Subtractive Technologies Research Articles

Equal–Additive–Subtractive Remanufacturing Integrated Laser Directed Energy Deposition with Shot Peening and Machining Induced High Performance of Plunger Rod

The number of easily destroyed parts with high value is increasing in industry, and green remanufacture engineering is now mainstream in this new and expanding industrial field. Equal–additive–subtractive manufacturing, as a new technology that combines strengthening technology, additive manufacturing, and machining technology has great potential for development in the area of remanufacturing. Aiming at the damage characteristics of a plunger rod, this paper carries out a study about the repair technology by equal–additive–subtractive manufacturing of laser-directed energy deposition and shot peening. It was found that the microstructure of the materials repaired by equal–additive–subtractive technology is finer and the tensile strength can reach 100.4% of the base material. The surface residual stress of cladding materials changes from tensile stress to compressive stress, which reduces forming defects. Equal–additive–subtractive manufacturing has great significance in expanding the application of hybrid manufacturing and promoting green remanufacturing of parts with high value.

The challenges of 3D metal printing and the machinability characteristics of additively produced materials: a review of hybrid machining

Abstract Recently, 3D metal printing technologies are rapidly spreading. The various types of additive manufacturing (powder bed fusion, directed energy deposition, binder jetting, and sheet lamination) use very different approaches to produce materials/geometries. The material properties (e.g. porosity/density, strength, surface roughness, hardness) of additively manufactured materials differ from the traditional ones and strongly depend on the applied 3D printing parameters. Therefore, a crucial research direction is how the parameters affect the material properties. Currently, 3D metal printing technologies have limitations in the achievable geometrical accuracy and surface roughness. Therefore, they can rarely be used for part production without further machining. For high-quality requirements, an additional subtractive machining procedure is usually required. Consequently, another intensively researched topic is the machinability of 3D metal printed materials. The industry is increasingly demanding to integrate different manufacturing processes (additive and subtractive technologies) into one machine. These hybrid machines have the advantage that they can produce high-quality parts in one step.

Fit comparison of interim crowns manufactured with open and proprietary 3D printing modes versus milling technology: An in vitro study.

This study aimed to assess the fit of interim crowns produced using DLP-based 3D printing with different manufacturing workflows-open and proprietary-versus milling technology. A total of 120 crowns were evaluated using the replica technique. The control group (Mill, n = 30) was manufactured via subtractive technology. Experimental groups were printed using a DLP printer (SprintRay Pro95). In the proprietary mode (SR100, n = 30), manufacturer resin was used with a 100-μm layer thickness (LT) and a splashing cleaning postprocessing. In the open mode, validated resin was used. Group B100 (n = 30) had a 100-μm LT, and group B50 (n = 30) had a 50-μm followed by postprocessing in an ultrasonic bath with full immersion in isopropyl alcohol. Kruskal-Wallis tests with Bonferroni correction was applied after normal analysis (α = 0.05). Group B50 exhibited the best overall fit (123.87 ± 67.42 μm), which was comparable to the gold standard Milling group, which demonstrated the lowest marginal fit (p = 0.760). SR100 showed significantly poorer performance compared to Mill, B50, and B100 (p < 0.001). 3D printed and milled interim crowns generally demonstrated clinically acceptable fit, with the exception of the SR100 group. Postprocessing notably influenced crown fit, with the open mode with total immersion in isopropyl alcohol being superior. The present study demonstrates that the selection of an optimal manufacturing and postprocessing workflow results in superior fit for interim crowns. This enables dental professionals to evaluate protocols and ensure reliable outcomes with improved clinical outcomes in interim crown fabrication.

Additive Technologies and Materials for the Next‐Generation CubeSats and Small Satellites

AbstractCubeSat and small satellites play a very important role in modern space exploration. Their success and diverse capabilities rely on the development of efficient and compact sub‐systems. This task is not trivial due to multiple challenges posed by their small size and mass, and the solution calls for conceptually new designs for the fabrication and integration of complex miniaturized satellite components. The importance of additive techniques in small satellite manufacturing is steadily increasing as they enable rapid, large‐scale production of sophisticated architectures, such as hollow, webbed parts with a cell‐like structure similar to animal bone, with lower mass and improved functionality. Moreover, these architectures feature higher strength, enhanced heat transfer, and efficient thermal and electromagnetic radiation shielding. When compared to traditional subtractive technologies like cutting and milling, additive manufacturing proves to be more versatile and effective in realizing architectures with an increasing intricacy of shapes, structures, and compositions. The perspective explores the suitability of 3D printing in various satellite production tasks, including the propulsion system components and satellite elements. Looking ahead, the challenges and advantages of integrating 3D printing technology into satellite production, emphasizing the need for continuous development through consolidated, proactive collaborative efforts of many devoted teams are outlined.

Comparison of the Intensity of Biofilm Production by Oral Microflora and Its Adhesion on the Surface of Zirconia Produced in Additive and Subtractive Technology: An In Vitro Study.

This in vitro study set out to find out how well oral cavity-dwelling bacteria can form biofilms and adhere on the surfaces of zirconium oxide samples created by 3D printing and milling technologies. 5 strains of microorganisms were used for the study, and 40 zirconium oxide samples were prepared, which were divided into two groups (n = 20)-20 samples produced using removal technology comprised the control group, while 20 samples produced by 3D printing technology comprised the test group. The prepared samples were placed in culture media of bacteria and fungi that naturally occur in the oral cavity. Then, the intensity of biofilm build-up on the samples was determined using qualitative and quantitative methods. The results for both materials were compared with each other. No variations in the degree of biofilm deposition on zirconium oxide samples were found for the microorganisms Streptococcus mutans, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. For Candida albicans fungi, more intense biofilm deposition was observed on samples made using 3D printing technology, but these differences were not statistically significant. The biofilm accumulation intensity of ceramics produced by additive technology is comparable to that of milled zirconium oxide, which supports the material's broader use in clinical practice from a microbiological perspective. This ceramic has demonstrated its ability to compete with zirconium oxide produced by milling techniques in in vitro experiments, but sadly, no in vivo tests have yet been found to determine how this material will function in a patient's oral cavity.

AUTOMATED SELECTION SYSTEM FOR MEASURING GEOMETRIC VALUES FOR TECHNOLOGICAL PREPARATION OF ADDITIVE AND SUBTRACTIVE ENGINEERING INDUSTRIES DETAILS OF COMPLEX SHAPE

Based on the analysis of the characteristics of modern measuring instruments, the functioning of automated systems&#x0D; of metrological equipment and the design of technological processes, methodological, algorithmic and software&#x0D; procedures for the selection of measuring instruments of geometric quantities of parts of complex shape for the technological&#x0D; preparation of additive and subtractive machine-building industries are proposed, taking into account the type&#x0D; of magnitude, metrological characteristics of measuring instruments, measurement conditions and application features&#x0D; related to the geometry of surfaces, the technology of their form formation, accessibility and location, which allows to&#x0D; reduce the complexity of design work and improve the quality of technological solutions. The system can be used in&#x0D; design bureaus of machine-building enterprises; IT companies for the creation and improvement of automated systems;&#x0D; educational process for the training of specialists in the production of products based on additive and subtractive technologies.

Enhancing angiogenesis in peri-implant soft tissue with bioactive silk fibroin microgroove coatings on zirconia surfaces.

Zirconia abutments and restorations have improved the aesthetic appeal of implant restoration, yet peri-implantitis poses a significant threat to long-term success. The soft tissue surrounding implants is a crucial biological barrier against inflammation and subsequent bone loss. Peri-implantitis, akin to periodontitis, progresses rapidly and causes extensive tissue damage. Variations in tissue structure significantly influence disease progression, particularly the lower vascular density in peri-implant connective tissue, compromising its ability to combat infection and provide essential nutrients. Blood vessels within this tissue are vital for healing, with angiogenesis playing a key role in immune defense and tissue repair. Enhancing peri-implant soft tissue angiogenesis holds promise for tissue integration and inflammation control. Microgroove surfaces have shown potential in guiding vessel growth, but using subtractive technologies to carve microgrooves on zirconia surfaces may compromise mechanical integrity. In this study, we utilized inkjet printing to prepare bioactive silk fibroin microgrooves (SFMG) coating with different sizes on zirconia surfaces. SFMG coating, particularly with 90 µm width and 10 µm depth, effectively directed human umbilical vein endothelial cells (HUVECs) along microgrooves, promoting their proliferation, migration, and tube formation. The expression of vascular endothelial growth factor A and fibroblast growth factor in HUVECs growing on SFMG coating was upregulated. Additionally, the SFMG coating activated the PI3K-AKT pathway and increased glycolytic enzyme gene expression in HUVECs. In conclusion, SFMG coating enhances HUVEC growth and angiogenesis potential by activating the PI3K-AKT pathway and glycolysis, showing promise for improving tissue integration and mitigating inflammation in zirconia abutments and restorations.

Ranking Technologies of Additive Manufacturing of Removable Complete Dentures by the Results of Their Mechanical Testing.

In this study, a methodology was developed for ranking manufacturing technologies of removable complete dentures (RCDs) according to the results of their full-scale mechanical tests. The actuality of the study is motivated by establishing the advantages and drawbacks of 3D-printed RCDs in contrast with ones manufactured via an analog protocol. The RCDs were fabricated via four technological routes that included various combinations of subtractive technologies (hot polymerization/HP and CAD/CAM milling) and additive manufacturing (digital light processing/DLP) ones and the installation of commercially available cosmetic denture teeth (DT). In the mechanical tests, different blocks of teeth (incisors, canines, premolars and molars) were loaded. To solve the ranking problem, it was proposed to interpret the results of the mechanical tests in terms of the reliability, durability and compliance/stiffness criteria. For this purpose, the combined AHP-VIKOR method was applied. In addition, a computer simulation of the mechanical loading conditions and the response of the RCDs was performed based on the finite element method (FEM). As the key conclusion, it was stated that additive manufacturing (AM) methods are competitive and cost-effective techniques for the fabrication of RCDs.

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies.

To evaluate the effect of coffee thermocycling (CTC) on the surface roughness (Ra ) and stainability of denture base materials with different chemical compositions fabricated by using additive and subtractive manufacturing. Disk-shaped specimens were additively (FREEPRINT denture, AM) or subtractively (G-CAM, GSM and M-PM, SM) fabricated from three pink denture base materials in different chemical compositions (n = 10). Ra was measured before and after polishing, while color coordinates were measured after polishing. Specimens were subjected to CTC (5000 cycles) and measurements were repeated. Color differences (ΔE00 ) after CTC were calculated. Ra among different time intervals within materials was evaluated by using repeated measures analysis of variance (ANOVA), while 1-way ANOVA was used to evaluate the Ra of different materials within each time interval and the ΔE00 values. Color coordinates within each material were compared by using paired samples t-tests (α = 0.05). Ra before polishing was the highest for all materials (p < 0.001), while SM had its lowest Ra after CTC and AM had its lowest Ra after polishing (p ≤ 0.008). Before polishing, AM had the highest Ra among the materials (p < 0.001). After polishing, SM had higher Ra than AM (p < 0.001). After CTC, GSM had the lowest Ra (p ≤ 0.048). SM had the lowest (p ≤ 0.031) and AM had the highest (p < 0.001) ΔE00 . CTC decreased the a* and b* values of SM and AM (p ≤ 0.017), and increased the L* values of AM (p < 0.001). Polishing significantly reduced the surface roughness of all materials. CTC did not increase the surface roughness of materials above the clinically acceptable threshold. Only AM had perceptible color change when previously reported threshold values for denture base materials were considered. Tested denture base materials may have similar surface stability after coffee thermocycling. However, subtractively manufactured denture base materials may have improved color stability when subjected to long-term coffee consumption.

Mechanical properties of additively manufactured zirconia with alumina air abrasion surface treatment

This study aimed to evaluate the mechanical properties of zirconia fabricated using additive manufacturing technology and compare them to those of zirconia fabricated using subtractive manufacturing technology. Sixty disc-shaped specimens were fabricated for the additive (n = 30) and subtractive manufacturing groups (n = 30), and each group was divided into two subgroups according to their air-abrasion surface treatment: control (n = 15) and air-abrasion groups (n = 15). Mechanical properties including the flexural strength (FS), Vickers hardness, and surface roughness were determined, and the values were analyzed by one-way ANOVA and Tukey’s post hoc test (α = 0.05). X-ray diffraction and scanning electron microscopy were used for phase analysis and surface topography evaluation, respectively. The SMA group exhibited the highest FS (1144.97 ± 168.1 MPa), followed by the SMC (944.58 ± 141.38 MPa), AMA (905.02 ± 111.38 MPa), and AMC groups (763.55 ± 68.69 MPa). The Weibull distribution showed the highest scale value (1213.55 MPa) in the SMA group, with the highest shape value in the AMA group (11.69). A monoclinic peak was not detected in both the AMC and SMC groups, but after air abrasion, the monoclinic phase content ({mathrm{X}}_{mathrm{m}}) reached 9% in the AMA group, exceeding that in the SMA group (7%). The AM groups exhibited statistically lower FS values than those of the SM groups under the same surface treatment (p < 0.05). Air-abrasion surface treatment increased the monoclinic phase content and FS (p < 0.05) in both the additive and subtractive groups, while it increased the surface roughness (p < 0.05) only in the additive group and did not affect the Vickers hardness in either group. For zirconia manufactured using additive technology, the mechanical properties are comparable to those of zirconia manufactured using subtractive technology.

Microstructure and mechanical properties of CuCrZr/316L hybrid components manufactured using selective laser melting

Additive/subtractive hybrid manufacturing technology is a new technology that combines product design, software control, and additive manufacturing (AM) with subtractive technology, which can realize the metallurgical bonding of dissimilar materials. In this study, hybrid parts made of two materials were fabricated by depositing CuCrZr on a 316 L stainless steel substrate by selective laser melting (SLM) technology. The microstructure and mechanical properties of the SLM-ed CuCrZr, 316 L matrix components and the 316 L/CuCrZr interface were studied. The microstructure of SLM-ed CuCrZr consisted of elongated columnar crystals that developed along the building direction, and the 316 L matrix material was characterised by large equiaxed grains. After the 316 L substrate was polished, there were no macroscopic cracks and only a few pores at the interface of 316 L/CuCrZr, and good metallurgical bonding was achieved. The complex and uneven metal flow occurred inside the molten pool because of the Marangoni effect under the action of the laser, resulting in drastic changes in the grain size at the interface.

Wire-Feeding Based Additive Manufacturing of the Ti–6Al–4V Alloy. Part II. Mechanical Properties

Currently, the interest in the application of metal additive manufacturing (AM), also known as 3D printing, is grown massively in the various fields of the industry and surgery. AM has significant multiple advantages compared to traditional subtractive technologies for making highly customized parts with complex geometries without causing noteworthy extra costs. Now, several powder-based AM technologies for metals’ 3D printing are in progress, in particular, selective laser sintering (SLS), selective laser melting (SLM), and electron-beam melting (EBM). In the past few decades, increasing research and developments are devoted to the wire-feeding-based 3D printing production of parts made of the Ti–6Al–4V alloy, which is widely investigated in different fields such as aerospace, automotive, energy, and marine industries as well as the prosthetics and the production of orthopaedic implants. Due to the feasibility of economical producing large-scale metal components with relatively high deposition rate, low machinery cost, high material efficiency, and shortened lead-time compared to powder-based AM, wire-feeding-based AM (WFAM) is attracting significant attention in the industry and academia owing to its ability for the production of the large components of the medium geometric complexity. In recent years, three options of WFAM are intensively researched, which differ by the wire-melting heating sources: wire + arc additive manufacturing (WAAM); wire-laser AM (WLAM), and wire electron-beam additive manufacturing (WEBAM). The purpose of the present review is systematic analysis of the mechanical properties of the Ti–6Al–4V alloy samples 3D-printed by WFAM with various heating melting sources, namely, arc, laser, and electron beam. Particularly, considering the literature data for the period of 2013–2020, such important properties as yield strength, tensile strength, elongation, and hardness are analysed for the samples in the as-printed and post-processed conditions.

Effect of sintering on the translucency of CAD-CAM lithium disilicate restorations: A comparative in vitro study.

The available independent data on the translucency of novel pre and fully sintered chairside computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate are limited. This comparative in vitro study evaluated the translucency degree of pre and fully sintered chairside CAD-CAM lithium disilicate crowns after optional, required, and additional firing processes. One hundred and five maxillary left central incisor crowns manufactured by three different CAD-CAM lithium disilicate brands shade A1 were assigned into seven groups as follows (n=15): (1) Straumann n!ce without sintering; (2) Straumann n!ce with one additional sintering process; (3) Straumann n!ce with two additional sintering processes; (4) Amber Mill with one sintering process; (5) Amber Mill with two sintering processes; (6) IPS e.max CAD with one sintering process; and (7) IPS e.max CAD with two sintering processes. The translucency of all crowns was evaluated with a color imaging spectrophotometer. All statistical analyses were performed using statistical software. A standard level of significance was set at α<0.05. All the milled crowns presented different degrees of translucency, and additional sintering processes altered it. IPS e.max CAD with two (4.33±0.26) and one (4.01±0.15) sintering processes displayed the highest translucency, whereas Straumann n!ce with no sintering process provided the lowest value (2.82±0.16). The translucency of chairside lithium disilicate single-unit full-coverage restorations manufactured with subtractive technology was significantly influenced by the brand and the number of sintering processes. The traditional presintered IPS e.max CAD and the fully crystallized glass-ceramic Straumann n!ce considerably increased the translucency after one additional firing process, whereas Amber Mill decreased its translucency.

Effect of build orientation on the trueness of occlusal splints fabricated by three-dimensional printing.

Scientific evidence pertaining to the evaluation of trueness of occlusal splints fabricated using different three-dimensional (3D) printers and build orientations compared to subtractive technologies is lacking. Overall, one hundred and ten occlusal splints were manufactured using two different 3D printers and a dental mill. Five groups of ten were fabricated using the 3D printers at different build orientations (0, 30, 45, 60, and 90 degrees). In addition, a comparison group of ten occlusal splints was subtractively manufactured using a five-axis dental mill. All occlusal splints were scanned and exported as a standard tessellation language file. Analysis was conducted with metrology software with root mean square estimate average positive deviation and average negative deviation used as the measured outcome. The 0 degree printing orientation was the most accurate for printer one with the root mean square value of 0.05 ± 0.01 mm, and 60 degree printing orientation was most accurate for printer two with the RMS value of 0.11 ± 0.01 mm. Subtractively manufactured occlusal splint had significantly higher trueness with the lowest RMS value of 0.03 ± 0.05 mm. Build orientations influence the trueness of additively manufactured occlusal splints while occlusal splints produced by subtractive manufacturing were statistically significantly more accurate.

Sustainable Additive Manufacturing and Environmental Implications: Literature Review

This study’s objective is to review the literature on the environmental impact of the additive manufacturing process. When this new manufacturing technology is employed, it aims to create a healthy environment free of pollutants. The work is motivated by the lack of universal guidelines on new design approaches, the classification of manufacturing materials, and processes that address environmental concerns. Using additive manufacturing over traditional subtractive technologies may result in considerable material and energy resource savings, especially if the component is appropriately designed for manufacture. In this scenario, additive manufacturing, regarded as a potential breakthrough innovation, has grown in popularity in producing parts with complex geometry. AM encourages constant product development and flexible modifications that enable stakeholders to create better products faster. This study examines the state-of-the-art essentials of the fast-expanding manufacturing technique known as additive manufacturing (or 3D printing) and compares the environmental impact caused due to environmental issues. With increasing pressure on firms to provide transparency in their product sourcing and manufacturing processes, sustainability is no longer a distant goal but a strategic requirement. Manufacturers must also pay particular attention to their products’ total energy usage and overall environmental impact.

The Effect of the Digital Manufacturing Technique, Preparation Taper, and Cement Type on the Retention of Aged Anterior Provisional Crowns: An In Vitro Study

A well-made provisional fixed prosthesis must present as a preview of the future prosthesis and may also augment the health of the abutments and periodontium. Provisional restorations have been prepared chairside with polymethyl methacrylate (PMMA) since time immemorial. CAD/CAM additive and subtractive technologies have revolutionized the fabrication of interim restorations in dental clinics. The current literature lacks substantial data about retention of provisional crowns manufactured using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) additive and subtractive techniques with various temporary cements. This in vitro study aims to assess and compare the retention of temporary/provisional anterior crowns based on the combined effect of different digital manufacturing techniques, preparation tapers, and the temporary cements used for cementation. Two maxillary right central incisor typodont teeth were prepared to receive all-ceramic crowns, one with a 10-degree taper and the other with a 20-degree taper. Forty 3D-printed working models with the 10° taper and forty working models with the 20° taper were prepared to receive the temporary crowns. Forty temporary crowns were 3D-printed and forty crowns were milled (20 from each taper group). Kerr Temp-Bond NE conventional cement and Kerr Temp-Bond clear cement were used for cementation in the two groups. The number of samples per test group was 10. All samples were thermocycled and subjected to a universal testing machine to measure the pull-off force until retention loss (N) under tension with a crosshead speed of 5 mm/min. The pull-off force was highest for group 8, i.e., 3D-printed crowns with a 20° taper and cemented with Kerr Temp-Bond clear cement, followed by groups 6, 7, 4, 5, 3, and 2. Group 1, i.e., milled crowns with 10° taper cemented with Kerr Temp-Bond NE conventional cement, exhibited the lowest pull-off retentive force. The clinical selection of long-term provisional crowns fabricated using 3D-printing technology, prepared with 10° or 20° tapers, and cemented with clear cement, is the most favorable in terms of the retention of provisional crowns. 3D-printed provisional crowns can be used as an alternative to conventional and CAD/CAM-milled crowns for long-term provisionalization.

Osteoblast behaviour on zirconia fabricated by additive and subtractive technology

Zirconia is an attractive material for the manufacturing of oral implants and patient-individual barriers for guided bone regeneration. This study compared osteoblast behaviour on additive manufactured and milled 3-mol% yttria-stabilized tetragonal polycrystal zirconia (ZrO2).Two groups of samples (Ø5 × 2 mm) were manufactured by stereolithography (LithaCon 230, Lithoz, Vienna, Austria) and subsequently heat-treated and sintered. One group remained superficially unmodified (AM-ZrO2-unmod.), while the other was polished according to DIN EN ISO 6872 standard using automated grinding (AM-ZrO2-pol.). For comparison, milled samples (e.max ZirCAD LT, Ivoclar Vivadent, Schaan, Liechtenstein) were sintered and polished similarly (Mil-ZrO2-pol.). Surface roughness was characterized using tactile profilometry. Adhesion, proliferation and coverage of human fetal osteoblasts (hFOB 1.19) as well as expression of osteogenic marker genes ALPL and RUNX2 were determined (and statistically compared using Kruskal-Wallis-analyses and Dunn's Post-hoc-tests).The surface roughness of AM-ZrO2-unmod. Was 45 times higher than that of the polished groups. No significant differences were detected between the three groups regarding cell adhesion and proliferation. With regard to cell coverage, AM-ZrO2-pol. Significantly outperformed the two other groups (p < 0.05). ALPL- and RUNX2-mRNA expression was insignificantly superior for AM-ZrO2-unmod. Compared to the two other groups. Therefor no detrimental effect on osteoblast behaviour caused by the investigated, acrylic binder-based 3D printing workflow was observed.

Value Chain Comparison of Additively and Conventionally Manufactured Multi-Cavity Tool Steel Inserts: An Injection Molding Industrial Case Study for High-Volume Production

The development of injection molding tools is an expensive, time-consuming, and resource-intensive process offering little to no flexibility to adapt to variations in product design. Metal additive manufacturing can be used to produce these tools in a cost-effective way. Nevertheless, in an industrial context, effective methods are missing for the selection of the most suitable technology for the given tooling project. This paper presents a method to compare process chains based on additive and conventional subtractive technologies for the manufacturing of metal tooling for injection molding. The comparison is based on a technology focused-performance analysis (TFPA) through computer simulation performed using Tecnomatix Plant Simulation developed by Siemens Digital Industries Software combined with a customized cost–benefit economic analysis tool. The analysis of the technology comparison highlights potential bottlenecks for production, such as the printing phase and the heat treatment. It also gives a deeper understanding of the technology maturity level of conventional milling machines against laser powder bed fusion machines. The result is that the total costs for an insert made by AM and CM are indeed rather similar (the cost difference between the two tooling process chains is lower than 5%). The cost analysis reveals major costs drivers in the production of high-performance molding tools, such as the cutting tools employed for the milling steps and their changeover frequency. The industrial case of a 32-cavity mold insert for plastic injection molding is used to perform the study, develop the analysis, and validate the results.

Marginal and Internal Gap of Metal Copings Fabricated Using Three Types of Resin Patterns with Subtractive and Additive Technology: An In Vitro Comparison.

This study analyzes the evidence of the marginal discrepancy and internal adaptation of copings fabricated using three types of resin patterns with subtractive (milling) and additive technology (3D printing), as it is not widely reported. Working casts (n = 15) were scanned and patterns were completed using computer-aided designing (CAD). Resin patterns were fabricated using the designed data and divided into three groups according to the method of fabrication of patterns: subtractive technology–CAD milled polymethyl methacrylate resin (Group-PMMA), additive technology [digital light processing (DLP) technique]–acrylonitrile–butadiene–styrene (ABS) patterns (Group-ABS), and polylactic acid (PLA) patterns (Group-PLA). Resin patterns were casted with Cobalt–Chromium (Co–Cr) alloy (lost wax technique). Internal and marginal gaps of the metal copings were analyzed with the replica technique under optical microscope. The Kruskal–Wallis test was used to compare values among the groups, and post hoc multiple tests confirmed the specific differences within the groups. The median marginal gap was least for CAD milled resin patterns, followed by PLA printed resin patterns and ABS printed resin patterns. There were significant differences between Group-PMMA and Group-PLA and Group-ABS (p = 0.0001). There was no significant difference between Group-PLA and Group-ABS (p = 0.899). The median internal gap was least for metal copings fabricated from Group-PLA, followed by Group-ABS and Group-PMMA. The differences were not statistically significant (p = 0.638) for the internal gap. Full metal Co–Cr copings fabricated from the milled PMMA group had a better marginal fit, followed by the PLA and ABS printed groups. Copings fabricated with the PLA printed group had the best internal fit, though the values were statistically insignificant between the groups.

What is the economic feasibility of manufacturing a metal-metal- polymer composite part compared to other technologies?

ABSTRACT The purpose of the article is to analyse the manufacturing factors that affect the cost of manufacturing a part. Nowadays the cost of equipment used for metal 3D printing, as well as metal powders, are still very expensive. The cost of additive manufacturing of metal parts is mainly dependent on the volume of printing, therefore, reducing the volume of printing can lead to a significant reduction in the cost of manufacturing the part. Manufacturing of a metal shell, the cavity of which is filled with a cheap metal polymer, can be an excellent alternative to an all-metal part. The article provides a method for calculating the cost of manufacturing a lever part using various technologies: subtractive, additive, and composite part manufacturing technology. According to the calculated data, the dependence of the cost of manufacturing a part on piece time has been built, which can be interpreted as the amount of machining. The constructed linear dependence can give an idea of the effectiveness of the application of a particular technology for obtaining a part. In addition, non-economic factors affecting the possibility of using various technological processes for manufacturing a part are described.