Manufacturing Technology Journal - Latest articles

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The Effect of Drill Bit Features on Surface Quality, Drill Wear and Drilling Cost – Sustainable Drilling

Murat Kiyak

Manufacturing Technology 2026, 26(2):176-184 | DOI: 10.21062/mft.2026.024  

In drilling operations, hole quality is affected by factors such as drill diameter, drilling parameters, drill bit properties, workpiece material. A large portion of the drilling energy is converted into thermal energy, which can be measured as temperature. In this study, surface roughness of holes, drill tip wear and drill tip temperatures were determined using two different workpiece materials and three different drill tips. Furthermore, the costs of holes drilled with different drill bits were determined and interpreted based on drill bit characteristics. The results obtained can be optimized according to the process parameters and it has been shown...

Process Parameter Effects on Cutting Efficiency and Specific Energy in Abrasive Water Jet Machining

Lianhuan Guo, Teng Ma, Jin Lan

Manufacturing Technology 2026, 26(2):164-175 | DOI: 10.21062/mft.2026.023  

The cutting performance of abrasive water jet (AWJ) machining is commonly evaluated using cutting depth, cutting efficiency, and specific cutting energy. To systematically investigate the influence of process parameters on AWJ cutting performance, a five-axis CNC cutting platform was developed, allowing precise control of operating conditions. Single-factor experiments were conducted to analyze the effects of pump pressure, traverse speed, cutting angle, abrasive mass flow rate, standoff distance, and nozzle diameter. Both qualitative analysis and quantitative evaluation were employed to identify parameter ranges that maximize cutting efficiency or...

Spinning Bath Evaporator Availability and Reliability Enhancement Proposal

Jan Palátka, Karel Mayer, Martin Pexa, Eva Olmrová

Manufacturing Technology 2026, 26(2):199-219 | DOI: 10.21062/mft.2026.022  

A single-stage evaporator with natural circulation was used to densify the plasticizing bath through continuous evaporation and to prepare a solution used in the production of viscose fiber. During the process, sodium calcium sulfate salts were formed, leading to fouling of the heat transfer surfaces in the heat exchangers. This fouling created a layer of deposits that gradually reduced the efficiency of the evaporation process in the evaporator. It was determined that a processing medium with a volumetric flow rate of 6 m³·h⁻¹ required a heat exchanger power of 1448 kW. A fouling layer with a thickness of 0.1 mm reduced the heat...

Finite Element Secondary Development of Constitutive Model for Titanium Alloy Vibration-Assisted Cold Upsetting Forming

Xu Yani, Wang Ying, Wei Chuhan, Lin Kai, Shu Xuedao

Manufacturing Technology 2026, 26(2):239-248 | DOI: 10.21062/mft.2026.021  

To achieve precise finite element simulation of the vibration-assisted cold heading process of titanium alloys, this study focuses on Ti-45Nb titanium alloy as the research object. A constitutive model for vibration-assisted cold heading is established, incorporating both viscoelastic and viscoplastic deformation. The model is transformed into a programmable incremental form, and the control equations for elastic-viscoplastic deformation are derived. Secondary development is conducted using the VUMAT interface of ABAQUS, and the model is applied in simulation. Multi-condition simulations of Ti-45Nb titanium alloy cold heading are performed, and the...

3D Printing – Dimensional Accuracy and Stability of PLA and PETG Prints Using the FDM Technology

Alexandr Fales, Vít Černohlávek, Marcin Suszynski, Jan Štěrba, Patrik Balcar, Pavel Houška

Manufacturing Technology 2026, 26(2):148-163 | DOI: 10.21062/mft.2026.020  

This study examines the influence of FDM printing parameters on replica parts for an educational robotics kit, targeting functional compatibility without post-processing. A VEX Robotics 2×12 Beam (228‑2500‑026) was used as the reference part. Reference dimensions were obtained as mean values from 10 original VEX IQ parts. Replicas were printed from PLA and PETG on Original Prusa MK4 printers using four infill patterns and six infill densities (15–70%). For each material–pattern–density combination, 10 parts were produced, resulting in 480 printed samples. Width, length, and height were measured with a Mitutoyo MiSTAR 555...

Evaluation of C45 Steel Hardening Process Using High-Speed Videography and ISO 9950 Test

Petr Beneš, Vojtěch Taubr

Manufacturing Technology 2026, 26(2):124-132 | DOI: 10.21062/mft.2026.019  

The paper deals with the influence of various quenching media based on polymer aqueous solutions on the quenching process of carbon steel C45, connecting theoretical knowledge about heat transfer, surface phenomena and phase transformations with experimental verification. Surface phenomena at the interface of the hardened sample and the quenching medium were monitored using a high-speed camera. Cooling curves of the samples were obtained using the method according to ISO 9950 (Determination of cooling characteristics – Nickel-alloy probe test method). The paper contains practical recommendations for optimizing industrial hardening processes,...

Thermoplastic Resin Flow Behaviour in Foam Core Sandwich Composites for Aerospace Applications During Vacuum Infusion Process

Jana Zemanova, Bohuslav Cabrnoch, Michal Kral

Manufacturing Technology 2026, 26(2):249-256 | DOI: 10.21062/mft.2026.018  

This article presents the research findings on the flow behaviour of thermoplastic resin in foam core sandwich composites for aerospace applications during the vacuum assisted infusion process. After optimizing the process parameters, two sandwich panels were manufactured using glass fibre fabrics, a polymethacrylimide (PMI) foam core, and a liquid acrylic resin. To compare the sandwich and monolithic structure process behaviour, a monolithic composite panel was also manufactured. By combining experimental monitoring with Darcy's law, permeability differences between the structures were evaluated. The results indicate that PMI foam does not significantly...

Machine Learning-Based Predictive Modelling of EDM and EAM-V Processes for Performance Analysis

Shrihar Pandey, Rajesh Kumar, Abhay Kumar Singh, Robert Cep, Priyanka Singh, Mihir Kumar Pandey, B. Swarna

Manufacturing Technology 2026, 26(2):220-232 | DOI: 10.21062/mft.2026.017  

Abstract- The promotion of Electrical Discharge Machining (EDM) and vibration aided Electric Arc Machining (EAM-V) processes is characterized in the study in terms of their capability for precision manufacture, mainly drawing any performance comparisons from a machine learning approach. The present machine learning study aims to predict some important metrics of machining utility, such as Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR), against process parameters like current, pulse-on/off time, etc. Some advanced models like Gradient Boosting and Random Forest are used to analyze the efficacy and effectiveness of EDM...

Hybrid ANN–GA Modeling and Experimental Optimization of GMAW-Based Additive Manufacturing of Aluminum 5083 for Enhanced Mechanical Properties

Teephet Chaiyason, Suriya Prasomthong, Panuwat Thosa, Sittichai Charonerat, Phattharapong Keidlaphi

Manufacturing Technology 2026, 26(2):133-147 | DOI: 10.21062/mft.2026.016  

Wire + Arc Additive Manufacturing (WAAM) based on Gas Metal Arc Welding (GMAW) has emerged as a cost-effective and high-deposition process for fabricating large-scale aluminum components. However, its application to non-heat-treatable aluminum 5083 remains limited by thermal-cycle in-stabilities, porosity, and non-uniform mechanical performance. This study presents an integrated experimental and artificial-intelligence framework for optimizing key GMAW parameters—welding current, wire-feed speed, and welding speed—to enhance the mechanical properties of WAAM-fabricated aluminum 5083 walls. An L9 Taguchi design was employed to quantify parameter...

Influence of the Manufacturing Route on the High-Temperature Oxidation Behavior of IN718 Alloy in Simulated Modern Energy Environments

Patrícia Lovašiová, Jan Hruška, Tomáš Lovaši, Miroslav Zetek, Yusuf Bakir, Ivana Zetková

Manufacturing Technology 2026, 26(2):185-198 | DOI: 10.21062/mft.2026.015  

The use of supercritical water in energy applications is motivated by the aim of increasing the thermal efficiency of power systems. However, structural materials exposed to this environment may undergo corrosive degradation. The objective of this study was to conduct experiments on samples exposed to simulated operational conditions in supercritical water, steam, and air. The material surfaces were sub-sequently analyzed using optical microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS). Particular attention was given to the formation of oxide layers on the nickel-based alloy Inconel 718 produced by additive...

Experimental Solution of the Influence of Tire Pressure on Vehicle Consumption and their Service Life

Patrik Balcar, Martin Svoboda, Milan Chalupa, Milan Sapieta, Pavel Houška, Alexandr Fales, Martin Novák

Manufacturing Technology 2026, 26(2):118-123 | DOI: 10.21062/mft.2026.014  

This article deals with the experimental investigation of the influence of tire pressure on fuel consumption and tire life in passenger cars. Using laboratory and real-world operational measurements, the dependence between tire pressure and temperature, contact patch size, tread wear, and changes in driving characteristics was analyzed. The results show that even slight deviations from the prescribed pressure can lead to increased fuel consumption, shortened tire life, and reduced driving comfort and safety. The article also draws attention to the insufficient use of pressure monitoring systems in practice and points to the economic and ecological...

Microstructure and Mechanical Properties of Biomedical Co-Cr-Mo Alloy Produced by Precision Casting and 3D Printing Technologies

Hana Thürlová, Dalibor Vojtěch

Manufacturing Technology 2026, 26(2):233-238 | DOI: 10.21062/mft.2026.013  

Cobalt-based alloys are widely used for orthopedic implants due to their excellent mechanical properties and corrosion resistance. Biomedical Co-Cr-Mo alloy, commonly applied in knee replacements, is typically produced by precision casting. However, in cases requiring patient-specific geometries, additive manufacturing technologies, such as Selective Laser Melting (SLM), offer promising alternatives. This study compares the microstructure and mechanical properties of Co-Cr-Mo alloy in the as-cast state and after SLM processing. The SLM-produced samples exhibited a fine, cellular microstructure and superior mechanical strength. Specifically, the printed...

Study on Thermo-Structural Coupling Mechanism and Multi-Field Evolution Law during the Firing Process of Ceramic Slabs

Xianewei Wang, Wenlong Xu, Hailong Yu, Chenyang Li, Haikuo Zhao, Yihang Feng, Caiqi Fang, Heng Zhang, Aihua Xu, Wentao Xie, Xiulian Li

Manufacturing Technology 2026, 26(1):106-116 | DOI: 10.21062/mft.2026.012  

To address cracking and deformation in large-size ceramic slabs during firing induced by thermo-structural coupling, this study established an indirect thermo-structural coupling finite element model in Ansys to analyze an 820 mm×100 mm×6.32 mm slab. The evolution of temperature field, stress field, and deformation was investigated across four firing stages. Results indicate that the rapid cooling stage, with a high convective heat transfer coefficient, forms the cycle’s maximum thermal gradient, showing the most asymmetric temperature field of mid-plane high, surfaces low and a ~17°C surface-mid-plane temperature difference. The stress field...

Beverage-Cans as a Source of Hydrogen – Analysis of Leaching Residues

Alena Michalcová, Pavel Novák, Šárka Msallamová

Manufacturing Technology 2026, 26(1):63-67 | DOI: 10.21062/mft.2026.011  

Aluminium beverage-can are common material for secondary utilization. Their recycling is slightly com-plicated by presence of organic materials in them and lack of collection points (although the legislative in this case is rapidly changing to be more friendly). Another approach to deal with beverage-cans is using them as a source of hydrogen. In this manuscript, the evolution of hydrogen in 10 wt. % NaOH solution is described. The leaching residues were analysed in detail. Their chemical and phase composi-tion were measured, and the amount of trapped hydrogen was also analysed. The beverage-cans are usually composed of 3004 and 5182. The residues...

Machine Learning Regression Approaches for Manufacturing Cost and Time Prediction: A Comprehensive Review

Michal Matějka, Milan Dian, Jan Lhota, Theodor Beran, Vojtěch Hlinák

Manufacturing Technology 2026, 26(1):53-62 | DOI: 10.21062/mft.2026.010  

Today, machine learning regression methods are quietly but fundamentally transforming cost and time estimation in manufacturing: from early pricing to labor planning to operational order management. This survey offers a comprehensive map of approaches - from linear models, to tree ensembles (RF, GBM, XGBoost) and shallow neural networks, to multi-target and tensor regressions that can exploit data structure across BOM items and sequences of operations. With an emphasis on SME conditions, we show how to reconcile three often conflicting requirements of practice: accuracy, explainability, and integration into existing data flows (MES/ERP). The paper...

Normalized Statistical Evaluation of Machining Parameters and Cutting Forces in Turning

Tanuj Namboodri, Csaba Felhő, Ashwani Kumar

Manufacturing Technology 2026, 26(1):68-77 | DOI: 10.21062/mft.2026.009  

Investigation of cutting forces in metal cutting is of great importance for defining the effectiveness of the production as well as its impact on product quality. Several researchers studied the effect of cutting parameters on the cutting forces through statistical analysis; however, very few studies use the normalization of the data. Normalization reduces the skewness in the data and increases the accuracy of the results, which can be beneficial in modern industry where AI is being integrated with manufacturing. This research aimed to study the statistical analysis of cutting parameters and cutting forces using log-normalization and compare the accuracy...

Influence of High–melting–point Metals on the Mechanical Properties of Selected Al–Si Alloys

Tomáš Vlach, Jaromír Cais, Veronika Chvalníková, Martin Slezák, Jiří Brejcha, Tomáš Burket, Dominik Fink, Jan Sviantek

Manufacturing Technology 2026, 26(1):95-105 | DOI: 10.21062/mft.2026.008  

This article is dedicated to exploring the potential enhancement of mechanical properties, such as hardness and tensile strength, in selected Al-Si alloys (AlSi7Mg0.3, AlSi7Cu4, and Al-Si10.5Cu1.2Mn0.8Ni1.2). High-melting-point elements, such as chromium and molybdenum, are rarely utilized as additives in Al-Si alloys. However, the article demonstrates the feasibility of improving the mechanical properties of these alloys through the addition of high-melting-point elements. High-melting-point metals, often referred to as refractory metals, typically have melting points above 2000 degrees Celsius. Common refractory metals include tungsten, molybdenum,...

Effect of Accelerated Aging on the Mechanical Properties of FFF-Manufactured Polymers

Marcel Kohutiar, Martin Bednařík, Ivan Labaj, Róbert Janík, Jan Hanzlík, Michal Krbata, Jakub Zatloukal

Manufacturing Technology 2026, 26(1):43-52 | DOI: 10.21062/mft.2026.007  

This study examines the effect of accelerated weathering on the mechanical and viscoelastic properties of thermoplastics produced by fused filament fabrication (FFF). Three polymers, acrylonitrile styrene acrylate (ASA), polyethylene terephthalate glycol (PETG), and polylactic acid (PLA), were subjected to alternating UV radiation and condensation cycles in a QUV chamber simulating environmental exposure. Tensile testing and dynamic mechanical analysis (DMA) were used to evaluate the changes in strength, stiffness, and glass-transition behavior. The results revealed distinct responses depending on the polymer structure. ASA maintained its ductility...

Conceptual Design with Strength Analysis Based on the FOPS Test for a Tubular Cover Dedicated to the Kubota M135GX-IV Tractor

Łukasz Gierz, Mikołaj Spadło, Antoni Kuchta

Manufacturing Technology 2026, 26(1):26-33 | DOI: 10.21062/mft.2026.006  

An agricultural tractor equipped with appropriately rated guards can often replace specialized forestry machinery. Currently, few authorized dealers on the Polish market offer tractors adapted to harsh forest conditions, so this work involved designing a tubular guard for the Kubota M135GX-VI agricul-tural tractor. The aim of this work was to develop a conceptual design for a tubular guard, together with a strength analysis based on FOPS procedures, dedicated to the KUBOTA M135GX-IV agricul-tural tractor. To properly design the tubular guard, applicable standards and regulations regarding the construction of cabs and tubular guards for agricultural...

Mechanical Properties of 3D Printed Porous Ti-6Al-4V Alloy for Biomedical Applications

Markéta Straková, Jiří Kubásek, Dalibor Vojtěch

Manufacturing Technology 2026, 26(1):88-94 | DOI: 10.21062/mft.2026.005  

Optimising the mechanical properties required for biomedical applications is something that porous Ti-6Al-4V structures offer the opportunity to do. Triply periodic minimal surface (TPMS) structures, such as the Diamond and Gyroid structures, provide interconnected pores that can be used to adjust strength, stiffness and deformation. The mechanical behaviour of these two architectures under compressive and bending loads is compared in this study, with the use of additively manufactured samples. The results demonstrate that pore geometry significantly impacts mechanical behaviour. Diamond structures exhibit higher stiffness and strength, whereas Gyroid...

Effect of Machining on 3D Surface Texture and Scratch Resistance of Structural Steel

Eva Jurickova, Oskar Zemcik, Stepan Kolomy, Josef Sedlak, Denisa Hrusecka, Felicita Chromjakova, Petra Sliwkova

Manufacturing Technology 2026, 26(1):34-42 | DOI: 10.21062/mft.2026.004  

This study experimentally compares how three common machining routes, turning, milling and grinding, affect the surface texture and tribological response of three structural steels (C45, 42CrMo4, 30CrMoV9) under conditions where the profile roughness Ra is deliberately aligned across routes. Areal topography was measured by coherence correlation interferometry and evaluated according to ISO 25178 (height metrics Sa, Sq, Sp, Sv, Sz, St). The bearing area curve (Abbott–Firestone) was used to derive functional descriptors Rpk, Rk and Rvk. Scratch resistance was determined on a UMT‑3 tribometer (Rockwell 120°, P = 50 N) as HSp = 8·P /...

Ultrasonic-Based Active Thermography for Determining Depth Detection Limits in Onyx Composites

Lucia Deganová, Vladimír Dekýš, Milan Sapieta, Alžbeta Sapietová

Manufacturing Technology 2026, 26(1):14-25 | DOI: 10.21062/mft.2026.003  

This paper examines the detection of internal defects in composite specimens composed of Onyx, a material featuring a nylon matrix reinforced with chopped carbon fibers. Artificial defects, in the form of flat-bottom holes of various geometries, were intentionally introduced during the additive manufac-turing process. The primary objective is to determine the depth detection capabilities of ultrasound by varying the excitation frequency and determining whether these defects remain identifiable at different subsurface levels. Ultrasonic lock-in thermography is utilized to excite specimens. As the frequency is modified, the depth of wave propagation...

Control Measurement of Car Tires during Transport on a Conveyor

Patrik Balcar, Pavel Houška, Martin Svoboda, Ondřej Vetchý, Milan Chalupa, Milan Sapieta, Roman Horký

Manufacturing Technology 2026, 26(1):2-13 | DOI: 10.21062/mft.2026.002  

The aim of this work is to verify the reliability of optical inspection of tires during their transport on a roller conveyor, with an emphasis on the accuracy of 3D scanning in real and simulated operating conditions. A measuring box was designed and constructed to eliminate environmental interference, and measurements were subsequently compared with different degrees of site coverage. Testing was carried out using a 3D sensor O3D302 operating on the Time-of-Flight principle, and spatial data in the form of point clouds were obtained and compared with the reference dimensions of the Nokian WR D4 tire. The effects of solar IR radiation, rain, surface...

Design and Life of a Ball Valve as per the ASME BPVC Section VIII by the Elastic Stress Analysis Method

Anupama Routray, Ripendeep Singh2, Lenka Cepova, V. Sandeep, B. Swarna B, Elangovan Muniyandy, Ankur Bansod, Pavel Krpec

Manufacturing Technology 2026, 26(1):78-87 | DOI: 10.21062/mft.2026.001  

The fatigue assessment of a Class 300 valve body with a bore diameter of 450 mm under vari-ous pressures is discussed using Section VIII, Division 2 of the ASME BPVC. Finite element analysis (FEA) results are compared to fatigue test results, and correlations are obtained. The material used for the valve is A216 WCB, which is widely used for making API ball valves. Elastic stress analysis was used to study the influence of various parameters on the results. This method is widely accepted and is used for static components. The body and flange de-signs were performed in accordance with ASME and API standards. Various pressure loads were applied to the...

Innovative Design of a Transtibial Prosthetic Socket through Integration of QFD, Reverse Engineering, and 3D Printing

Rosnani Ginting, Aulia Ishak, Fadylla Ramadhani Putri Nasution, Rinaldi Silalahi

Manufacturing Technology 2025, 25(6):778-787 | DOI: 10.21062/mft.2025.085  

This study focuses on addressing the challenges faced by individuals with physical disabilities, particu-larly lower body impairments, by developing a stump socket using Reverse Engineering (RE), 3D Printing, and QFD. The integration of these three methods is something new in product design devel-opment, especially prosthetic products. The research adopted a three-step methodology: 3D scanning the stump, obtaining precise measurements, and fabricating a stump socket using fused deposition modeling (FDM) technology. QFD will produce technical requirements (TR) derived from consumer needs and brainstorming with prosthetists. TR will be the basis for...

Comparison and Verification of Stress Measurement Results Using the Barkhausen Effect during Three-Point Bending

Tomasz Domański, Wiesława Piekarska, Milan Saga, Zbigniew Saternus, Marcin Kubiak, Milan Vasko

Manufacturing Technology 2025, 25(6):751-757 | DOI: 10.21062/mft.2025.084  

Non-destructive stress measurement techniques are extremely important and are still being developed in engineering research and diagnostics of materials. They allow for a quick assessment of their condition without damaging the structure. Their development is crucial for the safety of structures and extending the life of materials. One of the new methods is the measurement of stress using the Barkhausen effect. The MagStress 5d device was used for the tests. In this work, stress measurements were performed using the MagStress 5D device during three-point bending of a steel flat bar. The results were verified using resistance strain gauges and numerical...

Characterization of microstructure and defects in the Ti-6Al-4V alloy produced by 3D printing SLM technology

Kateřina Caldová, Andrea Školáková, Jan Pinc, Dalibor Vojtěch

Manufacturing Technology 2025, 25(6):735-741 | DOI: 10.21062/mft.2025.083  

The Ti-6Al-4V alloy is widely used as a material for medical implants. In the future, it may be employed for 3D printing using the selective laser melting method. The advantages of 3D printing are for example production of complex shapes or ability to create customized implants. One of the disadvantages of this method is the deterioration of mechanical properties, particularly the ductility of the alloy, caused by high residual stress resulting from rapid cooling during printing. This article aims to characterize the microstructure and defects of the printed alloy and the impact of hot isostatic pressing. Optical microscopy, scanning electron microscopy,...

Sinterhardening Process of Lean Cr-Mo Prealloyed Steel for Moderately Loaded Applications

Dmitriy Koblik, Miroslava Ťavodová, Monika Vargová, Richard Hnilica, Nataša Náprstková

Manufacturing Technology 2025, 25(6):771-777 | DOI: 10.21062/mft.2025.082  

The article deals with sinterhardening process of lean Cr-Mo prealloyed steel for moderately loaded applications. New material Astaloy CrS with low alloying volume of chromium and molybdenum was analyzed as possible basis for sinterhardening process. Standard mechanical properties of frequently used and more expensive materials such as DistaloyDH and Astaloy CrM are chosen as a compara-tive criterion. Astaloy CrS+0.85%C samples with different compaction densities and Ni content were studied, mechanical properties and hardness after sinterhardening process were compared. The influ-ence of additional high-temperature sintering on mechanical properties...

Study on the Molding Process of Corncob/Chitosan Composites

Yuping Xia, Zhe Luo

Manufacturing Technology 2025, 25(6):794-806 | DOI: 10.21062/mft.2025.081  

In order to address the pollution caused by petroleum-based plastics and increase the added value of agricultural waste, this study aims to develop an environmentally friendly wood composite material using agricultural waste corncob (CC) and biomass material chitosan (CS) as the matrix, and optimise its molding process to improve its physical and mechanical properties. Based on the single-factor test, the relatively optimal process parameters were preliminarily determined as follows: the CS concentration is 1.8%, the pressure is 25 MPa, and the temperature is 135 °C. At this time, the comprehensive properties of the material reach a density of 1.47...

Determining the Force Required to Remove a Screw from a Human Vertebra

Patrik Balcar, Petr Vachata, Martin Svoboda, Jan Lodin, Michal Lattner, Antonín Svoboda, Edita Pichlová

Manufacturing Technology 2025, 25(6):721-727 | DOI: 10.21062/mft.2025.080  

The article describes a pilot experiment of mechanical testing of 3D printed vertebrae with an inserted screw. The main goal of this work was to verify the design of a measurement methodology for experimentally determining the mechanical properties of vertebrae produced using 3D printing and also for determining the load-bearing capacity of a screw when it is drilled into a vertebra. The work describes the construction of a special fixture with which it is possible to clamp test samples for tensile testing. The stud screws were pulled out of a real or printed vertebra using a tearing machine. Testing was performed on porcine and 3D printed vertebrae....