Helical Milling Research Articles

Removal mechanism and hole quality of SiCp/Al composites by ultrasonic elliptical vibration-assisted helical milling

SiCp/Al composites are widely used in the aerospace field due to their excellent properties. However, the huge difference in the properties of silicon carbide and aluminum matrix materials can easily lead to machining defects. Ultrasonic vibration-assisted machining is an effective method to deal with difficult-to-machine materials. In this study, ultrasonic elliptical vibration is applied to the helical milling of SiCp/Al composites. Firstly, the ultrasonic elliptical vibration-assisted helical milling (UEVHM) cutting-edge trajectory is modeled, and the equation of the UEVHM tool-chip separation condition is established, which lays a foundation for the analysis of the cutting mechanism. Then, the influence of ultrasonic elliptical vibration on the removal mechanism of SiCp/Al composites was investigated by finite element simulation. It was found that UEVHM can reduce the tearing of aluminum matrix and reduce the hole damage by changing the direction of the cutting velocity and the relative position of the cutting edge and particles. Finally, the single-factor experiment was carried out, and the surface morphology and roughness of HM and UEVHM were compared. The influence of process parameters on the surface roughness of UEVHM was analyzed. The experimental results show that compared with HM, UEVHM can reduce surface defects and exit damage, to obtain better surface roughness and exit edge quality. The increase in cutting speed can reduce the roughness, and the increase in pitch and revolution speed will increase the surface roughness.

Study on wear mechanism of milling cutter and hole-making quality in ball helical milling process

Study on wear mechanism of milling cutter and hole-making quality in ball helical milling process

Analysis of exit delamination mechanism and critical axial force in ball helical milling of CFRP

Analysis of exit delamination mechanism and critical axial force in ball helical milling of CFRP

Experimental study on ultrasonic vibration‐assisted drilling performance of carbon fiber polyetherketoneketone laminate

AbstractParts made from carbon fiber reinforced polyetherketoneketone (CF/PEKK) primarily use mechanical connections during assembly, where the quality of hole processing directly impacts the connection strength. However, defects like delamination, burrs, and fiber pull‐out frequently occur during drilling. While existing research focuses on optimizing conventional drilling (CD) and helical milling (HM), ultrasonic vibration‐assisted drilling (UVAD) shows superior performance in reducing thrust force and defects. This study experimentally evaluates the hole‐making performance of CF/PEKK using the UVAD method. It examines the effects of ultrasonic vibration on thrust force, drilling temperature, processing damage, chip morphology, and surface microstructure, and discusses the damage suppression mechanism. The results show that the UVAD method significantly reduces thrust force and drilling temperature compared to the CD method, with similar trends in delamination and burr damage. This study demonstrates that using the UVAD method for drilling CF/PEKK laminates effectively reduces thrust force, drilling temperature, and machining damage, thereby significantly improving processing quality. The material removal mechanism of UVAD was analyzed, offering substantial insights and practical guidance for the efficient drilling of CF/PEKK laminates.Highlights The drilling performance of CF/PEKK was studied. The drilling quality of UVAD and CD is compared by experiments. UVAD has a lower thrust force and drilling temperature. UVAD can reduce machining damage and improve machining quality.

Research on axial cutting force fluctuation and periodicity in helical milling of CFRP

Research on axial cutting force fluctuation and periodicity in helical milling of CFRP

Comprehensive machinability assessment of Ti6Al4V alloy during drilling and helical milling using sustainable dry condition

Comprehensive machinability assessment of Ti6Al4V alloy during drilling and helical milling using sustainable dry condition

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.

Analytical modeling of cutting force in vibration-assisted helical milling of Al 7075 alloy

Vibration-assisted helical milling is considered a promising hole-making process in the aerospace industry. The prediction of cutting force magnitude and behavior is very important to determine the cutting power, produce tight tolerance, eliminate tool wear, and improve the hole quality. Therefore, the main goal of this work is to establish a cutting force model and evaluate the cutting force coefficients, based on a mechanistic approach, during vibration-assisted helical milling of aerospace aluminum alloy (Al 7075). The process kinematics, the chip geometry including the chip width and chip thickness variations, and the tool-workpiece engagement are theoretically analyzed throughout the whole machining time. A set of experimental tests is implemented at different conditions of tangential feed and helical pitch. Additionally, model validation is performed to discuss the quality and accuracy of the presented model. Consequently, the behavior of the cutting force components against the application of ultrasonic vibration at different cutting conditions is demonstrated. The results show that the analytical and the experimental results are well agreed with a relatively small error percentage. The cutting force components generally increase as tangential feed and helical pitch increase. Moreover, the superimposed ultrasonic vibration causes a rapid tool-workpiece separation increasing the analytical and the experimental oscillation of the cutting force components, thus decreasing the average calculated cutting force.

Experimental investigation on tool wear and hole quality in helical milling of CFRPs

Experimental investigation on tool wear and hole quality in helical milling of CFRPs

Comparison of joining hole making methods for fiber reinforced FDM 3D printing parts

In this paper, continuous fiber reinforced plastic composite fused deposition modeling (FDM) 3D printing and conventional material removal processing methods were combined to investigate the effects of hole-making methods (printing, drilling and helical milling) and fiber filling patterns (solid pattern and rhombic grid pattern) on the quality and mechanical properties of joining holes in printed parts. This study evaluated the cutting forces during hole machining and assessed hole quality based on defect analysis, diameter accuracy, roundness error, and wall morphology, complemented by cost comparisons. It was observed that holes manufactured by conventional material removal methods were of better quality, but were also more costly. Tensile tests were conducted on the bolted joint structures to evaluate the mechanical properties of the joining holes, and scanning electron microscopy (SEM) examinations were performed on the cross-sections of bolted joints to analyze the tensile damage patterns. It was found that helical milled holes exhibit unique damage patterns and greater ultimate tensile displacements due to the existence of fibers directly involved in load bearing at the hole walls. This leads to a significant increase in energy absorption performance. The tensile properties of the structures consisting of specimens with a fiber filling angle of 0°/90° were superior to those with a fiber filling angle of 45°/135°. Additionally, the mechanical properties were found to be slightly better using the rhombic grid pattern than the solid pattern for the same fiber filling density and fiber filling angle. These findings provide valuable insights into the choice of preparation methods for joining holes in 3D printed parts to achieve optimal performance in a variety of engineering applications.

Adaptive Machining Method for Helical Milling of Carbon Fiber-Reinforced Plastic/Titanium Alloy Stacks Based on Interface Identification.

CFRP/Ti stacks composed of carbon fiber-reinforced plastic composites (CFRP) and titanium alloys (Ti) are widely used in aerospace fields. However, in the integrated hole-making process of CFRP/Ti stacks, the machining characteristics of various materials are significantly different, and constant machining parameters cannot simultaneously meet the high-quality machining requirements of two materials. In addition, errors exist between the actual thickness of each material layer and the theoretical value, which causes an impediment to the monitoring of the machining interface and the corresponding adjustment of parameters. An adaptive machining method for the helical milling of CFRP/Ti stacks based on interface identification is proposed in this paper. The machining characteristics of the pneumatic spindle and the interface state in the helical milling of CFRP/Ti stacks are analyzed using self-developed portable helical milling equipment, and a new algorithm for the real-time monitoring of the machining interface position and adaptive adjustment of the machining parameters according to the interface identification result is proposed. Helical milling experiments were carried out, the results show that the proposed method can effectively identify the position of the machining interface with good identification accuracy. Moreover, the proposed parameter-adaptive optimized machining method for CFRP/Ti stacks can significantly improve hole diameter accuracy and machining quality.

Study on the removal mechanism and milling quality of helical milling hole of SiCp/Al composites

SiCp/Al composites have been widely used in the aviation field due to their excellent properties such as high strength and good wear resistance, but there are still some problems in their hole-making, such as unclear helical milling removal mechanism and poor hole quality. In this paper, the removal mechanism of SiCp/Al composites in helical milling was analyzed by finite element simulation and a three-factor four-level single-factor test. Then, the effect of process parameters on the surface quality of the hole wall is analyzed by a single-factor test. Finally, the formation mechanism of orifice damage and the influence of process parameters on the quality of the orifice edge are analyzed. The results show that in the helical milling process of SiCp/Al composites, the SiC particles are mainly broken and some fall off. Partial tearing of the aluminum matrix occurs. The quality of the hole wall and orifice becomes better with the increase of spindle speed, and worse with the increase of pitch. The revolution speed has a negative effect on the surface quality of the hole wall and a positive effect on the outlet quality. After the spindle speed increased from 500 r/min to 2000 r/min, the surface roughness decreased by 17.13 %. The surface roughness increased by 68.86 % when the pitch increased from 0.1 mm to 0.4 mm. The surface roughness increased by 9.1 % when the spindle speed increased from 30 r/min to 60 r/min. This paper can provide an important reference for SiCp/Al composites with high efficiency and low damage.

Material identification method for helical milling of CFRP/Ti stacks based on torque-speed model

Material identification method for helical milling of CFRP/Ti stacks based on torque-speed model

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.

A multi-objective robust evolutionary optimization approach applied to the multivariate helical milling process of super duplex steel

This work presents an approach for multivariate modeling and multi-objective robust evolutionary optimization for processes presenting as inputs control and noise variables and as outputs a set of correlated responses regarding process performance and product quality. Factor analysis is applied to obtain a transformed output set that is uncorrelated and retains most part of the information of the original outputs. Models that are robust regarding noise variables relating this transformed output set with the control variables are obtained through robust parameter design. Response models in the function of process and noise variables are obtained through the least squares method. Mean and variance models as a function of process variables are obtained through error propagation. Robust mean square error models are obtained to model the bias and variance of each latent variable. Finally, multi-objective evolutionary optimization is performed. Three evolutionary algorithms were applied and compared through hypervolume. The approach is applied in the helical milling of super duplex stainless steel UNS S32760. Tool overhang length, hole depth, and lubri-cooling flow rate were set as noise factors. Cutting forces were monitored, while roughness and roundness were measured to evaluate process performance and product quality. The three factors, obtained to represent the six outputs, guaranteed dimensionality reduction and minimized the redundancy in output space. The mean square error models obtained to these three factors as a function of control variables minimize both bias and variance regarding noise factors. The AGE-MOEA multi-objective evolutionary algorithm obtained the best performance considering the hypervolume. Some solutions with high trade-off were selected through pseudo-weights to aid the decision-making.

Machining Temperature, Surface Integrity and Burr Size Investigation during Coolant-Free Hole Milling in Ti6Al4V Titanium Alloy

Modern Aircraft structures use titanium alloys where the processing of holes becomes essential to assemble aerospace parts. Considering the limitations of drilling, the study evaluates the helical milling for hole processing in Ti6Al4V. The experimental evaluation was conducted by considering burr size, surface roughness, machining temperature, and microhardness under coolant-free conditions. The axial feed and cutting speed were varied at three levels, and nine experiments were conducted. The results exhibit a lower machining temperature during helical milling than during drilling. In addition, the helical milling helped to lower the surface roughness and size of the exit burrs. However, helical-milled holes showed higher subsurface microhardness than conventionally drilled holes. The process variables were influential on machining temperature magnitude. The highest recorded temperature of 234.7 °C was observed at 60 m/min of cutting speed and 0.6 mm/rev feed. However, the temperature rise did not affect the microhardness. Strain hardening associated with mechanical deformation was the primary mechanism driving the increase in microhardness. Helical-milled holes exhibited an excellent surface finish at lower axial feeds, while chatter due to tool deformation at higher feeds (0.6 mm/rev) diminished the surface finish. The surface roughness increased by 98% when the cutting speed increased to 60 m/min from 20 m/min, while a moderate increment of 28% was observed when the axial feed increased to 0.6 mm/rev from 0.2 mm/rev. Furthermore, the formation of relatively smaller burrs was noted due to significantly lower thrust load and temperature produced during helical milling.

Study on helical milling of SS 304 with small diameter tools under the influence of minimum quantity lubrication (MQL)

The objective of the present work is to study the effect of minimum quantity lubrication (MQL) on the performance of helical milling for machining high-quality holes with a small-diameter tool. Helical milling with small tools (diameter < 5 mm) has been a challenging domain due to the problem of tool deflection, which deteriorates the hole quality and adversely affects the process efficiency. In this study, helical milling of stainless steel (SS 304) is carried to machine holes using a 3 mm diameter coated carbide tool in minimum quantity lubrication (MQL), and the performance is compared with dry and conventional flood cooling based on the hole quality and tool wear. The findings of this study reveal that MQL results in high-quality holes with the least circularity and cylindricity errors compared to dry and flood lubrication. Surface morphology study of the machined holes shows that the holes generated in MQL have smoother surfaces with no evidence of severe surface defects. MQL can also significantly mitigate the problem of tool deflection encountered in small-diameter tools and reduce tool wear by 33.3% and 21.7% compared to dry and flood lubrication, respectively. As per ISO 286-2 standard, hole quality up to grade H8 is achieved with MQL, while dry condition and flood lubrication yield hole quality corresponding to H9 grade. This study concludes that MQL-assisted helical milling is one of the sustainable alternatives for the production of high-quality small-diameter holes in stainless steel.

Cumulative effect of Shearing parameters and Ramp angle on Hole surface quality in Ti6Al4V by Helical milling strategy

Hole creation is a common contour in drilling and milling. However, drilling big holes in Ti6Al4V is difficult. It is due to the thermally increased metallurgical behavior of Ti6Al4V, which mortifies drill bits and degrades hole quality. To solve this issue, the current research investigates Helical milling through Computer Aided Tool Path as a viable option for Hole production by functionally managing shearing parameters. This approach drives the process parameters helically at a certain Ramp angle to achieve improved surface quality in the Hole. The analysis of variance reveals that the Cutting Speed and Feed/tooth affect the Circularity of the Hole. Furthermore, Axial DOC and Ramp angle significantly impactHole surface texture. The cumulative impact of Cutting Speed at 60 m/min, Feed/tooth at 0.06 mm, and Axial Depth of Cut at 0.6 mm applied at a Ramp angle of 1.50 through theHelical milling tool path under Hybrid nano Flood lubrication catch the outstanding Hole Quality.

Using Nano-Fluids Minimum Quantity Lubrication (NF-MQL) to Improve Tool Wear Characteristics for Efficient Machining of CFRP/Ti6Al4V Aeronautical Structural Composite

The aeronautical industry constantly strives for efficient technologies to facilitate hole-making in CFRP/Ti6Al4V structural components. The prime challenge in this direction is excessive tool wear because of the different engineering properties of both materials. Nanofluid minimum quantity lubrication (NF-MQL) is the latest technology to provide synergistic improvement in tool tribological properties and lubrication function during machining. In the current study, an MoS2-based NF-MQL system was applied during helical milling using a FIREX-coated tool. In-depth analysis of wear, a scanning electron microscope (SEM), and electron deposition spectroscopy (EDS) were used to evaluate workpiece elemental transfer and tool wear mechanisms. Experimental findings showed that 1% nanoparticles concentration in lubricant resulted in low tool wear of 13 µm after 10 holes. The SEM and EDS analyses depicted formation of tribo-film on the surface, resulting less severe wear and a reduced degree of adhesion. However, a low nanoparticle concentration of 0.5% resulted in 106 µm tool wear after 10 holes with slight evidence of tribo-film. Parametric analysis based on eccentricity, spindle speeds (individual for CFRP and Ti6Al4V), axial pitch, and tangential feed showed correlations with mechanical damage. An extended study of up to 200 holes showed diffusion of C element at a high rate as compared to metal elements such as W and Co. The lowest tool wear was observed using eccentricity level 1, spindle speed Ti6Al4V 1000 rpm, spindle speed CFRP 7500 rpm, tangential feed 0.01 mm/tooth, axial pitch 1.5 mm, and 1% of MoS2 nanoparticles.

Investigation on cutting performance in ultrasonic assisted helical milling of Ti6Al4V alloy by various parameters and cooling strategies

Ti6Al4V alloy is one of the typical difficult-to-machine materials and often results in rapid tool wear, leading to poor machining quality in aircraft assembling. Compared to conventional helical milling, the ultrasonic assistant helical milling (UAHM) process has indicated its superior performance; however, it is still a great challenge to improve the hole surface quality and accuracy. In addition, few studies have been conducted on the effect of different variables and cooling strategies on the hole-making performance in longitudinal-torsional ultrasonic assisted helical milling (LT-UAHM). This paper, for the first time, reports effects of machining variables on geometric precision and surface roughness in LT-UAHM of Ti6Al4V. In addition, the lubrication/cooling mechanism on the simultaneous application of LT-UAHM and MQL is theoretically analyzed. The design approach of Taguchi experiment was employed to study how major variables such as the cutting speed, tangential feed, axial feed, and the workpiece hardness influence the dimensional and geometrical tolerances and surface roughness. This paper also discussed the effect of three cooling strategies, i.e., dry condition, air coolant, and minimum quantity lubrication (MQL) in LT-UAHM. Theoretical analysis demonstrated that the MQL coolant can be nebulized into hyper-fine droplets owing to the resonant cavitation phenomenon. Combined with the penetrating action caused by the separate-cutting principles of LT-UAHM, the cooling and lubrication performance of MQL was further enhanced. As a result, LT-UAHM with MQL had the most positive effect on circularity, cylindricity, nominal diameter, and surface roughness, contributing to 34%, 32%, 39%, and 40%, respectively. The second important machining factor was the cutting speed, contributing to 31%, 29%, 36%, and 22%, respectively. The tangential feed and workpiece hardness have the negative effect on geometrical accuracy, respectively.