Transforming plastic injection molding with additive manufacturing: a novel systematic review of innovative approaches to insert production

Additive manufacturing (AM) has revolutionized various engineering fields because of its ability to build high-quality parts more quickly and cost-effectively (Agnusdei and Del Prete, 2022). AM is an active area of research for the injection molding (IM) process, particularly in manufacturing mold inserts. Although techniques that involve chip removal via Computer Numerical Control Machining (CNC) have been used to manufacture traditional molds (Park et al., 2022; Gibson et al., 2020), AM currently offers several advantages in mold design over these conventional mold manufacturing techniques (Lozano et al., 2022; Rodriguez, 2016), showing the significance of combining both processes. These advantages include:

• More design flexibility: Mold inserts produced by AM processes can create virtually any geometric design, even highly complex ones that would be extremely difficult to machine (Kočov and Tuteski, 2018). Because of this design flexibility, the inserts produced by AM – unlike conventional molds – have the capability of producing conformal cooling channels involving an innovative technique in mold design that can achieve shorter cycle times (Lozano et al., 2022).

• Shorter lead times and lower costs: AM inserts can be produced faster than a conventional mold while, at the same time, they offer more cost advantages (Kampker et al., 2018). This is because the inserts can be produced by several AM processes using both polymeric and metallic materials (Mendible et al., 2017), which have a lower cost than conventional molds. The lead time could be reduced by up to 50% and the cost between 20% and 66% compared to conventional molds (Kampker et al., 2020).

Different AM processes are being used for injection mold insert manufacture:

• Material jetting (MJT) – also known as PolyJet – consists of depositing liquid drops to form layers that are cured to shape the piece.

• Vat photopolymerization (VPP), where a liquid photopolymer in a vat is selectively cured by light-activated polymerization via UV light through laser (VPP-UVL) – also called Stereolithography (SLA) – or via UV light through a mask (VPP-UVM) – also known as Digital Light Processing (DLP).

• Material extrusion (MEX) – commercially known as Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF) – which deposits molten material through a nozzle to produce each layer.

• Powder bed fusion with a laser beam (PBF-LB) by which metal material powders (PBF-LB/M) – popularly termed as Selective Laser Melting (SLM) – or plastic material powders (PBF-LB/P) – such as Selective Laser Sintering (SLS) – in a bed are selectively sintered or fused to form the final part layer by layer (American Society for Testing and Materials, 2022).

In general, the production of injection mold inserts through AM has constantly evolved, and their advancements have been documented in publications of recent years, showcasing the significant potential for the future of IM. However, there is no clearly defined methodology for manufacturing and using additive inserts in the IM process.

Only two studies that review the different research projects carried out for injection mold inserts were found in the literature. In 2018, Tuteski and Kočov conducted a study regarding the use of AM processes for manufacturing injection mold inserts, focusing on two AM processes (PBF and VPP-UVL) and their potential use for conformal cooling. They concluded that, with precise control of the injection process parameters, it could be possible to use these AM processes to produce short series of good quality parts. In 2022, Lozano et al. conducted a literature review on advancements in AM processes and materials used in insert manufacturing. They compared AM polymer molds against metal molds that were manufactured conventionally. However, this study focuses on an assessment of the costs associated with these AM processes and on the recommendations for the mold insert design. These two reviews were not carried out systematically following a PRISMA methodology, they have focused on specific AM processes or particular aspects, such as cooling, mold design and failure types, while considering a number of studies without a specific search protocol.

This paper aims to provide a comprehensive systematic review of AM processes and materials (polymer and metal) for producing inserts for IM plastic parts with the key findings from research articles presented in the last decade. This is the first systematic review on the topic that provides a detailed methodology for collecting articles and considers a larger number of articles (67) for evaluation and discussion. The results regarding the mechanical and thermal properties of inserts and the number of injection cycles achieved are analyzed.

For this systematic review, the PRISMA methodology was used. This methodology consists of a checklist with recommendations to properly structure the systematic review, providing more precise and transparent results. These recommendations include a series of steps, such as defining the research question and objectives, identifying all relevant study reports, determining inclusion and exclusion criteria, critically and accurately prioritizing studies and assessing the risk of bias during the study (Selçuk, 2019). It also provides a flow diagram for collecting and discarding the articles found. Below, each of the steps carried out for this review is described.

The first step to develop a systematic review is to set a clear, structured and focused research question (Bramer et al., 2017). In accordance with the PICO methodology (Higgins et al., 2008), the PICO question that defined the search strategy is as follows:

The PICO question involves the manufacture of inserts for IM as a problem, the AM processes as an intervention, the consideration of manufacturing inserts by conventional machining to make the comparison and the validation of AM processes for manufacturing inserts as outcomes.

The search used Scopus, Web of Science and Google Scholar databases. Google Scholar searches are generally limited to at least the first 200 relevant references (Bramer et al., 2017). In this case, the first 250 references found were selected according to relevance. The literature search considered two main terms, “additive manufacturing” and “injection molding,” manually filtered by some criteria: publication year (2013–2024), document type (review, conference paper and article), subject areas (engineering, materials science, physics and astronomy, computer science, chemical engineering, chemistry and mathematics) and language (English). A 10-year timeframe was set because AM has experienced a high growth, both in academic and industrial environments (Pérez et al., 2020) and because it has been mainly in the past decade where AM processes have been used specifically in terms of the production of injection mold inserts.

In addition, inclusion and exclusion criteria were established to select the articles that could provide the most transparent and precise answers to the research question. Table 1 shows the inclusion and exclusion criteria used to select the relevant studies to assess the feasibility of AM inserts for plastic IM.

Using a PRISMA diagram is encouraged to depict the flow of studies across the different stages of the systematic review with clarity and precision (Kahale et al., 2021). The diagram has four main stages. The first stage involved the main search using the selected keywords and the manual filtering process of the studies. In the second stage, 520 duplicate studies from Google Scholar, Web of Science and Scopus and studies with titles focused on other topics were excluded. On the other hand, in the third stage, the studies were evaluated, and those that did not comply with the specific inclusion criteria were removed. Finally, the studies to include in this systematic review were selected in the fourth stage. The PRISMA methodology was complemented by a final manual search to obtain relevant studies not identified with the PRISMA methodology but that were referenced in any of the 57 records. Ten articles were manually found. The PRISMA diagram procedure is shown in Figure 1.

In all review studies, assessing the risk of bias is essential to obtain as robust conclusions as possible (Higgins et al., 2008). Two reviewers were asked to make their selections independently to ensure the inclusion/exclusion criteria were clearly established and correctly understood. The concordance between the selection made by each of the two reviewers compared to the initial selection made by the first author of this paper was determined using Cohen’s kappa statistical method (McHugh, 2012). Cohen’s kappa coefficients were calculated, resulting in values of 0.73 and 0.48, indicating a “substantial” and “moderate” agreement. Subsequently, any uncertainties regarding established criteria were reviewed and clarified through discussion, and the principal reviewer conducted the bias risk assessment based on this discussion. The domain-based assessment is one of the most recommended tools for evaluating bias risk in a systematic review (Higgins et al., 2008). The Cochrane review (Higgins et al., 2008) suggests six primary domains for assessing the risk of bias; however, two of them focus more on assessing randomized studies rather than studies such as the present review, which is based on data obtained from a clear set of inclusion criteria. For this reason, four of the six domains were selected to assess the risk of bias in non-randomized studies. Table 2 displays the Cochrane-proposed domains used for bias risk assessment in this systematic review.

After describing the domains, a bias risk assessment was conducted for each of the 67 studies included in this review, considering compliance with the inclusion/exclusion criteria and the relevant information that the selected publications could provide regarding the research question posed. In this way, when addressing each study according to its characteristics, an assessment was made based on the response to a question. Thus, a “Yes” response indicates a low risk of bias, while “No” indicates a high risk of bias, and an “Unclear” response indicates uncertainty regarding bias (Higgins et al., 2008). Finally, an overall bias analysis was conducted based on each article’s independent bias risk assessment, obtaining an overall low bias risk (Figure 2).

The publication site and year were considered for the bibliometric analysis. Moreover, the open-access software VOSviewer 1.6.19 (Leiden University, Netherlands) was used to verify the keywords used in the search through an analysis of the co-occurrence of the keywords contained in the 67 articles included in this review, which reflects the semantic structure of the research field and display the descriptors used by both authors and journals.

Although there are different perspectives from which to evaluate the performance of an insert, depending on the outcomes desired in the final product (good surface quality, good mechanical properties, low or medium volume production and so on), this systematic review compares technical aspects related to mechanical properties and the number of cycles completed for different inserts in the case of polypropylene molding. In addition, it provides the most commonly used AM processes and materials for the manufacture of injection inserts.

The articles selected were relevant and able to correctly address the research question, obtaining an overall low bias risk and serving as a means to validate the results obtained regarding the feasibility of using AM processes for injection mold insert production. After selecting the articles according to the eligibility criteria, evaluating the risk of bias and obtaining an overall low risk of bias, the most relevant articles are summarized in Table 3.

According to the results obtained, the studies for producing injection mold inserts presented greater interest between 2017 and 2022, with 2019 being the year with the largest number of publications. Of the 67 publications selected for this study, 56.25% correspond to research articles, 40.63% to conference papers and 3.13% to bibliographic reviews. The site, the Impact Factor, the Journal Citation Indicator (Journal Citation Report, 2023), and the frequency of the most used channels for publishing research related to the use of AM processes in polymer injection mold production are: Procedia Manufacturing (-) with five articles; Journal of Manufacturing Processes (1.17), Polymers (0.93) and Rapid Prototyping Journal (0.83) with four articles; Procedia CIRP (-) with three articles; Manufacturing and Materials Processing (0.65), Materials (0.58), Additive Manufacturing (1.95), AIP Conference Proceedings (-) and The International Journal of Advanced Manufacturing Technology (0.57) with two articles. It is worth noting that conference journals do not have these indicators.

On the other hand, Figure 3 depicts the co-occurrence keyword map and the use of these keywords as descriptors increase over time. The most frequently used words proved to be “additive manufacturing” and “injection molding,” confirming the selection of terms used to locate the articles included in this systematic review as the primary terms encompassing this research area. In addition, Tosello, G. has produced the most publications in the research area. As such, it was found that Tosello G. and Pedersen D. are the authors who have collaborated the most in the area and that their studies have proved to be a reference for the rest of the publications.

Figure 4 shows the AM processes and the most commonly used materials to assess their potential application in inserts for injection molds. MJT is the most commonly used in the articles reviewed in this study, followed by VPP-UVL and PBF-LB/M.

The number of publications found shows that adopting AM processes to produce inserts for polymeric materials is feasible, with each study providing different approaches to evaluate these inserts and their performance in the IM. Thus, the main criteria to evaluate the feasibility of inserts have been:

• Mechanical properties: Mechanical strength is typically considered to evaluate the insert's performance in the process, as the mold is subjected to various forces and pressures during the IM process, which can deform or even break it. Figure 5 shows the tensile strength for different combinations of AM process and material used to produce inserts in some of the 67 studies selected in this review. The graph shows that the greatest tensile strength is achieved using a metallic material. The digital acrylonitrile butadiene styrene (ABS) material presents 58 ± 1,76 MPa, which matches the range provided by Stratasys (55–60 MPa) (Stratasys, 2021), except in one case where strength dropped to approximately 35 MPa. However, such a decrease could be attributed to a change in printing orientation (Mendible et al., 2022). As for VPP-UVL, the material that offers the greatest strength is Accura Bluestone (67 MPa), followed by Accura SL 5530 (60 MPa). However, these materials are not typically assessed, which may be attributed to their high cost compared to other materials used for the VPP-UVL process (High-Temperature and Tough resins) (Kampker et al., 2018).

• Thermal properties: Inserts reach high temperatures that they must be capable of withstanding; moreover, the cooling process induces warpage, which can break the insert's finest features during ejection. Therefore, it is suggested that optimal mold temperature be first determined and pressure gradually increased on the insert (Bagalkot et al., 2019a). To minimize degradation or deformation, inserts must effectively dissipate heat to avoid overheating and ensure a uniform temperature distribution; hence, thermal conductivity is essential to ensure that heat is uniformly distributed throughout the mold insert. As good thermal conductivity ensures uniform heat distribution, it has been demonstrated that thermal simulations are a useful and accurate tool for researching temperature evolution in IM inserts (Lozano et al., 2023). Table 4 shows the thermal conductivity values gathered from experimental studies included in some of the 67 articles evaluated in this systematic review. Tests were carried out, as this parameter is not included in the technical data sheets provided by manufacturers, despite being a relevant property – at least for this application. As good thermal conductivity ensures uniform heat distribution, it has been demonstrated that thermal simulations are a useful and accurate tool for researching temperature evolution in IM inserts (Lozano et al., 2023).

• Surface quality: The insert's surface should have a smooth and polished finish to ensure optimal insert performance and prevent the risk of injected material adhering to the insert walls. It has been demonstrated that inserts produced using processes such as VPP-UVL and MJT yield good surface finishes, unlike MEX, which causes delamination (Dizon et al., 2020). Apart from the process used, the layer height during the insert manufacturing process is one parameter that influences surface quality. Thus, with a lower layer height, the best surface definition is achieved (León et al., 2017). An alternative for improving surface roughness issues is the application of post-processing techniques. However, these processes represent an additional cost in terms of production (Moshiri et al., 2021).

• Number of injection cycles achieved: Another crucial industrial aspect is the life cycle of the inserts – how many parts they can produce correctly, fully and defect-free and how many injection cycles they can achieve without failure. Figure 6 shows the maximum number of cycles achieved in injecting PP using different materials/processes for the inserts. The graph shows that the most significant number of parts is obtained using metallic inserts, which can be attributed to their best mechanical properties and highest heat dissipation capacity compared to inserts made using other AM processes that use photopolymer resins or thermoplastic materials. It is essential to highlight that performance is relatively high when compared to the number of cycles achieved by resin-produced inserts. Among resins, digital ABS inserts have achieved the highest number of cycles through MJT.

• Quality of the molded part: According to the type of material to be molded, AM process, mold material and IM process conditions must be controlled, as they influence the mechanical, dimensional (warpage and deformation), morphological (crystallization) and surface (roughness) properties of the molded parts (Mendible et al., 2017; Moritz et al., 2022). Although several materials have been evaluated in the studies included in this systematic review, PP is the most frequently assessed molded material.

The choice of the best AM process for manufacturing injection mold inserts largely depends on the complexity of the design, the properties required for the final molded piece, the number of injected pieces required and the budget. This review has shown that the MJT process is the most extensively studied, which could be because the printing time using this process is lower compared to VPP-UVL and PBF-LB/P (León et al., 2017). Furthermore, in the case of the MJT process, it is possible to obtain pieces with a good superficial finish as well as with the VPP-UVL process, which is the second most commonly used process for insert manufacture, in comparison with to the MEX process, in which the pieces produced could evidence delamination (Dizon et al., 2020). Another AM process used that has also obtained good results is PBF-LB/M, which could be because the materials that it uses are metallic and have the best mechanical and thermal properties, which enable there to be a greater number of injection cycles and lower cycle times – they can even show similar behavior to machined inserts (Mendible et al., 2017). In the case of the PBF-LB/P process, although good results have been achieved regarding mechanical traction properties, this AM process does not obtain as good a surface finish as the others (León et al., 2017), which is an aspect that also influences the quality of the final part obtained by the IM process. No matter the technology used, it is essential to consider the configuration and conditions of the printing process, such as print orientation, layer height, curing times and temperatures, as these can influence insert properties.

The materials used for inserts should have good mechanical and thermal properties to resist the process parameters involved in IM. The combination Digital ABS – MJT is predominantly used for polymers. This can be attributed to the fact that it is a commercially validated material for manufacturing injection mold inserts. Additionally, it possesses good tensile properties and has withstood many cycles compared to other AM processes and plastic materials. Furthermore, this mechanical resistance and the material’s heat deflection temperature allow the insert to perform correctly within the most usual IM parameters (Bartlett et al., 2017). Even though the Digital ABS insert can be manufactured faster and more efficiently, major variation was evidenced in shrinkage and long cycle time (Mendible et al., 2017). Finally, in the case of digital ABS, times and costs may be lower than for some other materials (Kampker et al., 2018; Mendible et al., 2017; Simpson et al., 2019). Another relevant material for insert manufacture is the Rigid10K, a resin recommended by Formlabs for the manufacture of injection mold inserts via VPP-UVL process, because of its stiffness and excellent resistance to heat. Nevertheless, there are not many studies using this material as it is relatively new. As for materials not validated commercially, high-temperature and tough resins were also used with the VPP-UVL process. Although the inserts made of these two resins fail to crack, molded pieces can be observed with warping and shrinkage marks after each shot, attributed to deficient cooling in the cavity (Moritz et al., 2022). On the other hand, in the case of materials used in the MEX process, PEEK, ABS, PLA, PA6 and ULTEM1010 can be found in the literature. However, these materials have not been commercially validated to precisely manufacture inserts for injection molds, and more studies are required into their performance. Finally, regarding the materials required for metal printing, the production of these inserts has been studied using steel, bronze alloys, aluminum and titanium (Cao et al., 2021; Kočov and Tuteski, 2018). Literature has reported 200–500 injection cycles using some of these materials, showing great potential for insert manufacture compared to other AM processes. It is essential to ensure that the materials used in each process can withstand the high temperatures and pressures of IM. For this reason, some studies have extended their mechanical properties tests to include tensile tests at different temperatures (Mendible et al., 2017) and even tests that combine mechanical and thermal loads, such as dynamic-mechanical analysis. The latter makes it possible to evaluate the stiffness of a material as a function of temperature over time (Moritz et al., 2022; Krizsma et al., 2024).

In addition to the nature of the material and the process used to manufacture the mold insert, it has been demonstrated that injection process conditions are also highly influential in terms of its performance. Thus, during IM, an insert has two main loads: the mechanical load and the thermal load (Krizsma et al., 2021). Some studies have considered that AM inserts could not adapt well to the demanding thermal conditions of the IM process, leading to failure because of thermal degradation, while others concluded that abrupt deformation and failure of the inserts could be because of the inlet pressure of the polymeric material and reduction in the elastic limit of the insert as the injection cycles progressed (Bagalkot et al., 2022). In this regard, literature has reported that mold temperature is considered a critical parameter, along with injection pressure and injection temperature, as they contribute to the catastrophic failure of the inserts after a few injection cycles through a combined effect of the three parameters (Bagalkot et al., 2019b). For this reason, some recommendations have been implemented for the correct optimization of these parameters, such as the use of simulation software to determine the necessary pressure for cavity filling (Bagalkot et al., 2019a). Considering the influence of thermal and mechanical loading on the inserts, a recent study has presented a novel coupled simulation method to predict the thermal and deformation state during the operation of a mold insert produced by PBF-LB/P (Krizsma et al., 2024). Moreover, to obtain a comprehensive view of the operating behavior of the insert, the same study used integrated measurement technologies involving simultaneous measurement of operating stress, strain, temperature and cavity pressure.

Furthermore, process parameters such as injection and mold temperatures, flow rate and injection and holding pressures must be minimized when working with polymer inserts (Bagalkot et al., 2019b; Zink et al., 2019). This is because the mechanical properties of the polymeric materials are inferior to those of metallic materials and are also significantly affected by the glass transition temperature (Tg). In previous studies, an increase from 19 to 54 injection cycles has been obtained for molding the same geometry using the same material – polycarbonate (PC) – based on optimization of these parameters (Bagalkot et al., 2019a).

As evidenced in numerous publications over the past decade and compiled in this systematic review, the production of inserts for injection molds produced by AM processes is real. These publications show a wide range of practical applications of AM inserts in several fields. In the medical sector, a pharmaceutical birth control implant made of ethylene-vinyl acetate and injected using an insert produced with the MEX process (Gohn et al., 2022); and the production of optical prototypes with cylindrical lenses injecting PP and Cyclic olefin copolymer and using inserts produced by MJT (Noble et al., 2014) stand out. In cosmetics, compact bases for cosmetics have been created by inserts obtained through MEX, VPP-UVL and MJT, injecting high-density polyethylene and ABS (Vella et al., 2023). In engineering and electronics, interior components for aircraft and electronic enclosures made of PC (Bagalkot et al., 2019b) and battery cell holders made of PP (Schuh et al., 2020) have been successfully fabricated using MJT inserts. In addition, other studies have explored applications in the commercial sector, demonstrating the feasibility of producing items such as spinning tops with PE and ABS and using VPP-UVL, MJT and PBF-LB/P inserts (León et al., 2017), chess pieces and clips made of PS (Whlean and Sheahan, 2019) through VPP-UVL inserts. Thus, the use of AM processes for injection mold inserts constantly evolves, driven by the development of new processes and materials. This progress suggests excellent potential for the future of IM. However, it is essential to assess how each technology and material used affects the final performance of the insert during the IM process in terms of the number of cycles it can withstand, the quality of the final part and the associated costs. Thus, factors such as the number of injected parts, geometric accuracy and final properties, including surface quality, directly depend on the type of insert used.

In comparison with previous reviews, Tuteski and Kočov concluded that SLA is a process with the capability to manufacture inserts for functional and design testing of injection molded products, thus replacing aluminum soft tooling, which until recently was the only alternative for manufacturers in this regard. However, this systematic review identified that not only the SLA process is suitable for this purpose but also technologies such as PolyJet and even FDM, DLP and SLS, can be viable options depending on the characteristics of the insert and the number and expected characteristics of the injected parts. This is because, as well as Lozano et al. (2022), this systematic review evidenced that the injected material is significantly influenced by the properties and characteristics of the insert, as the thermal and mechanical behavior of molds made by three-dimensional printing (more specifically in those produced from polymeric materials) is very different from that of conventional metallic molds. Although these literature reviews conclude that additive molds of polymeric materials are recommended for low-medium volume, molds produced from AM processes of metals for high volume, this review evidenced that most of the studies injected materials of relatively low melting temperature, as is the case of PP, so it would be necessary to extend the studies conducted with materials of higher melting point and considering geometries of low-medium and high complexity, to establish clear feasibility of these inserts.

Regarding their possible application in the design of channels for conformal cooling, both previous literature reviews agree that AM processes offer great flexibility in designing these channels. However, most studies have focused on AM with metallic materials (Li et al., 2024), with the goal of applying them in large-scale production. In this review, although no specific conclusions on conformal cooling were obtained, it was identified that this technique has been little explored in AM processes based on polymeric materials. In addition, it was observed that inserts with conformal cooling channels manufactured from polymeric materials could produce low-quality parts (Rodriguez, 2016).

Finally, depending on the desired outcomes in the IM process, some AM processes may be more suitable than others. From the 67 studies analyzed in this systematic review, Table 5 was elaborated to compare the most representative technologies used in mold insert production.

This systematic review and analysis of various advancements in the field determined that AM can be a feasible option for insert production for IM of plastic parts, primarily to obtain short series such as prototypes, temporary molds or applications with specific requirements. The main findings of this study are:

• AM can be a feasible option for insert production for IM plastic parts, especially for obtaining short series such as prototypes, temporary molds or applications with specific requirements.

• The most used AM processes for producing injection mold inserts are MJT and VPP-UVL for polymeric inserts and PBF-LB/M for metallic inserts.

• AM processes use several materials of both a plastic and metallic nature, such as Digital ABS, high-temperature resins and metallic alloys, including steels and bronzes. However, manufacturers have commercially validated and recommended only two materials for injection mold inserts, namely, Digital ABS and Rigid 10K.

• The injection pressure, mold temperature and injection temperature are the most critical parameters to consider for extending the life of the inserts. Consequently, they must be quantified before selecting any AM process.

• MJT and VPP-UVL provide a good surface finish but poor thermal performance and a relatively low number of cycles, being more aimed at low-demand geometries in low quantities. On the contrary, PBF-LB/M delivers inserts capable of withstanding more cycles with good thermal conductivity but poor surface roughness unless post-processed.

• According to the type of material to be molded, the AM process, mold material and IM process conditions must be controlled, as they influence the mechanical, dimensional, morphological and surface properties of the molded parts.

Using AM processes to produce IM inserts presents challenges that must be addressed. Based on the systematic review carried out, further work is suggested on these topics:

• Stronger conclusions can be obtained if AM processes and materials are tested using inserts with a unified cavity geometry and with the same injected material. Injections with materials with a higher melting point are also a path to follow.

• In addition to tensile properties, considering the combined loads the insert is subjected to during injection, it could be interesting to increase the studies of some other relevant properties for the insert materials: compression, hardness, bending and fatigue properties. These characterizations can be done under temperature conditions in a thermal chamber to mimic the thermal conditions while injecting.

• Although the potential of lattice structures and conformal cooling channels is evident (Park et al., 2022; Coranic et al., 2021; Shen et al., 2024), further studies are needed to explore a broader range of AM processes, including those that do not rely solely on metallic materials. The thermal performance achieved because of conformal cooling channels could be even improved, especially for polymeric inserts, if new materials with higher thermal conductivity values can be used for printing.

Funding: Diputacion Foral de Gipuzkoa no. 2022-CIEN-000041–01; Gobierno Vasco no. ELKARTEK KK-2022/00020.