Drilling Depth Research Articles

Bit Bounce Detection and Alarm Optimization Based on Domain Generalization for Drilling Process

Fault detection is crucial for ensuring the safety of the drilling process. Without proper detection and treatment of bit bounce, it could aggravate the wear of drill string and lead to another serious incident. Yet the data distribution of drilling parameters will shift as drilling depth increases, which may result in poor fault detection performance. The alarm optimization strategy of the fault detection model is also rarely discussed in the drilling process. Hence a bit bounce detection and alarm optimization approach based on domain generalization is proposed for the drilling process. The conditional invariant domain generalization is utilized to learn the optimal invariant representation from the historical data in the previously drilled well section. The Bayesian classifier is performed for fault detection. The corresponding alarm optimization strategy is designed based on the alarm performance evaluation. The data from an actual drilling field is utilized for experiment to illustrate the efficiency of the proposed method. The application of the proposed bit bounce detection method will contribute to maintaining a satisfactory fault detection performance across different drilling depths.

Mineralogy, geochemistry, and genesis of glauconite mineral from paleotsunami deposit in Lebak, Banten, Indonesia

Bagedur coast in Lebak regency, Banten province, Indonesia is part of lowland-swampy swale area that consist of various sediment deposit. Based on its sediment characteristics and geomorphology profile, Bagedur coast is assumed as depositional environment of paleotsunami deposit. Hand Auger drilling method is used to collecting loose sediment sample from eight observation stations. The depth of hand drilling in BG 01 station to BG 08 station is consecutively as follows: 115 cm, 100 cm, 80 cm, 700 cm, 400 cm, 450 cm, 160 cm, and 143 cm. This research is carried out to understand the diagenetic process of glauconite mineral in presumption paleotsunami deposit. The diagenetic process of glauconite mineral is identified based on its mineralogical and geochemical characteristics by petrography and X-Ray Fluorescence (XRF) methods. Observation samples is taken from green sand sediment bed in hand drilling core. Petrographic analysis under polarized microscope shows various glauconite mineral which recognized as matrix, oval pellets, replacement of precursor mineral, and bioclastic shell infillings. XRF analysis result show that glauconite in observation site are classified as glauconitic-illite type. The diagenetic stage is interpreted as early stage of diagenetic (nascent) which characterized by low Fe2O3 and K2O content relative to Al2O3 content.

Geophysical and Borehole Studies for Optimum Drilling Depth and Groundwater Yields in a Typical Basement Terrain, South-western Nigeria

Geophysical and Borehole Studies for Optimum Drilling Depth and Groundwater Yields in a Typical Basement Terrain, South-western Nigeria

Analysis of the work of steps using the eccentricity limiter for drilling wells with a diameter of 393,7 mm

Based on the results of the analysis of theoretical and practical studies of drilling large diameter boreholes, a method is proposed for designing the bottom hole assembly with two rock cutting tools, taking into account geological and technical factors that influence the formation of the well trajectory. Prospects for controlling the direction of the wellbore are substantiated using the limiter of the eccentricity value. The calculation of double-hole assemblies of the bottom of the drill string with different diameters of eccentricity limiters, allowing to achieve eccentricities of 10 mm, 20 mm, 30 mm and 40 mm has been performed. The analysis of the operation of the mentioned bottom hole assemblies when drilling a well to a depth of 900 m is carried out. The analysis is carried out in the field of construction of deep boreholes of large diameter and the efficiency of drilling a pilot hole of a smaller diameter with simultaneous formation of the final diameter using a reamer is substantiated. A brief analysis of modern foreign and domestic studies and publications related to the expansion of the pilot wellbore is presented, as well as the influence of the expansion eccentricity on the elastic-deformation state of the BHA and, as a result, on the deviation of the well is considered. A conclusion is made about the possibility of using the phenomenon of eccentric expansion to control the trajectory of the wellbore. The graphical dependences of the change in the intensity of the borehole deviation during deepening using the eccentricity of the limiter for a specific BHA, including a bit with a diameter of 295.3 mm and a reamer with a size of 393.7 mm, are shown. It is shown that with this type of arrangement at different values ​​of eccentricities, it is possible to achieve the intensity of borehole curvature in the range from 0 deg/10 m to 0.44 deg/100 m, 0075, indicating a change in the direction and magnitude of eccentricity during drilling. The graphical dependences of the change in the zenith angle of the well when deepening it for the assembly of the bottom of the drill string with different diameters of the eccentricity limiter are given. The graphical dependencies indicate that when using stops of different sizes, which make it possible to control the eccentric displacement of the reamer at the final drilling depth of a section of 500 m, it is possible to reduce the increase in the zenith angle of the well from 17.5 degrees to 10 degrees. It is concluded that by using the limiters of the eccentric displacement of the expander relative to the pilot borehole, it is possible to control the deviation of the well during the construction of conditionally vertical and inclined sections.

Smart Modulation for Control Systems with High Regulation Capabilities for Cooling Systems Optimisation and Carbon Footprint Reduction in Industry

Nowadays, every large enterprise is concerned about reducing CO2 emissions. Along with legislation, management, packaging, and transportation decisions, optimising the operation of automated systems in the industry is important. Overheating processes or large cooling systems of one machine during product assembly may seem minor but at the industry level it is quite significant. Either an optimisation of cooling systems or an intelligent machine control which will prevent heat strokes and allow the transition to passive cooling of the whole system is an important issue for improving machine tools efficiency and contributing therefore to CO2 reduction in the industry sector. This research is a transitional phase from the creation of a control system to solve the problems of resonance in the control of systems with parallel piezo kinematics, which were designed to automate the iterative process of non-circular drilling with a precise shape and the subsequent research on the implementation of smart control to optimise the cooling of industrial machines. The total dynamics of the example system in this research is unknown and consists of the dynamics of electrical converters, piezo kinematics, and mechanics. The control signal of this system is generated by the model of the system state with assumptions and simplifications in combination with machine learning techniques considering the previous errors of the transient characteristics with the possibility of re-drilling without damaging the workpiece and with possibility of further trainings to eliminate the iterative process in general. Algorithms for further training at different resonances with a drilling depth change for cylinders of internal combustion engines are offered. These algorithms are proposed for accurate transmission of the input signal amplitude even in resonant situations, power optimisation, increase the system efficiency, as well as reducing the carbon footprint when used in industry in specific applications.

A novel dynamic model for the online prediction of rate of penetration and its industrial application to a drilling process

Accurate prediction of the rate of penetration (ROP) is a difficult issue in the drilling process, especially under complex formation conditions. Many methods, such as mechanism and machine learning, were introduced to investigate it. However, most of them are offline prediction methods which may not be capable of capturing the online trend of ROP. In this paper, a novel dynamic model for ROP prediction is proposed considering the process characteristics, which consists of three stages. In the first stage, the correlations between ROP and eight drilling parameters are analyzed, and the rotational speed, weight on bit, depth are selected as the model inputs. In the second stage, the drilling data are pre-processed by using the filtering and re-sampling techniques. In the last stage, the moving window strategy, extreme learning machine, and 10-fold cross validation are used to establish the ROP model. Our main idea of online prediction of ROP lies in this last stage. Specifically, two steps (modeling and prediction) are executed alternately in the moving drilling depth windows so as to predict the ROP more accurately. Finally, the proposed ROP prediction model is applied to the drilling well ZK3 in Xiangyang area, Central China. The prediction accuracy is improved by at least 7% compared with seven well-known ROP prediction methods, two online and five offline, which validates the effectiveness of the proposed method. It is believed that the proposed model provides a basis for intelligent optimization control in drilling process.

3D Active Source Seismic Imaging of the Alpine Fault Zone and the Whataroa Glacial Valley in New Zealand

AbstractThe Alpine Fault zone in New Zealand marks a major transpressional plate boundary that is late in its typical earthquake cycle. Understanding the subsurface structures is crucial to understand the tectonic processes taking place. A unique seismic survey including 2D lines, a 3D array, and borehole recordings, has been performed in the Whataroa Valley and provides new insights into the Alpine Fault zone down to ∼2 km depth at the location of the Deep Fault Drilling Project (DFDP)‐2 drill site. Seismic images are obtained by focusing prestack depth migration approaches. Despite the challenging conditions for seismic imaging within a sediment filled glacial valley and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged. A set of several reflectors dipping 40°–56° to the southeast are identified in a ∼600 m wide zone that is interpreted to be the minimum extent of the damage zone. Different approaches image one distinct reflector dipping at ∼40°, which is interpreted to be the main Alpine Fault reflector located only ∼100 m beneath the maximum drilled depth of the DFDP‐2B borehole. At shallower depths (z < 0.5 km), additional reflectors are identified as fault segments with generally steeper dips up to 56°. Additionally, a glacially over‐deepened trough with nearly horizontally layered sediments and a major fault (z < 0.5 km) are identified 0.5–1 km south of the DFDP‐2B borehole. Thus, a complex structural environment is seismically imaged and shows the complexity of the Alpine Fault at Whataroa.

Study on Distribution of Wellbore Temperature in Gas Drilling with Gradient Equations

Precise calculation of gas temperature profile is the key to gas drilling design. It is traditionally assumed that the gas temperature distribution in the wellbore is equal to the formation temperature, without considering the influence of fluid flow and Joule-Thomson cooling effect. This paper puts forward a gradient equation method for gas temperature distribution in wellbore considering gas flow and Joule-Thomson local cooling of the bit. The method applies pressure, temperature, density, and velocity equations to gas flow in drillstrings and annulus. The solution of the gradient equation is in the form of the fourth-order Runge-Kutta equation. Bottom wellbore temperatures measured at depths of 700 to 2000 m in an actual well are consistent with those predicted by the gradient method. Due to the Joule-Thomson cooling effect at the bit nozzle, the temperature drops by about 30°C. The sensitivity analysis is carried out by gradient method, and the results show that the temperature drop range of different nozzle sizes can reach 60°C due to the Joule-Thomson cooling effect. Stable temperature curves can be established within a few minutes of the gas cycle. Due to the influence of gas flow and Joule-Thomson cooling, the gas temperature in the wellbore deviates significantly from the geothermal temperature in the formation under the flow condition. The temperature of the gas in drillstrings increases as the drill depth increases and then decreases rapidly near the bottom of the hole. As the gas flows upward along the annulus, the gas temperature rises first, surpasses the formation temperature, and then decreases gradually along the geothermal gradient trend.

Effect of different dental implant drilling template designs on heat generation during osteotomy - an in vitro study.

This in vitro study examined the effect of different implant drilling template designs on heat generation during osteotomy and on cooling fluid distribution. Five different template designs were investigated in a standardized setup against a control group and a negative control group: Occlusal-splint-design (OSD), OSD-covering, OSD-lateral opening, Bar design, and Orientation template. Pilot and one consecutive drill were run at 800rpm with external irrigation and 2-kg load. Thermocouples recorded temperature changes at depths of 3, 6, and 9mm in a bovine rib model. In the second experimental setup, the drill channel of one rib sample was perforated, and the irrigation volume passing through the drill channel was collected separately over time. Following mean temperature rises occurred [in °C]: control, 4.9; negative control, 12; OSD, 5.6; OSD-covering, 4.7; OSD-lateral opening, 3.8; Bar design, 5.1; and Orientation template, 4.9. The highest temperature increases were found at a drilling depth of 6mm (p<.006). The 2.2-mm drill resulted in a significantly higher temperature rise than the 2.8-mm drill (p<.001). The mean volume (ml/min) of irrigation through the drill channel was Control group-flow, 28.5; OSD, 4.1; OSD-covering, 2; OSD-lateral opening; 5.8; bar design, 4; and Orientation template, 24.1. Within the limitations, it was shown that fully guided drilling templates reduce the amount of cooling liquid at the point of osteotomy. The template designhad an influence on the effective volume of the cooling liquid. However, this did not seem to increase the intraosseous temperature significantly.

Wellbore stability mechanism of igneous rock in Shunbei block

Shunbei area is located in the belt structural of the northern margin of the shuntuogole low uplift. The proven oil reserves of the adjacent blocks are 142.93 million tons, which has the potential of exploration and development. In the igneous strata of Shunbei block, there are many complicated conditions, such as wellbore collapse, stucking pipe and so on, which seriously restrict the exploration and development speed and benefit of the block. In order to solve this problem, firstly, the composition, microstructure, mechanical properties and other parameters of igneous rock intrusion in Shunbei block are determined through laboratory experiments. The experimental results show that the igneous rock intrusion in Shunbei block does not contain expansive clay minerals, has weak hydration ability, and has developed micro fractures. Thirdly, the wellbore stability model considering fractures is established, and the influencing factors of wellbore instability are analyzed by combining the mechanical properties of igneous rocks, porosity and permeability characteristics, and in-situ stress state. The results show that the micro fractures and weak surfaces have a controlling effect on wellbore stability. The longer the immersion time is, the deeper the drilling fluid invasion depth is, and the higher the wellbore collapse pressure is. Finally, according to the microstructure and physicochemical properties of igneous intrusions, the main points of drilling fluid technology are determined, that is, the anti sloughing drilling fluid technology is mainly strong plugging. In this paper, through the analysis of the rock characteristics of igneous rocks and the main controlling factors of wellbore instability mechanism in Shunbei block by using the method of mechano-chemical synthesis, the clear main controlling factors of wellbore stability are of positive significance for ensuring the safe well construction, shortening the drilling cycle, reducing the drilling cost and improving the development efficiency in Shunbei block.

Guest Editorial: Why Multistage Stimulation Could Transform the Geothermal Industry

Geothermal energy is “having a moment.” It has been part of the global energy mix for many decades, but growth has been limited by the relatively limited number of sites with optimal geologic conditions. Technologies developed in the oil and gas sector have the potential to overcome these limitations and unlock dramatically increased geothermal production in the US and worldwide. Success is far from certain, but with the enthusiasm, ingenuity, and capital flowing toward these technologies, there is a realistic shot at breakthrough success. Geothermal energy comes in a variety of flavors, from shallow heat-pump systems used for residential heating and cooling to deep, hot wells drilled for electricity production. While opportunities exist across this spectrum, this column is specifically concerned with the drilling of deep, high-temperature wells for electricity production. Flow rate is a major challenge for geothermal. The energy content of one barrel of hot water is much lower than the energy content of one barrel of oil. Thus, to achieve profitability, geothermal wells must produce the equivalent of tens of thousands of barrels of water or steam per day. Across much of the western US, temperatures are hot enough for geothermal electricity production within reasonable drilling depth. However, in the absence of special geologic conditions from a hydrothermal system, wells usually cannot produce sufficient rate. Dating back to the 1970s, hydraulic stimulation has been tested as a way of increasing flow rate per well. Designs utilize injection and producer wells, with fluid heating up as it circulates between the wells. If engineers could use stimulation to consistently achieve high flow rates, a vast resource would be unlocked. The US Department of Energy’s (DOE) 2019 GeoVision report estimates that more than 60 GWe could be produced in the US by 2050. To date, success with hydraulic stimulation has been limited. Conventionally, geothermal wells have been drilled vertically and then stimulated by injecting only water (no proppant) into a single openhole section (without using multiple stages). Engineers have hoped that the injected water would shear-stimulate a dense network of natural fractures, with a large amount of surface area and fracture conductivity. These designs can yield modest success because geothermal wells are usually drilled in high-strength rock in the crystalline basement, and so fractures have considerable self-propping capability. However, rather than creating a dense network, flow tends to localize into a small number of dominant flowing pathways. Without a large number of flowing pathways, the reservoirs lack the ability to sustain high rate and are subject to thermal short circuiting that prematurely reduces the production temperature. Fortunately, similar problems have been encountered and solved by the shale industry. The shale revolution was unlocked by the application of multistage hydraulic fracturing along horizontal wellbores. Mechanical isolation allows sequential injection into sections of the well. Within each stage, perforation pressure drop is used to force fluid to flow into multiple pathways along the well. Perforation clusters are spaced tightly—typically from 10 to 50 ft. Recent core-through studies confirm that stimulation is creating hundreds or thousands of conductive fractures along each fractured lateral.

Review of the Heat Flow Mapping in Polish Sedimentary Basin across Different Tectonic Terrains

Heat flow patterns variability related to the age of the consolidated, and differences in, sedimentary thickness of the sedimentary succession are important constraints upon the thermal state of the sedimentary fill and its geothermal energy potential. Heat flow in the Permian basin of central Europe varies from a low of 40 mWm−2 in the Precambrian Platform to 80 mWm−2 in the Paleozoic basement platform influencing temperature for geothermal potential drilling depth. Continuity of thermal patterns and compatibility of heat flow Q across the Permian basin across the Polish–German basin was known from heat flow data ever since the first heat flow map of Europe in 1979. Both Polish and German heat flow determinations used lab-measured thermal conductivity on cores. This is not the case for the recent heat flow map of Poland published in 2009 widely referenced in Polish geological literature. Significant differences in heat flow magnitude exist between many historical heat flow maps of Poland over the 1970s–1990s and recent 21st century patterns. We find that the differences in heat flow values of some 20–30 mWm−2 in Western Poland exist between heat flow maps using thermal conductivity models using well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivity versus those measured on cores. These differences in heat flow are discussed in the context of resulting mantle heat flow and the Lithosphere-Asthenosphere Boundary depth modelled differences and possible overestimates of deep thermal conditions for enhanced geothermal energy prospects in Poland.

The rock breaking capability analyses of sonic drilling

Sonic drilling technology uses the longitudinal vibration of a drill string to realize fast and effective drilling. By setting the top and bottom boundary conditions of the drill string during drilling, a dynamic model of flexible sonic string percussive drilling is established in this article. At a certain drilling depth, with the excitation frequencies as the control parameters, the maximum impact force and rock breaking energy utilization rate are used to evaluate the rock breaking capability of the sonic drilling system under the linear bit–rock model. A surface diagram of the maximum breaking force reached within the working frequencies and at varying drilling depths is obtained. The curve graph of the rock breaking energy utilization rate varying with drilling depth under the first six orders of resonance is also calculated. Analysing the influence of changing drilling parameters on the rock breaking capability of sonic drilling systems can provide theoretical guidance for the actual drilling process.

Effective Modified Xanthan Gum Fluid Loss Agent for High-Temperature Water-Based Drilling Fluid and the Filtration Control Mechanism.

Xanthan gum (XG) was widely used as an oilfield chemical treatment agent because of its environmental protection and diverse functions. With the increased drilling depth and formation complexity, the shortcomings such as poor solubility and low resistance to temperature were gradually exposed. In this study, a modified XG derivative XG-g-AAA was synthesized by grafting XG with acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The chemical structure of XG-g-AAA was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance (1H NMR). Then, the solubility, high-temperature rheology and filtration properties, resistance to Na+/Ca2+, and compatibility were investigated. Results show that (1) both in aqueous and salt solutions, XG-g-AAA can completely be dissolved within 15 min. The significant improvement of the solubility of XG-g-AAA makes it more suitable for field use. (2) XG-g-AAA is less sensitive to high temperatures, and the viscosity decay decreased by 23.3 and 21.3% than XG at 150 and 180 °C, respectively. XG-g-AAA-based drilling fluid is a high-quality drilling fluid with significant shear thinning behavior, and the power-law model is the optimal model to describe its high-temperature rheology. Within 150 °C, 1.5% XG-g-AAA can maintain a reasonable value of the flow behavior index (n) (0.55–0.69), filtration volume (<11.6 mL), and sufficient gel strength (GS). At 150–200 °C, 3% XG-g-AAA is recommended. The value of n was in the range of 0.45–0.62, and the fluid loss was within 10 mL. However, 3% XG-g-AAA cannot provide enough GS at 200 °C; thus, a shear strength-improving agent is recommended to be added. (3) XG-g-AAA showed excellent contamination tolerance and compatibility. It could resist 2 wt % CaCl2 and 35 wt % NaCl at room temperature and 0.75% CaCl2 and 5% NaCl after 150 °C aging. (4) XG-g-AAA showed compatibility with sulfonated drilling fluids and could replace commercial fluid loss agents in the formula. Furthermore, the high-temperature fluid loss control mechanism was discussed by analyzing the effects of XG-g-AAA on the bentonite layer spacing, particle size distribution, stability of the colloidal system, and mud cakes.

Reconstruction of distorted structures in the fault shadow zone based on the fully connected network

Lateral changes in velocity about faults can give rise to fault shadow (FS) zones on time-migrated data volumes, which can result in structural interpretation artifacts in the fault trap reservoir. To address this issue, we have adopted a new reconstruction method of FS distortion structures based on a deep learning fully connected network (FCN). We use the 3D stratigraphic dip attributes to quantitatively delineate the extent of the FS zone. Then, we train a model to construct a nonlinear trend surface based on the structures of the stratigraphic reflectors that fall outside of the shadow zone. Finally, we use this nonlinear trend surface to compensate for the distorted structure within the FS zone. We calibrate our method using synthetic data and find that the method can accurately recover structural data within the FS distortion zone. We then test the effectiveness of our workflow by applying it to recover real FS distortion structures in the Pearl River Mouth Basin of the South China Sea. The results confirm that our method significantly reduces drilling depth errors in the FS zone. Compared to the traditional polynomial fitting method, the multilayer, multiparameter, and flexible nonlinear activation function of FCN is more capable of reconstructing nonlinear geologic structures in the FS zone. We find the FCN-based geologic reconstruction method to be efficient and effective for exploring potential structures in the FS zone and thereby in avoiding the risks of structural failure.

Research on Drilling Depth Measurement Technology based on Drilling Rig Parameter Monitoring

In view of the problem that the drilling depth is measured by manually counting drill pipes in the process of underground drilling construction in coal mine, combined with the multi-channel sensor parameters loaded on the parameter monitoring device of mining tunnel drilling rig, a new drilling depth measurement method is proposed. This method mainly relies on multiple pressure sensors assembled on the drilling rig to reflect different drilling rig operation states, and the drilling depth is obtained by increasing or decreasing the displacement parameters of the power head. It is suitable for tunnel drilling rig equipped with drilling rig parameter monitoring device. It not only saves hardware cost, but also adds a monitoring function of the device. At the same time, it provides a new technical path for accurate and reliable drilling depth measurement.

Hole Depth Measuring Device based on Mechanical Wave Reflection

In view of the problems of low efficiency and large human factors in the current quality acceptance of underground drilling construction in coal mine, which mainly depends on the manual counting of drill pipes during drilling withdrawal, a portable drilling depth measurement device is designed based on the principle of mechanical wave reflection in drill pipe string, using the propagation speed of mechanical wave in the drill string and the time of one cycle of mechanical wave back and forth in the drill string, the length of drill string in the drill hole is calculated and the drilling depth is determined. The designed mine drilling depth measuring device is mainly composed of three parts: exciter, probe and host. The key functions of data processing and human-computer interaction are realized by the software and hardware of the host. The field tests in Dafosi Coal Mine and Sihe Coal Mine verify that the measuring depth of the device is greater than 200m and the maximum error is no more than 10m, which can meet the urgent needs of underground hole depth measurement in coal mine.

Vibration Behavior during Underground Drilling Based on an Innovative Measurement Method and the Application

Pressure relief drilling is one of the most common techniques to reduce the impact of rock burst, but the useful dynamic phenomena in the drilling process are ignored due to the lack of corresponding technical methods. Based on the fact, an innovative measurement method for vibration signals during the drilling construction by pneumatic drill rig is presented in this study. The acquisition and analysis of vibration signals show that the vibration information can reflect the drilling depth, the amplitude of different depth can reflect the pressure, and the vibration events of different depths can reflect the pressure relief effect. The method proposed in the study is of great significance to the supervision of the relief work quantity, the disclosure of the pressure situation, and the evaluation of the pressure relief effect.

Assessment of cylindricity and roughness tolerances of holes drilled in marble using multiple regression and artificial intelligence

The Calacatta-Carrara marble is widely used due to its excellent physico-chemical characteristics and attractive aspect. However, the sensitivity of this materiel, when performing delicate manufacturing operations, presents for the engineers a hard challenge to overcome. This issue is mainly encountered with complex shapes of parts, for which it is difficult to preserve surface integrity and avoid geometric defects. The paper aims at finding out optimal drilling parameters of cutting in the Calacatta-Carrara white marble material, in order to minimize the holes cylindricity (HC) and surface roughness (HR) using six controlled operating factors, namely, the rotation speed ( N), the feed speed ( F), the drill bit diameter (BD), the drill bit height (BH), the number of pecking cycles ( P), and the drilling depth (DD). The experimental design uses a [Formula: see text] fractional factorial plan that is replicated once for cost consideration. The optimization process, that is, minimum cylindricity and roughness tolerances, is carried out using the Gray Relational Analysis (GRA) technique. Numerical modeling of machining parameters is performed using Multi-Layer Perceptron Artificial Neural Network (MLP ANN) and Multiple Regression Model (MR) to predict surface quality. For the sake of completeness these two models were compared in terms of fitness and predictability. The models were assessed statistically using the correlation coefficient. Results showed that either solution predicts a roughness tolerance which is in good agreement with the test data (both R-sq.(adj.) and R-sq.(pred.) &gt;94%). However, the holes cylindricity tolerance response was shown to be superior with MLP-ANN model (R-sq.(adj.) 50.64% and R-sq.(pred.) 48.67%). The GRA analysis shows that minimum cylindricity and roughness are met when N and F are set high, BD and BH low, P high and DD low.

Rapid manufacturing of micro-drilling devices using FFF-type 3D printing technology

Micro-drilling devices with different blade shapes were fabricated with a rapid and facile manufacturing process using three-dimensional (3D) printing technology. The 3D-printed casting mold was utilized to customize the continuous shape of the blades without the need for expensive manufacturing tools. A computational fluid dynamics simulation was performed to estimate the pressure differences (fluidic resistance) around each rotating device in a flowing stream. Three types of blades (i.e., 45°, 0°, and helical type) were manufactured and compared to a device without blades (i.e., plain type). As a result, the device with the 45° blades exhibited the best drilling performance. At a rotational speed of 1000 rpm, the average drilling depth of the device with the 45° blades to penetrate artificial thrombus for 90 s was 3.64 mm, which was ~ 2.4 times longer than that of helical blades (1.51 mm). This study demonstrates the feasibility of using 3D printing to fabricate microscale drilling devices with sharp blades for various applications, such as in vivo microsurgery and clogged water supply tube maintenance.