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Open research questions in Advanced machining processes and optimization

35 unresolved questions extracted from the limitations and future-work sections of 851 Advanced machining processes and optimization papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • 062 mm per side) was insufficient to completely remove the printing-induced surface texture, resulting in significantly higher and more variable Ra and Rz values.

    Influence of Machining Allowance, Build Orientation, and Cutting Parameters on Hole Quality in Additively Manufactured ABS Components · 2026 · DOI

  • When the analysis was limited to the machining-dominated regime, the lowest score was obtained for the vertical build orientation, Dstart = 9 mm, a cutting speed of 40 m/min, and a feed rate of 0.

    Influence of Machining Allowance, Build Orientation, and Cutting Parameters on Hole Quality in Additively Manufactured ABS Components · 2026 · DOI

  • Thus, in this work, two different representations of the machining setup, including curved workpiece geometry, which is more rarely studied, are compared for the case of Ti-6Al-4V ELI turning under various conditions, and their effect on the accuracy of the prediction of the cutting force and chip morphology is investigated.

    Comparison of FE Modeling Approaches for the Prediction of Cutting Forces and Chip Morphology During Turning of Ti-6Al-4V ELI Alloy · 2026 · DOI

  • The workflow implemented in DEFORM with interfaces to NX CAD/CAM enables automated setup of machining strategies and cutting steps and supports distortion simulation during and after machining. DEFORM’s Boolean subtraction is well suited for toolpath updates because it avoids repeated segmentation and re-modelling of the workpiece. The approach supports complex geometries, including forged aerospace components, and can transfer multi-operation, multi-tool, and multi-clamping strategies from CAM into multi-step FEM simulations, reducing model handling effort and runtime compared to state-of-the-art workflows. Regarding model accuracy, the developed FEM model reflects the distortion trend measured in the described experiments qualitatively. The dominant residual stress related distortion occurring during fixture release is visible in the simulation results. In particular, the direction of distortion during sequential release of clamping boundary conditions is captured consistently. However, the model underpredicts distortion magnitudes compared with the experiments, indicating limited quantitative accuracy under the current input and modelling assumptions. Future work should improve the predictive quality of the FEM model by further analysing and refining the boundary conditions and underlying model assumptions. In particular, the modelling of contact conditions should be extended in more detail, including 16 G. Mauthner et al. / Journal of Machine Engineering, 2026, Vol. 26, friction and an improved contact definition, to quantify their influence on distortion and to achieve more accurate simulation results. In addition, the workflow should be used to investigate more advanced milling strategies by refining material removal from a single cutting volume to a sequence of cutting volumes derived from successive in process workpieces from CAM. This would represent the effects of machining sequences and progressive stiffness changes more realistically, while also addressing a possible source of deviation between FEM and experimental results. The proposed FEM-CAM workflow is readily extensible in this direction, making the investigation of the quantitative influence of this modelling choice a suitable topic for future work. Current qualitative simulation results are sufficient to compare various milling strategies to each other and to derive main impact factors on the observed results. A focused parameter study executing a series of new machining strategies using the same demonstration part geometry may show opportunities for overall part distortion optimization strategies in the process planning phase.

    Simulation of part distortion in milling operation of forged aerospace components using boolean subtraction · 2026 · DOI

  • This paper presents a simulation-based framework for integrating measured residual stress depth profiles into a digital workpiece twin and using them for FE-based deformation analysis of thin-walled aluminium components. The approach links residual stress measurement, dexelbased material removal simulation, spatial stress mapping, and static structural analysis. The main contribution is the implementation of a continuous data chain that transfers depth-resolved residual stress information into an FEreadable initial stress field and enables the calculation of residual-stress-induced deformation. The results indicate that reliable residual stress input data are a prerequisite for reproducing the deformation tendency with sufficient accuracy. For the high-quality residual stress dataset, the selected setup reproduced the dominant deformation morphology and the locations of the displacement extrema. The dominant positive z-displacement was predicted with a relative error of 5.6%. This demonstrates that the proposed process chain is suitable for transferring measured residual stress information into a digital workpiece representation and using it to calculate the resulting structural response. At the same time, the results show that the absolute displacement field is sensitive to the quality of the residual stress input data and to the numerical transfer into the FE model. The peak-to-peak displacement range was overestimated by 64.6% for the high-quality dataset, mainly due to the overestimation of the negative displacement extremum. For the repeated dataset with lower residual stress measurement quality, the deformation was strongly overestimated. This confirms that discontinuities, overshoots, or physically implausible residual stress extrema can directly propagate into the deformation simulation. The investigated numerical settings further show that boundary conditions, stress-mapping strategy, and mesh resolution influence the predicted deformation. Remote-displacement constraints in combination with Kriging-based stress mapping provided the best agreement with the measured deformation morphology. The mesh study showed that the resolution in the thickness direction is particularly relevant, since local extrema of the residual stress depth profile can be missed by a coarse FE discretization. A high potential for improving the approach lies in the combined characterization of residual stress depth profiles and the targeted extraction of characteristic points, such as surface values, extrema, zero crossings, and settling depths. These characteristic profile points can be used to reduce the amount of transferred data while preserving the mechanically relevant information of the stress profile.

    Implementation of residual stress models in a technological material removal simulation · 2026 · DOI

  • Future studies may explore the extension of this mod- el to simulate rock cutting under more complex condi- tions, such as the presence of joints, anisotropy, and het- erogeneity within the rock mass. (2007) have provided valuable frameworks for analysing disc cutter forces, they are limited by the reliance on complex specific energy cal- culations and simplified analytical assumptions.

    CASE STUDY ON OPTIMIZING DISC CUTTER SPACING BASED ON VERTICAL FORCE THRESHOLD IN COLORADO RED GRANITE CUTTING USING LS-DYNA SOFTWARE · 2026 · DOI

  • The core selective ablation characteristics of laser–CFRP interaction are completely ignored, and the unique mechanical behavior of bare fiber under a large cutting angle is not modeled, and the quantitative correlation between cutting force evolution and machining damage is lacking.

    A Novel Cutting Force Prediction Model and Damage Analysis of Laser-Assisted Cutting CFRP at 135° Cutting Angle · 2026 · DOI

  • The main limitations of this study are the high computa- tional cost inherent to FEM-based machining simulations and the absence of new experimental tests.

    Artificial intelligence-based cutting tool geometry optimization for cutting force minimization in machining · 2026 · DOI

  • The physics-informed constraints embedded in Branches A and C (e.g., Rath, Achip, ln(1 + Rath)) are derived from established Ti-6Al-4V cutting mechanics but no comparison is provided between PISRE-NF and alternative physics-derived feature sets or Bayesian optimization of the constraint set across different material classes.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • While hyperparameter sensitivity analysis (Section 4.8.7) covers Ridge regularisation α and neighbourhood size k, the sensitivity of the four-branch symbolic regression structure itself (Branches A–D physics-derived features) to variations in feature engineering or constraint parameterization has not been systematically explored.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • The full PISRE configuration (with force signals) is recommended only for 'real-time monitoring and offline analysis contexts' but no experimental validation of its diagnostic capability for tool condition or cutting stability assessment is provided; the complementary diagnostic value claimed for force-dependent branches remains unquantified.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • The paper demonstrates PISRE-NF performance on a small-sample LOO cross-validation (n=19); scalability and stability of the uncertainty-weighted ensemble mechanism and Ridge regularisation have not been evaluated on larger datasets (n > 100) with higher-dimensional input spaces typical of industrial multi-parameter turning studies.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • The strong collinearity between cutting velocity and thrust force (rs = +0.932) in this dataset is a consequence of CCD design structure; it is unclear whether this collinearity persists in factorial or random experimental designs, or whether PISRE-NF's superior performance is contingent on this specific design property.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • PISRE-NF was developed and validated exclusively on Ti-6Al-4V dry turning with a 19-sample CCD design; generalization to other titanium alloys (e.g., Ti-5Al-5V-5Fe-3Cr), different cutting fluids (wet/flood cooling), or alternative tool materials and geometries remains undemonstrated.

    Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning · 2026 · DOI

  • The study demonstrated that MoS₂ bio-lubricant reduces tool wear and improves surface quality in sustainable manufacturing; however, the long-term tool life extension beyond the tested machining duration and the quantitative relationship between MoS₂ film thickness and tool wear rate were not characterized.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • While the paper states that hybrid nanofluids and new lubricating technologies warrant investigation, it does not specify whether MoS₂-Jatropha oil should be combined with secondary nanoparticles (graphene, TiO₂, etc.), what concentration ratios should be tested, or how such hybrid formulations would affect the currently identified optimal machining parameters.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • The ANOVA analysis showed that feed rate and depth of cut had statistically insignificant effects on surface roughness (F-values: 1.29 and 0.049 respectively); however, the study did not investigate whether this insignificance holds across extended cutting durations or higher MoS₂ concentrations beyond 1.5%.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • The thermal analysis measured temperatures at three zones (work-piece/tool interface: 190°C, chip: 250°C, work-surface: 160°C) but did not investigate the mechanisms by which MoS₂ protective films reduce thermal softening across varying cutting speeds, feed rates, and depths of cut combinations.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • While the study identified MoS₂ concentration (1.5%) and cutting speed (120 m/min) as statistically significant parameters for surface roughness and tool wear reduction, the interaction effects between MoS₂ concentration and cutting speed on thermal generation and protective film formation at the tool-workpiece interface were not systematically characterized.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • The study investigated MoS₂-Jatropha oil nano-lubricant only in CNC turning operations; the performance of this bio-lubricant formulation across other machining processes (milling, grinding, drilling) and with different workpiece materials beyond the tested conditions remains unexplored.

    Tribological and Thermal Performance Enhancement using Molybdenum Disulfide Based Bio Lubricant in Machining Operations · 2026 · DOI

  • Further work on refining the functional form of machining errors will focus on expanding ANN inputs to include wheelset design parameters, enhancing the model’s generality and compensation capabilities.

    A hybrid Modelling for Machining Error Compensation in Specialized Machine Tool for Train Wheel Sets. · 2025 · DOI

  • Despite the large amount of research devoted to the drilling of CFRP /titanium alloy stacks, a comprehensive understanding of the basic parameters of drilling and their influence on the accuracy and quality of holes is insufficient.

    Critical Analysis of the Current Trends in Ensuring the Holes Quality when Drilling CFRP/Titanium Alloy Stacks · 2023 · DOI

  • Abstract Flank face surface texturing has proven to be an effective approach to improve tool wear resistance, yet the impact of texture shape on flank wear remains insufficiently explored.

    Influence of textures on cutting tool tribology in dry machining of super duplex stainless steel · 2026 · DOI

  • The influence of spindle speed n on minimum diameter dm requires further clarification, particularly for copper alloy where somewhat stronger influence is observed but not fully explained.

    Experimental evaluation of the ability of some metallic materials to allow turning sharp conical tips · 2026 · DOI

  • The empirical mathematical models have limited validity; the aspects reported highlight some limitations of the validity of the experimental results obtained, particularly regarding the relationship between material hardness changes and mechanical properties during the cutting process.

    Experimental evaluation of the ability of some metallic materials to allow turning sharp conical tips · 2026 · DOI

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35 open questions have been extracted from the limitations and future-work passages of 851 Advanced machining processes and optimization papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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