Drill Tip Research Articles

Drilling Tool Geometry Effects on the Hole Quality of Glare

Recently machining of hybrid stacking materials are much interested and challenging in manufacturing domains. Mostly, drill hole quality depends the machining parameters and type of cutting tool. This work investigates the experimental study for effects of drill bit geometry on hole quality of glass laminate aluminum reinforced epoxy (GLARE). GLARE have manufactured by alternative stacking of aluminum (AA7475) and glass fiber (E-glass)/epoxy composite through compression molding machine. Machining of GLARE by using of Computer numerical controller. Hole quality were studied with the aid of optical microscopic. Results show that a drill tip geometry to promote the reduction of delamination and structural damage. Superior hole quality is achieved with 2 fluted drill bit than 3 fluted drill bit.

On the effect of load on vibration amplitude in ultrasonic-assisted drilling

The ultrasonic-assisted drilling (UAD) process is a technology that applies ultrasonic vibrations in the feed direction of the drill to improve drilling conditions and productivity. In recent years, UAD has been the subject of extensive research due to its advantages over the conventional drilling (CD) process, these being reported as thrust force and torque reduction, burr height reduction, improvements in surface roughness, and hole accuracy. The results of the research also showed that these benefits do not necessarily equally occur for all drilling conditions but can vary with machining and ultrasonic conditions. In particular, it is found that the drill vibration amplitude is a key factor in determining UAD benefits. However, a critical difficulty is that the all-important matter of the drill vibration amplitude at the point of material engagement, the so-called “down-the-hole” amplitude, is not known due to inaccessibility. This difficulty, not faced, for example by the ultrasonic-assisted turning (UAT) process due to its visual access, has prevented measurement of load effects on UAD, as well as verification of analytical models of the process. In this study, a technique to measure the effect of load on drill vibration amplitude during UAD is presented. The technique is based on examining the surface of the drilled hole, where minute, oscillatory traces of the vibrating drill tip are found that correspond to drill tip vibrational amplitude. This data, when coupled with in-process laser vibration measurements at the drill chuck, as well as no load amplitude measurements, permit the effects of load on vibration amplitude to be determined. Results have shown that drilling loads cause measurable reductions in drill vibration amplitude and must be accounted for in UAD procedures.

Variation characteristic of drilling force and influence of cutting parameter of SiCp/Al composite thin-walled workpiece

In this paper, the variation characteristic of the drilling force, and the influences of cutting speed, feed rate, and workpiece thickness on the drilling force, were evaluated when drilling a silicon carbide particle reinforced aluminum matrix (SiCp/Al) composite thin-walled workpiece with a high volume fraction. Under the condition that the workpiece thickness was less than the drill tip height, three characteristic stages of drilling force variation were proposed. The results indicate that there is a significant difference between the variations in the drilling force when drilling a thin-walled workpiece compared to thick-walled workpiece. When the chisel edge drills out the lower surface of the workpiece, there is an abrupt decrease in the thrust forces of the thin-walled and thick-walled workpieces. In addition, there is an abrupt decrease in the torque of the thick-walled workpiece, whereas that of the thin-walled workpiece increases. According to the thickness of the thin-walled workpiece, the instant of the abrupt decrease in the thrust force may lead or lag behind the theoretical instant at which the chisel edge reaches the lower surface of the workpiece without deformation. When drilling a thin-walled hole, the cutting speed has a slight influence on the thrust force, and there is a slight increase in the torque in accordance with an increase in the cutting speed. The thrust force and torque increase in accordance with an increase in the feed rate. When drilling a thin-walled workpiece with a thickness of 1 mm, the critical thickness of workpiece cracking decreases in accordance with an increase in the cutting speed, and increases in accordance with an increase in the feed rate. When drilling a thin-walled workpiece with a thickness of 0.5 mm, the concave deformation of the workpiece and the critical thickness of the workpiece cracking increase in accordance with an increase in the feed rate. However, the increment in the critical thickness of the workpiece cracking is less than that in the concave deformation of the workpiece.

Mechanical analysis of local cutting forces and transient state when drilling of heat-resistant austenitic stainless steel

In the present research work, mechanical aspect of transient state in drilling operation is investigated by analyzing together the cutting forces and the chip formation. Particularly, a sudden peak occurring on cutting forces during transient state is observed and deeply studied. To do so, new experimental methodologies to analyze local cutting forces when drilling heat-resistant austenitic stainless steel are introduced. The chisel edge and the cutting edge of each studied drill are numerically discretized as series of elementary cutting edges. Therefore, local cutting force evolution is correlated with the local cutting geometry variation along the cutting edge. On one hand, results have shown that for high ductile materials, local cutting geometry affects deeply not only the chip shape but also the chip flow direction. This strongly disrupts the monotony of the cutting forces evolution in transient state and lead to a sudden peak occurrence on cutting forces. On the other hand, linear local cutting forces could be determined by numerical decomposition of the global cutting forces measured during the drill tip engagement.

Forming method and experimental research on wire cutting of twist drill cone flank

To solve the problems involving several forming movements and the complex sharpening structures required for the flank face of a traditional grinding wheel-sharpening twist drill, a new method based on the wire electrical discharge machining is here proposed and a mathematical model of twist drill flank faces formed by wire electrical discharge machining (WEDM) is established. Based on the forming principle of the conical flank face of twist drills and the processing characteristics of the wire-cutting machine, a wire-cutting and forming device was designed and its motion analyzed. Using the UG NX (Unigraphics NX) software, a virtual prototype of the wire-cutting and forming device was established, with the simulation and measurement analysis performed using the VERICUT software. After analyzing the feasibility of its motion, the wire-cutting and forming device was developed and the wire-cutting and forming test was conducted. The feasibility of the device was analyzed by measuring the angle of the drill tip and the surface quality of the flank face of the twist drill. The utility model has a simple structure and provided us with a new idea and solution for the “grinding” of the twist drill.

Early experimental investigations on slotted-in steel plate connections with self-perforating dowels in CLT

ABSTRACT The purpose of this paper is to provide a better understanding of the behaviour of self-perforating dowels made of high-strength steel in CLT. The strength and stiffness of the connection is experimentally investigated and discussed, as are the influencing parameters. The results show the influence of the rope effect and drill tip on the load-carrying capacity of a connection with threaded dowels. Embedment tests revealed the analytical equations for embedment strength may overestimate results by up to 20%. In contrast, the analytical formula for the fastener’s yield moment may underestimate the real value up to 30% for high-strength steel dowels.

Analytical modeling of exit Burr in drilling of Ti6Al4V alloy

Burrs affect precision components and cause assembly related problems, and in general, decrease manufacturing productivity. Drilling burr formation involves multiple stages that are influenced by variation in thrust forces, temperature, stress conditions, and deformation modes in the unsupported length of the work-material below the drill. Several of these have not been adequately investigated so far. Therefore, the objective of this work is to model the complex phenomena that occur just before the exit of the drill tip from the bottom surface of the hole, and up to the complete exit of the drill point from the work surface. Accordingly, two models have been developed: (i) to estimate onset of bending in conjunction with theory of plasticity, which leads to the formation of a small drill cap under the pressure of steady-state drilling thrust forces, and (ii) to evaluate exit burr size that involves stretching and bending of a thin layer below the drill tip, using the principle of energy conservation. It is observed that a fracture is initiated at the chisel edge corner resulting in the formation of a small drill cap. The exit burr size predicted by the model is within one standard deviation from the average burr height as determined from the experimental data.

Comparison of between direct and peck drilling for large aspect ratio in Ti-6Al-4V alloy

Drilling is a crucial cutting operation as it represents 40 to 60% of the total material removed in the aircraft frame industry. Drilling difficult-to-cut materials, such as Ti-6Al-4V, is still a challenge due to their high chemical reactivity with different tool materials and low thermal conductivity. The application of cooling approach is needed to reduce the generated cutting temperature at the machining area. However, in drilling, the coolant does not sufficiently reach to the drill tip at the cutting zone because of the counter flow of the chips limits further penetration, especially in deep-hole drilling. To overcome such problems during direct drilling, different drilling techniques are followed. Peck drilling is among these methods in which the drilling process is conducted in a number of steps to achieve holes with large aspect ratio. The current study presents a detailed comparison between direct drilling and peck drilling of Ti-6Al-4V in terms of tool life, surface roughness, thrust force, torque, and burr formation. In terms of flank wear, thrust force, and burr formation, peck drilling showed better results when compared to direct drilling; however, direct drilling offers slightly better results in terms of surface quality.

Robotic System for Bone Drilling Using a Rolling Friction Mechanism

Bone drilling procedures are frequently performed in various surgical fields using computed tomography. The robotic systems employed to perform such procedures can improve the targeting accuracy and reduce the radiation exposure to surgeons. This report presents the mechanism, navigation system, and experimental evaluation of a proposed robotic drilling system. This system provides automatic drill tip alignment and target drilling. Unlike previously proposed robotic drilling systems, the system developed here employs a drilling mechanism based on rolling friction and an orientation mechanism using a four-bar linkage with a linear actuator. It also implements a release mechanism between the robot and drill to enhance surgical safety. The proposed orientation mechanism was proven to provide a high drilling location accuracy. To guide the robot and enable automatic target drilling, we developed a vision-guided navigation system, which was integrated with the proposed robot using a stereo camera. The effectiveness of the proposed robotic system was demonstrated by performing ex vivo drilling on swine femur samples.

Comparison of Curved and Straight Anchor Insertion for SLAP Repair: A Cadaveric Study

To compare a curved drill guide with a straight guide for suture anchor placement into the posterosuperior glenoid from an anterolateral portal with respect to glenoid perforation, drill contact with the suprascapular nerve, and maximum load. Ten bilateral pairs of fresh human cadaveric shoulders were randomized to the curved technique on 1 side and the straight technique on the contralateral side. An anterolateral trans-rotator cuff portal was used for placement of anchors at the posterior (11 o'clock right shoulder) and far posterior (10 o'clock right shoulder) positions on the glenoid with a 24-mm drill stop, and the drill tip was marked with ink. Specimens were dissected for glenoid perforation and drill contact with the suprascapular nerve. The maximum load of each anchor was measured using a material testing system. Glenoid perforation occurred in 30% in the curved group and 60% in the straight group overall (P= .01). Ink markings demonstrated a direct hit on the suprascapular nerve in most of the penetrations (13 of 18) but was not significantly different between the curved and straight guides (P= .25). Maximum load of the posterior anchor was greater in the curved group than that in the straight group (199.5 vs 146.7N, respectively; P= .01). The curved technique has a lower rate of glenoid perforation and greater maximum load than the straight technique. However, the curved technique can result in glenoid perforation and injury to the suprascapular nerve, and we do not recommend it. Placing suture anchors through an anterolateral portal with a curved guide provides a more optimal trajectory with decreased risk of glenoid perforation and superior biomechanical strength than that with the straight guide, but it is not safe.

Application of percutaneous foraminotomy with a specially designed drill tip for foraminal stenosis patient - A case report -

Application of percutaneous foraminotomy with a specially designed drill tip for foraminal stenosis patient - A case report -

Proposal for a new trajectory for subaxial cervical lateral mass screws.

Lateral mass screws combined with rods are the standard method for posterior cervical spine subaxial fixation. Several techniques have been described, among which the most used are Roy Camille, Magerl, Anderson and An. All of them are based on tridimensional angles. Reliability of freehand angle estimation remains poorly investigated. We propose a new technique based on on-site spatial references and compare it with previously described ones assessing screw length and neurovascular potential complications. Four different lateral mass screw insertion techniques (Magerl, Anderson, An and the new described technique) were performed bilaterally, from C3 to C6, in ten human spine specimens. A drill tip guide wire was inserted as originally described for each trajectory, and screw length was measured. Exit point was examined, and potential vertebral artery or nerve root injury was assessed. Mean screw length was 14.05mm using Magerl's technique, 13.47mm using Anderson's, 12.8mm using An's and 17.03mm using the new technique. Data analysis showed significantly longer lateral mass screw length using the new technique (p value < 0.00001). Nerve potential injury occurred 37 times using Magerl's technique, 28 using Anderson's, 13 using An's and twice using the new technique. Vertebral artery potential injury occurred once using Magerl's technique, 8 times using Anderson's and none using either An's or the new proposed technique. The risk of neurovascular complication was significantly lower using the new technique (p value < 0.01). The new proposed technique allows for longer screws, maximizing purchase and stability, while lowering the complication rate.

Dry and minimum quantity lubrication high-throughput drilling of compacted graphite iron

ABSTRACTThis research studies the sustainable and high-throughput drilling of compacted graphite iron (CGI), a high strength, lightweight material for automotive powertrain applications. CGI drilling experiments were conducted using a 4 mm diameter coated carbide drill at 26.5 mm/s feed rate. In two repeated tests under three lubrication conditions: dry, dry with through-the-drill compressed air, and through-the-drill minimum quantity lubrication (MQL), the drills were able to produce a maximum of 1,740, 3,150 and 2,948 holes, respectively, before the breakage of the drill. The Joule–Thomson effect due to the expansion of high pressure air from through-the-drill holes at the drill tip, chip shape, chip size and chip speed are investigated. Flank wear of the drill cutting edge is measured and results are correlated to drill life. Results indicate that dry machining of CGI is technically feasible. Chip evacuation and advanced tool cooling are important factors that affect drill life for high-throughput sustainable dry drilling of CGI.

Effective Locomotion and Precise Unclogging Motion of an Untethered Flexible-Legged Magnetic Robot for Vascular Diseases

We propose an untethered flexible-legged magnetic robot (FLMR) manipulated by an external rotating magnetic field (ERMF) to generate effective locomotion and precise unclogging motion to treat vascular diseases. The proposed FLMR is composed of a front body with a drill tip, a cylindrical permanent magnet, a rear body, and flexible legs. The flexible legs are obliquely attached to the bodies like blades of a propeller, so that the FLMR can generate propulsive force in a fluidic environment for locomotion and unclogging motions. To provide manipulation guidelines for locomotion and unclogging motions, we developed a dynamic model of propulsive force, axial force, and friction force, and we established a control method of propulsive force according to the rotating frequency of the ERMF and the diameter of the tube, based on the proposed dynamic model. Finally, we prototyped the FLMR and conducted several experiments to verify its navigation performances and the control method of the propulsive force. Also, we conducted an in vitro experiment with a pseudo blood clot to demonstrate the validity of the locomotion and unclogging motions of the FLMR.

Simulation Analysis of RuT450 Drilling Force Based on LS-DYNA Gun Drilling

Cutting force is one of the most important parameters in the machining process, it significantly influenced machining precision of the workpiece, power consumed in the machining process, wear of the cutting tools and so on. There are many factors that affect the cutting force, such as the performance of the workpiece material, cutting speed, usage of the cutting fluid, etc. Single factor variable method was used in this paper, RuT450 was used as workpiece, welded cemented carbide gun drill was used as cutting force and LS-DYNA was used as simulation platform to established the cutting simulation model to analyzed the impact of the cutting speed and feed rate to the drilling force. Simulation results show that, at the low speed drilling stage, drilling force increases with the increase of the feed rate and decreases with the increase of the rotation feed, from the stress cloud it could be seen that the equivalent stress near the drill tip reached the maximum in the drilling process.

Mechanical study in drilling of heat resistant austenitic stainless steel

Machining of difficult-to-cut-materials like heat resistant stainless steels leads to the rapid tool wear and tool failure. The analysis of drilling process of these steels is even more difficult as it is not easy to investigate the cutting process at the drill tip. Therefore for this critical operation, modelling of cutting forces is very important. The study of the mechanical loading is based on the cutting tool geometry variation along the cutting edge. This study aims to investigate the drilling of heat resistant stainless steels with two geometries of twist drills, by analyzing specific cutting energy and forces at a global and a local scale.

A multi-modality tracking, navigation and calibration for a flexible robotic drill system for total hip arthroplasty.

This paper presents a novel multi-modality tracking and navigation system that provides a unique capability to guild a flexible drill tip inside the bone with accurate curved tunnelling. As the flexible drill tip cannot be tracked optically inside the bone, this research focuses on developing a hybrid tracking and navigation system for tracking a flexible drill tip by using both optical and kinematic tracking. The tracking information is used to guide the THA (total hip arthroplasty) procedure, providing a real-time virtual model of the flexible drill. The flexible and steerable drill tip system is then tested on total hip arthroplasty followed by evaluation of the positioning and orientation of femoral stem placement by femoral milling. Based on this study, we conclude that the tracking and navigation system is able to guide the flexible drill to mill inside femoral canal.

An Experimental Study on Nano-Carbon Films as an Anti-Wear Protection for Drilling Tools

Carbon thin films of 50–100 nm thickness were synthesized by Pulsed Laser Deposition in vacuum at different laser fluences from 2 to 6 J/cm2. The deposited films were characterized by Raman spectroscopy for compositional assessment, scanning electron microscopy for morphology/thickness evaluations, and X-ray reflectivity for density, thickness, and roughness determinations. The films were ~100 nm thin, smooth, droplet-free, made of a-C:H type of diamond-like carbon. The mechanical properties of synthesized films were studied by nanoindentation and adhesion tests. The films that were obtained at low laser fluences (2, 3 J/cm2) had better mechanical properties as compared to those synthesized at higher fluences. The mean values of hardness were around 20 GPa, while the friction coefficient was 0.06. The deposition conditions of carbon thin films that displayed the best mechanical properties were further used to coat commercial drills. Both uncoated and coated drills were tested on plates that were made of three types of steel: Stainless steel 304, general use AISI 572 Gr 65 steel (OL60), and AISI D3 tool steel (C120). All of the drill edges and tips were studied by optical and scanning electron microscopes. The coated samples were clearly found to be more resistant, and displayed less morphological defects than their uncoated counterparts when drilling stainless steel and OL60 plates. In the case of C120 steel, carbon coatings failed because of the high friction between drill and the metal plate resulting in tip edges blunting that occurred during processing.

Analysis of thrust force and delamination in drilling GFRP composites with candle stick drills

Drilling is an indispensable process for assembling the composites components. The drilling-induced delamination damage generally refers to the peel up delamination on the entrance surface and the push down delamination on the exit surface. Many researchers have carried out studies on drilling force and delamination damage in composites using special drills. Candle stick drills have been recognized as advantageous tools for the reduction of thrust force and delamination damage in drilling composites. Drilling experiments of glass fiber-reinforced plastic (GFRP) composites and finite element simulations were carried out in this paper. Three candle stick drills with different drill tip geometries and one twist drill were compared in terms of thrust force, peel up delamination, and push down delamination. The results revealed that, compared to twist drill, not all candle stick drills could get relatively good drilling results. What is more, drilling results of candle stick drills had a great relationship with the drill tips geometry angles. Finally, an optimized candle stick drill with appropriate drill tip geometry achieved relatively excellent drilling results.

High frequency vibration analysis in drilling of GFRP laminates using candlestick drills

The vibration signal contains a lot of information closely related to the tool performance in drilling the composite material. However, due to the limit of the frequency response characteristics of piezoelectric accelerometer, the monitored vibration signals used in researches were usually below 10kHz. Thus, the high frequency vibration signal was ignored. Drilling experiments of Glass Fiber Reinforced Plastic (GFRP) laminates were carried out utilizing candlestick drills in this article. The high frequency vibration signals of ten candlestick drills with different drill tip geometry parameters were analyzed and compared in time domain, frequency domain and in bispectrum. The results revealed that there was high frequency vibration signal above 10kHz in the process of drilling GFRP laminate. These signals were sensitive to the changes of the drill tip geometry parameters. The changes of the bispectrum energies of these signals could reflect the changes of the cutting performances and the delamination factors for the drills.