Hole Cylindricity Research Articles

Study of Hole Cylindricity and Surface Roughness in Drilling Application on Aircraft Wings

This study aimed to determine the effect of drilling parameters on hole cylindricity and surface roughness in drilling applications on aircraft wings. It was determined that increasing feed rate resulted in poor hole cylindricity and surface roughness. The ideal feed rate for better hole cylindricity is 0.230 mm/rev, while the ideal feed rate for better surface roughness is 0.200 mm/rev. Both hole cylindricity and surface roughness have a minimum correlation with each other in producing a good quality of drilled holes.

Formation of the quality of holes obtained by drilling in aviation structures made from polymer composite materials

The subject of this study is the quality indicators (geometric accuracy, roughness, cylindricity and taperness) of holes obtained by drilling in aircraft structures (AS) made of polymeric composite materials (PCM). The quality indicators of holes in AS made from PCM were studied by using kinematic schemes across and along the direction of drilling. A kinematic scheme of formation of the predicted surface roughness of the hole in AS made from PCM has been built. The calculation of the predicted roughness of PCM holes taking into account the geometry of the drill and drilling modes has been proposed. Experimental studies have been implemented to establish the parameters of predicted roughness, geometric accuracy, taperness, as well as deviations from cylindricity. The methods used were the method of expert assessments and experimental studies of quality indicators of PCM openings. The following results were obtained: the roughness in full-scale experiments turned out to be lower than the theoretical calculated values with a difference of not more than 10...15 %. It was found that roughness, taperness, deviations from geometric precision and cylindricity differ in characteristic rotation zones of the drill from 0° to 360° and depend on the drilling parameters and PCM properties. It was found that the deviation from the hole cylindricity is affected by the shrinkage of the material. The appearance of ovality in the holes of prototypes was established. The results of experimental studies of measurements of hole diameters to establish deviations from cylindricity, geometric accuracy, and taperness met the production requirements for the accuracy of their manufacture. For geometric precision and deviation from cylindricity, the results ranged from 7 to 12 IT grades, and for taperness, from 0.083 to 0.28 % per a hole in AS made from PCM and 9–10 IT grades

Rotary ultrasonic machining of advance materials: A review

With its superior machining quality, rotary ultrasonic machining (RUSM) is the best alternative to machine complex, brittle materials like ceramics, glass, composites, and quartz. These materials are complex to machine with the conventional process. Other advanced materials during ultrasonic machining also result in poor machining characteristics. To achieve fine machining, hole accuracy was primarily focused on hard-to-cut materials like ceramics regarding deep drilling of holes. Hybrid machining is one of the best methods for RUSM to experience these challenges. The main objective of this review paper was to identify the different machining variables of rotary ultrasonic machining and their influence on the output response variables such as material removal rate (MRR), tool wear rate (TWR), and surface roughness (S.F.), etc., considered especially for different glass composites. In rotary ultrasonic machining, a review of the material removal methods, a description of the operation, the rate of material removal, and problems with tool wear are discussed. Based on the literature studied, the experimental results obtained for machining of advanced materials such as composites, silicon, advanced glass, CFRP, titanium, and carbides, etc., on RUSM, the various input parameters were analyzed to figure out the effect on output responses critically. Future research in rotary ultrasonic machining should optimize output responses such as cutting force, chipping size, hole cylindricity, and tool wear using advanced optimization techniques.

Linear regression and artificial neural network models for predicting abrasive water jet marble drilling quality

Marble is a fragile and heterogeneous material whose properties vary depending on the nature and origin of the marble. Therefore, the marble machining process requires the skills and know-how of the stone cutter to manually configure the machining parameters for each piece of marble. This study addresses the enhancement of quality achieved by marble drilling processes in the industry. The objective of this work is to drill marble with high quality performance and avoid fracturing the material. This article focuses on the process of drilling white Carrara marble with an abrasive water jet. This unconventional tool significantly reduces unwanted damage resulting from the drilling process (fractures, spalling) compared to the conventional drilling process (rotating abrasive tools). The effect of waterjet cutting parameters, namely jet pressure, stand-off distance, nozzle traverse speed, abrasive flow rate, and hole diameter on drilling tolerances is studied. Five defects in the drilling process are modeled in this work: surface roughness, hole circularity, hole cylindricity, hole location error, and hole taper, using analysis of variance of linear regression models and an artificial neural network width high accuracy. These models could be of great interest to stone cutters to configure marble machining parameters and improve marble manufacturing quality.

Performance analysis of closed-loop electrochemical discharge machining (CLECDM) during micro-drilling and response surface methodology based multi-response parametric optimisation

ABSTRACT In electrochemical discharge machining (ECDM), sustaining the effective machining gap during micro-drilling is strenuous because of the tool contact with the material. It deteriorates the geometrical features and causes high tool wear. Closed-loop ECDM (CLECDM) works on the adaptive tool feed that retracts the tool upon its contact with the material. Thermal cracks and hole cylindricity of the micro-hole is improved alongside the improvement of 15.9% in material removal rate (MRR) and 14.8 % in tool wear rate (TWR). A study on the number of tool contacts (NTC) is performed concerning distinctive parameters since it influences both MRR and TWR. Moreover, the response surface methodology (RSM) based mathematical models are established to correlate the relationship between the parameters and to obtain multi-response optimisation. Applied voltage, electrolyte concentration, tool feed rate, and inter-electrode gap (IEG) are chosen as input parameters while MRR, TWR, and NTC are chosen as response parameters. The model’s adequacy is checked through analysis of variance (ANOVA) and found significant. The multi-response optimisation is acquired using desirability function (D = 0.7574) for maximising MRR and minimising both TWR and NTC. The obtained parameters are applied voltage: 50 V, concentration: 25 wt.%, tool feed rate: 4 mm/min, and IEG: 42.35 mm.

Characterization and Performance of Minimum Quantity Lubricants in Through-Tool Drilling

This study characterized airborne microdroplet diameters and size distribution from two commercially available lubricants A and B for internal minimum quantity lubrication (MQL). The effects of air pressure, oil channel size, physical properties of lubricants on the resultant microdroplets and through-tool MQL drilling performance were studied. Airborne microdroplet diameters were highly sensitive to the coolant channel sizes and air pressure. Cluster method was used to divide microdroplets into smaller clusters for comparison. Experimental data show that the average airborne microdroplet of lubricant B was larger than that of lubricant A at different air pressures and channel sizes. The contact angle of lubricant A was at least 10° less than that of lubricant B when depositing on glass or aluminium. High-speed imaging showed the tendency of more viscous lubricant B sticking to the drill tip, and higher pressure and longer time was required to atomize this viscous oil. Built-up-edges were less significant when drilling A380 aluminium with lubricant A. Due to high machinability of A380 aluminium, variation of hole diameter and hole cylindricity were minimal when drilling with different lubricants. Insignificant improvement in hole quality was observed when drilling with excessive amount of MQL lubricants or high concentration of lubricant C in flood coolant.

Percussion Drilling of Deep Holes Using Picosecond Ultrashort Pulse Laser in Ni-Based Superalloy Coated with Ceramic Thermal Barrier Coatings

Ni-based superalloy with ceramic thermal barrier coatings (TBCs) is a composite material, which can be used in special environments with high temperature and high pressure such as aeroengine blade. In order to improve the cooling effect of the aeroengine, it is necessary to perform multi-size and large-area holes processing on the surface of blades. As a non-contact processing method with fast processing speed, good processing quality and almost no deformation, laser processing has been one of the important processing methods for film cooling hole processing of aeroengine blades. Percussion drilling is presented using picosecond ultrashort pulse laser in order to explore processing of deep holes in Ni-based superalloy, ceramic TBCs, and ceramic TBCs/substrate multilayer material. The effects of pulses, threshold and wavelength on hole diameter have been discussed, and the experiment on the deep hole ablation with 1064 nm wavelength has been performed. By analyzing the hole size and morphological characteristics of multiple processing parameters, the variation of hole cylindricity is obtained. A high-quality hole, without spatters around the periphery of hole entrance and without recast layer on the side-wall surface, in Ni-based superalloy coated with ceramic TBCs has been drilled. This research has potential applications to blade film cooling holes.

Multiple Sensor Monitoring of CFRP Drilling to Define Cutting Parameters Sensitivity on Surface Roughness, Cylindricity and Diameter.

Machining parameters affects the final quality of components made in carbon fiber reinforced plastic (CFRP) composite materials. In this framework, the work here presented aims at studying the right combination of cutting speed (vc) and feed rate (vf), for dry drilling of carbon fiber reinforced plastic composite materials, which obtained better results regarding roughness, hole cylindricity, and diameter. A series of experimental tests were carried out under different drilling conditions (vc/vf), monitoring the thrust force (Fz), torque (T), and electric power (EP), to define which one can help more for industrial daily life production. Results validation was carried out using the analysis of variance, in order to relate main machining parameters cutting speed and linear feed, with thrust force, drilling torque, main spindle electric power and hole quality parameters (average roughness, cylindricity and diameter). The conclusions show that thrust force is not proportional to the cutting speed and the best combinations of cutting speed and feed were found out around the average values of tested parameters. Spindle electric power is an interesting element to take into account because it is easy to consider in real production.

The effect of cutting tool coating on the form and dimensional errors of machined holes in GLARE\xae fibre metal laminates

Fibre metal laminates (FMLs) are multilayered metal composite materials currently used in aeronautical structures, especially where fatigue and impact resistance are required. FMLs are produced in large panels and often require assembly using the drilling process for riveting purposes. Hole making is a critical machining process in the joining and assembly of aeronautical components, which has to meet stringent tolerance requirements. This paper reports a systematic analysis of hole integrity when drilling an FML known as GLARE®. In particular, the primary objective is to investigate the impact of three different drill coatings (TiAlN, TiN and AlTiN/TiAlN), against several important hole parameters: thrust force, hole size, circularity, cylindricity and perpendicularity. The results show that TiAlN-coated drills produced the highest thrust force, while TiN-coated drills produced holes with the lowest deviation between the hole diameter measured at the entry and the exit and that the drill coating was the most influential parameter for the resulting hole size. TiAlN-coated drills resulted in the highest circularity at the upper part of the hole, while hole cylindricity tended to be best when using AlTiN/TiAlN- and TiN-coated drills. The ANOVA analysis shows that the drill coating and the spindle speed had a significant influence on hole size and circularity, while drill coating was the only influential parameter on hole cylindricity, and spindle speed was the only contributing parameter on hole perpendicularity. Finally, scanning electron microscopy analyses showed two distinct hole wall surface damage phenomenon due to broken fibres and evacuated metallic chips.

Investigation of minimum quantity lubrication effects in drilling CFRP/Ti6Al4V stacks

ABSTRACTMinimum quantity lubrication (MQL) has been extensively applied to the machining processes of various metallic materials; however, its impact on the drilling characteristics of metallic-composite stacks has not been thoroughly investigated. The present paper is thus aimed at identifying the influences of the MQL environments on the drilling process of one type of composite-titanium compound stacks constituted by T700/FRD-YZR-03 carbon/epoxy laminates and the Ti6Al4V sheets. A series of drilling trials were performed using tungsten carbide twist drills to investigate the feasibility of the MQL for the multilayer stack machining. A quantitative analysis was conducted on various drilling outputs including the drilling forces, surface morphologies of cut composite holes, hole defect extents, hole geometrical accuracy and tool wear signatures. A comparative investigation between the MQL and dry cutting conditions on the stack machinability was also carried out in order to quantify the potentials gained by the MQL machining process. The results indicate that the MQL drilling can yield several benefits in improving the surface morphologies of cut composite holes and in alleviating the drill wear severity, but it fails to reduce the drilling thrust forces, decrease the delamination extents and minimize the hole cylindricity errors when compared with the conventional dry cutting conditions.

Peck drilling of CFRP/titanium stacks: effect of tool wear on hole dimensional and geometrical accuracy

The effect of tool wear on dimensional and geometrical accuracy of holes machined by peck drilling in carbon fibre reinforced plastic (CRFP) and titanium (Ti) stacks is studied. Coated and uncoated tungsten carbide drills of both fine and ultra-fine microstructures are employed to assess the importance of grain size and coating on hole accuracy. Hole profiles show two maxima: one at the hole entry and the other at the CFRP/Ti interface. Hole cylindricity as function of tool wear shows a minimum. It firstly decreases due to flank wear and subsequent reduction of the drill diameter. Then the rise of tool instability prevails with the result that an increase of the cylindricity with tool wear is brought about. Less wear-resistant drills attain this minimum in a shorter time of cutting.

Experimental study of drilling white Calacatta–Carrara marble using artificial neural approach

Highly accurate marble processing is increasingly needed to comply with tight parametric/geometric tolerances and surface integrity specifications encountered while structuring, sculpture, and decorating. In this study, a new approach based on the artificial neural network technique is evaluated for the prediction of process parameters in the machining of white Calacatta–Carrara marble. The rotation speed, feed speed, drill bit diameter, drill bit height, number of pecking cycles, and drilling depth were considered as input factors. Corresponding surface roughness, hole circularity, hole cylindricity, and hole-location error were sought in output. A series of experiments was carried out using a 5-axes computer numerical control vertical machining center (OMAG) to obtain the data used for the training and testing of the artificial neural network with reasonable accuracy, under varying machining conditions. A MATLAB TM interface was developed to predict surface roughness and geometric defects (circularity, cylindricity, and localization). A 6 × 4 size multilayered neural network was developed. The number of iterations was 1000 and no smoothing factor was used. The drill quality (hole-location error, hole circularity, and hole cylindricity) and the surface roughness were modeled and evaluated individually. One hidden layer used for all models, with the number of neurons for all the responses being executed separately, was 12 while the number of neurons in the hidden layer, with all the responses executed together, was 14. In conclusion, from the obtained verified experimentally optimization results, the errors are all within acceptable ranges, which, again, confirm that the artificial neural network technique is an efficient and accurate method in predicting responses in drilling.

Rotary ultrasonic drilling of Ti6Al4V: Effects of machining parameters and tool diameter

This article presents the use of the rotary ultrasonic machining process for drilling holes in Ti6Al4V alloy which is regarded as a difficult-to-cut material due to its high-temperature strength and low thermal conductivity. This research presents an experimental investigation on the effect of the key rotary ultrasonic machining input parameters including ultrasonic power, spindle speed, feed rate, and the tool diameter on the main output responses including cutting force, hole cylindricity and overcut errors, and tool wear. No previous reports were found in literature to experimentally investigate the effect of the rotary ultrasonic machining parameters and the tool diameter on tool wear, surface integrity, and the accuracy of the drilled holes in Ti6Al4V alloy. The results showed that the rotary ultrasonic machining input parameters within the current ranges can significantly affect the quality of the drilled holes. Through proper selection of input parameters, holes could be drilled in Ti6Al4V alloy with smoothed surface morphology, low tool wear (0.7 mg) and very low cylindricity (2 µm) and overcut (120 µm) errors. Moreover, it was found that the selected level of any input parameter has the ability to significantly affect the influence of the other input parameters on the output responses.

A study on the effect of main process parameters of rotary ultrasonic machining for drilling BK7 glass

BK7 glass is an important engineering material with extensive applications in high-quality and precision transmissive optical components. However, BK7 glass is considered to be a difficult-to-cut material due to its high brittleness and nonconductivity. This article presents the use of rotary ultrasonic machining process for drilling holes in BK7 glass. No previous reports have been found in the literature to experimentally investigate the response of the BK7 glass to rotary ultrasonic drilling. The experimental investigations take into account the effect of the key rotary ultrasonic machining input parameters including the ultrasonic power, spindle speed and feed rate on the output responses of cutting force, exit chipping, surface roughness, hole cylindricity and overcut errors, and surface integrity. The results show that the input parameters within the current ranges can significantly affect the quality of the drilled holes. Moreover, the selected level of any input parameter has the ability to significantly affect the influence of the other input parameters on the output responses. Through proper selection of input parameters, holes could be drilled in BK7 glass with less fractured topography, low surface roughness (1.32 µm), low exit chipping size (0.85), and very low cylindricity (3 µm) and overcut (73.6 µm) errors.

The force system and performance of the welding carbide gun drill to cut AISI 1045 steel

This paper focused on the force system and performance of the welding carbide gun drill to cut AISI 1045 steel. A carbide gun drill force system had been established by the integration of forces on the main cutting edge, wear pad and outer diameter (OD) relief, and the mechanical equilibrium equations, applying specific energy model, which consisted of the geometry parameters, machining parameters, and material properties. Both the calculated and experiment data revealed that the force and torque increased with the cutting feed ascending and the cutting speed descending. The wear mechanical was the combination of the adhesive wear, diffusion wear, oxidation wear, and breakage in the gun drill. The chip length became short with the high cutting feed and the low cutting speed. The hole machining quality was highly dependent on the hole diameter and cylindricity. The high cutting feed associated with the high cutting force generated the large beating and lower the hole cylindricity deviation. Thus, the fluctuations of hole cylindrical decreased with the increasing of cutting speed. Considering the force system and the gun drilling performance, the optimized cutting parameters could be chosen basically.

Analysis of the machining characteristics in reaming AlSi12 alloy with PCD reamer

Machining characteristics were studied for the reaming AlSi12 alloy using six flutes polycrystalline diamond reamer on DMG DMU 50 linear five-axis CNC machine. The output measures for this experiment comprise of cutting torque, cutting thrust, hole diameter, hole cylindricity, and workpiece surface finishing. Cutting forces were in real time monitored by Kistler Dynamometer during the experiments. Hole diameter, hole cylindricity, and surface finishing (surface roughness and surface integrity) of the machined surfaces were measured after machining. It is indicated that the cutting force of thrust and torque decreased with increase of cutting speed and decrease of cutting feed. High accuracy of hole was achieved because the hole measurements satisfied the standard deviation. Hole diameters were within tighter tolerance value of 330 0.025, and cylindricalities varied in the range from 0.002 to 0.014 um (less than 0.02 um). As to surface finishing, high surface performance could be obtained by eliminating surface defects on initial hole such as cavities and voids after subsequent finishing operating of reaming. However, the reamed surface damages of AlSi112 alloy under inapposite cutting conditions were involved with re-deposited work material (chip), surface grooves and notch, feed marks, surface shrinkage cavities and porosities, metal debris, and micro-pits. Moreover, surface roughness improved with an increase in the cutting speed from 2,000 to 6,000 rpm, but it deteriorated evidently when the cutting speed increased from 6,000 to 10,000 rpm. Cutting speed of 6,000 rpm and cutting feed of 3,000 mm/min were the recommendable cutting parameters to ream AlSi12 alloy because best hole quality could be produced in comparison of other cutting parameters.

Mechanical microdrilling of negative-tapered laser-predrilled holes: a new approach for burr minimization

Despite considerable research effort being concentrated on improving hole quality, minimisation of burrs still remains a key challenge in mechanical microdrilling of ductile materials. Recently, a sequential laser-mechanical microdrilling technique, which was developed by the authors, has proved effective in improving tool life and reducing burr size. The improvement in burr size was achieved by means of laser predrilling a pilot hole before utilising a twist drill to finish the hole. This paper presents further development of the sequential laser-mechanical microdrilling process based on negative-tapered laser-drilled pilot holes. In the sequential laser-mechanical microdrilling process, although a large predrilled hole reduces the burr size, it has a negative effect on roundness and cylindricity of the hole. The results of further studies highlight that a smaller entry hole size supports the drill and suppresses tool wander which, in turn, improves hole cylindricity. Furthermore, a larger exit hole size significantly reduces burr size. Compared to pure mechanical drilling without any pilot hole, the reduction in burr size for the mechanical microdrilling of near zero tapper and negatively tapered laser-predrilled holes was observed to be 2.5 and 6 times, respectively. Moreover, the mechanical finishing of these holes does not compromise tool life and/or surface integrity. Thus, the use of a negative taper laser-predrilled hole presents a significant improvement in burr control in microdrilling of nickel-based super alloys in addition to providing a step change increase in tool life.

Limitations of Cl2/O2‐based ICP‐RIE of deep holes for planar photonic crystals in InP

AbstractA detailed study of dry‐etching of high‐aspect‐ratio holes into an indium phosphide substrate is presented for a Cl2/O2‐based plasma chemistry. The etching is performed in an inductively coupled plasma reactive ion etching reactor. The separate influence of the various etching parameters on the quality of the etched holes is identified. Quality measures such as high aspect ratio, hole cylindricity and verticality as well as sidewall smoothness can be controlled by varying the ICP power, the relative O2 flow rate and the self‐bias of the plasma. We were able to clearly identify trade‐offs that have to be made and limitations of the etching chemistry/technology used: If the aspect ratio improves, then the cylindricity also improves, whereas the verticality and the sidewall smoothness degrade. In previous reports, a certain ambiguity is generally observed in the sense that different process parameters exhibit partially contradicting trade‐offs. We show that this behaviour can be remedied by a careful selection of the variable parameters. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)