Drilling Force Research Articles

Characterization of machinability of sintered steel foams having different porosities during drilling operations

Steel foams are a new class of engineering materials with exceptional structure and properties. Foams produced by powder metallurgy generally have a near-net shape, however, sometimes machining operations may be required. The presence of porosity in steel foams significantly affects the cutting process and causes poor machinability. This study deals with the evaluation of the machinability of Cu-Ni-Mo-based steel foams having different porosity produced by powder metallurgy. High speed steel and carbide-tipped drills were used for the drilling. All tests were performed in dry condition with drill diameter of 3 mm. The drilling characteristics were evaluated in terms of the surface roughness, chip formation, drilling force, tool wear, microstructure and hardness change after drilling. The machinability was also evaluated by measuring average width of breakout and skewness values of the hole drilled. The results indicated that the increase of porosity negatively affected the drilling quality of high porous steels. Both drills broke the chips in powder form and produced discontinuous chips. High porous parts exhibited higher hardness change as compared to lower ones. The carbide drill showed acceptable drilling forces and surface quality. HSS drill is not suitable for drilling due to poor hole quality and high drill wear. Highlights Steel foams exhibit poor machinability due to highly porous structure. Porosity and tool type significantly affect the surface integrity of steel foams. Surface roughness and drill wear increased with increasing porosity; however, feed force decreased. Intense presence of pores decreases the tool life remarkably. The skewness values of hole are positive in all porosities. Carbide-tipped drill produced the finest hole quality. The larger damage was observed at the exit of the drilled holes with HSS drill.

Optimized selection of process parameters based on reasonable control of axial force and hole-exit temperature in drilling of CFRP

Drilling is a key link of manufacturing carbon fiber-reinforced polymer (CFRP) components. However, due to CFRP’s anisotropy and heterogeneity, effects of drilling induced axial force and hole-exit temperature are much more complicated than conventional metals, which always results in undesirable surface damages at hole exit hindering the engineering application of CFRP. Since the axial force and the hole-exit temperature are highly correlated to process parameters in drilling of CFRP, for effectively overcoming such difficulties, this study focuses on optimized selection of process parameters. The suitable ranges of the axial force and the hole-exit temperature are figured out, upon the specific analysis on the combined effects of the axial force and the hole-exit temperature on the formation of hole-exit surface damages. With that, through establishing the relations between the axial force, the hole-exit temperature, and the drilling parameters, the optimized drilling parameters are finally given. By experimental verifications, it is found that the optimized drilling parameters can control the axial force and the hole-exit temperature within the suitable ranges, and thereby effectively suppress the hole-exit surface damages in drilling of CFRP. The findings of this study will be helpful to further improve the drilling qualities of CFRP.

An experimental investigation of thrust force, delamination and surface roughness in drilling of jute/carbon hybrid composites

Purpose This paper aims to deal with the influence of cutting parameters on drill thrust force, delamination and surface roughness in the drilling of laminated jute/carbon hybrid composites. Design/methodology/approach The hybrid composites were fabricated with four layers of fabrics, which are arranged in different sequences using the hand-layup technique. Drilling experiments involved drilling of 6 mm diameter holes on the prepared composite plates using high-speed steel and solid carbide drill materials. Analysis of variance was used to find the influence, percentage contribution and significance of drilling parameters on drilling-induced damages. Scanning electron microscopy analysis was also conducted to understand the fracture behavior and surface morphology of the drilled holes. Findings The experimental study reveals that the most significant effect was the feed rate influenced the drill thrust force and the drill speed influenced both delamination factor and surface roughness of hybrid fiber-reinforced composites. From observations, the suggested combination for drilling jute/carbon hybrid composites is carbide drill, spindle speed of 1,750 rpm and feed of 0.03 mm/rev. Originality/value The new lightweight and low-cost hybrid composites were developed by hybridizing jute with carbon fabrics in the epoxy matrix with interplay arrangements. The influence of cutting speed and feed rate on delamination damage and surface roughness in the drilling of hybrid composites have been experimentally evaluated.

High throughput deep-hole drilling of Inconel 718 using PCBN gun drill

Overcoming the myriad challenges in the high-speed machining of Inconel 718, especially for deep-hole drilling (DHD), has been a long-standing area of research for several manufacturers and researchers. Owning to the difficult-to-machine characteristics of Inconel 718, the traditional carbide-tipped gun drills often get worn at an accelerated pace and require repetitive re-sharpening or replacement. This lowers productivity and increases costs. Furthermore, it is also a challenging task to meet the stringent hole-straightness requirement of 1/1000 mm for DHD of such difficult-to-machine materials, especially using those carbide gun drills. Hence, this study presents a development of polycrystalline cubic boron nitride (PCBN)-tipped gun drill to address the rapid tool degradation and poor hole-straightness issues. The developed PCBN-tipped gun drill has a layer of PCBN on its cutting tip and bearing pads. Several gun drilling tests on Inconel 718 have been performed at high drilling speed conditions to assess the performance of developed gun drill. In contrast to traditional carbide-tipped gun drills, the developed PCBN-tipped gun drill has the capability of not only performing in the higher cutting speeds but also reducing drilling forces, drilling torques, and tool wear. Furthermore, the surface quality of drilled holes is also much better than those drilled by traditional carbide gun drills. With these results, it further validates the credibility of the developed PCBN gun drill in enhancing the deep-hole drilling process with high throughput productivity and superior quality of drilled holes, especially for difficult-to-machine materials.

Mechanistic force modeling in drilling of SiCp/Al matrix composites considering a comprehensive abrasive particle model

SiCp/Al composite is one of the key light metal matrix composites widely used in aerospace and electronics industries due to its excellent material properties. Understanding the mechanism of abrasive particle action and the cutting force generation is crucial for achieving desired hole quality and machining accuracy. However, there is no research on cutting force modeling in drilling of SiCp/Al composites. This paper proposes an energy-based mechanistic modeling method to predict the cutting force in drilling of SiCp/Al composites for the first time. A new comprehensive abrasive particle model considering different particle action mechanisms, such as cracking, debonding, and squeezing, is presented to depict the energy consumed by abrasive particle action. Experiments with a wide range of particle volume fractions and feed rates, and different particle sizes were carried out to validate the accuracy of the proposed model. Results show that the proposed model can accurately predict the cutting force with an average error of 6.55% in drilling of SiCp/Al composites. Furthermore, the energy consumed on abrasive particle action is estimated to be 8.2–13.6% of total cutting energy. The proposed model on SiCp/Al composites can be extended to other particle reinforced metal matrix composites.

Experimental investigation on the performance of novel double cone integrated tool in one-shot drilling of metal stacks

In order to reduce misalignment, enhance tight tolerance, and improve machining efficiency, a novel double cone integrated tool was developed and experimentally investigated during one-shot drilling of aluminum and aluminum alloy stacks in this paper. This special tool geometry can finish drilling, reaming, and countersinking processes at the same time. Its machining properties were comparatively evaluated with a standard twist drill (reference drill) by means of a series of experiments. Experimental results highlighted the influence of tool geometry on cutting force and vibration signals for drilling, reaming, and countersinking processes, respectively. The results indicated that the double cone integrated drill can induce a little larger thrust force than a reference drill due to its longer cutting edge. In addition, the chip morphologies generated by different processes and cutting variations also have been comparatively analyzed. The double cone drill under a larger feed rate was prone to produce smaller chips. Furthermore, the double cone drill can achieve smaller burrs, better surface integrity, and lighter tool wear compared with reference drill. The information obtained from this study can provide a better understanding of the one-shot drilling process and guidance for achieving higher efficiency and better hole quality.

Mechanistic force modelling in drilling of AFRP composite considering the chisel edge extrusion

Aramid fiber–reinforced plastic (AFRP) composites have been widely used in automotive, aerospace, and defense industries. The common AFRP drilling process tends to cause damage to the composite structures which subsequently affects their fatigue lives and in-service performance. Understanding the mechanism of cutting force generation is crucial in controlling the cutting process for achieving desired hole quality and machining accuracy. This study proposes a novel mechanistic model considering both the cutting action and the extrusion action of the chisel edge. For the first time, the extrusion force generated by the chisel edge has been considered as a rigid wedge penetrating into an elastic half space based on the Hertz contact theory. The total thrust force in AFRP drilling is divided into three components: (i) thrust force generated by the cutting lips, (ii) thrust force generated by the chisel edge cutting action, and (iii) extrusion force generated by the chisel edge extrusion action. The proposed model was then validated by experiments and data was compared with the case where extrusion was not considered. The results show that our novel mechanistic model can provide a more accurate thrust force prediction. The average error of our model was 2.54% against the experimental data, whereas the error seen in conventional model without accounting extrusion was 8.22%. This suggests that the chisel edge extrusion plays a significant part in the drilling of AFRP and hence confirms the necessity of considering extrusion in establishing the associated mechanistic model.

Modeling and Optimization of Bidirectional Clamping Forces in Drilling of Stacked Aluminum Alloy Plates.

Interlayer burrs formation during drilling of stacked plates is a common problem in the field of aircraft assembly. Burrs elimination requires extra deburring operations which is time-consuming and costly. An effective way to inhibit interlayer burrs is to reduce the interlayer gap by preloading clamping force. In this paper, based on the theory of plates and shells, a mathematical model of interlayer gap with bidirectional clamping forces was established. The relationship between the upper and lower clamping forces was investigated when the interlayer gap reaches zero. The optimization of the bidirectional clamping forces was performed to reduce the degree and non-uniformity of the deflections of the stacked plates. Then, the finite element simulation was conducted to verify the mathematical model. Finally, drilling experiments were carried out on 2024-T3 aluminum alloy stacked plates based on the dual-machine-based automatic drilling and riveting system. The experimental results show that the optimized bidirectional clamping forces can significantly reduce the burr heights. The work in this paper enables us to understand the effect of bidirectional clamping forces on the interlayer gap and paves the way for the practical application.

Optimization of thrust force in drilling of carbon-basalt hybrid composites through Taguchi and RSM

The main object of the present work is to obtain better quality holes during drilling operation. Carbon-Basalt hybrid composite is a better performing composite with lesser price. For the present work, the hybrid composite test specimen was prepared by hand layup method. General purpose polyester resin is used as the matrix material. During the manufacturing process, alternate layers of carbon and basalt are stacked to prepare the composite. The maintained weight fraction of the fiber is 50%. The thickness of the obtained composite specimen is 6 mm. Delamination is the major reason for the rejection of drilled composites. The magnitude of delamination is directly proportional to the thrust force generated during drilling. Hence in the present work, an attempt has been made to reduce the thrust force to minimize the damage by optimizing the machining variables using Taguchi and RSM methods. The experiments were designed by DOE method. Taguchi’s 3 levels and 3 factors array was used to get the combination of parameters for each experiments. Totally 27 holes are drilled with different combinations of process parameters. The considered process parameters and their levels are: Drill diameter (6 mm, 8 mm & 10 mm), feed rate (50 mm/min, 75 mm/min & 100 mm/min) and spindle speed (750 rpm, 1000 rpm & 1250 rpm). Drilling process was carried out on a high precision CNC machine using HSS drill bits. The thrust force was measured by a Kistler dynamometer. Using ANOVA, the significant effect of considered parameters on the generated thrust force was also predicted. The result reveals that, the parameter feed rate has the most significant effect on thrust force, which is followed by the drill diameter. The least significant parameter is spindle speed. Both Taguchi and RSM methods suggest that, DD1, F1 and S3 combination parameters yields the lowest thrust value.

Effects of rotary ultrasonic bone drilling on cutting force and temperature in the human bones.

Efficacy and outcomes of osteosynthesis depend on various factors including types of injury and repair, host factors, characteristics of implant materials and type of implantation. One of the most important host factors appears to be the extent of bone damage due to the mechanical force and thermal injury which are produced at cutting site during bone drilling. The temperature above the critical temperature (47 °C) produces thermal osteonecrosis in the bones. In the present work, experimental investigations were performed to determine the effect of drilling parameters (rotational speed, feed rate and drill diameter) and techniques (conventional surgical bone drilling and rotary ultrasonic bone drilling) on cutting force and temperature generated during bone drilling. The drilling experiments were performed by a newly developed bone drilling machine on different types of human bones (femur, tibia and fibula) having different biological structure and mechanical behaviour. The bone samples were procured from male cadavers with the age of second to fourth decades. The results revealed that there was a significant difference (p < 0.05) in cutting force and temperature rise for rotary ultrasonic bone drilling and conventional surgical bone drilling. The cutting force obtained in rotary ultrasonic bone drilling was 30%-40%, whereas temperature generated was 50%-55% lesser than conventional surgical bone drilling process for drilling in all types of bones. It was also found that the cutting force increased with increasing feed rate, drill diameter and decrease in rotational speed, whereas increasing rotational speed, drill diameter and feed rate resulted in higher heat generation during bone drilling. Both the techniques revealed that the axial cutting force and the temperature rise were significantly higher in femur and tibia compared with the fibula for all combinations of process parameters.

A novel self-centring drill bit design for low-trauma bone drilling

Drilling is one of the most common procedures in orthopaedic surgery. However, drilling-induced trauma occurs frequently and affects the processing damage and position accuracy of the holes, which strongly influence the postoperative recovery. Therefore, there is an urgent need to design a dedicated drill bit that can satisfy low-trauma requirements such as low cutting force, low temperature, self-centring, and low surface damage during orthopaedic surgery. In this work, a novel three-step drill structure is proposed to modify the cutting conditions at the entrance and exit of drilling, to effectively reduce the mechanical and thermal damages and improve the position accuracy in bone drilling. As the first step drill, a unique tip with thinned web was adopted by considering the drill skidding mechanisms under a non-perpendicular drilling condition. The second step was achieved by using an optimal point angle for balancing the effects of the cutting force and temperature. Moreover, a transition arc design was proposed as the third step to adjust the point angle during the finishing stage for switching the cutting mechanism from ‘fracture & shear crack’ cutting to ‘shear’ cutting in association with a certain range of feeding rates. This could reduce the mechanical and thermal damages to the finished hole surface. Drilling experiments under various process conditions demonstrated that the proposed drill design significantly reduced the drilling force, temperature, and damage and also improved the position accuracy of the holes compared to the conventional drill design. The proposed design provides an effective tool to achieve low-trauma bone drilling in orthopaedic surgery.

On the improvement of analytical delamination model for drilling of laminated composites using Galerkin method

Despite the fact that fiber reinforced polymer composite laminates have high strength to density ratio, they have machinability limitations. Drilling operation is one of the mostly used machining processes on the laminated composites as it plays a significant role on assembly of composite parts. The most critical damage, affecting drilled composites, is delamination. Using Galerkin method, this paper, proposes a new model, removing most of the assumptions of previous models. The result of this study can be used to precisely and more reliably predict the critical thrust force-feed rate at which delamination could occur. The model uses the results of cutting theory to predict the distribution of the drilling load on delaminated area, a modified variety of Mindlin–Reissner plate theory in conjunction with the linear elastic fracture mechanic theory in mixed mode loading condition for the prediction of critical thrust force. Comparing with the previous proposed models, it has no assumptions for the load distribution and it considers mode I and mode II simultaneously for the growth of the delaminated zone, which makes it possible to consider non-uniform loading conditions of the drilling process. Using this model, the effect of the distribution of the drill force on the composite is investigated. The critical thrust force was studied for load-controlled and displacement-controlled loading conditions. For the experimental validation, the onset of the growth of the crack was detected using acoustic emission. The results of the experiment were compared with that of model.

A prediction model of thrust force for drilling of bidirectional carbon fiber-reinforced carbon matrix composites.

Carbon fiber-reinforced carbon matrix composites have been widely used for the manufacturing of thermostructural parts for several industries such as the aerospace and automotive. Drilling is an extremely common method used in the machining of carbon fiber-reinforced carbon matrix composites before assembly. However, their non-homogeneous, anisotropic, and brittle nature make difficult to guarantee the hole quality in drilling. Some severe drilling defects, such as burrs, delamination, and tear, usually occur. In this regard, it is necessary to accurately predict the thrust force in drilling of carbon fiber-reinforced carbon matrix composites. Therefore, in this article, based on the cutting theory of fiber-reinforced polymer composites, an alternative thrust force prediction model for drilling of bidirectional carbon fiber-reinforced carbon matrix composites is proposed. The cutting force of the cutting lips is established by dividing the cutting deformation zone into three regions according to the machined material structure based on the Zhang's model in cutting of fiber-reinforced polymer. The periodic variation of fiber orientation is considered in detail. The experimental results show that the relative deviations of the predicted and experimental values of the thrust force are less than 14.36%.

Evaluation of different tool geometries in the finite element simulation of ultrasonic-assisted drilling of Ti6A14V

This paper attempts to analyze the effect of various drilling parameters such as feed rate, spindle speed and vibration frequency on performance characteristics such as thrust force, effective stresses, temperature and chip morphology in conventional drilling (CD) and ultrasonic-assisted drilling (UAD) of Ti6A14V using three different point angle (140°, 120°, 90°) drill bits in order to optimize the chip breakability of Ti6A14V. The three different point angle drill bits are utilized to establish the finite element models (FEM) to simulate the drilling process with Lagrangian approach in DEFORM-3D software. The simulations are validated by the experimental findings and analytical data of thrust forces, and the percent errors in results range approximately between 3 and 7%. The results obtained prove that UAD can produce segmental discontinuous chip, lower thrust force, lower process temperature and lower effective stress. The point angle of 120° drill achieved the thinnest chip thickness and the excellent effects of chip breaking. The achieved results are assumed to help for the optimization of the drill tool geometries, drilling parameters and chip breakability.

Mathematical modeling and experimental studies on axial drilling load for rotary ultrasonic drilling of C/SiC composites

Ceramic matrix composites of type C/SiC have great potential in space applications because of their superior properties such as low density, high wear resistance, and high-temperature resistance. However, due to their heterogeneous, anisotropic, and unstable thermal properties, the machining is still challenging to achieve desired efficiency and quality. For advanced materials, rotary ultrasonic machining (RUM) is considered as a highly efficient technology. Predicting mechanical load in RUM can help to optimize input variables and reduce processing defects in composites. In this research, a mathematical axial drilling load (force and torque) model has been developed based on the indentation fracture theory of material removal mechanism considering penetration trajectory and energy conservation theorem for rotary ultrasonic drilling (RUD) of C/SiC. Experiments were conducted on C/SiC composites to validate the model, and experimental results agreed well with model predictions with less than 14% (force) and 10% (torque) error. Therefore, this theoretical model can be effectively applied to predict axial drilling load during RUD of C/SiC. The relationships of axial drilling force and torque with machining process parameters, including spindle speed, feed rate, and ultrasonic power, were investigated. A specific range of experiments was carried out to demonstrate the benefit of ultrasonic vibration in RUD over conventional drilling (CD) on mechanical load for a designed drilling tool. It was noticed that RUD outperformed CD with a maximum of 38.11% and 34.30% in axial drilling force and torque reduction, respectively. The influence of drilling tool flute length on drilling performance was also elucidated based on a set of experiments using several designed drilling tools.

MULTI-OBJECTIVE OPTIMIZATION FOR SURGICAL DRILLING OF HUMAN FEMURS: A METHODOLOGY FOR BETTER PULL-OUT STRENGTH OF FIXATION USING TAGUCHI METHOD BASED ON MEMBERSHIP FUNCTION

Drilling through bone is one of the common cutting processes involved in many of the orthopedic surgeries. In bone drilling, spindle speed, feed rate, diameter of the drill bit, drill bit geometry and method of cooling are the important parameters to influence the in-situ temperature, drill thrust force and quality characteristics of the drilled hole. Because of the selection of inappropriate drilling parameters, uncontrolled large drilling forces, continuous increase in temperature and mechanical damage to the local host bone were observed. As these adverse effects lead to poor bone–implant contact and often a revision surgery, performing a surgical drilling with optimal parameters is essential to succeed in the surgical procedure. It was observed that in addition to the variations in apparent bone density, the orientation of osteons influences the drilling thrust force and temperature in bone drilling. Ten adult cadaveric human femurs from the age group of 32–65 years were considered and drilling experiments were conducted on proximal-diaphysis, mid-diaphysis and distal-diaphysis regions in the longitudinal, radial and circumferential directions. Bone drilling with different spindle speeds (500, 1000 and 1500[Formula: see text]rpm), feed rates (40, 60 and 80[Formula: see text]mm/min), and apparent density in the range of 0.98[Formula: see text]g/cm3 to 1.98[Formula: see text]g/cm3 was investigated in this work using a 3.20[Formula: see text]mm diameter surgical drill-bit. The generation of in-situ temperature as well as thrust force at each target location was measured using [Formula: see text]-type thermocouple and Kistler[Formula: see text] dynamometer, respectively. Taguchi method based on membership function was used to optimize the drilling process. Then the efficacy of the method in reducing the in-situ temperature and thrust force, and quality of the drilled hole in respect of anatomical region and drilling direction was investigated using pull-out strength of the bone screws. Results revealed that the optimal parameters obtained from the Taguchi method based on membership function could simultaneously minimize the temperature as well as thrust force in bone drilling. The proposed method can be adopted to minimize the temperature and thrust force, and choose the best location nearest to the defect site for strong implant fixation by using CT datasets of the patient as the only input.

A quasi-static model for kinematic analysis of a feed driving mechanism

A quasi-static model is proposed for kinematic analysis of the feed driving mechanism designed for China's Chang'e Lunar Exploration Program, which is a type of rope-pulley system used to provide driving force for drilling and sampling of lunar soil. This model does not take into account the inertia force acting on the rope because the mechanism is operated in a relatively enclosed device and the drilling speed is low. First, an appropriate method for spatial description of the rope-pulley system is applied on the basis of the model. Next, variables for kinematic description of the rope-pulley system are determined. Some key spatial points on the rope in contact with two pulleys, the winch, and the drilling rig are formulated. Then, the slip phenomenon occurs at the output terminal of the rope on the winch when the rope is not wrapped closely is analyzed. The results from numerical examples show that the rope tension and the driving moment vary depending on the way the rope is wrapped around the winch and the driving velocity.

Effect of dipped cryogenic approach on thrust force, temperature, tool wear and chip formation in drilling of AZ31 magnesium alloy

Magnesium alloys tend to have inflammable nature and chip self-ignition at high cutting speeds under dry machining condition, although they can be easily machined with good surface quality. In the drilling process, cooling and lubrication have a critical impact as it controls heat generation, tool wear, surface quality, and cutting force. In the present study, drilling tests on AZ31 magnesium alloy were performed with dry and cryogenic conditions at various feed rates and cutting speeds. The effect of dipped cryogenic application during drilling on thrust force, temperature, tool wear, and chip formation were investigated. The results showed that the applied cryogenic drilling method provided less tool wear, smaller chips and reduced amount of adhesions. Drilling tests performed in the cryogenic environment increase the thrust forces by 32 %–39 % compared to dry cutting. Spark and chip ignition were not observed even at high cutting speeds during dry cutting.

Neural network modeling of forces in drilling of glass/epoxy composites filled with agro-based waste materials

In this paper, the drilling behavior of a new class of composite materials has been experimentally investigated. Thecomposite laminates have been manufactured using glass fibers, epoxy resin, and filler materials. The abundantly availableagro-based waste materials (coconut coir, rice husk, and wheat husk) have been used as filler materials. The drillingexperiments have been performed at several levels of feed (0.03 to 0.3 mm/rev.) and speed (90 to 2800 RPM) using differenttypes of drill bits. The effect of these parameters on the drilling forces (axial thrust and torque) has been analyzed for alltypes of laminates under investigation. The artificial neural network-based models have also been proposed to compute thedrilling forces. The fitness of the models has been measured in terms of mean percentage error between the predicted andactual values. From the investigation, it has been found that the drilling forces computed by the neural network models werequite close to the experimental values.

Trust Force and Hole Quality Observation in Various Major Penetration Angle Drilling of Carbon Fibre Reinforced Plastic (CFRP)

Trust Force and Hole Quality Observation in Various Major Penetration Angle Drilling of Carbon Fibre Reinforced Plastic (CFRP)