Drilling Force Research Articles

Study on hole machining for the constant feed rate of Al2O3 engineering ceramics through low-frequency axial vibration

Engineering ceramics are increasingly extensively applied in the aerospace, vehicle, armor protection and other fields due to their excellent performances such as high compression strength, high hardness, low density and high protection performance. However, engineering ceramics are typical difficult-to-machine materials, especially in the hole machining under constant feed rate, which limits the promotion and application. In this study, by combining a specially developed novel thin-wall diamond trepanning bit with a low-frequency axial vibration machining, the hole machining process for the constant feed rate of Al2O3 engineering ceramics was experimentally studied and the influence of the low-frequency axial vibration process on the axial drilling force, hole-wall surface roughness and edge chipping size of holes machined was analyzed. The results showed that the low-frequency axial vibration machining obtained a lower axial drilling force and a smaller edge chipping size compared to the traditional drilling process. Moreover, both the axial drilling force and the edge chipping size declined markedly with the rise in amplitude. However, the hole-wall surface roughness presented a rising trend due to the hammering effect of vibration. The process technology proposed in this article realizes the hole machining for a constant feed rate of Al2O3 engineering ceramics and provides a reference for the engineering lot-size hole machining of engineering ceramics.

Study on ultrasonic-assisted drilling of Ti6Al4V using 3-flute drill in the finite element simulation

Continuous chip is one of the major problems during drilling Ti6A14V, and chip breaking is dependent on many factors such as drilling parameters, tool geometries and type of drill bits used. This paper attempts to analyze the effect of various drilling parameters such as feed rate, spindle speed on performance characteristics such as chip morphology, thrust force, temperature, and tool wear in conventional drilling and ultrasonic-assisted drilling of Ti6A14V using twist drill bit and 3-flute drill bit in order to optimize the chip breakability of Ti6A14V. The twist and 3-flute drill bit are utilized to establish the finite element models to simulate the drilling process with Lagrangian approach in DEFORM-3D software. The results of the simulations not only reveal obvious varying regular pattern of thrust force, temperature, tool wear depth, chip thickness and damage with the increasing of feed rates, spindle speeds, which confirm the capability and advantage of finite element model of the drilling process, but also provide a more profound knowledge about the drilling mechanism including the effect of 3-flute drill bit in ultrasonic-assisted drilling on chip breakability and tool wear.

Measurement and prediction of drilling force in fresh human cadaver mandibles: A pilot study.

Bone drilling is a vital procedure in implant surgery and dental implant training systems based on virtual reality technology. Predict and update drilling force in real time based on a virtual dental implant training system and lay the foundation for realizing force feedback in dental implant training instruments. An experimental platform was established to measure the drilling force for human mandibles from donors of different ages. Response surface methodology was applied to analyze the drilling force. Force regression equations for different age groups were acquired. The order of the effects (from greatest to least) of the drilling parameters on the drilling force was the drill bit diameter, feed rate, and rotational speed. To obtain the minimum force, higher rotational speeds, lower feed rates, and smaller diameters were preferred within the range of commonly used medical reference parameters of bone drilling. The experimental data were confirmed to be scientific for the predicted models of drilling force.

Research progress and perspective trend of drilling technology for carbon fiber reinforced polymer

Carbon fiber reinforced polymer (CFRP) has been widely used in the aviation, space and automobile structural parts manufacturing due to its excellent physical and mechanical properties. However, the properties of CFRP materials with inhomogeneity and anisotropy are vastly different from metals. In the process of drilling, it is easy to produce delamination, tearing, burr and other defects, which seriously affect the quality of drilling. Therefore, drilling technology of CFRP-metal stacks has become a difficult problem in aircraft assembly process. This paper summarizes the researches of drilling mechanism of CFRP in recent years. The relationship between chip formation mechanism and fiber orientation angle is generalized. Meanwhile, the relationship between axial drilling force, drilling temperature and tool shape, workpiece material, process parameters is summarized. The causes, detection, evaluation methods and restraining measures of typical machining damage during CFRP drilling processes, such as delamination, burr and tearing are analyzed. The latest advances in material, geometric structure of CFRP drilling tools, and development of simulation technology of CFRP drilling process are expounded. It is also proposed that the establishment of accurate and reliable constitutive model is the key to the research of drilling simulation technology. The development trend of CFRP drilling technology is prospected by introducing new CFRP drilling technologies, such as variable process parameters drilling, robotic automatic drilling and suction-type internal chip removal drilling.

Experimental investigations and statistical modeling of cutting force and torque in rotary ultrasonic bone drilling of human cadaver bone.

Cutting force and torque are important factors in the success of the bone drilling process. In the recent past, many attempts have been made to reduce the cutting force and torque in the bone drilling process. In this work, drilling on human cadaver bones has been performed using rotary ultrasonic bone drilling process to investigate the effect of drilling parameters on cutting force and torque. The experimental work was carried on a recently developed rotary ultrasonic bone drilling machine for surgical operations. The experimental work was performed in two phases. The first phase includes a comparative study between rotary ultrasonic bone drilling and conventional surgical bone drilling, to study the influence of various drilling parameters (rotational speed, drill diameter, and drilling tool feed rate) on the cutting force and torque. The results revealed that the cutting force and torque produced during drilling operations in rotary ultrasonic bone drilling were lesser (30%-40%) than conventional surgical bone drilling. In the second phase, response surface methodology was used to perform the statistical modeling of cutting force and torque in rotary ultrasonic bone drilling process. Analysis of variance was performed at a confidence interval of 95% to analyze the significant contribution (p < 0.05) of process parameters (drilling speed, feed rate, drill diameter, and abrasive particle size) on the responses (cutting force and torque). The confirmatory experiments were performed to validate the developed statistical models. It was found that both cutting force and torque decrease with increase in drilling speed and increases with the increasing drill diameter, feed rate, and abrasive particle size.

Measurement and analysis of thrust force and torque in friction drilling of difficult-to-machine materials

Thrust force and torque applying in friction drilling contain some important information related to sufficient heat generation which can improve product quality and reduce tool wear. This concern becomes more challengeable when friction drilling is applied on difficult-to-machine materials. In the present study, temperature, thrust force, and torque for friction drilling of difficult-to-machine materials namely AISI304 and Ti-6Al-4V and Inconel718 are measured and analyzed. It contributes to provide an enhanced understanding of how friction in workpiece-tool interface increases the temperature. Subsequently, the sufficient heat generation, the effective thrust force, and torque that are needed to form a proper bushing with optimum features can be predicted. It is found that increasing in number of drilled holes reduces the quality of bushing shape. It is observed that thermal conductivity of workpiece material has significant effect on bushing formation quality. The findings indicate that better bushing formation and longer tool life are obtained from friction drilling of Inconel718. The microstructural changes of workpiece and tool wear are also analyzed and a relationship between them, temperature, thrust force, and torque, is explored. The maximum tool wear is observed on conical region where the process is in critical cycle time and temperature is on peak point.

Modeling, multi-objective optimization and cost estimation of bone drilling under micro-cooling spray technique: an integrated analysis

In bone fixation, frictional heat effect in orthopedic surgery has a potentially hazardous for soft tissues. Saline water irrigation has frequently been practiced preventing the thermal damage and limiting the applied cutting forces in high-speed orthopedic drilling. The application of excessive cutting fluids limits the heat and applied forces; however, it isn’t an environmentally friendly solution. In this work, a novel micro-irrigation system was developed to provide a mixture of air and saline water, having a small quantity of cooling spray (SQCS) at higher pressure into the cutting zone. This SQCS limits the frictional heat and providing lubrication and near to dry clean operative zone through a superior cooling effect compared to conventional irrigation. The carbide drills were used to make a hole in the fresh calf tibia bone. In addition, response surface methodology (RSM) was used to design the experiments. The regression models were developed between the input design parameters and performance measures to explore the relation under proposed micro-irrigation and facilitate the multi-objective optimization. Besides, cost analysis for the process has been performed. Thus, this work offers an integrated analysis to purely study and understand the bone drilling process under employing micro-cooling spray.

Investigation on thrust force in rotary ultrasonic drilling of CFRP/aluminum stacks

The stacks of carbon fiber-reinforced polymer (CFRP) and aluminum are widely used in aviation industry due to its excellent mechanical and physical properties. Recently, rotary ultrasonic drilling technology which is recognized as a useful machining method has been introduced to machining these stacks. Thrust force influences the machinability directly such as tool wear, cutting temperature, and hole qualities. In this study, a theoretical model of thrust force for rotary ultrasonic drilling of CFRP/aluminum stacks is proposed. Based on the analysis of kinematic characteristics, the axial uncut chip thickness of rotary ultrasonic drilling is presented. Then the whole machining process of stacks is divided into five different states. Forces on cutting edge and chisel edge in different materials are modeled, respectively. After that, the thrust forces of five-state rotary ultrasonic drilling process are achieved by integrating with integral limits analysis in each state. Finally, verification experiments are conducted, and experimental results show that the trends of thrust forces agree well with the thrust force model. Therefore, this theoretical model can be used to evaluate the thrust force in rotary ultrasonic drilling of CFRP/aluminum stacks.

Information feedback self-adaptive harmony search algorithm for the bovine cortical bone vibration-assisted drilling optimization

In orthopedics and surgery, bone drilling is an important operation. Increasing demands call for bone drilling force prediction and minimization. Vibration-assisted drilling (VAD) provides an opportunity to reduce the force. In the study, the information feedback self-adaptive harmony search (IFSHS) algorithm is presented for the thrust force minimization in bovine cortical bone VAD. The IFSHS improves the drilling parameters which leads to the optimal cutting state. The dynamic searching parameters, optimization parameters evaluation, and evaluation information feedback are applied to search the optimal solution. This force model was developed and employed with IFSHS. The VAD drilling experiments and parameters analysis are carried out. Experimental results have shown that the VAD has the potential to reduce the thrust force. Compared with conventional drilling (CD), the thrust force decreased by 18.4%–33.2% under suitable VAD parameters. Compared with the results of the original VAD parameters, the optimized thrust force decreased by 20.19%.

Drilling resistance: A method to investigate bone quality.

Bone drilling is a major part of orthopaedic surgery performed during the internal fixation of fractured bones. At present, information related to drilling force, drilling torque, rate of drill-bit penetration and drill-bit rotational speed is not available to orthopaedic surgeons, clinicians and researchers as bone drilling is performed manually. This study demonstrates that bone drilling force data if recorded in-vivo, during the repair of bone fractures, can provide information about the quality of the bone. To understand the variability and anisotropic behaviour of cortical bone tissue, specimens cut from three anatomic positions of pig and bovine were investigated at the same drilling speed and feed rate. The experimental results showed that the drilling force does not only vary from one animal bone to another, but also vary within the same bone due to its changing microstructure. Drilling force does not give a direct indication of bone quality; therefore it has been correlated with screw pull-out force to provide a realistic estimation of the bone quality. A significantly high value of correlation (r2 = 0.93 for pig bones and r2 = 0.88 for bovine bones) between maximum drilling force and normalised screw pull-out strength was found. The results show that drilling data can be used to indicate bone quality during orthopaedic surgery.

Design and experimental investigation on longitudinal-torsional composite horn considering the incident angle of ultrasonic wave

The composite vibration mode type of ultrasonic horn has been widely employed in ultrasonic vibration drilling. In order to explore the effect of the incident angle of the ultrasonic wave on longitudinal-torsional composite (LTC) horn, the reason for the mode-conversion and the vibrational characteristics of such horn firstly were analyzed on the basis of elastic wave-field theory. Then, a 3D model was developed with helical slots with different angle set in the conical section of the composite horn, and the vibration modal of the output end face of the horn was analyzed using the finite element analysis (FEA) method. It was found that the incident angle of ultrasonic wave exhibited a significant influence on the vibration modal at the output end face of the horn. The torsional vibration and the longitudinal vibration were changed significantly at the output end face of the horn when the incident angle was 47.6° and 67.2°, and the measured amplitude ratio of the torsional vibration to the longitudinal vibration in the former was improved by 4.9 times than that in the latter. Simultaneously, in both cases, the error of resonant frequency between the measurement and the simulation value reached 1.9% and 1.3%, respectively. It was observed from the ultrasonic vibration drilling test that the higher the amplitude ratio of the torsional vibration to the longitudinal vibration (AT/AL), the more the average drilling force was reduced and the better machined quality could be obtained. The results of this study should be well considered for further reference when designing longitudinal-torsional composite horn with different materials in ultrasonic vibration drilling.

Investigation on thrust force in rotary ultrasonic drilling of CFRP using Brad drill

The carbon fiber reinforced plastic (CFRP) has been widely used in manufacturing industry due to its excellent mechanical and physical properties. Brad drill, as a representative of new-type structural drills, is applied in processing of CFRP. Meantime, rotary ultrasonic drilling (RUD) is regarded as a superior method for machining composite materials, due to its outstanding performance in lowering thrust force and improving processing quality. However, there are few reports about RUD with Brad drill in CFRP drilling. In this study, the theoretical model of thrust force for RUD of CFRP using Brad drill is developed. The dynamic uncut chip thickness and average uncut chip thickness in RUD are obtained based on kinematic characteristics analysis. After that, the structure of Brad drill is analyzed and thrust force of the cutting lip is molded. Then a theoretical model is proposed to predict the thrust force. Finally, pilot experiments are conducted for the model verification. Experimental results show that the trends of thrust force agree well with the thrust force model and the prediction error is less than 10%.

Axial cutting force prediction model of titanium matrix composites TiBw/TC4 in ultrasonic vibration–assisted drilling

Ultrasonic vibration–assisted drilling (UVAD) can significantly improve the quality of the hole while reducing the axial force of drilling, which has important application prospects. In order to reveal the variation law of drilling force under the joint action of ultrasonic vibration and cutting heat, and to guide the optimization of high-efficiency UVAD process, titanium matrix composites TiBw/TC4 (TiB whisker volume fraction of 8.5%) is taken as the research object. Firstly, based on the theory of fracture indentation and the theory of ordinary drilling (OD), the comprehensive softening coefficient of the material under the action of ultrasonic impact and cutting temperature is introduced, and the model of axial drilling force considering the softening effect is established. Secondly, the experiment of UVAD was carried out, and the interaction mechanism about drilling force and vibration impact and drilling temperature was analyzed. Finally, the experimental data was used to establish the softening coefficient response surface, which described visually the variation law of the softening coefficient. The feasibility of the drilling force model was verified, and the trend between the drilling parameters and the drilling force was analyzed. The results show that the error between experimental axial drilling force value and prediction value of UVAD is less than 10%, and the maximum axial drilling force is about 23.1% lower than OD.

Optimization of drilling parameters on carbon fiber reinforced polymer composites using fuzzy logic

The research and market attention towards advanced carbon fiber based composites are very significant in recent days because of their very good mechanical properties and are widely used in applications include automotive, aerospace, and construction industries, etc. The drilling experiments are conducted using Taguchi L 9 orthogonal array in the design of experiments. In the present work fuzzy logic is used in determining the performance characteristics like thrust force, torque and de-lamination factor in drilling of CFRP composite. Good agreement is observed between fuzzy results and the experimental values. The ANOVA analysis is carried out to find out parameter significant during drilling CFRP composite.

Drilling force model for forced low frequency vibration assisted drilling of Ti-6Al-4V titanium alloy

Forced low frequency vibration assisted drilling (forced LFVAD) is an important machining method, in which the prediction of drilling thrust force and torque is necessary to optimize the drilling parameters. However, drilling force prediction remains a problem in forced LFVAD. This article presents a novel analytical model that predicts the drilling thrust force and torque, by incorporating the vibration amplitude and frequency correction, drill working angle, drilling forces within different cutting lip positions, and their transformation into thrust force and torque. In particular, the drilling forces investigated here include indentation force at chisel edge, chipping force, bouncing force, ploughing force in the ploughing area of the primary edge, and chipping and bouncing forces in the remaining part of the primary edge. Drill micro-displacement is also considered. Finally, the maximum, mean, and minimum values of the thrust force and torque predicted using this new model are verified as valid by performing a the drilling experiment of Ti–6Al–4V titanium alloy. The prediction error of maximum thrust force, maximum torque, mean thrust force and mean torque can reach 12%, 9%, 6.5%, and 10.1%, respectively. The effect of vibration amplitude on the cutting force at different positions along the drill lip is analyzed using the prediction model. Critical chip breaking amplitude is proposed and an optimization case of drilling parameters is presented.

Optimized tabu search estimation of wear characteristics and cutting forces in compact core drilling of basalt rock using PCD tool inserts

Monitoring of cutting tool wear is crucial in machining operations where planning for longer tool life would result in economical savings. While deterministic and stochastic methods were sought for identifying optimal cutting conditions, efficiency and/or accuracy of the generated model fits were found to suffer when dealing with large number of variables. In this work, we present a novel method for tool wear optimization that combines tabu search algorithm with regression analysis (dubbed TS-REG). First, this method is validated against literature-reported model equation fitting of several modeling studies of turning, end milling, and drilling processes. Corroboration of TS-REG is established having found that it outperforms other techniques such as REG, artificial neural networks (ANN), and genetic algorithm (GA). Then, TS-REG is utilized to estimate tool wear and cutting forces for efficient core drilling of basalt rock, a hard and abrasive component of the Martian surface. For cutting data, this work utilizes previously reported tool wear and force data by Hamade and coworkers of polycrystalline diamond (PCD) compact core drilling experiments. The cutting data is comprised of dependent variables of tool wear (flank wear and cutting edge radius wear) and forces (thrust force and torque)as function of several independent variables (process parameters) namely rake angle, spindle speed, tool feed, rock specimen’s ultimate compressive strength, UCS , specimen rock type, and drilled depth. These independent variables and their combinations resulted in fit equations with total number of 117 different variables. As compared with conventional REG and ANN fit estimates of the same data, TS-REG was found to yield the best statistical estimates of tool wear and cutting forces model equations where all dependent parameters were included in the model. Statistical metrics used for assessment of the fitted models were p-value, R-squared, and mean absolute percentage error.

Study of cutting forces and surface integrity in micro drilling of a Ni-based superalloy

Accomplishment of good dimensional accuracy and acceptable surface integrity in micro drilling of Ni-based superalloys has always been a challenge. The current study seeks to explore these aspects and correlate the same with spindle speed, feed and forces in micro drilling of Incoloy 825 under flood cooling condition. Spindle speeds of 10,000, 20,000 and 30,000 rpm along with four different feeds of 1, 4, 8, 12 μm/rev were considered in the present work. Thrust force exhibited increasing trend with cutting parameters. The dynamic fluctuation (%) for radial forces was considerably higher compared to that of thrust force. A gradual transition from ploughing to shearing was discernible when feed was increased from 1 to 4 μm/rev. Oversize error was found to be closely related with radial forces. Circumferential deformation layer, white layer and plastic deformation zone at sub-surface region along hoop direction showed distinct relationship with spindle speed and feed. However, spindle speed has more pronounced influence on white layer formation than feed. After careful analysis of results, it was observed that optimal results in the form of superior dimensional accuracy, minimum circumferential damage, burr formation, minimum radial force, and reasonably less value of thrust force were achieved under the feed of 4 μm/rev and spindle speed of 10,000 rpm.

Tool wear mechanism in low-frequency vibration–assisted drilling of CFRP/Ti stacks and its individual layer

In this paper, a novel tool wear mechanism in low-frequency vibration–assisted drilling (LFVAD) of carbon fiber–reinforced plastic (CFRP)/Ti stacks and its individual layer has been proposed. Firstly, the difference of the effective rake angle, effective clearance angle, undeformed chip thickness, and tool-workpiece contact length between low-frequency vibration–assisted drilling and conventional drilling (CD) was analyzed based on the kinematic model. Then, the strength at different positions of the cutting edge was evaluated. Furthermore, the drilling experiments of CFRP/Ti stacks, CFRP plate, and Ti plate individually were taken under LFVAD and CD processes. Finally, the tool wear mechanism and the benefit of CFRP/Ti stacks and CFRP plate processed by LFVAD were expounded by kinematic analysis results, the analysis of drilling force, SEM images, and the profile of the cutting edge. The results show that the inner edge close to the chisel edge could be the weakest position of the drill in LFVAD. As the mean drilling force of LFVAD is lower than CD, the total wear volume of LFVAD is smaller than CD. Due to the change in the resultant cutting speed angle and the undeformed chip thickness, LFVAD produces the longer tool-workpiece contact length on the rake face and the flank face, which directly leads to a more uniform tool wear and a self-sharpening effect on the cutting edge. Thus, the reduction in the effective rake of the drill used in LFVAD is obviously smaller than the reduction in conventional drilling. The reduction in the effective clearance angle of the drill used in the LFVAD is also less than the reduction in conventional drilling, while this difference is attenuated as the cutting radius increases. The edge radius of the cutting edge is found to be much smaller than CD. In summary, the difference in the cutting edge geometry between LFVAD and CD is the root cause of the tool used in LFVAD to avoid severe edge chipping.

Theoretical Modeling and Experimental Verification of Rotating Ultrasonic Drilling

Aiming at the problems of large drilling ability and serious wear of drill bit tool in the process of drilling, the connecting plate workpiece in the high strength engineering mechanical connection parts of carbon fiber reinforced composites is studied, and the theoretical model of ultrasonic drilling is established, and the simulation analysis is carried out by using the professional numerical calculation software MATLAB. The influence of the main parameters such as tool feed speed, spindle angular velocity and ultrasonic amplitude on the drilling force during ultrasonic drilling is studied, and the relevant parameters under the same working conditions of simulation are verified by experimental method. The simulation and experimental results show that with the increase of tool feed speed, the drilling force shows the trend of increasing gradually, and with the increase of spindle angular velocity and ultrasonic amplitude, the drilling force shows a decreasing trend, and the simulation value of maximum drilling force under different parameters is basically close to the experimental value, which verifies the correctness of the theoretical model. It provides theoretical basis and important reference for the improvement of the comprehensive performance and product quality of the ultrasonic drilling parts of carbon fiber reinforced composites, the popularization and application of the theoretical model of ultrasonic drilling, the optimization of ultrasonic drilling process parameters, and the ultrasonic processing and molding of composite materials.

Optimization and prediction of thrust force, vibration and delamination in drilling of functionally graded composite using Taguchi, ANOVA and ANN analysis

Composite materials offers many advantages over traditional materials in terms of weight, strength and design flexibility. However, machining of these materials leads to some critical problems such as delamination, inferior surface finish and excessive tool wear due to their anisotropic and inhomogeneity structure. In particular, in manufacturing of the functionally graded composite (FGC) materials, this situation becomes more complicated since these composites have been made with different stacking sequences. In this work, drilling performance of FGC, depending on delamination, thrust force and vibration, has been investigated experimentally by using different cutting parameters, which are feed rate, spindle speed and material directions (carbon/epoxy and glass/epoxy). From the results of experiments, the material direction has deeply affected the delamination (89.5%) but has rarely affected the thrust force (0.1%) and vibration (8.4%). Feed rate is the most impactful factor on thrust force and vibration generation. Whereas the feed rate has a direct proportion to the thrust force and delamination, the spindle speed has an inverse proportion to these responses. When the results evaluated generally, In addition to that, a surrogate model is created through ANN to estimate the responses or cutting parameters on the drilling process in a wider range.