a high aspect quality with a short cycle time, a better concept has to be used to control the fast variation of temperature in the mold, close to the injected part. Recently, with advanced manufacturing technologies like 3D-printing, rapid heat cycle molding are developing, using for example lattice structures as heat exchanger inside the mold. Our work proposes an experimental study to analyze the influence of four lattice structures that were specifically designed for this industrial application. An instrumented bench was developed at the laboratory scale, to test the thermal efficiency of the lattice. The material and geometry of the lattice structures were selected based on their thermomechanical properties and their efficiency as a heat-exchanger. The instrumentation of the bench consists in measuring the flow rate and the pressures in the fluid, and also the temperatures at various locations. This allows us to determine the performances of the lattice structure. The results show that the denser the lattice structure, the better, whether considering the mechanical resistance or the thermohydraulic performances. The key element to understand this phenomenon is the average velocity of the fluid flowing inside the lattice structure, accelerating when the porosity decreases and thus bringing a more intense heat exchange.

Abstract: Cooling channels are critical in injection mould tooling as cooling performance influences component quality, cycle time, and overall process efficiency. Additively Manufactured moulds allow the incorporation of cooling channels conforming to the shape of the cavity and core to improve heat removal. These conformal channels can reduce the cycle time, reduce mould temperature, and enhance the temperature uniformity on the mould's surface, leading to improved quality of the moulded components and reduced wastage in the production. The design of such channels is more challenging than conventional channels; thus, Computer-Aided Engineering (CAE) has a significant role within the design process. In this paper, a novel design for conformal cooling channels for the production of a commercial component from an industrial partner is investigated. This component had issues of high cycle time and a high defect rate due to residual stresses, resulting in component shrinkage. First, the existing conventional drilled cooling channels in the mould were simulated in Autodesk Moldflow Insight to evaluate temperature distribution and cycle time. Based on the temperature distribution, conformal cooling channels were designed in Solidworks, addressing the problem areas. Next, a simulation of fluid flow in the conformal channels was conducted in ANSYS-Fluent to ensure equal flow distribution in the entire circuit, iteratively arriving at an optimal configuration. Finally, the results of the new conformal channels, including mould temperature and cycle time, were compared with conventional cooling channels in simulation. The results showed a significant reduction in cycle time and improvement in the temperature distribution, thereby minimising residual stresses and shrinkage.

Abstract: Commodity polymers are a common part of everyday life. They consist mainly of polyolefins such as polyethylene, polypropylene. They are primarily used for ease of processing, cost and especially chemical resistance. The disadvantages of these polymers are low mechanical properties as well as temperature resistance. Any improvement in the mechanical properties can extend the application possibilities of the commodity polymers to the areas reserved for the construction polymers. This paper deals with changing two injection moulding process parameters - melt and mould temperature to high-density polyethylene (HDPE) surface hardness. HDPE hardness was measured using the method of Depth-Sensing Indentation (DSI) on three different instruments (ultranano-, nanoand micro-hardness tester). It has been found that as the melt and mould temperature increases, the hardness slightly increases.

Abstract: 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.