Defect and Diffusion Forum Vol. 450

Abstract: This study presents a static finite element analysis of the milling of a flexible unidirectional glass fiber–reinforced polymer (UD-GFRP) plate. The workpiece is modeled as a clamped–free cantilever, with cutting forces evaluated independently of structural deflections and applied along the machined edge. SC8R continuum shell elements are employed to accurately represent through-thickness loading and bending behavior. A mesh sensitivity analysis is conducted to determine a suitable discretization, leading to a 64 × 56 × 8 element mesh. For the investigated configuration (, mm/tooth), the out-of-plane displacement reaches approximately 120 µm near the free end of the plate, whereas in-plane displacements reach up to-75 µm. These in-plane displacements are greater than or equal to the nominal feed per tooth, indicating a highly significant influence on chip formation. This work provides a basis for understanding the structural response of flexible composite plates during trimming and emphasizes the need for coupled force–deformation formulations.

Abstract: Laser surface texturing (LST) is increasingly adopted to functionalize the surface in injection molding, enabling the control of interfacial and tribological phenomena without altering bulk material properties. While most studies have focused on mold cavities, the functionalization of ejection system components remains largely unexplored, despite its critical role in part release and process stability. This work presents a preliminary investigation of laser surface texturing for cylindrical ejector pins to promote lubricant retention at the pin–mold interface. A parametric study was first carried out on a flat to define a process window compliant with the maximum allowable groove depth constraint (20 µm). Based on this campaign, a stable ablation regime was identified and transferred to cylindrical ejector pins, where textures were fabricated along axial length. Different micro-texture geometries and spatial distributions were designed to generate controlled micro-reservoirs for lubricant retention. The textured surfaces were characterized in terms of groove depth, morphology and uniformity, confirming the feasibility of producing shallow and well-defined features within industrial constraints. The preliminary results demonstrate the technical feasibility of laser texturing on cylindrical ejector pins and its potential to modify the pin–mold interface. However, the comparative effectiveness of the different texture geometries in promoting lubricant retention will be further evaluated under extended service conditions. The study, therefore, establishes the basis for the functional optimization of textured ejection systems in injection molding applications.

Abstract: Drilling of Fiber Metal Laminates (FMLs) is a very important manufacturing operation, as the metal-composite layered structure tends to undergo delamination, burrs, and dimensional errors. Although to date research work has mainly focused on cutting conditions, drilling tools, and lubrication methods for improved performance, the role of surface engineering on metal sheets prior to laminate fabrication has not received significant consideration. In this study, the effect of the variation of feed rate values during the drilling operation of FMLs with laser-textured titanium sheets is examined. Specifically, prior to FML consolidation, a unidirectional pattern with spacing characteristics of 200 µm was created on the titanium sheets; then, drilling tests using twist drill bits were carried out at a fixed cutting speed while varying the feed rate on two levels. The results show that a higher feed rate value induces both greater thrust force – and therefore improved adhesion resistance at the interface between the various materials of the multilayer – and a deterioration in the surface quality of the hole, increasing the occurrence of fiber pull-out and metal transfer phenomena.

Abstract: This study proposes an automated framework for online cutting tool wear classification in CNC turning using low-cost optical equipment and Convolutional Neural Networks (CNNs). Longitudinal turning experiments were performed on CK45 medium carbon steel using a HAAS TL1 lathe under dry machining conditions. Tool wear evolution was monitored via a lathe-mounted digital microscope, with images classified into three distinct stages: Low (Vb<160 μm), Medium (160≤Vb≤200 μm), and Critical (Vb>200 μm). A shallow CNN architecture, consisting of three convolutional blocks and a Softmax output layer, was developed to balance model complexity with computational efficiency for potential edge deployment. To enhance robustness against positional changes, data augmentation techniques including random translations and rotations were applied. The results demonstrate good performance, with the model achieving 94.7% accuracy and a weighted F1-score of 95.4% on the testing subset. While the model showed exceptional performance in identifying Low and Medium wear, data scarcity in the Critical wear class remained a limiting factor for recall. Overall, the study confirms that shallow CNNs can accurately capture spatial hierarchies for image-based wear assessment.

Abstract: Titanium is a Critical Raw Material for the European aerospace sector, yet its manufacturing is characterized by high buy-to-fly ratios and significant waste in form of chips. Solid-state recycling (SSR) presents a low-energy alternative to remelting for chip revalorisation. However, its viability is strictly limited by their oxidation. This study investigates the influence of milling parameters (cutting speed and radial depth of cut), and coolants (emulsion, LCO2 and dry), on cutting forces and chip quality (morphology and oxidation) to define a process window for generating low oxidation chips, enabling further SSR routes. By correlating cutting forces with chip analysis, the results reveal that emulsion cooling yields the chips with the least oxidation, despite potential oil contamination of the feedstock with oils. While LCO2 effectively reduces oxidation at lower material removal rates, high thermal loads overwhelm its cooling capacity, resulting in oxidation comparable to dry cutting. These findings establish the machining parameters necessary to produce high-quality, recyclable feedstock, bridging the gap between subtractive manufacturing and circular material flows.