Drill Wear Research Articles

Tool wear in TBM hard rock drilling – backgrounds and special phenomena

AbstractIn hard rock TBM drilling, wear issues play a crucial role in the success of a tunnelling project. Thus, excavation tools must be selected carefully and be adapted to ground conditions. Wear‐related changes in the tools that occur over the course of the tools' operating lives must also be taken into account. This paper presents five basic types of macroscopic wear for cutter rings: (1) abrasive/normal wear, (2) tapering, (3) mushrooming, (4) brittle fracture of the cutter ring (special wear type 1) and (5) blockade of the roller bearing (special wear type 2). These basic wear types lead to distinct cutter ring shapes which allow deriving some fundamental characteristics of the interacting rock types. In addition, a microscopic analysis of the surfaces and associated metallographic sections from worn cutter tools has been performed. As a result, the tribological processes under the cutter, leading to tool wear, can be better understood. In summary, the investigations may contribute to a better understanding to make it easier to choose the proper TBM disc cutter for a distinct rock type in order to minimize the risk of tool‐related downtimes.

EXPERIMENTAL STUDY ON THE EFFECT OF DRILL QUALITY ON BONE TEMPERATURE IN DRILLING

Bone drilling is widely performed in orthopedics for fixation and reconstruction of bone. In bone drilling, a hard metallic drill penetrates into the bone tissue which may cause trauma. Shear deformation of the bone material and friction between the drill and bone may induce elevated temperature in bone tissue. Temperature above a certain level may seriously harm the tissue, leading to several postoperative complications. The purpose of the current study is to measure and compare temperature in bone drilling using sharp and worn drill. Drilling tests were performed on cortical bone obtained from femoral shaft of a cow. A parametric study was conducted to quantify bone temperature using a range of drilling speeds and feed rates using drills having sharp and worn cutting edges with and without cooling environment. The temperature was measured using thermocouples, and wear of the cutting edges of the drill was measured using a scanning profilometer. Experimental results demonstrated lower temperature in bone using a sharp drill compared with a worn drill for similar drilling conditions. The bone temperature was found to rise with drill rotational speed, rate of penetration and size of the drill with and without cooling. Blunt drills were found more crucial for inducing thermal necrosis in bone.

Wear Detection of Drill Bit by Image-based Technique

Image processing for computer vision function plays an essential aspect in the manufacturing industries for the tool condition monitoring. This study proposes a dependable direct measurement method to measure the tool wear using image-based analysis. Segmentation and thresholding technique were used as the means to filter and convert the colour image to binary datasets. Then, the edge detection method was applied to characterize the edge of the drill bit. By using cross-correlation method, the edges of original and worn drill bits were correlated to each other. Cross-correlation graphs were able to detect the difference of the worn edge despite small difference between the graphs. Future development will focus on quantifying the worn profile as well as enhancing the sensitivity of the technique.

Rotary ultrasonic machining of rocks: An experimental investigation

Rock drilling is widely used to explore and mine energy resources. It has also been used to extract samples to study the earth’s geological composition and topography and to explore different planets. Percussive drilling is, as of right now, the most commonly used rock drilling method. Due to the high hardness and abrasiveness of rock, tool wear in rock drilling is severe, thus limiting its penetration rate and resulting in high cost. Therefore, it is crucial to develop more cost-effective rock drilling processes. Rotary ultrasonic machining has been used to drill many materials including metal alloys, ceramics, and composites, and its cost advantages have been demonstrated in many previous studies. This article presents the first experimental investigation of rotary ultrasonic machining of rocks. Three types of rocks (basalt, marble, and travertine) were used. Six input variables (tool rotation speed, feedrate, ultrasonic power, abrasive size, abrasive concentration, and drill bit diameter) were examined...

Diamond tools wear in drilling of SiCp/Al matrix composites containing Copper

Although SiCp/Al matrix composites possess numerous excellent physical and mechanical properties, high hardness and high wear resistance characteristics of SiC reinforcement lead to low tool life and resultant poor machined surface quality in cutting. The aim of this paper is to investigate the micromechanism underlying the macro-scale wear of diamond tools in drilling of high volume fraction SiCp/Al composites. To achieve this, the worn morphologies and possible crystal structure evolution of diamond tools after drilled 10 holes were examined using Laser Scanning Microscope and Raman spectroscopy, respectively. Additionally, based on drilling forces and hole quality, the machinability assessment of SiCp/Al6063 composites was carried out. The results indicate that the mechanically induced abrasion and thermodynamically activated chemical graphitization is the dominant and common wear mechanisms for PCD and CVD diamond coated tools in drilling of 65vol% SiCp/Al6063 composites containing copper. The reciprocating actions of thin graphite layer formed by oxidizing hydrogen chemisorbed on diamond surface by Copper oxides and graphite removal due to SiC particulates’ high-frequency scrape lead to continual and significant occurrence of diamond graphitization. In air atmosphere, the thermodynamic conditions of diamond-graphite transformation in machining of SiCp/Al6063 composites containing Copper are investigated. The coupled abrasive-chemical wear model is formulated based on analytical description of diamond wear mechanisms above. In terms of machinability of high volume fraction SiCp/Al composites, CVD diamond coated carbide drill is preferred, due to its stable cutting force, less wear and its ability to produce acceptable machined quality with increasing hole number.

A Prediction Model of Casing Wear in Extended-Reach Drilling With Buckled Drillstring

Buckled drillstring easily existed in extended-reach drilling (ERD) engineering, causing casing wear more severe. However, the effect of the buckled drillstring on casing wear prediction is going unheeded in long-term studies. To solve the issue, this paper proposes a new model, named as circumferential casing wear depth (CCWD) model, based on the energy principle and the more complicated geometry relationship than that in casing wear groove depth (CWGD) model. Meanwhile, sensitivity analysis of parameters clearly describes the changing trends among them. With the established composite wear models, the change of casing wear depth versus drilling footage under different composite wear cases is also discussed. The results show that the severe casing wear may occur if there is the buckled drillstring; due to the greater contact force and more sophisticated wear shape than those under nonbuckling condition, a shorter drilling footage could make a larger calculation error when only CWGD model is used. In the case study, the method of the inversion of casing wear factor from the drilled well can be used to predict the well whose structure resembles it; the revised coefficient, the maximum risky casing wear depth can be evaluated for each wellbore section to avoid drilling engineering failure. The new model provides a practical method to improve the prediction accuracy of casing wear in ERD. Neglecting the effect of the buckled drillstring will make the prediction underestimated and a great economic loss, which is significant for ERD.

Tool wear and hole quality in drilling of CFRP/AA7075 stacks with DLC and nanocomposite TiAlN coated tools

Drilling of multi-material stacks, constituted by two laminates in carbon fiber reinforced plastic and a core plate in AA7075, was widely investigated. Experiments were performed on a 5-axis CNC machining center, equipped with a dynamometer for the thrust force measurement, using different twist drills coated with DLC and nanocomposite TiAlN. Each hole, 6.8mm in diameter, was obtained with a chip removal cycle involving two passes spaced by a back motion. Optical and scanning electron microscopy techniques were used to quantify tool wear and delamination of composite layers. Finally, hole diameter in the different layers of composite/aluminum stack was measured by means of a coordinate measuring machine.The analysis of experimental results showed that the main wear mechanisms operating during drilling of stacks with the DLC coated drill are chipping, edge rounding and abrasion, while wear is mainly affected by abrasion with the nanocomposite TiAlN coated tool, even though adhesion of AA7075 particles on the rake surface also occurs. The evolution of flank wear with number of holes showed that the DLC coated drill underwent a much lower wear than the TiAlN coated one. Thrust force on both CFRP and AA7075 exhibited an increase with number of holes. Delamination of composite layer was already present in drilling performed with the wear free tool. However, a growth in delamination with number of holes was observed. Progression of hole diameter with number of holes, in the three different layers of multi-material stack, showed that diameter decreases with rising number of holes. Finally, systematic correlations between tool wear, thrust force, hole diameter and delamination factor were defined. Owing to the plot characteristics, the third-degree polynomial regression was found adequate to model interactions among the process results.

Sensitivity analysis of drill wear and optimization using Adaptive Neuro fuzzy –genetic algorithm technique toward sustainable machining

Machining processes have an important place in the manufacturing industry and it indeed contributed to the economic growth of a country. About 75% of machining processes involved drilling operation. Tool wear is a common phenomenon in the machining operation and significantly affects the product dimension accuracy, machining efficiency, manufacturing downtime, surface roughness and economic loss. Hence, an intelligent tool condition monitoring system is needed to maximize tool life and reduce machine downtime due to the tool replacement. In this study, experiments were conducted to investigate the influence of different drilling parameters on average drilling torque and thrust force. Effects of spindle rotational speed, feed rate and diameter of drill on tool wear were determined through Adaptive Neuro Fuzzy Inference System (ANFIS). Next, genetic algorithm (GA) was used to identify the optimal drilling parameter for different diameters of drill. Experimental results agreed well with the GA prediction results with a relative error of 3%. Hence, the results showed that ANFIS-GA is a faster and more accurate alternative to the existing methods for tool wear prediction.

Adaptive and Real-Time Optimal Control of Stick–Slip and Bit Wear in Autonomous Rotary Steerable Drilling

Deviated, horizontal, and multilateral wells are drilled to increase the contact area between the well path and the reservoir and as a result, the well productivity will be increased. Directional steering systems (DSS) are used to control the direction in nonvertical wells. Rotary steerable system (RSS) is the current state of the art of DSS. In this research, the problem of real-time control of autonomous RSS with unknown formation rock strength was presented. The aim of this study is to develop a real-time control scheme for real-time optimization of drilling parameters to (1) maximize the rate of penetration (ROP), (2) minimize the deviation from the planned well bore trajectory, (3) reduce the stick–slip oscillations, and (4) assess the degree of bit wear. Nonlinear model for the drilling operation was developed using energy balance equation, where rock specific energy (RSE) is used to calculate the minimum power required for a given ROP. A proposed mass spring system was used to represent the phenomena of stick–slip oscillation. The model parameters have been adaptively estimated at each control iteration to tackle any disturbances or variations in the formation properties. The bit wear is mathematically represented using Bourgoyne model. Detailed mathematical formulation and computer simulation were used for evaluation of the performance of the proposed technique based on real well field data. The obtained results showed excellent ability to accommodate the changes in the formation properties. In addition, the rates of bit wear and stick–slip oscillations have been optimized.

Wear of cemented tungsten carbide percussive drill–bit inserts: Laboratory and field study

Design of the drill–bit and selection of the Cemented Tungsten Carbide (CC) grade for drill–bit inserts are crucial for efficient percussive drilling. This study presents the results of an experimental campaign executed with the aim to identify the distinctive wear mechanisms and behaviour of different CC grades. Three laboratory and one full–scale drilling tests were performed using nine CC grades with different binder contents, binder chemical compositions, mean tungsten carbide (WC) grain sizes, and grain size distributions. Wear traces found on the drill–bit inserts after the full–scale drilling test show noticeable differences depending on their position on the drill–bit. Tensile forces present on the leading edge of the inserts due to the sliding contact with rock are suspected to play a significant role. Laboratory tests performed include: (i) single impact tests using a modified Split Hopkinson Pressure Bar (SHPB) apparatus, (ii) Abrasion Value (AV) rotating disk tests, and (iii) impact abrasion (LCPC) tests. Volume loss and shape change were used as macroscopic measures of wear. Greater volume losses were found for the grades with nickel–based binders compared to those with pure cobalt binder. The use of a narrower WC grain size distribution leads to lesser volume loss in drilling and AV tests. Surface analysis of the damaged microstructure was performed using scanning electron microscope. Distinct meso–scale (few dozens of WC grain sizes) patterns of damaged microstructure zones surrounded by the intact surface were found on the surfaces of specimens after single impact test. The pattern indicates the potential influence of a non–uniform contact due to the rock roughness and internal rock heterogeneities, which is supported by the study of the rock crater roughness. Size of such zones could be seen as a certain length–scale, which determines the insert–rock contact behaviour. A specific “peeling” mechanism of material removal was observed in the full–scale drilling test, where portion of the CC microstructure fused with the rock tribofilm gets removed when that tribofilm peels off.

Cutting edge—flatting and roughness measurement—to monitor blunting and chipping of the drill cutting edge when drilling CFRP

Tool wear is a major challenge when drilling CFRP. Cutting edge rounding quantifies the blunting of the cutting edge by considering the events happening in the flank–cutting edge–rake zone together by fitting a circle to this zone. The two interface zones, however, undergo wear in different ways. While the flank–cutting edge interface becomes rounded, the rake–cutting edge interface flattens out with drilling. Two new parameters, flank rounding (FR) and cutting edge flatting (CEF), are introduced to measure the damage to the flank and cutting edge, respectively. The nature of CEF and FR variation along the cutting edge shows that both are related. The chipping of the cutting edges is studied using a parameter called cutting edge roughness by monitoring the cutting edge topography. The progression of FR and cutting edge roughness along the length of the cutting edge shows that chipping may be related to the nature of FR progression. CEF could be easily measured using a simple measuring microscope and can be used to monitor drill wear.

Artificial neural network based tool condition monitoring in micro mechanical peck drilling using thrust force signals

Micro scale machining process monitoring is one of the key issues in highly precision manufacturing. Monitoring of machining operation not only reduces the need of expert operators but also reduces the chances of unexpected tool breakage which may damage the work piece. In the present study, the tool wear of the micro drill and thrust force have been studied during the peck drilling operation of AISI P20 tool steel workpiece. Variations of tool wear with drilled hole number at different cutting conditions were investigated. Similarly, the variations of thrust force during different steps of peck drilling were investigated with the increasing number of holes at different feed and cutting speed values. Artificial neural network (ANN) model was developed to fuse thrust force, cutting speed, spindle speed and feed parameters to predict the drilled hole number. It has been shown that the error of hole number prediction using a neural network model is less than that using a regression model. The prediction of drilled hole number for new test data using ANN model is also in good agreement to experimentally obtained drilled hole number.

FEM Simulation of Tool Wear in Drilling

The objective of this study is to simulate tool wear in drilling of nickel-based alloys, in particular Inconel 718. When machining these kind of materials, the impact of the thermal and mechanical phenomena generated by tool wear on the surface integrity is of prime concern. For this reason, it important to study the influence of tool wear on tool life, on final part quality and on cutting force and power consumption. Tool wear is caused by several phenomena (adhesion, abrasion, erosion, diffusion, corrosion, fracture etc.) depending on selected cutting parameters (cutting velocity, feed rate, etc.). In some cases these wear mechanisms can be described by analytical models which are function of physical quantities involved in process (temperature, pressure and sliding velocity along the cutting surface). Usually, commercial FEM software allows to implement these tool wear models but without tool geometry update. To overcoming this limitation, a suitable subroutine considering tool geometry update was developed and implemented in SFTC DEFORM-3D FEA software to simulate tool wear in drilling of Inconel 718. A good agreement was obtained between the predicted and measured tool wear data.

プリント配線板の小径穴あけ加工における工具摩耗が加工穴品質におよぼす影響

In the current manufacturing of printed circuit boards (PCBs), micro-drills are generally used to make smaller diameter through-holes in PCBs. The purpose of this paper is to clarify the effect of flank wear and margin wear on drilled hole quality. Series of PCBs drilling tests are carried out to investigate hole quality, hole location accuracy and hole wall roughness. The cutting torque and cutting force are measured by Kistler 9329 and 9257B respectively. Detailed observation of drilled hole surface is made by SEM. The hole location accuracy does not get worse with increasing flank wear of drill. On the other hand, the hole location accuracy becomes worse with increasing margin wear of drill. The hole wall roughness when using the margin wear type drill is worse than using the flank wear type drill. In addition the cutting torque when using the margin wear type drill is larger than using the flank wear type drill.

DLCコーテッドドリルを用いたプリント配線板の小径穴あけ加工に関する研究

In recent years, needs for micro drilling are increasing, accompanying the development of higher wiring density of printed circuit board (PCB). When drilling PCB for the purpose of making the electric through holes, it has been said that the drill breakage is caused by being filled the chips of GFRP and copper of PCB in the drill flutes. The aim of this study is to clarify the effect of PCB drilling using DLC coated drill on tool wear, chip evacuation and cutting torque. Series of drilling tests of PCB have been carried out to investigate the amount of drill wear, the chips evacuation behavior out of drilled hole with the drill, the shape of chips produced and the cutting torque using DLC-coated drill and non-coated drill. The chips evacuation behavior out of drilled hole with the drill is filmed by a high-speed motion camera and the shape of chips produced is observed by a microscope. The cutting torque is measured by a dynamometer; Kistler 9329A. The amounts of drill flank wear and margin wear using DLC-coated drill and non-coated drill are almost the same. The chips of GFRP using DLC-coated drill are shorter and smaller than those using non-coated drill. The chips evacuation out of drilled hole with the drill using DLC-coated drill is better than those using non-coated drill, and cutting torque using DLC-coated drill is lower than those using non-coated drill.

Diagnostic System of Drill Condition in Laminated Chipboard Drilling Process

The paper presents an on-line automatic system for recognition of the drill condition in a laminated chipboard drilling process. Two states of the drill are considered: the sharp enough (still able to drill holes acceptable for processing quality) and worn out (excessive drill wear, not satisfactory from the quality point of view of the process). The automatic system requires defining the diagnostic features, which are used as the input attributes to the classifier. The features have been generated from 5 registered signals: feed force, cutting torque, noise, vibration and acoustic emission. The statistical parameters defined on the basis of the auto regression model of these signals have been used as the diagnostic features. The sequential step-wise feature selection is applied for choosing the most discriminative set of features. The final step of recognition is done by support vector machine classifier working in leave one out mode. The results of numerical experiments have confirmed good quality of the proposed diagnostic system.

On-Line Monitoring of Drill Wear in Machining of AISI 1040 Steel Using Virtual Instrumentation

In this research work, an attempt is made to develop the on-line wear state monitoring system during drilling process on Vertical Machining Centre (VMC). The main objectives of the present work is to predict the drill wear states of High Speed Steel (HSS) drill bit during the drilling of a AISI 1040 Steel work piece using standard data acquisition software Lab VIEW by the application of Virtual Instrumentation (VI). The drill bit wear states were analyzed using spindle motor cutting current signals. The effective drill wear model have been developed using spindle motor cutting current signals and the various cutting parameters through Lab VIEW, to predict wear states of the drill-bit. The developed on-line drill wear process monitoring system has been used for the continuous monitoring of the drill-bit status, and to exhibit the drill wear states. It was found that the developed model show a good agreement with the experimental data where the deviation in drill-bit wear is less than 7% for varying cutting conditions.

Developing automatic recognition system of drill wear in standard laminated chipboard drilling process

Abstract The paper presents an automatic approach to recognition of the drill condition in a standard laminated chipboard drilling process. The state of the drill is classified into two classes: “useful” (sharp enough) and “useless” (worn out). The case “useless” indicates symptoms of excessive drill wear, unsatisfactory from the point of view of furniture processing quality. On the other hand the “useful” state identifies tools which are still able to drill holes acceptable due to the required processing quality. The main problem in this task is to choose an appropriate set of diagnostic features (variables), based on which the recognition of drill state (“useful” versus “useless”) can be made. The features have been generated based on 5 registered signals: feed force, cutting torque, noise, vibration and acoustic emission. Different statistical parameters describing these signals and also their Fourier and wavelet representations have been used for defining the features. Sequential feature selection is applied to detect the most class discriminative set of features. The final step of recognition is done by using three types of classifiers, including support vector machine, ensemble of decision trees and random forest. Six standard drills of 12 mm diameter with tungsten carbide tips were used in experiments. The results have confirmed good quality of the proposed diagnostic system.

Surface Modification of AISI 440B Stainless Steel and its Influence on Surgical Drill Bits Performance

Abstract The development of modern invasive surgery is highly dependent on the performance of surgical instruments, understood as long-term efficiency arising from high resistance to wear and corrosion. In order to maintain sufficient reliability, surgical cutting instruments are often made of martensitic stainless steels. Nevertheless, the use of ferrous alloys in medical applications is still a concern due to their questionable corrosion and wear resistance. To extend their biocompatibility, improve stability in variable environmental conditions, improve ease of handling, and maximize their performance, diffusion layers and coatings are applied to the surface. The aim of this work was to evaluate the effect of TiN and diamond-like carbon (DLC) surface modification on the performance of surgical drill bits, that is, wear and corrosion resistance, measured in model and field tests. Based on the findings presented, DLC layers can be recommended as anti-wear and anti-corrosion coatings for surgical drill bits.

A comparative study on tool wear and laminate damage in drilling of carbon-fiber reinforced polymers (CFRP)

Preliminary to successful assembling, drilling of composites like carbon-fiber reinforced polymers (CFRP) is an important but difficult process. The anisotropic and heterogeneous structure of the laminates and the highly abrasive nature of the carbon fibers make it prone to critical damages in the workpiece as well as extensive tool wear. In this work, drill series with uncoated and diamond coated tungsten carbide hard metal tools were performed in two CFRP laminates with significant differences in their microstructure. The tool wear behavior and the corresponding workpiece damage were intensively studied to figure out the correlations between wear and delamination damage. Therefore, novel and well established methods in tool wear analysis and delamination assessment based on light optical microscopy were applied and critically evaluated.The abrasive tool wear on uncoated carbide drill can be well described by the cutting edge rounding (CER) allowing strong correlations with the inflicted workpiece damage, whereas for coated tools measuring CER is not an appropriate method. The machinability of CFRP was found to be highly influenced by the presence of residual porosity in the composite laminate. Hence, the benefit in lifetime of the diamond coating can only be utilized in machining of high quality laminates.