Chip Evacuation Research Articles

A Study on the Cutting Characteristics of Bottom Abrasive Grains in Helical Grinding Tools

Helical grinding is crucial for manufacturing small holes in hard-to-machine composite ceramics. This study introduces a geometric model of undeformed chips to analyze the cutting characteristics of abrasive grains on both the bottom and side edges of the tool. It reveals for the first time that the distribution of cutting grains—pure bottom-edge, pure side-edge, and mixed-edge—is influenced by the tool diameter and eccentricity. A novel calculation method for the distribution range (Dp) of pure bottom-edge grains is proposed, demonstrating that using a tool diameter at or below two-thirds of the target hole diameter effectively eliminates pure bottom-edge grains, improving chip evacuation, reducing chip adhesion, and optimizing cutting performance. Experimental validation on small holes in SiCp/Al composites (65% volume fraction) confirmed these findings and provides practical guidance for optimizing cutting parameters and tool design.

Stacked generalization ensemble learning strategy for multivariate prediction of delamination and maximum thrust force in composite drilling

The complexity of drilling carbon fiber reinforced polymers (CFRP) requires accurate predictive models. This study addresses the challenge using an ensemble machine learning (ML) approach with stacked generalization. The model captures the relationships between key input variables—such as graphene nanoplatelet (GNP) content, ultrasonic assistance, tool type, stacking sequence, and feed rate—and output parameters, specifically thrust force and delamination. A nested feature scoring (NFS) method was employed for importance analysis, revealing tooling type and feed rate as key features for minimizing delamination and reducing thrust force, respectively. The machinability results revealed that ultrasonic drilling lowered thrust force by improving chip evacuation and reducing fiber breakage. HSS tools with cobalt content, alongside symmetrical stacking sequence, helped to further minimize both thrust force and delamination. However, the inclusion of GNPs led to an increase in thrust force and delamination, attributed to the increased strength of the CFRP/GNP composite. The process involved meticulous training, resulting in four optimal-fit models serving as inputs for the stacked meta-model. Iterative enhancements fortified the ensemble robustness, with fine-tuning of hyperparameters through Bayesian optimization. The ensemble superiority over individual models manifested in a remarkable reduction of mean absolute error (MAE) and root mean squared error (RMSE) by up to 97% and 124% for delamination, and 205% and 154% for thrust force, compared to the best base learner. Visual and statistical assessments effectively illuminated the intricate interactions between variables in the drilling process. The methodology resulted in a highly adaptable predictive model with applications across diverse manufacturing contexts.

Investigating the performance of the pressurized injection lubrication technique in the turning process

Efficient lubrication and cooling are crucial in machining operations to enhance tool life and workpiece quality. Sustainable methods like minimum quantity lubrication (MQL) and dry cutting often face limitations in cooling efficiency and chip evacuation, especially under high-speed conditions or when machining difficult-to-cut materials such as stainless steel. This study introduces the novel pressurized injection lubrication (PIL) technique designed to address these challenges by optimizing lubrication, cooling, and chip evacuation during the turning operations of stainless steel 304. Using flaxseed oil as the lubricant, the PIL system employs a 0.26 mm stream diameter at a pressure of 16 bar to provide the necessary cooling and lubrication to the cutting zone. Cutting temperature and surface roughness were selected as the primary responses. Experimental runs were designed using the Taguchi L9 method. Analysis of variance showed that the lubrication method significantly affected the cutting temperature, with a contribution percentage approaching 94%. The experimental results demonstrated that PIL reduced the cutting temperature by up to 55%, while MQL reduced it by about 48%, both compared to dry cutting at the highest utilized speed. The lubrication method was also found to be the most significant factor affecting surface roughness, with a contribution percentage of 72.8%. Experimentally, PIL improved surface roughness by a maximum of 16.2% compared to MQL. Additionally, PIL maintained low oil consumption (0.9 l/h) and energy usage (< 0.017 kWh). The cost-effective PIL setup, priced under 65 USD, underscores its potential as a sustainable and efficient alternative for machining processes. The system’s components are readily available, facilitating easy integration into existing metal-cutting machines. Finite element analysis (FEA) modeling was used to predict residual stresses under different lubrication methods. The FEA model indicated that PIL and MQL reduced residual stresses by about 81.2% and 76.6%, respectively, compared to dry cutting at a speed of 500 rpm. These findings suggest that PIL can significantly enhance machining performance and sustainability, offering a viable solution to modern manufacturing challenges.

Experimental Analysis of Robotic Cortical Bone Specimen Drilling Performance: Effect of Cryogen.

In orthopedic surgery, precise bone screw insertion is crucial for stabilizing fractures, necessitating a preliminary cortical bone drilling procedure. However, this process can induce temperatures exceeding 70 °C due to the low thermal conductivity of cortical bone, potentially leading to thermal osteonecrosis. Furthermore, significant cutting forces and torque pose risks of tool breakage and bone damage, underlining the need for high precision and optimal processing parameters. Traditionally, drilling relies on the surgeon's experience and often results in imprecise outcomes due to inconsistent feed rates. Therefore, this study proposes the use of a 6-axis robot for controlled drilling, offering precise control over angular velocities and consistent feed rates. Additionally, explore the use of cryogenic liquid nitrogen (LN2) as a novel cooling method compared to conventional saline solutions, examining its efficacy under various cutting conditions. The results demonstrate that LN2 cooling conditions lead to a reduction in thrust and torque under specific processing conditions, and facilitate smoother chip evacuation. Additionally, LN2 significantly lowers the peak temperature around the drilling site, thus minimizing the risk of thermal osteonecrosis. Consequently, the use of a 6-axis robot provides consistent feed rates, and LN2 cooling achieves optimal processing conditions, enabling a more controlled and effective drilling process.

Comparison of Modulation-Assisted Machining Strategies for Achieving Chip Breakage When Turning 17-4 PH Stainless Steel

Chip morphology is an intrinsic characteristic of the machining process that determines the quality of the process. When machining low machinability materials, the chips formed are usually long, continuous, and difficult to break. Due to the negative effect of the accumulation of the chip along the process, chip breakage and the correct extraction out of the machining area have become indispensable requirements. Although numerous chip-breaking methodologies have been proposed, modulation-assisted machining (MAM) is one of the most promising approaches, due to its independence from the workpiece material, tool geometry, and cutting conditions. In this work, a comparison of different modulation-assisted machining strategies, based on the modulation of the feed (F-MAM) or the depth of cut (D-MAM), were experimentally evaluated and compared to conventional turning in terms of chip morphology, surface roughness, and tool wear. Results showed that both MAM strategies enabled chip breakage and improved chip evacuation in comparison to conventional turning; however, D-MAM showed a better performance in terms of tool wear and surface roughness.

Effect of Different Feed Rates on Chip Evacuation in Drilling of Lead-Free Brass with a Small-Diameter Drill

Effect of Different Feed Rates on Chip Evacuation in Drilling of Lead-Free Brass with a Small-Diameter Drill

Performance Analysis of Helical Milling and Drilling Operations While Machining Carbon Fiber-Reinforced Aluminum Laminates

Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed.

Exploring the viability of alternative cooling-lubrication strategies in machining processes: A comprehensive review on the performance and sustainability assessment

This paper explores the challenges of machining difficult-to-cut metals using tools like coated carbide, ceramics, and CBN under dry conditions, addressing issues such as heat generation, tool wear and friction, chip evacuation, surface integrity, vibration, and chatter. Though cutting fluids have historically improved machinability, environmental concerns, such as toxicity and non-biodegradability, are significant. Researchers aim to enhance the economic and ecological aspects of machining by reducing cutting fluid usage. This paper provides an overview of the performance assessment and sustainability evaluation of various cooling and lubrication methods during the machining of hard-to-machine as well as difficult-to-cut metals. Additionally, the literature review highlights various environmentally friendly cooling strategies, such as minimum quantity lubrication (MQL) and cryogenic arrangements. According to the results of this review, the utilization of various cooling and lubrication technologies has the potential to enhance both sustainability and machinability properties while prolonging the lifespan of cutting tools. The findings also show that there is a lot of room for improvement in terms of optimizing and making these cooling-lubrication solutions more practical and effective.

Finite element simulation of the mechanical loads during low frequency vibration-assisted drilling utilizing the CEL-method

Poor chip evacuation during drilling leads to increased heat generation in the contact zone and a decreased in borehole quality. This disadvantage can be overcome by low frequency vibration assisted drilling (LFVAD), which produces small, uniform shaped chips that allow better chip evacuation. The study presents the results of simulations of chip formation in conventional drilling (CD) and LFVAD based on the Coupled Eulerian-Lagrangian (CEL) method. The method does not require time consuming remeshing despite the high strains and strain rates that occur. In this work, a mesh refinement analysis in different spatial directions is performed in order to reduce the computational effort and preserve the accuracy of the numerical results.. A comparison with experimental data is performed for validation.

Reducing delamination risk with response surface methodology-supported drilling analysis for Nomex® aramid fiber composites

This article presents a comprehensive experimental investigation into the drilling behavior of Nomex®, a type of aramid fiber. The study specifically examines the impact of various cutting parameters and drill bit types on drilling outcomes. While Nomex® offers many advantages, difficult chip evacuation during drilling of aramid fiber composites can lead to surface defects and delamination. The research aims to explore how drilling parameters—such as spindle speed, feed rate—and four distinct drill bit types affect drilling performance. The analysis encompasses factors such as thrust force, torque, and surface roughness, studied under different drilling conditions and with various drill bit types. Moreover, the research assesses peeling and push-out delamination factors to gain insights into drill bit and coating characteristics. An examination of burr and chipping further enhances the comprehension of drilling performance. To determine the most effective drilling conditions, the study employs multi-response optimization. The optimal drilling performance is achieved with a combination of a 0.1 mm/rev feed rate, 1402.82 r/min spindle speed, and HSS-TiN drill type. This configuration successfully integrates responses, resulting in a composite desirability value of 0.95.

Surface Characteristics and Residual Stress Variation in Semi-Deep Hole Machining of Ti6Al4V ELI with Low-Frequency Vibration-Assisted Drilling

This study examined the impact of vibration-assisted drilling (VAD) on hole quality and residual stress in Ti-6Al-4V ELI (Extra Low Interstitials) material. Ti-6Al-4V ELI possesses excellent mechanical properties but presents challenges in machining, including chip evacuation, burr formation, and elevated cutting temperatures. VAD, particularly low-frequency vibration-assisted drilling (LF-VAD), has been explored as a potential solution to address these issues. The research compares LF-VAD with conventional drilling (CD) under various cutting and cooling conditions. LF-VAD exhibits higher maximum thrust forces under specific conditions, which result in accelerated tool wear. However, it also demonstrates lower RMS (root mean square) forces compared to CD, offering better control over chip formation, reduced burr formation, and improved surface roughness within the hole. Furthermore, LF-VAD generates greater compressive residual stresses on the hole’s inner surface compared to CD, suggesting enhanced fatigue performance. These findings indicate that LF-VAD holds promise for improving the hole’s surface characteristics, fatigue life, and overall component durability in Ti-6Al-4V machining applications.

Experimental comparison of the indexable drilling with different U drills on hole quality

U drills are estimated to account for around 53% of all drilling equipment’s market share. This study compared and contrasted the impacts of the balance angle, the U drill length/diameter ratio, and the extra coolant hole opened in the chip evacuation channel on the hole quality when drilling AA 7075-T651 material. Hole quality was investigated by deviation from diameter, deviation from circularity, deviation from cylindricality, surface roughness, forces, and torque. Three cutting speeds, three feed rates, and four distinct U drills were chosen as input parameters. The studies revealed that when the U drill’s length/diameter ratio increased, the hole quality deteriorated. The best hole quality was nonetheless achieved by the tool with the additional coolant hole. The higher balance angle resulted in improved hole quality. However, it was discovered after looking at the chips and inserts that the chatter only happened while drilling with a U drill that had an additional coolant hole. While the extra coolant hole opened to the chip evacuation channel, it affected the hole quality positively but caused chatter, which negatively affected the inserts. The reasons for these results are discussed in detail.

Influence of Technological Parameters on Chip Formation and Chip Control in Precision Hard Turning of Ti-6Al-4V.

This article presents the results of an experimental investigation into the effect of process parameters in the precision hard turning of Ti-6Al-4V on chip morphology at both macro and micro levels. It also reports on the control of chip generation to improve chip evacuation and breakability at the macro level by varying the process parameters, namely, feed rate, cutting speed and depth of cut during turning tests. A scanning electron microscope (SEM) was used to examine the chips produced for a better understanding of chip curling mechanisms at the micro level. Surface roughness of the machined specimens was measured to assess the effect of chip evacuation on obtainable surface quality. From the results, it was found that the interaction of process parameters has a significant effect on the control of chip formation. In particular, the interaction of higher cutting speeds and greater depths of cut produced chip entanglement with the workpiece for all values of feed rates. Using relatively higher feed rates with a low depth of cut showed good results for chip breaking when machining at higher cutting speeds. Different chip curling mechanisms were identified from the SEM results. Chip side-curl formation showed different segmentation patterns with an approximately uniform chip thickness along the chip width, while chip up-curl occurred due to variations in chip thickness. Finally, it was found that the tangling of the chip with the workpiece has a significant effect on the final surface quality.

Multi-attribute optimization of drilling CFRP/Ti-6Al-4V alloy hybrid stacks using VIKOR

Drilling carbon reinforced polymer composites (carbon fiber-reinforced polymers, CFRP) and the hole quality produced are highly critical and significantly influence the performance and reliability of structures used in aircraft components. When CFRP composites are stacked together with titanium alloy, the damage caused by the machining operation is incalculable due to the burr and chip evacuation of metallic phases. In this article, efforts were made toward the identification of optimal machining conditions in drilling CFRP/titanium hybrid stacks. Experimental investigations on dry drilling of CFRP/titanium stacks were conducted with the aid of tungsten carbide drills. This research article discusses an improved compromise ranking method named VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) to determine the optimal machining parameters in drilling of CFRP/titanium stacks to produce high-quality holes. Attributes measured from experimental trials are: delamination factor of CFRP, burr height of titanium alloy, thrust force, torque, surface roughness, roundness and hole diameter of CFRP and titanium alloy. Experimental trial 13 with a combination of speed of 30 m/min, feed of 0.025 mm/rev was chosen as an ideal machining parameter in drilling CFRP/Ti-6Al-4V stacks without any trade-off. Confirmation tests convey that the results agree well with optimal parameters and the decision making in drilling such multimaterial stacks is highly consistent and judicious. In regard to the optimal parameters determined, investigations on tool life were performed and a tool life of 20 min for 0.10 mm flank wear land was observed.

Quality Evaluation and Analysis of Force Signals in CFRP Helical Milling

Nowadays, drilling is one of the most widespread operations due to the need to obtain holes for mechanical joints. This operation is particularly relevant in the aeronautical sector due to the high number of operations performed, the high demands and the use of materials that are difficult to machine. The use of materials that enhance aircraft performance, such as carbon fiber composites (CFRP), poses a challenge for axial drilling operations. The characteristics of these materials and typical defects such as delamination are difficult to control due to the axial forces produced during drilling operations. Therefore, more efficient alternatives are required. In this context, helical milling operations have advantages such as lower axial stress, higher flexibility, and higher efficiency in heat and chip evacuation that put it in the spotlight. In this work, research has been carried out in which helical milling operations have been performed on CFRP. The main objectives were the analysis of surface quality, delamination, tool wear and force analysis. For this purpose, a working methodology has been developed combining machining parameters that define the kinematics of the cutting process (cutting speed, axial feed rate, and tangential feed rate). Finally, this information has allowed finding a correlation between quality indicators such as delamination and the forces generated during the cutting process and associated with progressive tool wear. The results show that the force signal could be used for on-line monitoring of the machining process.

ОСОБЕННОСТИ СТРУЖКООБРАЗОВАНИЯ ПРИ УЛЬТРАЗВУКОВОМ СВЕРЛЕНИИ УГЛЕПЛАСТИКОВ

The article is devoted to the description of chip formation during ultrasonic drilling of small diameter holes in structural carbon fiber. Established that generated when drilling with ultrasound chip is qualitatively different from the chip during normal drilling less compartilhamento and the presence of truncated fragments of carbon fibres, reflecting greater uniformity of the cutting process and to facilitate chip evacuation and describes the possibility of increasing the quality of processing by reducing the number of surviving unidirectional fibers.

Investigating the material removal mechanism and cutting performance in ultrasonic vibration-assisted milling of carbon fibre reinforced thermoplastic

Carbon fibre reinforced thermoplastic (CFRTP) has emerged as a sustainable alternative to carbon fibre reinforced plastic (CFRP) due to its improved reparability and recyclability. CFRTP, particularly carbon fibre reinforced polyetheretherketone (CF/PEEK), is a high-performance material known for its excellent mechanical, thermal, and corrosion resistance properties, making it well-suited for extreme environments in civil aviation equipment. However, machining processes such as milling often result in defects due to the material’s high toughness and anisotropic nature. This study aims to investigate the material removal mechanism in ultrasonic-assisted milling (UAM) of CF/PEEK and compare the effects of fibre cutting angle (θ) and milling processes on milling performance. To simulate the fibre fracture mechanisms under different θ, finite element analysis (FEA) is employed. The results reveal different fracture modes, including bending, bending-shear, compression, and compression-shear, at various θ. Additionally, UAM demonstrates lower cutting forces and temperatures compared to conventional milling (CM). Notably, UAM greatly improves surface quality by reducing burr height and facilitating chip evacuation, while also enhancing surface integrity by minimizing cavity defects and fibre pull-out phenomena. These findings contribute to the development of low-damage machining methods that aim to achieve higher accuracy in CFRTP.

Investigation of the Cutting Fluid Incidence Angle Direction in Turning Grade 5 ELI Titanium Alloy under High-Pressure Cooling Conditions.

The use of high-pressure cooling (HPC) in machining can increase the efficiency and improve process stability through more effective breaking and chip evacuation. Turning tests of the Grade 5 ELI titanium alloy were carried out using cemented carbide tools and taking into account the direction of feeding of the cutting liquid. Measurements of the components of the total cutting force were carried out for feeds in the range f = <0.08; 0.13> mm/rev and two angular settings (i.e., angle α = <30°; 90°> and β = <0°; 60°>) of the nozzle. The chip breakage coefficient was determined. It was shown that the cutting force values depended on the feed value, and the angle of feeding of the cutting fluid did not significantly affect the values of the cutting forces. Despite the different forms of chips obtained, the applied method of searching for the best conditions was unsuccessful and no significant effect on the values of the chip breaking coefficient Cch was observed. To determine the best nozzle setting, it is useful to determine the working area of the chip breaker. Due to the shape of the chip, the optimal angular setting for the nozzle that supplied the cutting fluid was α = 60° and β = 30°. In addition, it was observed that the angle of incidence of the cutting fluid jet could affect the chip formation process and support the chip cracking process.

A systematic review on non-contact methods to estimate the surface roughness

Information and Communication Technology (ICT) is used in recent industries to advance into a decision-making environment in manufacturing. The objectives of this are efficiency, flexibility, innovation, quality, and cost reduction. Controlling and monitoring the machining operation is an area of interest for most researchers. Drilling is the process of making a hole by using different cutting tools and continuously removing material to create the desired feature. It often rubs against the produced surface during chip evacuation. As a result, the produced roughness is distinct from that of other machining operations like milling or turning. Surface roughness may therefore differ from the one that is predicted theoretically. In this paper, we are studying the various non-contact methods to estimate the surface roughness of the machined surfaces.

A review on the balancing design of micro drills.

In recent years, micro-hole drilling with a diameter of less than 1 mm has been widely applied in electronic information, semiconductor, metal processing, and other fields. Compared with conventional drilling, the engineer problems that micro drills are more prone to suffer failure in advance have restricted further development of mechanical micro drilling. In this paper, the main substrate materials of micro drills were introduced. And two important technical means to improve properties of tool material, namely, grain refinement and tool coating, were also introduced, which are current main research directions of micro drills from the perspective of materials. The failure mechanisms of micro drills were briefly analyzed, mainly tool wear and drill breakage. In the structure of micro drills, cutting edges and chip flutes are directly related to tool wear and drill breakage, respectively. So the structural optimization and design of micro drills, especially for key structures such as cutting edges and chip flutes, have to face great challenges. Based on the above, two pairs of requirements for micro drills were proposed, that is, the balance between chip evacuation and drill stiffness and the balance between cutting resistance and tool wear. So some innovative schemes and related researches of micro drills regarding cutting edges and chip flutes were reviewed. Finally, a summary of micro drill design and existing problems and challenges is proposed.