Dry Drilling Research Articles

An Inverse Heat Transfer Method for Determining Workpiece Temperature in Minimum Quantity Lubrication Deep Hole Drilling

This study investigates the workpiece temperature in minimum quantity lubrication (MQL) deep hole drilling. An inverse heat transfer method is developed to estimate the spatial and temporal change of heat flux on the drilled hole wall surfaces based on the workpiece temperature measured using embedded thermocouples and analyzed using the finite element method. The inverse method is validated experimentally in both dry and MQL deep-hole drilling conditions and the results show good agreement with the experimental temperature measurements. This study demonstrates that the heat generated on the hole wall surface is significant in deep hole drilling. In the example of deep hole drilling of ductile iron, the level of thermal power applied on the hole wall surface is about the same as that on the hole bottom surface when a 10 mm drill reached a depth of 120 mm.

Experimental Results of Dry Drilling of Wear Resistant Steel

Nowadays, adverse human induced impacts on the environment are constantly increasing, which urges engineers to make their production planning activities more environmentally conscious. In addition, during the realization and manufacturing processes of goods, the application of environmentally demanding and polluting materials is expected to be reduced or even eliminated. The application of the increasingly popular minimal lubrication method or even dry cutting could be considered to be efficient methods for reducing adverse environmental impacts. On the other hand, the mentioned methods have drawbacks since they considerably shorten tool life, result in a more significant cutting tool wear and lead to increase in friction. As a result, the tool and the work place temperature rise. This article aims to give an overview of how the feed direction force, the cutting torque, the tool wear, and the surface roughness change during the cutting procedure, if cutting is done under dry conditions while different cutting speed and feed motion parameters are applied.

Performance Evaluation of Different Twist Drills in Dry Drilling of AISI 304 Austenitic Stainless Steel

This article evaluates the performances of HSS, K20 solid carbide, and TiN-coated HSS tools in dry drilling of AISI 304 austenitic stainless steel. The roles of spindle speed, feed rate, drill point angle, and number of holes on the surface roughness, tool flank wear, exit burr height, and enlargement of the hole size were experimentally investigated. The structure of this analysis has been determined by means of the technique called the design of experiments (DOE), which allows us to perform a relatively small number of experiments. An L 9 orthogonal array was used to collect the experimental data. The experimental results demonstrated that the above mentioned drilling performances showed a tendency to increase in response to the cutting parameters. TiN-coated HSS drill showed the highest performance with longer tool life and higher hole quality, as well as lower surface roughness, followed by the K20 carbide and the HSS tools.

Study of dry and minimum quantity lubrication drilling of novel austempered ductile iron (ADI) for automotive applications

Abstract Coolants and lubricants for machining can improve the machinability of the workpiece, increase productivity, and extend tool life by reducing tool wear. However, for environmental and economic reasons, recent research in industry and academia has sought ways to reduce the use of machining fluids. This paper reports the use of dry and minimum quantity lubrication (MQL) to drill austempered ductile iron (ADI), a new class of materials used for light weight automotive components like connecting rods and crankshafts. In this study, ADI is produced by a novel processing technique known as continuous casting-heat treatment process. The novel technique is developed by the integration of casting (in die casting) and heat treatment processes in the foundry to save energy and time. This paper deals with an experimental investigation on the role of MQL drilling on the cutting forces, tool wear and surface roughness of newly produced ADI at industrial speed-feed combinations by TiAlN-coated tungsten carbide tool. MQL drilling, performance is then compared with the dry and conventional drilling process under the same experimental conditions and environment. The results include significant reduction in tool wear, cutting forces and surface roughness by MQL drilling, mainly through reduction in the cutting zone temperature.

The role of diamond-like carbon coated drills on minimum quantity lubrication drilling of magnesium alloys

Minimum quantity water lubrication (H 2O-MQL) and dry drilling behavior of a cast magnesium alloy (AZ91) were investigated using non-hydrogenated diamond-like carbon (NH-DLC) coated HSS drills and by measuring cutting torque as well as the temperature generated in the workpiece. Due to adhesion of magnesium to the drills that caused rapid drill failure neither uncoated HSS nor NH-DLC coated drills could be used in dry drilling of AZ91. In drilling with NH-DLC coated tools flank type drill wear was also observed as a result of coating degradation induced by high temperature generated (271 °C) during contact. Application of H 2O-MQL at a rate of 30 ml/h increased tool life of NH-DLC coated drills and also reduced drill torque as well as the temperature to levels comparable to the conventional flooded drilling using mineral oil. AZ91 workpiece experienced recrystallization during dry drilling using both uncoated HSS and NH-DLC coated drills but while drilling with NH-DLC under H 2O-MQL condition no evidence of recrystallization was found. The low coefficient of friction of NH-DLC under H 2O-MQL condition limited the temperature increase to below 55 °C and hence both drill wear and magnesium adhesion were effectively reduced.

Drilling of Al—Mg—Cu alloys and Al—Mg—Cu/SiC composites

Metal matrix composites are widely used in engineering applications including automotive, aircraft, and military industries. In this study, different Al—4 wt%Mg—Cu alloys, and Al—4 wt%Mg—Cu/SiC composites were drilled on a vertical drilling machine using moderate speed and general purpose high-speed steel tools. The machinability parameters studied in this research were drilling forces (torque and thrust force) and surface roughness of the drilled holes. The results showed that the effect of the addition of copper as alloying element (up to 5 wt%) to Al—4 wt%Mg tends to decrease torque and thrust force. Also, it was found that the addition of SiCP (up to 10 vol.%) to the Al—4 wt%Mg—Cu alloys had little effect on the drilling torque and thrust force, but tends to improve the surface roughness of the drilled surfaces. Moreover, the analysis of the produced chips indicates that most of the produced chips by dry drilling of aluminum-based materials were of continuous type.

An XPS Study of the Stratified Built-up Layers Developed onto the Tool Surface in the Dry Drilling of Ti Alloys

Secondary tool adhesion wear is commonly provoked by two effects, whose nature depends on the placement of the adhered material. The so-called Built-Up Layer (BUL) is formed on the tool rake face and the Built-Up Edge (BUE) is developed on the cutting tool edge. These effects can be developed by different causes depending on both the cutting conditions and the material to be machined. In this work, X-Ray Photoelectron Spectroscopy (XPS) has been used to analyze the built-up layers formed during the dry drilling processes of aeronautical Ti-6Al-4V alloy. Changes in the Ti oxidation state in each layer have allowed proposing a BUL formation mechanism based on chemical reactions of the workpiece material during the drilling process. Effects of these reactions have been contrasted through the XPS analysis of the chip generated in the process. In parallel, SEM and EDS have been used as complementary techniques for obtaining further information about the BUL nature.

Wear of Uncoated HSS Tools in Drilling Difficult-to-Machine Materials with Water Vapor as Coolant and Lubricant

Drilling is a semi-enclosed cutting process. Drilling of difficult-to-machine materials generates thermal/frictional damage at the cutting edges of drill bit and decreases the life. In this paper, a new cooling and lubricating technique in drilling difficult-to-machine materials is developed to improve the life of drill bit. For this study, a water vapor generator and feeding system is developed. Comparative experiments are performed for various difficult-to-machine materials under the conditions of oil water emulsion, water vapor as coolant and lubricant and dry drilling, respectively. The effectiveness of water vapor on the basis of drill bit wear is studied. Experimental results show that with water vapor as coolant and lubricant the flank wear is reduced by 45-80% and 10-15% in comparison with dry drilling and oil water emulsion, respectively.

Research on Cutting Performance of Graphite-Like Carbon Coated Tools in Dry Drilling of Ferrous Metal

The graphite-like carbon (GLC) coating was deposited onto high-speed steel (HSS) twist drills by magnetron sputter ion plating technique. The drilling tests were performed on the ferrous metal under dry cutting conditions. By the analysis and comparison of the flank wear and the drilling forces on drills, the cutting performance of GLC coated HSS tools was researched. The results show that GLC coating with high hardness and low friction coefficient, due to its good adhesion and match with HSS substrate, can significantly improve the cutting performance of HSS twist drills, prolong the tool life, decrease the drilling forces in drilling the ferrous metal. And its cutting performance is better than the hard coated drills in the lower speed, but its thermal stability is inferior to the hard coated drills in the higher speed.

Calibration of Shallow Borehole Drilling Sites Using the Electrical Resistivity Imaging Technique in the Granitoids of Central Region, Ghana

The electrical resistivity imaging (ERI) technique has been used to calibrate existing successful and dry borehole drilling locations in the Cape Coast Granitoid Complex of the Central Region of Ghana. The area has a low groundwater potential and most of the communities do not have access to potable water. Surface water is generally expensive to treat and is therefore not considered as a good water supply option in such rural and dispersed communities where incomes are low. Supply of water to communities from existing boreholes is inadequate. Therefore, there was the need to construct more boreholes to increase access to potable water to meet coverage targets. Results show that the ERI technique is capable of detecting shallow bowl-shaped conductive zones up to 75 m represented by low resistivity values mainly due to weathered granitoids and/or fractures within the granitoids. Resistivity values typically less than 500 Ω-m obtained between depths of 10–50 m on model resistivity sections accounted for about 80% of successful productive boreholes. Resistivity values in the range 500–1,500 Ω-m represented marginally successful borehole locations which could be suitable for hand-pump installation and values greater than 1,500 Ω-m were confirmation for dry borehole locations.

Experimental Studies for Burrs in Dry Drilling of Stacked Metal Materials

During the drilling of stacked materials, burrs forming on both the surface layer and the interlayer have some undesirable characters with regard to assembly quality, and deburring is a time-consuming and costly operation. This paper presented an experimental study on dry drilling of Ti-6Al-4V titanium alloy and 7075-T6 aluminium alloy stacked materials, which was performed by using uncoated cemented carbide drills. The burr size was evaluated at various spindle speeds, feed rates, stacking sequence and clamp force. Finally, the burr morphology was observed and analyzed. The best process parameters recorded in this paper were at the spindle speed of 2000r/min, the feed rate of 0.075mm/r, the pressure of 0.3MPa and the stacking sequence of the Ti-6Al-4V titanium alloy on top of the 7075-T6 aluminium alloy.

Experimental studies and optimization of process parameters for burrs in dry drilling of stacked metal materials

In the drilling of stacked materials, burrs produced on both the surface layer and the interlayer have some undesirable characters with regard to assembly quality, and deburring is a time consuming and costly operation. This paper presented an experimental study on the dry drilling of Ti-6Al-4V titanium alloy and 7075-T6 aluminum alloy stacked materials, which was performed by using uncoated cemented carbide drills. The burr size was evaluated at various spindle speeds, feed rates, stacking sequences, and clamp forces. After which, the burr morphology was observed and analyzed. Finally, a new multi-objective optimization algorithm, which was derived from the game theory, was used to select optimum process parameters to minimize burr size. The best process parameters recorded in this paper were at the spindle speed of 2,000 r/min, the feed rate of 0.075 mm/r, the pressure of 0.3 MPa, and the stacking sequence of the Ti-6Al-4V titanium alloy on top of the 7075-T6 aluminum alloy.

CVD-diamond technologies for dry drilling applications

CVD-diamond for dry drilling applications is reported. Specifically, the fabrication of nanostructured diamond-coated drills is outlined. Tool life is evaluated by dry drilling of aluminum alloy and nanostructured diamond-coated drills show a superior performance to uncoated drills. In addition, different surface treatments have been studied with the effects on diamond film deposition and delamination investigated. Moreover, drill edge geometry has been evaluated. Major findings indicate that the drill edge radius plays a critical role to the drilling performance. A slightly honed edge may lead to improved performance due to the reduction of deposition stresses at the tool edge.

Study on the dry electrical discharge machining

The dry electrical discharge machining is considered by the researchers as an environment friendly machining process and different specific aspects of this machining method are presented in the specialty literature. To obtain holes by electrical discharge machining, tubular rotating electrodes tools could be used. The paper presents a relatively simple device proposed to be used for applying the dry electrical discharge drilling. The rotation of the electrode tool could contribute to the diminishing of the errors of the circular shape in a cross section through the hole. Some preliminary experiments proved the possibilities to use this device to achieve holes in workpieces of low thickness. Test pieces made of stainless steel were machined by dry EDM and by common EDM. For the applied operating conditions, the dry electrical discharge drilling presents some advantages regarding the machined surface quality and the electrode tool wear, in comparison with the machining that uses liquid dielectric.

Compact core drilling in basalt rock using PCD tool inserts: Wear characteristics and cutting forces

Abstract The hardest component of the Martian surface is believed to be basalt rock, which is highly abrasive in nature. It will be important to operate a Martian drill under conditions that are conducive to minimal tool wear. In preparation for a Mars drilling project, this paper reports results of an experimental study of dry drilling in basalt and related tool wear. It also reports the effect of the tool wear on increasing the forces and torques required when drilling in basalt rock (on earth) using polycrystalline diamond (PCD) compact core drill inserts. Force and torque data measured for a variety of cutting conditions are shown along with experimental wear data obtained while drilling in basalt rock having different strengths. It is found that flank wear, VB, and cutting edge radius, CER, wear rates increase with rock strength, VB-wear rates and CER-wear rates exhibit opposite trends in their dependence on the remainder of the cutting parameters. For example, while VB-wear rates decrease with an increase in tool feed and spindle speed values, CER-wear rates increase with increases in tool feed and remains unchanged with increases in spindle speed. VB-wear rates decrease as the rake angle becomes more negative, while CER-wear rates increase as this occurs. It is found that basalt rock strength manifests itself via larger (smaller) generated forces/torques for rocks of harder (softer) composition. Strong correlations are found between both modes of tool wear (VB and CER) and the measured values of thrust force and torque. Equations for progressive tool wear as functions of the process variables are developed. A model for the changing drill forces and torques required by the progressive tool wear is developed for drilling in basalt.

Experimental characterization of material removal in dry electrical discharge drilling

Dry electrical discharge machining is one of the novel EDM variants, which uses gas as dielectric fluid. Experimental characterization of material removal in dry electrical discharge drilling technique is presented in this paper. It is based on six-factor, three-level experiment using L 27 orthogonal array. All the experiments were performed in a ‘quasi-explosion’ mode by controlling pulse ‘off-time’ so as to maximize the material removal rate (MRR). Furthermore, an enclosure was provided around the electrodes with the aim to create a back pressure thereby restricting expansion of the plasma in the dry EDM process. The main response variables analyzed in this work were MRR, tool wear rate (TWR), oversize and compositional variation across the machined cross-sections. Statistical analysis of the results show that discharge current ( I), gap voltage ( V) and rotational speed ( N) significantly influence MRR. TWR was found close to zero in most of the experiments. A predominant deposition of melted and eroded work material on the electrode surface instead of tool wear was evident. Compositional variation in the machined surface has been analyzed using EDAX; it showed migration of tool and shielding material into the work material. The study also analyzed erosion characteristics of a single-discharge in the dry EDM process vis-á-vis the conventional liquid dielectric EDM. It was observed that at low discharge energies, single-discharge in dry EDM could give larger MRR and crater radius as compared to that of the conventional liquid dielectric EDM.

Dry and minimum quantity lubrication drilling of cast magnesium alloy (AM60)

Dry and minimum quantity lubrication (MQL) drilling of cast magnesium alloy AM60 used in the manufacturing of lightweight automotive components have been studied. The maximum and average torque and thrust forces measured during drilling using distilled water (H 2O-MQL) and a fatty acid-based MQL fluid (FA-MQL), both supplied at the rate of 10 ml/h, were compared with those generated during flooded (mineral oil) drilling. Tool life during dry drilling was inadequately short, due to excessive magnesium transfer and adhesion to the (HSS steel) drill causing drill failure in less than 80 holes. The use of MQL reduced magnesium adhesion and built-up edge formation, resulting in an increase in tool life as well as reductions in both average torque and thrust forces—prompting a performance similar to that of flooded drilling. The maximum temperature generated in the workpiece during MQL drilling was lower than that observed in dry drilling, and comparable to flooded condition. The mechanical properties of the material adjacent to drilled holes, as evaluated through plastic strain and hardness measurements near the holes, revealed a notable softening in the case of dry drilling, but not for MQL drilling. MQL drilling provided a stable drilling performance, which was evident from the uniform torque and force patterns throughout the drilling cycles and also resulted in desirable machining characteristics, including a smooth hole surface and short chip segments.

Design and experimental study of an end effector for robotic drilling

This paper presents the development of a drill end effector for use on industrial robots. The end effector has low weight and high rigidity. The drill end effector is fully programmable and will realize different drilling mode. The real-time force feedback can detect dull or broken bits, drill to breakthrough, and plot thrust force while drilling. Additionally, the end effector can also be equipped with a coolant/lubricant device. Based on the drill end effector, an experimental study on dry drilling of Ti-6Al-4V alloy and 7075-T6 alloy bimetal stacks was performed by using an uncoated cemented carbide drill. The hole quality (hole size, surface roughness) and thrust force were evaluated at various spindle speeds, feed rates, stacking sequence, and clamp force. This study indicates that the spindle speed and feed rate have an effect on the hole quality and thrust force by means of changing the temperature and plastic deformation of cutting zone. The results show that drilling 7075-T6 alloy firstly would be most efficient because of the high hole quality and the low thrust force. It was also found that high clamp force is helpful to improve the hole quality.

Sensor Fusion by Neural Network and Wavelet Analysis for Drill-Wear Monitoring

The objective of the study is to construct a sensor fusion system for tool-condition monitoring (TCM) that will lead to a more efficient and economical drill usage. Drill-wear monitoring has an important attribute in the automatic machining processes as it can help preventing the damage of tools and workpieces, and optimizing the drill usage. This study presents the architectures of a multi-layer feed-forward neural network with Levenberg-Marquardt training algorithm based on sensor fusion for the monitoring of drill-wear condition. The input features to the neural networks were extracted from acoustic emission (AE), vibration and current signals using the wavelet packet transform (WPT) analysis. Training and testing were performed at a moderate range of cutting conditions in the dry drilling of steel plates. The results indicated that the supervised neural networks were effective for drill-wear monitoring and the output of the neural networks can be directly utilized for the planning of tool life management.

Evaluation of Thrust Forces in Dry Drilling of UNS A97050 Alloy

This paper presents a study of the thrust forces in the aluminium alloy, UNS A97050-T7. The measurement of these forces during the dry drilling in plates is evaluated under cutting different conditions and in through and blind holes. The experiments have been performed in a CNC milling and HSS Co drills have been utilised with unlike diameters (6.3 mm and 4 mm). The thrust forces have been measured by means of a piezoelectric dynamometer. In addition, the results have been compared with theoretical forces, obtained by the Kronenberg equation. The ANOVA study has allowed confirming the similitude between the forces obtained, independently of number of holes drilled, with the exception of through holes of 4 mm, in whose case the Kruskal-Wallis test has corroborated the dissimilitude. Moreover, the comparison with Kronenberg forces is coherent for diameters 6.3 mm, but it is very different for diameter 4 mm. Thus, the results respect to through and blind holes are dependent of diameter of drill, and also the differences found in the theoretical forces. The high variability of the forces for minor drills, in through and blind holes, points to an inadvisable use in this material.