Drill Breakage Research Articles

Quantitative Analysis of Force and Torque in Bone Drilling

Bone drilling is an important and the most frequent operation in orthopaedics and other bone surgical procedures. Prediction and control of drilling force and torque are critical to safe and efficient surgeries. This paper studies the drilling force and torque arising from bone drilling process. Drilling parameters such as drilling speed, feed rate, drill size and drill condition (sharp and worn) were changed to measure the force and torque in the direction of the drill penetration. Experimental results demonstrated lower drilling force using a sharp drill compared to a worn drill for similar drilling conditions. Contrary to the drilling force, lower torque was measured using a worn drill compared to a sharp drill. The drilling force was found to decrease with increase in drill speed and increased with rise in the feed rate using both types of drills. A linear drop in drilling torque was measured with increase in drilling speed. This study provided scientific information to orthopaedic surgeons and technicians to use appropriate surgical drill and cutting parameters to avoid overstressing of the bone tissue and drill breakage during drilling operations.

DLCコーテッドドリルを用いたプリント配線板の小径穴あけ加工に関する研究

In recent years, needs for micro drilling are increasing, accompanying the development of higher wiring density of printed circuit board (PCB). When drilling PCB for the purpose of making the electric through holes, it has been said that the drill breakage is caused by being filled the chips of GFRP and copper of PCB in the drill flutes. The aim of this study is to clarify the effect of PCB drilling using DLC coated drill on tool wear, chip evacuation and cutting torque. Series of drilling tests of PCB have been carried out to investigate the amount of drill wear, the chips evacuation behavior out of drilled hole with the drill, the shape of chips produced and the cutting torque using DLC-coated drill and non-coated drill. The chips evacuation behavior out of drilled hole with the drill is filmed by a high-speed motion camera and the shape of chips produced is observed by a microscope. The cutting torque is measured by a dynamometer; Kistler 9329A. The amounts of drill flank wear and margin wear using DLC-coated drill and non-coated drill are almost the same. The chips of GFRP using DLC-coated drill are shorter and smaller than those using non-coated drill. The chips evacuation out of drilled hole with the drill using DLC-coated drill is better than those using non-coated drill, and cutting torque using DLC-coated drill is lower than those using non-coated drill.

Preparation and performances of coated and aluminous entry boards with water-soluble resins for PCB drilling

Purpose This paper aims to provide a new drilling entry board for printed circuit board (PCB) process, superior in heat dissipation, lubrication, water solubility and hole location accuracy, achieving an excellent drilling process. Design/methodology/approach Using a mixture of polyethylene glycol (PEG) and water-soluble adhesives as hydrosoluble, endothermic and lubricant resins and aluminum foils as baseplates, a series of coated and aluminous entry boards (CABs) for PCB drilling was successfully prepared. The surface appearance of the entry boards was observed clearly by scanning electron microscopy (SEM). The endothermic and lubricant effects of the resins applied on the CABs was characterized by differential scanning calorimetry (DSC) and their water solubility was tested in the normal-temperature water (25°C). Moreover, the CABs’ good drilling properties were tested when they were used for PCB drilling. Findings The SEM analysis showed that the surfaces of the resin layers coated on the CABs whose coating thicknesses were less than 80 μm were smoother and flatter, which could improve hole location accuracy and reduce drill breakage ratio. By virtue of DSC, the endothermic and lubricant effects of the CABs were proven. The fusion of PEG in the resin layers could absorb the heat produced by drilling, restrain the temperature of the drill bit and hole rising and lubricate the drill bit efficiently when a hole was being drilled, which could achieve high-quality holes with good production efficiency. The water-soluble test showed that the prepared CABs had excellent water solubility at normal temperature, enabling the resin left on the hole walls and in the flute of the drill bit to be washed away easily and thereby improving the drilling efficiency and quality. The drilling tests showed that the increase in the thickness of the CABs’ coating could improve the hole location accuracy and alleviate the bit wear. In addition, the suitable coating thickness could ensure the firm adhering of the resin coating the aluminum foil, effectively avoid drill intertwist and prevent the resin debris from blocking the drilled holes on the surface of the entry board, which could hinder chip removal, resulting in poor hole wall quality and drill breakage. Originality/value This paper has a remarkably high industrial practicality in the PCB manufacture process.

Recent advances in twist drill design for composite machining: A critical review

In the field of composite technology, inefficient and poor designs of twist drills contribute immensely to the challenges facing drilling of composite materials. An attempt to report some of the drill design methods and their inherent challenges confronting composite machining necessitates the writing of this article. A critical review has been conducted to offer a clear understanding of the current advances in the field of mechanical drilling of composite materials, focusing on geometry, material and parametric tool designs. The inter-dependable effects of thrust force, cutting speed, feed rate, cutting force and torque on drill design are similarly reviewed. This article also reveals other associated issues facing composite drilling including delamination, surface roughness, rapid tool wear and drill breakage. Well-designed drill geometry and good knowledge of drilling parameters afford the producers of polycrystalline diamond, carbide and high-speed steel tooling materials better opportunity of developing a drill that will minimise delamination of the reinforced composites and tool wear and produce a high-quality surface. Twist drill manufacturers and users will benefit from this article as they seek to have well-designed and improved drills.

Mechanistic approach for prediction of forces in micro-drilling of plain and glass-reinforced epoxy sheets

Aerospace and automobile industries extensively use components made of plastics and fiber-reinforced plastics which require micro-machining operations including micro-drilling to be carried out. Various attempts are reported in the literature to study different strategies and model the forces in micro-drilling with a view to produce micro-holes having large aspect ratio and to reduce drill breakage. The force models are more statistical than mechanistic in approach. In the present work, an attempt is made to develop mechanistic models of thrust and torque in micro-drilling of plain epoxy sheets. Material model capturing strain rate and temperature-dependent yield strength of epoxy material and basic principles of machining are employed for this purpose. The mechanistic model for prediction of thrust and torque is validated using well-planned full factorial design of experiments. Experiments are carried out using a carbide drill of 0.5-mm diameter with three levels for speed and feed on a high-speed miniature machine tool specially developed at the laboratory. The material model is extended to glass-reinforced plastics (GRP), and drilling forces are predicted using the proposed mechanistic model. In both cases of plain and GRP sheets, the model predictions are close to the experimentally measured drilling forces.

Fractured drill bit in ORIF mandible - precautions and developing guidelines for its management

Abstract Figure 1. OPG showing fracture of the mandible, with fracture line running obliquely to the left side. Figure 2. Reduction & approximation of the fracture segments. Fractured drill bit in ORIF mandible - precautions and developing guidelines for its management Arvind Karikal 1 (a rvikarikal at gmail dot com) #, Arathi K 21 Department of Oral and Maxillofacial Surgery, A.B. Shetty Memorial. Institute of Dental Sciences, Nitte University, Mangalore 575018, Karnataka, India. 2 Department of Oraland Maxillofacial Pathology, A.J. Institute of Dental Sciences, RGUHS, Mangalore 575004, Karnataka, India# : corresponding author A case of a drill breakage during open reduction and internal fixation (ORIF) of a mandibular fracture is reported. Documentationand literature on this type of peri-operative complication is deficient. The clinical decision, diagnosis and surgical management of complicationare discussed. Introduction Fractures of the mandible which are not associated with any other fracture of the face or skeleton can be treated with or without inter-maxillaryfixation [1] [2] [3]. The reported complications of open reduction and internal fixation include: disturbed wound healing, infection, mal-union, non-union, hypoesthesia or paresthesia, impalement of tooth root or the inferior alveolar canal and fracture of mini-plate [4], facial asymmetry, fibrousunion [5]. Complications involving the breakage of surgical drills or mini-plates have been very rarely reported in maxillofacial literature. Drill bitfracture is usually encountered by every surgeon in his/her operating career; its causes, cases and methods to retrieve the same have rarely beenreported. Orthopedic literature shows an overall rate of 0.3 to 0.35% of instrument breakage [6] [7] [8]. The aim of the present report is to describean unusual case of a drill breakage during ORIF of a mandible fracture and its diagnosis, operative and postoperative management.

Monitoring of tool collision in drilling by disturbance observer

Disturbance observation is a sensorless process monitoring technique that has not yet been applied to the monitoring of tool collision in the use of machine tools. This paper presents a monitoring algorithm that detects collisions that involve the breakage of drills through observation of the disturbance force change rate. A comprehensive experimental study of diverse operator-induced collisions was conducted to analyze the collision detection potential of the disturbance observer. It was found that collision monitoring by the disturbance observer is more sensitive and responsive than that using a sensorless jerk observer.

Experimental Investigation of Tool Breakage in Micro Drilling of EN AW-5083 Aluminium

Nowadays micro hole drilling is more and more applied machining operation. Because of less than 1 millimeter diameter, and of the relatively high thrust force, micro drills are more easily break than conventional ones. In this paper the experiences of micro drilling tests are summarize in order to demonstrate that measuring thrust force is efficient way to recognize the tool breakage. In order to evaluate the micro drill breakage monitoring method the authors carried out experimental measurements varying the cutting conditions, too.

Preparation and performances of coated and aluminous entry boards with endothermic and lubricant resins for PCB drilling

PurposeThe purpose of this paper is to provide a new entry board for drilling holes on the PCBs, superior in heat removal effect, lubricating effect and hole locating effect in forming holes, resulting in an excellent process of forming holes with a high quality.Design/methodology/approachWith the mixture of PEG, PEO and adhesive used as endothermic and lubricant resins and aluminium foils used as baseplates, a series of coated and aluminous entry boards (CABs) for PCB drilling were successfully prepared. Scanning electron microscopy (SEM) was employed to observe the surface appearance of the entry boards. The endothermic and lubricant effect of the resin applied on the CABs was characterized by differential scanning calorimetry (DSC) and polarizing microscope (POM). Moreover, the CABs' good drilling properties were tested when they were used for PCB drilling.FindingsFrom the result of SEM analysis, it was found that compared to the common aluminium foil, the surfaces of the CABs were smoother and flatter, which could improve the hole location accuracy and reduce the drill breakage. By means of the DSC and POM, the endothermic and lubricant effect of the CABs was proved. The crystalline substances (PEG and PEO) in coated resin could absorb the heat of the drill bit from heat generation and lubricate it through the phase transition of they own when a hole was being made, which could give high‐quality holes with good production efficiency. The drilling tests showed that due to the endothermic and lubricant resins, the CABs were superior to the common aluminium foil, not only in hole location accuracy, but also in hole wall quality and protection of a drill bit.Originality/valueThis paper has a remarkably high industrial practicality in the PCB manufacture process.

微小穴あけにおけるドリル振れの穴位置精度への影響

Micro drilling operation is always exposed the risk of breakage of micro drills. Therefore, it is considered that micro drills should be rotated as accurately as possible. In the other hand, reasonable tolerance of rotating accuracy, however, should be defined for economical and engineering reason. In this paper, contact behavior of a run-out rotating drill tip with a work face is discussed according to measurement of high frequency contact force using a dynamometer. As a result, transient dynamic contact force reveals a run-out rotating drill tip is wandering just after making a contact with a work face. Wandering time depends on sliding characteristics of interface between a drill tip and a work face. For instance, centering behavior is better in drilling non-ferrous metal, where it takes 2-3 revolutions (5-7.5ms) until a drill tip stops wandering. However, it takes several times longer for hard-to-machine metals, where a drill tip diverges in the worst case . Additionally, the bending stress of a drill increases steeply with the increase of hole depth. In deep drilling, therefore, run-out of a drill must be depressed the least one for preventing drill breakage.

On-Line Fuzzy Monitoring of Micro-Hole Drilling Based on Genetic Algorithm

In automated micro-hole drilling system, in order to improve the drilling performance and reduce of production costs by maximizing the use of drill life and preventing drill failures, the drill bit wear state monitoring is more important. However, drill bit wear is difficult to measure in drilling process. By observation, wear failure of the drill bit could cause related changes of the spindle current signal, so construct fuzzy control mathematical models with the relationship between drill bit wear and spindle current, genetic algorithm and fuzzy control theory are applied to micro-drilling system in this paper .The membership functions of fuzzy control model are optimized by genetic algorithms. Through calculation, we can get drill bit wear value which used as monitoring threshold value in micro-hole drilling on-line monitoring system to avoid the drill breakage and improve the monitoring reliability.

Tool Breakage Feature Extraction in PCB Micro-Hole Drilling Using Vibration Signals

Tool breakage monitoring is crucial to automation fabrication, especially for high-density hole machining, such as PCB (Printed Circuit Board). A tool breakage feature extraction method in PCB micro-hole drilling is presented in this paper. The vibration signal is analyzed by wavelet transform. The decomposed signals energy ratio at each frequency band is computed as monitoring features. The monitoring performance of different features selection is given. The vibration signals are observed to provide the capability in distinguishing micro drill breakage with proper features extraction and classifier design.

Time dependent buckling and critical speed in a twisted micro drilling process

The buckling and the critical speed of a micro drill in a drilling process were investigated in this study. The trend towards higher density printed circuit boards (PCB), requires smaller holes, down to 0.3 mm in diameter, to be drilled through the board. Due to the micro scale, the drilling fracture is frequently found in a micro drilling process. In all drilling fracture cases, fractures caused by buckling are most frequently found, because of the super high spinning speed and the micro scale. To improve the quality, produce a higher production rate and avoid the drill breakage, the buckling load and critical speed in the micro drilling process must be studied. A stepped pre-twisted beam is used to simulate the micro drill. A moving Winkler-Type elastic foundation is used to approximate the drilling process. A time dependent vibration model for drilling is presented. In an actual engineering application, the drill fracture is frequently found in a micro drilling process. In many cases, it would be caused by the time dependent buckling. The investigation on the buckling and critical speed properties in the micro drilling process to depress the time dependent buckling is presented in this work. The effects of rotating speed, pre-twisted angle and thrust force on the buckling and critical speed of the micro drill are considered. The numerical analysis indicates that the buckling load is reduced suddenly as the micro drill moves into a work piece.

Thrust and torque analyses for different strategies adapted in microdrilling of glass-fibre-reinforced plastic

Aerospace and automobile industries use components made of composites which require micromachining operations to be carried out. Microdrills are expensive and hence attempts are always made to reduce the drill breakage. In this paper, microdrilling of glass-fibre-reinforced plastic (GFRP) has been attempted using a carbide drill of 0.32 mm diameter. Apart from the selection of process parameters such as speed and feed rate, drilling strategy also plays an important role in realizing good-quality holes and improved drill life. Microdrilling experiments on GFRP have been carried out using a full-factorial design with five levels for speed and feed rate and three repetitions for each run. For the purposes of comparison, microdrilling of plain sheet made out of matrix material has also been carried out. The experiments on blind-hole drilling reveal that there is a reduction in maximum thrust force and torque in peck drilling. Encouraged by this, with peck cycle, through-hole drilling of 2.25 mm thick GFRP specimens has been carried out successfully. Regression models developed for the thrust force show good correlation between the measured and predicted values, while the torque values lie scattered with respect to the predicted trends. The results indicate that micro-holes of large aspect ratio could be produced by selecting proper process parameters and drilling strategy.

Research on Built-in Adaptive Drilling

For solving the problem of drill breakage and increasing productivity, a built-in adaptive drilling control scheme has been proposed. The torque of the spindle detected using a floating torque measuring mechanism has been regulated by controlling the feed rate of the spindle using PID control algorithm. The adaptive control algorithm has been integrated into a numerical controller. Motor control functions are performed in a timer interrupt subroutine to realize real-time parallel processing. An experimental system has been established. Experiments have demonstrated that the system is applicable in preventing drill breakage and increasing productivity.

Monitoring deep twist drilling for a rapid manufacturing of light high-strength parts

In this work the manufacturing of high strength and/or high functional components is presented, using a new technique based on considerably long twist drills, called Deep Twist Drilling (DTD). This technology opens a rapid and economical method to manufacture parts for structural applications. Components made with this technique can reach high mass reduction and better stress distribution in comparison with welding or bolted parts with the same weight. However the application of DTD must be optimized to improve the reliability of the process and to make it economically feasible. In order to reach it, previous optimization by process monitoring was performed in AISI 1045, stainless steels, Ti6Al4V and nodular cat iron GGG70(AISI A536, SAE-ASTM 100-70-03). These materials are commonly used for structural applications in several sectors. Monitoring opened the way to improve cutting conditions and allow the application of the DTD technique focusing on a new design concept. In the same way monitoring makes drilling process reliable enough to be systematically used in industrial applications by a controlled increase of the performance demanded from the tool. In this manner, not only the objective to produce high-strength and light pieces is achieved, but also a high repetitive process is reached. In this research work a case of study is presented. A monolithic satellite-type component, its mass were reduced from 25 to 4.5 kg. The structural behavior of the component was studied under FEM analysis and the results showed high strength to compression and shear forces. During the machining of this element there was a serious risk of drill breakage due to the depth of the holes and crossing points between them; however, the previous process optimization eliminated this drawback. As a matter of fact, this paper brings out a good example where manufacturing technology allows a better performance of mechanical components within the philosophy of “new processes drive to new products and better performances”.

Experimental study on drilling force in printed circuit board micro drilling process

PurposeThe purpose of this paper is to present a system for accurately measuring drilling force in the printed circuit board micro drilling process and to characterize the drilling force to provide a better understanding of the micro drilling process.Design/methodology/approachThe drilling force measurement system was established first. Then the drilling force in printed circuit board micro drilling process was characterized experimentally. In particular, the drilling forces in drilling halogen‐free and lead‐free assembly compatible printed circuit boards and the drilling force characteristics in ultra small hole drilling were investigated.FindingsA drilling force measurement system, with the key component of a KISTLER 9256C2 dynamometer, can accurately measure the drilling forces in the printed circuit board micro drilling process. The micro drilling process can be characterized by drilling force. Meanwhile, drilling force is very sensitive to drill breakage and drilling force can be utilized to detect drill breakage in the micro drilling process.Originality/valueThe paper presents a system for accurately measuring the drilling force. Drilling force provides fundamental information for the optimal design of micro drill bits. Drilling force can also characterize the micro drilling process, especially the ultra small hole micro drilling process.

Sequential Laser Mechanical Microdrilling of Inconel 718 Alloy

Mechanical microdrilling of nickel-based aerospace alloys suffers from premature drill breakage due to the fragile nature of the microdrill. Additionally, burr size reduction in both macro- and microscales has become one of the key problems in the drilling process. This paper presents a new method to microdrill Inconel 718 alloy using laser followed by mechanical drilling (sequential drilling). The aim of this research was to understand and evaluate the capability of using sequential laser mechanical drilling method as an effective and efficient method in drilling difficult-to-cut metals. Two new approaches were developed, namely, a two-step process of laser pilot drilling followed by twist drilling and a three-step process of laser pilot hole drilling followed by mechanical pilot drilling and then twist drilling. The holes produced by the new approaches were compared with those by mechanical microdrilling (pilot drilling and then twisting drilling). The results show that mechanical drilling eliminates the laser drilling defects. Furthermore, while large nonuniform burrs with attached cap were found in pure mechanical drilling, 75% reduction in burr size was achieved with the complimentary sequential drilling technology. Additionally, when compared with purely mechanical microdrilling, the new drilling method resulted in 240–430% tool life increase. Thus, the new drilling method presents an opportunity for industry to extend tool life and decrease burr.

Influence of machining parameters on microdrill performance

There is an increasing interest in microdrilling of metallic and other miniaturised components. Drill breakage is the most prevalent problem with microdrill that possesses high length-to-diameter ratio. In this paper, finite element modelling approach is used to determine the buckling load of a microdrill while drilling metallic components. The influence of variation in flute length, diameter, helix angle and lip angle on buckling load during machining of metallic components is studied. Empirical loading equation based on the material hardness, feed and diameter of the microdrill is also used to estimate the loading condition during microdrilling operation. Results are in agreement with the buckling loads predicted by proposed finite element model. In the present work emphasis is made on estimating the critical feed and the speed based on modal analysis while machining various materials. Tool failure can be avoided by maintaining the machining conditions within these critical operating parameters.

Development of a micro drill bit with a high aspect ratio

PurposeThe purpose of this paper is to present key points relating to the development of micro drill bits with high aspect ratios and to provide a solution for high aspect ratio hole drilling.Design/methodology/approachBased on the analysis of challenges in high aspect ratio hole drilling, key points for the development of micro drills bit with high aspect ratio are discussed. A design example of a micro drill bit with 0.3 mm diameter and a 7.2 mm flute length is presented. Experiments are conducted to verify the performance of the developed micro drill bit.FindingsHelix angle, web thickness and flute land ratio are three key parameters that significantly influence the behaviour of micro drill bits with high aspect ratios. Large helix angle, web thickness and flute land ratio are beneficial in terms of improving the performance of high aspect ratio micro drill bits. Step drilling is essential to prevent drill breakage and to ensure smooth debris evacuation. Meanwhile, proper steps and drilling parameters are of great importance to complete high aspect ratio hole drilling.Originality/valueThe paper highlights key points relating to the development of micro drill bits with high aspect ratios that can provide a satisfactory solution for high aspect ratio micro drill bit design.