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Micro-drilling in ballpoint pen tip production faces persistent challenges of tool wear and premature breakage, which limit manufacturing efficiency and dimensional accuracy. In this study, an integrated framework combining finite element simulation (FEM) and orthogonal experimental design was developed to optimize the geometry of micro twist drills. A three-dimensional FEM model was established in Deform‑3D to analyze the effects of apex angle, helix angle, chisel edge length, and chisel edge angle on cutting force and torque. Range analysis of the orthogonal design revealed that chisel edge length and apex angle were the most influential parameters. The optimal configuration (b = 0.05 mm, 2Φ = 135°, Ψ = 76.5°, β = 3°) reduced average torque by 22.2% and extended tool life by 43.9% compared with the original design, while maintaining hole dimensional accuracy within ± 0.01 mm. These results confirm FEM as a reliable predictive tool and demonstrate that the proposed FEM–orthogonal framework provides a structured and cost-effective strategy for micro-tool geometry optimization, with direct industrial applicability to precision manufacturing of ballpoint pen tips.

In recent years, the use of CFRP with titanium and/or aluminum to form materials for stacking has gained popularity for aircraft construction. In practice, single-shot drilling is used to create perfectly aligned holes for the composite-metal stack. Usually, standard twist drills, which are commonly available from tool suppliers, are used for practical reasons. However, existing twist drill bits exhibit rapid wear upon the drilling of composite-metal stack layers in single shot, due to the widely contrasting properties of the composite-metal stack, which causes poor surface quality. The stringent quality requirements for aircraft component manufacturing demands frequent drill bit replacement and thus incurs additional costs, a concern still unresolved for aircraft component manufacturers. Owing to highly contrasting properties of a composite-metal stack, it is obvious that standard twist drill cannot fulfil the rigorous drilling requirements, as it is pushed to the limit for the fabrication of high-quality, defect-free holes. In this work, customised twist drills of a tungsten carbide (WC) material with different geometric features were specially fabricated and tested. Twenty drill bits with customised geometries of varying chisel edge angle (30–45°), primary clearance angle (6–8°), and point angle (130–140°) were fabricated. The stacked-up materials used in this study was CFRP and aluminum alloy 7075-T6 (Al7075-T6) with a total thickness of 3.587 mm. This study aims to investigate the effect of twist drill geometry on hole quality using drilling thrust force signature as indicator. All drilling experiments were performed at spindle speed of 2600 rev/min and feed rate of 0.05 mm/rev. Design of experiments utilising response surface methodology (RSM) method was used to construct the experimental array. Analysis of variance (ANOVA) was used to study the effect of parameters and their significance to the thrust force and thus the hole quality. The study shows that the most significant parameter affecting the drilling thrust force and hole surface roughness is primary clearance angle, followed by chisel edge angle. Correlation models of CFRP thrust force (Y1), Al7075-T6 thrust force (Y2), CFRP hole surface roughness (Y3), Al7075-T6 hole surface roughness (Y4) as a function of the tool geometry were established. The results indicated that the proposed correlation models could be used to predict the performance indicators within the limit of factors investigated. The optimum twist drill geometry was established at 45° of chisel edge angle, 7° of primary clearance angle, and 130° of point angle for the drilling of CFRP/Al7075-T6 stack material in a single-shot process. The error between the predicted and actual experiment values was between 6.64% and 8.17% for the optimum drill geometry. The results from this work contribute new knowledge to drilling thrust force signature and hole quality in the single-shot drilling of composite-metal stacks and, specifically, could be used as a practical guideline for the single-shot drilling of CFRP/Al7075-T6 stack for aircraft manufacturing.

The present study examined the effects of drilling parameters such as spindle speed ( N ), feed rate ( f ), diameter of the tools ( d ) and drill geometry such as twist drills (HSS-TiN) and brad and spur drills (BSD) used on delamination damage in a biosandwich structure consisting of an epoxy matrix reinforced with bidirectional jute fibres and cork (JFCE). Response surface methodology (RSM) and artificial neural networks (ANNs) were exploited to evaluate the influence and interaction of the cutting parameters on the delamination factor ( F d ) at the output during drilling. In addition, several optimization methods, such as desirability-based RSM, the genetic algorithm (GA) and the fmincon function, were applied to validate the optimal combination of cutting parameters ( f , N and d ) in the structures studied in biosandwiches during this research. According to the experimental results, severe damage was indeed observed with the BSD tool ( F d = 1.684) compared to the HSS-TiN tool ( F d = 1.555) for the same cutting conditions. To obtain the minimum F d , the optimum conditions obtained by GA were respectively 1397.54 rev/min, 51.162 mm/min and 5.981 mm for HSS-TiN for f , N and d .

Chip evacuation is the main difficulty of deep hole drilling process. For deep hole drilling with large depth-to-diameter ratio over 10, drilling force increases significantly with the drilling depth due to the friction and pressure reaction between the continuing generated chips and the drill flutes as well as the hole wall. In practical deep hole drilling process, overlarge drilling depth will cause drill breakage due to the low rigidity of the deep-hole twist drill, while using too small drilling depth is inefficient. The existing methods for drilling depth optimization are still faced with troubles, including lack of prior knowledge input of the monitoring method and difficult to measure or calibrate model parameters of the prediction model. To overcome these problems, a novel and practical chip evacuation force model for deep hole drilling is developed in this paper. Firstly, the chip evacuation forces in deep hole drilling are derived based on the elemental chip flow method, with the expression including three chip evacuation force coefficients for the practicability of the model. Then, the chip evacuation force coefficients are calibrated in a set of drilling tests under different cutting parameters, and the relations between chip evacuation force coefficients and cutting parameters are investigated with range analysis and analysis of variance. Finally, validation experiment results show that the proposed chip evacuation force model is able to predict the drilling force with increasing drilling depth in deep hole drilling, and the maximum drilling depth can be obtained accurately with the error less than 3%.

The effective design of tool geometry and optimization of process parameters play a pivotal role in mitigating damage such as tearing, burrs, and delamination during the drilling of braided carbon fiber reinforced polyether ether ketone (BCF/PEEK). This study introduces a novel method for selecting optimal drilling tools and damage prediction analysis in BCF/PEEK drilling. First, a scale-span drilling finite element (FE) model is established based on an analysis of twist bit geometry and BCF/PEEK composition. Simulation and experimental validation identify the causes of damage in prefabricated holes. Subsequently, three innovative types of drilling tools are evaluated based on factors such as hole morphology, thrust force, and delamination. Finally, regression models are established to correlate damage factors, thrust force, and process parameters. The research findings indicate that using twist drill bits results in higher thrust forces, which lead to delamination defects at hole exits. Conversely, employing a tapered drill-reamer could enhance the exit quality of prefabricated holes, consistently maintaining damage factors below 1.14 under identical process parameters. The proposed method effectively predicts optimal process parameters, with a maximum error of only 0.276% in drilling BCF/PEEK.

Many factors (material properties, drill bit type and size, drill bit wear, drilling parameters used, and machine-tool characteristics) affect the efficiency of the drilling process, which could be quantified through the delamination factor, thrust force, and drilling torque. To find the optimal combination among the factors that affect the desired responses during drilling of wood-based composites, various modelling techniques could be applied. In this work, an artificial neural network (ANN) and response surface methodology (RSM) were applied to predict and optimize the delamination factor at the inlet and outlet, thrust force, and drilling torque during drilling of prelaminated particleboards, medium- density fiberboard (MDF), and plywood. The artificial neural networks were used to design four models—one for each analyzed response. The coefficient of determination (R2) during the validation phase of designed ANN models was among 0.39 and 0.96. The response surface methodology was involved to reveal the individual influence of analyzed factors on the drilling process and also to figure out the optimum combination of factors. The regression equations obtained an R2 among 0.88 and 0.99. The material type affects mostly the delamination factor. The thrust force is mostly influenced by the drill type. The chipload has a significant effect on the drilling torque. A twist drill with a tip angle equal to 30° and a chipload of 0.1 mm/rev. could be used to efficiently drill the analyzed wood-based composites.

This study aimed to analyze the influence of multiple uses of zirconia implant drills on their cutting performance and bending strength. The hypothesis was that drill usage and sterilization cycles would not affect drilling time or flexural strength. Sixty zirconia twist drills from Z-Systems were used to drill in the angulus mandibulae region of fresh porcine jaws. The drills were divided into four groups based on the cycle count, and the drilling time was measured. Bending strength tests were conducted using a universal testing machine, and statistical analysis was performed using ANOVA tests. The results showed that drilling times followed a normal distribution, and significant differences were observed in drilling times between group 1 and the other groups for the pilot drill. However, no significant differences were found for ø3.75 mm and ø4.25 mm drills, and drilling times also varied significantly among different drill diameters, regardless of the cycle count. Flexural strength did not significantly differ among drill diameters or sterilization cycles. Overall, using and sterilizing zirconia implant drills had no significant impact on drilling time or flexural strength. Nevertheless, drilling times did vary depending on the diameter of the drill. These findings provide valuable insights into the performance and durability of zirconia implant drills, contributing to the optimization of dental implant procedures.

The burr removal and finishing of drilled hole walls typically require multiple post-processing steps. This experimental study introduces a novel single-step drilling approach using modified drill bits for simultaneous burr removal and surface finishing in aluminum 6061-T6. The odified-1 drill, equipped with a deburring micro-insert, achieved superior results, with a chamfer height of −2.829 mm, drilling temperature of 40.28 ◦C, and surface roughness of 0.082 µm under optimal conditions. Multi-objective optimization using the RSM and MOGA-ANN identified the optimal drilling parameters for the Modified-1 drill at 3000 rpm under water lubrication as compared to dry conditions and kerosene. Experimental validation confirmed the high prediction accuracy, with deviations under 6%. These results establish the Modified-1 twist drill bit with a deburring micro-insert as a highly effective tool for burr-free high-quality drilling in a single operation. This innovative drill design presents an efficient, single-step solution for burr elimination, chamfer formation, and surface finishing in drilling operations.

For comparison, the drilling behaviour of abaca fiber-reinforced polymer (AFRP) composites and Kevlar-reinforced epoxy polymer (KFRP) composites has been studied in the specified experimental condition. The different geometrical drilling tools have been used for the investigation, namely, candlestick (T1), core (T2), standard twist drill (T3), and step cone (T4). The tool feed of 30, 45, and 60 m/min and rotational speed of 1000, 1500, and 2000 rpm have been used for the investigation. The thrust force is chosen as a response parameter for this study. The results revealed that, at lesser rotational speed and tool feed, the thrust force has declined. The result obtained correlates with the abaca fiber-based systems. However, the thrust force of KFRP is higher compared to AFRP composite systems. The axial force generated by candlestick drill is minimal compared to the other drill bits. The following may be responsible for lower thrust force: (1) the axial force distributes circumferential of the cutting tool instead of focusing at the center and (2) the interfacial adhesiveness between the matrix and the fiber is higher. The optimization of drilling process parameters, namely, tool feed and rotational speed on thrust force, has been studied. The results reveal that the tool feed contributed more to axial force compared to rotational speed.

Reducing energy consumption (EC) is an essential strategy for improving the sustainability of manufacturing industry. Machining processes have been widely applied in manufacturing industry, and current research has demonstrated that the machining parameter optimization is an effective energy-saving measure under the given processing conditions. Drilling is a typical machining process, and it is convenient to make deep holes through peck drilling with twist drills in practice. However, owing to the inefficiency of peck drilling with twist drills, many efforts have been devoted to improving the performance of peck deep-hole drilling process (PDDP). Correspondingly, the parameter optimization considering traditional performance indicators, such as processing time, tool wear, and drilling force, has been fully investigated. Nevertheless, the existing research rarely touches on the EC optimization or the improvement of EC-related environmental impacts. To bridge this gap, an approach based on the operating parameter optimization is proposed to fulfill the energy saving of PDDP, and the corresponding mathematical model considering EC and processing time simultaneously is established. To evaluate the EC of PDDP reliably, the Therblig-based energy supply models of machines are utilized. Further, a particle swarm optimization algorithm-based solution method is adopted, which can make a trade-off between two optimization objectives objectively and acquire the most suitable operating parameters. Moreover, experiments have been made to evaluate the energy-saving potential and the performance of the algorithm. Experimental results show that there could be significant potential for improving optimization objectives simultaneously through the operating parameter optimization, and the solution method is feasible.