Moulding Tools Research Articles

Developing a hybrid-built pre-hardened alloy steel for injection moulding tools using the laser powder bed fusion process

Hybrid additive-subtractive manufacturing has been adopted as a cost-effective alternative for manufacturing plastic injection moulding tools with conformal-cooled inserts created by fusing powder and wrought material. This article reports the development of a hybrid power-wrought pre-hardened alloy steel to supplement the current material choice for fabricating injection mould inserts using this advanced manufacturing strategy. In this study, MS1 (maraging 300) steel powder was additively deposited onto pre-machined wrought Nimax steel to form a hybrid alloy material. The mechanical and microstructural properties of the fusion-bonded interface were examined. Microstructural observation revealed a 280 μm thick interfacial region consisting of a homogenous mixing of powder and substrate materials. As a result of solid solution strengthening within the region, tensile tests established robust powder-substrate bonding with tensile ruptures occurring well away from the interface. The as-built hybrid-alloy steel possessed excellent mechanical properties, with 1200 MPa in ultimate tensile strength, 12.4 % in elongation at fracture and 39 HRC (Nimax)/42 HRC (MS1) in hardness. The overall results suggested that hybrid MS1-wrought Nimax steel is a suitable pre-hardened material for manufacturing durable and high-performance injection mould inserts as part of a cost-effective hybrid additive-subtractive manufacturing strategy.

Comparative evaluation of vat photopolymerization and steel tool molds on the performance of injection molded and overmolded tensile specimens

AbstractThis study explores the use of vat polymerization stereolithography (SLA) for fabricating mold tooling, subsequently utilized in injection molding (IM) and overmolding of tensile specimens and directly compared to those produced using metal molds. The results first find the manufacturing time for an SLA‐fabricated mold is remarkably short, approximately 6 h, presenting a substantial improvement over traditional methods. Mechanical testing revealed that the tensile specimens from the SLA‐fabricated molds exhibited the highest tensile strength among all overmolding batches. This performance was consistent with the tensile bars produced using metal molds, demonstrating the viability of SLA‐fabricated molds for overmolding applications and highlighting the potential of FDM to customize the properties of final products. However, variations in mold types impacted the dimensional tolerance and tensile strength of the final specimens. Metal mold‐fabricated tensile bars exhibited superior dimensional accuracy and maximum tensile strength (50.6–61.7 MPa) compared to those produced with SLA‐fabricated molds (46.9–55.9 MPa). These differences are attributed to the rougher surface finish inherent to the layer‐by‐layer construction of SLA and the internal stresses and defects resulting from lower thermal conductivity and uneven cooling. In conclusion, this study underscores the promising future applications of SLA‐fabricated molds in overmolding, offering reduced manufacturing costs and enhanced design freedom. The findings support the potential of SLA to revolutionize mold fabrication, thereby extending its utility and optimizing the production of polymer components with customized properties.Highlights SLA molds compared to metal molds for direct injection molding and overmolding. FFF preforms with varied geometries were overmolded to finalize the specimens. Joint configurations in overmolding improved tensile performance. Overmolding showed better dimensional accuracy than FFF specimens. SLA mold preparation significantly reduced manufacturing costs.

Investigation of the Replication Quality of Microstructures on Injection Moulded Specimens Made from Recycled Polypropylene Composites Reinforced with Carbon Nanotubes

During the research, functional microstructures were created on the cavity surface of the injection moulding tool using femtosecond laser technology. Automotive-grade polypropylene (PP), as well as its recycled and carbon nanotube-reinforced composites, were used as the raw materials. The replicated structures were examined using confocal microscopy. It is expected that by optimizing the process parameters, the filling of the structured cavity surface with nanocomposite materials can reach a quality level comparable to plastic specimens made from non-reinforced raw materials. The aim is to provide results of scientific and industrial value to demonstrate the influence of the modified mould surface on the flow of the polymer melt and thus on the filling of the injection moulded products.

Design of Work Facility Improvements with a Macroergonomic Analysis and Design (MEAD) Approach in SMEs Andri Tofu

Small and Medium Enterprises Andri tofu is an industry engaged in food production which is located in Ngrampal District, Sragen. In the production process there is a non-optimal working system, where the process of setting up the mold tool takes more than 1 minute and the pressing process uses a load of more than 17 kg in the form of using a 20 liter bucket full of water. The purpose of this study is to identify the factors that influence the work system, measure complaints and posture, and design work facility improvement designs. The method used is in the form of Macroergonomic Analysis and Design to design work systems and facilities based on the location of the highest deviation. The results of the study found that there were dominant body complaints on the right hand by 5.18% and mild complaints on the thighs by 1.41%. Improvements to the design of the tool have an adjustable height of 140-170 cm, a width of 72 cm, a height of 57 cm for the feet of the tool, and the pressing uses a gear system with a rack gear of 70 cm and diameter a spin gear of 6 cm which is driven using a rotary press stirrer.

Study on the Effect of Recycled Brass-Filled Epoxy Mould Inserts for Rapid Tooling

Rapid Tooling able to produce complex prototypes directly from three-dimensional CAD software using materials such as polymer, wax, and paper, but it is typically used for low-volume production. The current technology uses epoxy filled with metal fillers such as aluminum or copper to enhance the mechanical properties of rapid tooling molds. This study aims to investigate the effect of using recycled brass filler mixed with epoxy resin as mold inserts for Rapid Tooling in injection molding applications. An optimal ratio of brass filler particles will be evaluated to determine the best physical and thermal properties for the mold inserts. Significantly, this study will encourage the use of recycled materials such as metal waste from machining to offer great help in environmental sustainability.

Generative design of conformal cooling channels for hybrid-manufactured injection moulding tools

Effective cooling systems for injection moulding (IM) tools are critical to reducing manufacturing costs and cycle time for the polymer parts produced. This work presents a novel automated methodology for designing conformal cooling channels (CCCs) for IM tools via interlinking commercial moulding simulation tools with custom scripts. These scripts adjust CCC design in response to the spatial variability in global and local temperatures at the mould tool-part interface (MTPI) via generative design (GD). Four tool designs for manufacturing a simplified part were analysed numerically simulation and experimentally, including tools with either straight-drilled (non-conformal) cooling channels (tool steel), a manually designed CCC system (stainless steel or bronze alloy), or an automatically designed CCC system (stainless steel). While both manually designed CCC tools cool the part faster than the non-conformal tool (3–5% predicted vs. 40% measured for stainless steel and 9–12% predicted vs. 40% measured for bronze alloy), the GD-optimised CCC tool outperformed both (15–30% predicted faster cooling vs. 70% measured). The predicted MTPI temperature feature achieves reductions to both maximum and spatial variability in MTPI temperatures, which lead directly to significant reductions in manufacturing cycle time and polymer part warpage. These findings could have a major impact on the IM industry by reducing tool design costs and raw material waste via improving moulded part quality.

Analysis of self-supporting conformal cooling channels additively manufactured by hybrid directed energy deposition for IM tooling

Additive manufacturing (AM) of injection moulding (IM) tools has attracted significant interest in the polymer manufacturing industry for quite some time. However, hybrid manufacturing (HM) using directed energy deposition (DED), which involves concurrent additive and subtractive manufacture, has not been a commonly used process for IM tooling manufacture. This is apparent despite several advantages over the prevalent laser-powder bed fusion (L-PBF) alternative, including higher build rate, lower cost and integrated machining to directly achieve higher tolerances and surface finish. A key reason for this low utilisation is the limited ability of DED processes to produce circular channel profiles typically used in IM tooling, due to stricter constraints on the manufacturability of overhanging geometry. To address this, a range of self-supporting IM cooling channel profiles suited for hybrid laser and powder-based DED manufacture are proposed in this work. Numerical and experimental evaluations are conducted of the cooling performance of several non-circular conformal cooling channel (NCCC) profiles to identify a profile which achieves the maximum heat transfer for a constant cross-sectional area and coolant flow rate. Experimental studies included AM builds to evaluate the DED manufacturability of the selected NCCC profile on a conformally cooled HM benchmark model, followed by cooling performance characterisation, including a comparison against a reference L-PBF manufactured benchmark model. In conclusion, a shape correcting factor is obtained using response surfaces. This factor is used to convert thermal performance calculations for non-circular profiles to a conventional circular channel profile to simplify the DED manufacturing process for non-circular IM cooling channels.

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Precise tooling is vital for defect-free production of micro injection moulded (μ-IM) or hot-embossed products. The demoulding stage of such moulding and forming processes poses a serious challenge to the integrity of thin miniature features because of friction, adhesion, and thermal stresses. Typically, micro moulds involve geometrically textured patterns or features such as linear ridges, pillars, channels, and holes, the characteristic dimensions of which range from 10 to 300 μm. Realistically complex mould designs, containing precision micro features (enhanced fillet radius and positive draft angle) and high surface quality, are presented in this work. Electropolishing based on forward pulse currents (PC) has been used to shape and polish Ni micro moulds that contain sets of micron-scaled linear ridges and star patterns in order to ease the separation of moulded polymeric parts from the metallic mould during ejection and demoulding. The use of forward pulsed currents improved the mould design by increasing the fillet radii and draft angle while keeping the surface roughness low and maintaining a good surface shine. An optimization study of forward PC using a green solution of nickel sulfamate varied EP times (0–70 min) and duty cycles (40, 50, 60, and 70%) at a process conditions of 2.8 V, 50 °C, and 250 rpm. The best topographical and morphological changes were observed for a typical microfluidic channel (w × h, 100 × 110 μm) with an EP time of 70 min and 50% duty cycle: fillet radius increased by 3.8 μm, draft angle by 3.3°, and the channel width reduced by 11.4% while surface roughness changed by 8.6% and surface shine improved by 48.9%. Experimental validation was performed using hot embossing wherein the electropolished Ni mould replicated the micro channels and star patterns in PMMA chips with notably fewer burrs, material pile up, and no feature distortion. Moreover, there was a reduction in the side wall roughness of micro channels in PDMS casting with electropolished Ni mould by 16%. Hence, this work presents a significant scientific contribution to improving the efficiency of micro mould tools and reduces the defects caused by friction and adhesion in replicated polymeric parts.

Embedding a surface acoustic wave sensor and venting into a metal additively manufactured injection mould tool for targeted temperature monitoring

Injection moulding (IM) tools with embedded sensors can significantly improve the process efficiency and quality of the fabricated parts through real-time monitoring and control of key process parameters such as temperature, pressure and injection speed. However, traditional mould tool fabrication technologies do not enable the fabrication of complex internal geometries. Complex internal geometries are necessary for technical applications such as sensor embedding and conformal cooling which yield benefits for process control and improved cycle times. With traditional fabrication techniques, only simple bore-based sensor embedding or external sensor attachment is possible. Externally attached sensors may compromise the functionality of the injection mould tool, with limitations such as the acquired data not reflecting the processes inside the part. The design freedom of additive manufacturing (AM) enables the fabrication of complex internal geometries, making it an excellent candidate for fabricating injection mould tools with such internal geometries. Therefore, embedding sensors in a desired location for targeted monitoring of critical mould tool regions is easier to achieve with AM. This research paper focuses on embedding a wireless surface acoustic wave (SAW) temperature sensor into an injection mould tool that was additively manufactured from stainless steel 316L. The laser powder bed fusion (L-PBF) “stop-and-go” approach was applied to embed the wireless SAW sensor. After embedding, the sensor demonstrated full functionality by recording real-time temperature data, which can further enhance process control. In addition, the concept of novel print-in-place venting design, applying the same L-PBF stop-and-go approach, for vent embedding was successfully implemented, enabling the IM of defectless parts at faster injection rates, whereas cavities designed and tested without venting resulted in parts with burn marks.

Enhancing Metal Forging Tools and Moulds: Advanced Repairs and Optimisation Using Directed Energy Deposition Hybrid Manufacturing

This article investigates the efficacy of directed energy deposition (DED) processes in repairing forging tools and moulds, comparing mechanical properties between specimens fabricated from conventional sheet metal and those manufactured by DED techniques. A comparative analysis reveals significant mechanical differences between subtractive and DED-manufactured specimens, emphasising the nuanced balance between tensile strength and ductility in DED-produced components influenced by layering. Notable insights from scatter plot analyses highlight distinct material behaviours, particularly layer-dependent tendencies in DED-manufactured specimens. Regression-based predictive models aid in understanding material behaviours, aiding in informed material selection for manufacturing processes. Additionally, this article underlines the advantages of DED-based repair processes, highlighting precision, material efficiency, reduced lead times, and cost-effectiveness. The article studies die and mould repair, tool restoration, and critical considerations like material compatibility and quality assurance. The study concludes by emphasising the role of hybrid manufacturing in extending product lifecycles, in conformity with specific mechanical requirements, and fabricating complex geometries, despite potential higher costs in materials and technologies. Overall, this research demonstrates the efficacy of DED processes in enhancing component reliability and lifespan in metalworking industries.

LCA and LCC of wire arc additively manufactured and repaired parts compared to conventional fabrication techniques

Multi-material wire arc additive manufacturing (MM-WAAM) exhibits considerable promise for producing functional gradient materials, components with complex design, and enable a more local supply chain. However, it is still to be determined for which industrial applications MM-WAAM present more benefits than conventional production routes both in terms of environmental and economic impacts. This study undertook a comprehensive cradle-to-grave assessment encompassing two distinct metallic components, manufactured via either additive manufacturing (AM) or conventional fabrication procedures. One of those is a repair case of a forging die, and the other is the production of an industrial tool. Analysis outcomes manifestly revealed pronounced benefits associated with MM-WAAM for these components. For instance, the utilization of MM-WAAM in crafting an optical fiber case injection mould tool yielded energy consumption reduction, attributed to enhanced conformal cooling channels. Additionally, the repair of a forging die via MM-WAAM showcased the potential to curtail new scrap generation during post-processing, prolonging tool lifespan. This study conclusively shows the application-specific nature of MM-WAAM's favourability over traditional processes, thereby offering valuable insights for strategic implementation.

THE EFFECT OF CRYOGENIC TREATMENT ON THE INCREASE OF PROPERTIES OF A PLASTIC MOULD STEEL

The article presents experiments aimed at increasing the properties of a plastic mould tool steel with a special heat treatment technology called shallow cryogenic treatment. Our chosen steel grade was Böhler M340 ISOPLAST. We would like to show how cryogenic treatment affects the wear and corrosion properties of this particular steel grade. We can conclude with tests and calculations that the cryogenically treated specimen showed at least 40% better wear and corrosion resistance properties, then the one treated with conventional heat treatment. Based on these findings, we expect that the tool life will also be longer using this heat treatment technology.

Studies on Protective Coatings for Molding Tools Applied in a Precision Glass Molding Process for a High Abbe Number Glass S-FPM3

Precision glass molding (PGM) is an efficient process used for manufacturing high-precision micro lenses with aspheric surfaces, which are key components in high-resolution systems, such as endoscopes. In PGM, production costs are significantly influenced by the lifetimes of elaborately manufactured molding tools. Protective coatings are applied to the molding tools to withstand severe cyclic thermochemical and thermomechanical loads in the PGM process and, in this way, extend the life of the molding tools. This research focuses on a new method which combines metallographic analysis and finite element method (FEM) simulation to study the interaction of three protective coatings—diamond-like carbon (DLC), PtIr and CrAlN—each in contact with the high Abbe number glass material S-FPM3 in a precision glass molding process. Molding tools are analyzed metallographically using light microscopy, white light interferometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results show that the DLC coating improved process durability more than the PtIr and CrAlN coatings, in which the phenomenon of coating delamination and glass adhesion can be observed. To identify potential explanations for the metrological results, FEM is applied to inspect the stress state and stress distribution in the molding tools during the molding process.

Additively manufactured cure tools for composites manufacture

This research presents a novel framework for the design of additively manufactured (AM) composite tooling for the manufacture of carbon fibre-reinforced plastic composites. Through the rigorous design and manufacture of 30 unique AM tools, the viability of a design for AM framework was evaluated through measuring the performance with respect to geometrical accuracy and thermal responsiveness, and simulating the tool specific stiffness. The AM components consisted of a thin layup facesheet, stiffened by a low density lattice geometry. These tools were successfully used to layup and cure small composite components. The tooling was highly thermally responsive, reaching above 93% of the applied oven heating rate and up to 17% faster heating rates compared to similar mass monolithic tools. The results indicate that thermal overshoot has a greater dependence on the lattice density while the heating rate was more sensitive to the facesheet thickness. Lattice densities of as little as 5% were manufactured and the best overall geometry was a graded gyroid lattice with thicker walls near the surface and thinner walls at the base, attached to a 0.7 mm thick facesheet. The outputs from this research can provide a new route to the design and manufacture of mould tools, which could have significant impacts in the composites sector with new, lighter, more energy efficient tooling.

A Novel Feature-Based Manufacturability Assessment System for Evaluating Selective Laser Melting and Subtractive Manufacturing Injection Moulding Tool Inserts

Challenges caused by design complexities during the design stages of a product must be coordinated and overcome by the selection of a suitable manufacturing approach. Additive manufacturing (AM) is capable of fabricating complex shapes, yet there are limiting aspects to surface integrity, dimensional accuracy, and, in some instances, design restrictions. Therefore, the goal is essentially to establish the complex areas of a tool during the design stage to achieve the desired quality levels for the corresponding injection moulding tool insert. When adopting a manufacturing approach, it is essential to acknowledge limitations and restrictions. This paper presents the development of a feature-based manufacturability assessment system (FBMAS) to demonstrate the feasibility of integrating selective laser melting (SLM), a metal-based AM technology, with subtractive manufacturing for any given part. The areas on the tool inserts that hold the most geometrical complexities to manufacture are focused on the FBMAS and the design features that are critical for the FBMAS are defined. Furthermore, the structural approach used for developing the FBMAS graphical user interface is defined while explaining how it can be operated effectively and in a user-friendly approach. The systematic approach established is successful in capturing the benefits of SLM and subtractive methods of manufacturing, whilst defining design limitations of each manufacturing method. Finally, the FBMAS developed was validated and verified against the criteria set by experts in the field, and the system’s logic was proven to be accurate when tested. The decision recommendations proved to correlate with the determined recommendations of the field experts in evaluating the feature manufacturability of the tool inserts.

Life cycle assessment of injection moulding tools and multicomponent plastic cap production

Long-term product improvement requires detailed analysis that includes information from the entire product life cycle. Life cycle assessment according to the standards ISO 14040 and ISO 14044 provides information on the environmental impact of products throughout their life cycle. The aim of the study is to analyze the environmental impact of a multicomponent plastic product in two variants and the associated customized tools using life cycle assessment. The subject of this analysis is the previous and the improved design of a multicomponent plastic cap for 19 l water bottles and the associated custom-manufactured tools. The main improvements of the custom-made tools are in the larger number of cores, and the new cap design was improved with fewer components and mass. The results show that the production and packaging of the improved multicomponent plastic cap has more than two times lower environmental impacts in the categories of global warming potential, freshwater eutrophication, terrestrial acidification ozone formation, human health and non reneweable, fossil. The environmental impact of custom injection moulding tools is strongly influenced by the capacity of the injection moulding machine and the number of cores or number of products that can be produced in a batch. In addition, the results of the improved 19 l multicomponent plastic cap showed a lower environmental impact compared to previous studie of the 5 l plastic cap.

Precision electroforming of nickel nanocomposite mould for defects-free demoulding in polymer micro replication: Surface properties, performance validation and mould release mechanism

Microinjection moulding and micro/nano hot embossing are two promising manufacturing processes for the mass production of polymer workpieces with micro/nano structures. However, adhesion and friction between polymer workpieces and mould tools can cause structural distortion and surface damage. Besides, the nickel mould's lifetime is limited by its low hardness and wear resistance. To address these issues, we proposed a new methodology to codeposit micro/nanomaterials into nickel mould for microhardness enhancement and effective mould release. In this study, polytetrafluoroethylene (PTFE) microparticles, tungsten disulfide (WS2) and molybdenum disulfide (MoS2) nanosheets were incorporated into nickel mould by electroforming. Cobalt was added as a secondary phase to improve the microhardness and wear resistance of the composite mould. The result indicated that WS2 nanosheets achieved the most significant performance enhancement among three micro/nanomaterials, represented as the microhardness improved from 191 HV for pure nickel to 564 HV for nickel/WS2 nanocomposites, along with the coefficient of friction (COF) against the polymethyl methacrylate (PMMA) pin reducing from 0.72 to 0.10 in the initial stage of the sliding. With the incorporation of micro/nanomaterials, the wettability altered from hydrophilic for pure nickel to hydrophobic for the composite moulds. The study shows that the addition of cobalt improved the microhardness of the composite moulds but meanwhile induced more adhesive wear during the pin-on-disc test. Finally, a nickel/WS2 nanocomposite mould is successfully fabricated via electroforming with feature sizes from 70 to 180 μm and its lubricating properties are validated by micro hot embossing PMMA microfluidic chips with good surface quality and structural integrity.

Adhesion-Induced Demolding Forces of Hard Coated Microstructures Measured with a Novel Injection Molding Tool

The demolding of plastic parts remains a challenging aspect of injection molding. Despite various experimental studies and known solutions to reduce demolding forces, there is still not a complete understanding of the effects that occur. For this reason, laboratory devices and in-process measurement injection molding tools have been developed to measure demolding forces. However, these tools are mostly used to measure either frictional forces or demolding forces for a specific part geometry. Tools that can be used to measure the adhesion components are still the exception. In this study, a novel injection molding tool based on the principle of measuring adhesion-induced tensile forces is presented. With this tool, the measurement of the demolding force is separated from the actual ejection step of the molded part. The functionality of the tool was verified by molding PET specimens at different mold temperatures, mold insert conditions and geometries. It was demonstrated that once a stable thermal state of the molding tool was achieved, the demolding force could be accurately measured with a comparatively low force variance. A built-in camera was found to be an efficient tool for monitoring the contact surface between the specimen and the mold insert. By comparing the adhesion forces of PET molded on polished uncoated, diamond-like carbon and chromium nitride (CrN) coated mold inserts, it was found that a CrN coating reduced the demolding force by 98.5% and could therefore be an efficient solution to significantly improve demolding by reducing adhesive bond strength under tensile loading.

In-cavity pressure measurements for failure diagnosis in the injection moulding process and correlation with numerical simulation

The pressure profile analysis for monitoring and diagnosis processing failures during an injection moulding process, such as burn marks and short shots, is a useful instrument for process and part quality control and production with zero defects and greater efficiency. Therefore, this work aims to demonstrate the in-cavity pressure monitoring feasibility for failure diagnosis and injection moulding process optimization. The methodology used to analyse the obtained pressure variation is presented. The results were correlated to the typical cavity pressure profile, which enables the acquisition of information about the process and the moulding tool. This way, it was possible to determine the origin of the defects present in the injected parts, focusing not only on the velocity to pressure switchover but also on the initial part of the curve, related to the filling phase. Moreover, the obtained results and the studied processing conditions were correlated with the injection moulding process simulation.

Condition Monitoring of Additively Manufactured Injection Mould Tooling: A Review of Demands, Opportunities and Potential Strategies.

Injection moulding (IM) is an important industrial process, known to be the most used plastic formation technique. Demand for faster cycle times and higher product customisation is driving interest in additive manufacturing (AM) as a new method for mould tool manufacturing. The use of AM offers advantages such as greater design flexibility and conformal cooling of components to reduce cycle times and increase product precision. However, shortcomings of metal additive manufacturing, such as porosity and residual stresses, introduce uncertainties about the reliability and longevity of AM tooling. The injection moulding process relies on high volumes of produced parts and a minimal amount of tool failures. This paper reviews the demands for tool condition monitoring systems for AM-manufactured mould tools; although tool failures in conventionally manufactured tooling are rare, they do occur, usually due to cracking, deflection, and channel blockages. However, due to the limitations of the AM process, metal 3D-printed mould tools are susceptible to failures due to cracking, delamination and deformation. Due to their success in other fields, acoustic emission, accelerometers and ultrasound sensors offer the greatest potential in mould tool condition monitoring. Due to the noisy machine environment, sophisticated signal processing and decision-making algorithms are required to prevent false alarms or the missing of warning signals. This review outlines the state of the art in signal decomposition and both data- and model-based approaches to determination of the current state of the tool, and how these can be employed for IM tool condition monitoring. The development of such a system would help to ensure greater industrial uptake of additive manufacturing of injection mould tooling, by increasing confidence in the technology, further improving the efficiency and productivity of the sector.