Drill Point Geometry Research Articles

Analysis of drilling behavior of flax/PP composites

ABSTRACT The current research investigation aims to use and compare three different population-based optimization approaches to optimize the operating factors of drilling process to reduce thrust force (TF) and subsequently delamination in flax/PP laminates. Five different tool point geometries and three levels of spindle speed (SS) and feed rate (FR) were considered. Analysis of variance indicated that drill point geometry was most significant parameter affecting the TF, whereas SS had the most negligible impact. Moreover, the lowest and maximum TF and delamination factor (DF) were recorded for the U-shape drill bit and 135°- point angle twist drill bit, respectively. The outcome of the experimental investigation revealed that a low FR value (0.05 mm/rev) and medium-range SS value (1500–1800 RPM) were optimum parameters for each drill geometry. Although all optimization techniques provided almost the same optimum values, but TLBO (teaching learning-based optimization) technique’s convergence rate was fast compared to others.

An applied explicit mathematical model of conical drill point geometry without flank rubbing

Conical point drills are often used for making holes. In drill design, three drill point parameters, namely, drill point angle (or semi-point angle), chisel edge angle, and lip clearance angle, are specified. Geometrically, the conical point geometry is generated by two symmetric and oblique cones intersecting at the end of drill land. Thus, the drill point has to be designed in detail, which is to calculate the cone location and orientation parameters so that the drill point parameter values are equal to the specifications. Unfortunately, the previously proposed methods of drill point detailed design cannot be implemented in cutting tools companies, because one set of drill point parameter specifications can correspond to many sets of cone parameters which determine different drill point shapes. Moreover, the heel clearance flanks of some drills could rub stock material at the hole bottom while drilling, resulting in a large amount of force and heat, tool breakage, and severe wear. Drills with flank rubbing are invalid. However, the previous researches and applied industrial software cannot eliminate flank rubbing. To address the above problems, a practical and explicit mathematical model of conical drill point geometry without flank rubbing is established in this work. This work derives close-formed equations of the cone parameters and establishes a new criterion of flank rubbing detection. It can efficiently and consistently compute the cone parameters and detect flank rubbing for a valid drill point design. This explicit mathematical model is verified, and an approach to conical point detailed design is applied on two twist drills in the authors’ company. The differences between the drill point parameter values in the ground drill and the drill design parameter specifications are within an acceptable tolerance. Thus, the proposed method can be directly used in drill design and manufacturing in the tooling industry.

Micro-drilling of AISI 1045 steel using a centering micro-drill

Micro-hole drilling is experiencing a very rapid growth in precision production industries. The micro-drills play a critical role in manufacturing industry. There are many factors which influence the micro-drill performance including the drill point geometry, the drill material, and the workpiece material, among which the most fundamental factor is the drill point geometry. In this paper, a new micro-drill point geometry, termed the centering micro-drill point, is developed. A mathematical model for this new micro-drill point has been established. Micro-drilling tests in AISI 1045 steel are performed with different cutting conditions. By contrasting centering micro-drill and planar drill point micro-drill, the cutting performance of the centering micro-drill has been investigated. The results showed that, when the cutting speed is 35 m/min and the feed rate is 44 mm/min, the thrust force of the centering micro-drill reduces by 21.7% than that of planar micro-drill and the drilling hole amounts increase by 13.5%. The roundness of the thirtieth hole drilled by centering micro-drill is 1.02, and it is 1.08 by planar micro-drill; the centering micro-drill has better position accuracy than planar micro-drill, and further gets good size and shape accuracy.

Multi-objective Optimization in Drilling Kevlar Fiber Reinforced Polymer Using Grey Fuzzy Analysis and Backpropagation Neural Network–Genetic Algorithm (BPNN–GA) Approaches

An integrated approach has been applied to predict and optimize multi-performance characteristics, such as optimum thrust force (Fz), torque (Mz), hole surface roughness (Ra), delamination (D) and hole roundness (R), in drilling process of Kevlar fiber reinforced polymer. The experiments were performed by varying drill point geometry and drilling process parameters, i.e., drill point angle, feed rate, and spindle speed. The quality characteristics Fz, Mz, Ra, D, and R were the smaller the better. Taguchi orthogonal array (OA) L18 was used as the design of experiments. Grey fuzzy analysis was first applied to obtain a rough estimation of the optimum drill point geometry and drilling process parameters. Backpropagation neural network (BPNN) model was developed and utilized to predict the optimum Fz, Mz, Ra, D, and R. Genetic algorithm (GA) was performed to search for global optimum of drilling process parameters combinations. The analysis of the effect of drill point angle, as well as drilling process parameters, on the individual performance characteristics was conducted by examining both the percentage contribution of drill point geometry and drilling process parameters on the total variance of three responses individually, and the response graphs. The results of the confirmation experiment showed that the BPNN based GA optimization method could accurately predict and also significantly improve the multiple performance characteristics.

The influence of drill point geometry on tool life

Drilling is a cutting process that uses a rotary cutting tool to cut a cylindrical hole in a solid material. During machining, drill bits are exposed to rapid wear at high temperature. Sometimes, due to an ecological need for dry technology without any lubricant, the use of drill bits with coatings is required, typically titanium nitride (TiN), titanium carbon nitride (TiCN) or titanium aluminium nitride (TiAlN). This paper presents research on drilling done to determine how drill point geometry affects the drill lifetime and finished surface quality. We compared the chip removal ability and surface quality of bored holes in Hardox 500 created with high-speed steel drill bits and drill bits manufactured from hard metals, with and without coatings, under constant processing parameters. A cost/efficiency comparison was also carried out with respect to drill bit fabrication, sharpening, and use. Based on the data obtained on the damage drill points, the most economical drill bit for processing holes was determined.

Effects of process parameters and drill point geometry in deep drilling of SAE 4144M under MQL

Deep drilling is a difficult machining operation, it often presents problems related to chip evacuation and efficiently cooling and lubrication of the cutting zone. Minimum quantity of lubrication (MQL) is an ecological alternative to wet machining. It provides better lubrication, however, it has low cooling effect and the chips are not removed away from the cutting zone by coolant. In this paper a combination of cutting speed, feed-rate and tool geometry is determined to produce smaller chips and lower workpiece temperature for deep drilling of SAE 4144 M steel under MQL lubrication condition. Full factorial design of experiment was used to plan the set of the experiments. Tool wear behavior and cross sections of the drilled holes were compared to a pressurized oil condition. Split point geometry, lower cutting speed and higher feed-rate resulted in the best chip shape and relatively low workpiece temperature in deep drilling of SAE 4144 M with MQL. The worn drill presented microchipping, adhered workpiece material on the rake face and exposed substrate resulted from abrasion of TiNAl coating. MQL resulted in longer tool life and more surface defects compared with the pressurized oil condition.

EFFECT OF DRILLING PARAMETERS ON THRUST FORCE AND TORQUE DURING DRILLING OF ALUMINIUM 6061 ALLOY - BASED ON TAGUCHI DESIGN OF EXPERIMENTS

Hole generating process with drill bit called as drilling, which is very important because large portion of overall machining of any component in production industry needs assemble of parts to make a final shape with rivets and fasteners. It is well known that the drill point geometry has a significant effect on thrust force exerted by a drill bit while drilling. In this study, experimentally investigate the influence of drilling parameters such as pointangle, clearance angle, cutting speed, feed rate and drill diameter on the thrust force and torque in drilling. Drilling experiments have been conducted over a wide a range of machining conditions such as cutting speed varied in the range 500 rpm to 1000 rpm in 3steps, feed rate varied from 0.3 to 0.6mm /min in three steps using two flutesuncoated conventional twist drills of three different diameters (8, 10 and 12mm) with 1180 point and 450 helix angles. Drill bits tool geometry altered by tool&cutter grinder and obtained 1100, 1000 point angles also clearance angles varied by 40, 60 and 80. Holes are performed on Aluminium 6061 alloy material of rectangular cross section having dimensions 300mmx50mmx10mm as per taguchi technique. A kistler (type 9272), four components drill tool dynamometer was used to measure thrust force (Th) and torque (M) exerted by the drill bit during hole making on a work material further the signal was processed to a computer by a multichannel signal amplifier (Kistler 5070 type) was used to record the thrust force and torque. Finally, ANOVA test have been carried out to confirm thesignificance of factors considered during drilling and compare the predicted values with the experimental values on influence of factors on responses.

Effect of modified drill point geometry on drilling quality characteristics of metal matrix composite (MMCs)

The abrasive reinforcement present in ‘Metal matrix composites’ (MMCs) is responsible for numerous machining challenges for the research fraternity. The increase in tool wear, burr formation, surface roughness, and increase in cutting forces are few of such machining challenges during the drilling of MMCs. The present research investigation explores the effect of change in drill point geometry on the drilling Quality characteristics (QCs) of the drilled hole wall. The drilling QCs under investigation are, Specific cutting pressure (SCP) and Surface roughness (SR) of the drilled hole wall. The levels of the input process parameters for optimum values of the output responses were established by Taguchi’s methodology. SEM images and contour plots of drilled hole wall have been used to qualitatively explain the drilling behavior of MMCs. The chip formation mechanism observed during drilling establishes the cutting behavior of the different cutting edges of the modified drill point geometry. It has been observed that the single conical chips were produced by primary cutting edge and single ring type chips were produced by secondary cutting edge. The step diameter is the main factor which influences the SCP followed by the feed and point angle. The surface roughness of the drilled hole wall has been governed by the cutting speed, feed and step diameter. Burnishing and honing effect were observed on the drilled hole wall surface because of entrapped free SiC particles using SEM.

Study the drilling behaviour of aluminium 6061 metal matrix composites using Taguchi's methodology

Drilling of holes in MMCs with conventional tool lead to a novel set of challenges for researchers. The abrasive nature of the reinforcement causes high tool wear rate, increase in cutting forces and surface roughness of the drilled hole wall. The various machine tool parameters and cutting tool parameters (tool material, point angle, drill point geometry, etc.) have been investigated to obtain an optimum combination of parameters for optimised output quality characteristics.

Prediction of forces during drilling of composite laminates using artificial neural network: A new approach

Drilling of fiber-reinforced plastics (FRP's) is an inevitable machining operation, because it facilitates assembly of several components by means of mechanical fastening. But, drilling of FRP leads to delamination which results in reduced life and efficiency of the FRP part. The delamination that induced during drilling is directly affected by the thrust force and torque. In the present research endeavour, four different types of drill point geometries have been used for making of holes in two different types of composite laminates. The drilling of composite laminate has been conducted at three different levels of spindle speed and feed rate. A new artificial neural network (ANN) approach has been proposed to predict the drilling-induced thrust force and torque. The values of thrust force and torque predicted by the proposed ANN models are in close agreement with the experimental values.

A study about hole making in woven jute fabric-reinforced polymer composites

The time has come for natural fibres to stand as potent substitutes for synthetic fibres in various industrial applications. Recently, jute fibre is being used as reinforcement material in the development of reinforced plastics for various engineering products. The production cycle of a composite product often necessitates certain degree of machining operations. Drilling is one of the most widely practised machining operation for making holes in composite laminates. Hole making is imperative to ascertain the assembly of intricate composite products. The literature available indicate that not much research work has been reported on the machining behaviour of jute fibre-reinforced polypropylene composites. Hence, in the present experimental endeavour, drilling of woven jute fabric-reinforced polypropylene composite has been performed. The effect of operating variables on thrust force and torque signals was investigated. Drilling-induced damage in the developed composite was quantified using stereo microscope. The experimental values indicate close relationship between the tool geometries and the delamination factor. SEM analysis was also conducted to understand the drilling behaviour and surface morphology of the drilled holes. Among the solid drills compared, parabolic drill reveals better cutting behaviour in terms of lower drilling forces and better quality of holes. This may be attributed to the better tool-work piece interaction in case of parabolic drill point geometry.

A novel intelligent software-based approach to predict forces and delamination during drilling of fiber-reinforced plastics

Drilling of fiber-reinforced plastics (FRPs) results in drilling-induced damage which leads to reduced part life and extensive part rejection. Thus far, there exists no standard handbook or knowledge-based tool that can predict drilling-induced forces and damage. Therefore, the present research initiative is an attempt to develop a software tool based on artificial intelligence which can predict drilling-induced thrust force, torque and delamination factor during drilling of FRPs. The developed intelligent software has a friendly graphic user interface (GUI). The user just interacts through the GUI and fills the input choices, and upon execution, the software predicts the drilling forces and delamination factor. In order to generate the database for the software, drilling experiments have been performed in two different types of composite materials with four different types of drill point geometries of two distinct diameters. The drilling of composite laminate has been conducted at three different levels of spindle speed and feed rate. The software results are based on three different artificial intelligence techniques namely artificial neural network (ANN), fuzzy logic (FL) and adaptive neuro-fuzzy inference system (ANFIS). The values of thrust force, torque and delamination factor for given inputs predicted by the developed tool are in close agreement with the experimental values.

Effect of drill point geometry on quality characteristics and multiple performance optimization in drilling of nonlaminated composites

Extensive work has been carried out in the drillability study of thin laminated composites, which are utilized in the light engineering work. Heavy engineering works like construction of bridges, prefabricated platforms, and ballistic applications utilizes thick nonlaminated composites because of its enhanced mechanical properties. Since there is no sufficient literature on the drillability study of thick nonlaminated composites, an experimental investigation has been carried out to study the effect of process parameters on quality characteristics for standard and special geometry design of a drill body. The drilling experiments using carbide drills were conducted using response surface methodology. Special geometry (ratio) drill performs better than the standard geometry (twist) drill. The optimal process parameter levels for twist drill were determined as feed of 0.052 mm/rev and spindle speed of 1059 r/min and that for ratio drill as feed of 0.05 mm/rev and spindle speed of 750 r/min.

Mechanistic modeling of bone-drilling process with experimental validation

In this paper, an improved mechanistic model is developed to predict the thrust force and torque for bone-drilling operation. The cutting action at the drill point is divided into three regions: the cutting lips, outer portion of the chisel edge (the secondary cutting edges), and inner portion of the chisel edge (the indentation zone). Models that account for the unique mechanics of the cutting process for each of the three regions are formulated. The models are calibrated to bovine cortical bone material using specific cutting pressure equations with modification to take advantage of the characteristics of the drill point geometry. The models are validated for the cutting lips, the chisel edge, and entire drill point for a wide range of spindle speed and feed rate. The predicted results agree well with experimental results. Only the predictions for the drilling torque on the chisel edge are lower than the experimental results under some drilling conditions. The model can assist in the selection of favorable drilling conditions and drill-bit geometries for bone-drilling operations.

Drilling behavior of sisal fiber-reinforced polypropylene composite laminates

Recently, natural fiber-reinforced composites are becoming a viable alternative to synthetic fiber composites in many applications. Secondary processing in terms of hole making in composites is an almost unavoidable operation for facilitating the assembly operations. In the present experimental investigation, the drilling process of natural fiber-reinforced thermoplastic bio-composites has been evaluated in terms of the drilling forces. The cutting speed, feed rate and the drill point geometry have been taken as the input process parameters. Two types of drill geometries (solid and hollow in shape) have been used for drilling in the present work. The cutting mechanism of solid and hollow drill point geometry are substantially different which consequently affects the drilling forces and drilling-induced damage.

Wavelet-based acoustic emission characterization of residual strength of drilled composite materials

Drilling composite materials is one of the secondary processes of manufacturing industrial structures. However, drilling composite materials presents a number of problems such as degradation of mechanical behavior. In this study, effects of spindle speed, feed rate, and drill point geometry on residual tensile strength are studied. Acoustic emission technique with a wavelet-based signal processing method is developed to monitor the residual tensile strength of drilled laminates. Cumulative count, amplitude, and energy are used as time-domain parameters to characterize the process. According to wavelet analysis, frequency distribution and energy percentage of each damage mechanism (matrix cracking, fiber breakage, and fiber slipping) during tensile test are determined.

Effects of geometric structure of twist drill bits and cutting condition on tool life in drilling 42CrMo ultrahigh-strength steel

To investigate the influence of the geometric structure of coated cemented carbide twist drills on the drill tool life, drilling experiments of 42CrMo steel were carried out at various cutting parameters. The geometric structure parameters of the specially manufactured drill bits were designed by the multifactor orthogonal experiment method. The effects of cutting edge preparation, drill point geometry, and flute geometry on the tool wear were investigated by the range analysis and variance analysis. And their effects on chip pattern were also studied. Then the influence of cutting parameters on the tool life was investigated. Based on these investigations and extending the tool life, the optimized geometric structure was the honed cutting edge with a radius of 0.06 mm and conventional conical flank, and the corresponding cutting parameters were 80 m/min and 0.18 mm/rev. At last, the tool wear characteristics were discussed and the main wear mechanisms were abrasive wear, adhesive wear, coating exfoliation, and tipping.

Drilling of composite laminates with solid and hollow drill point geometries

Drilling is one of the most important method for hole making in composite materials. Drilling of polymer matrix composites causes substantial damage around the drilled hole. Damage free holes can be made using modified drill geometry. The present research investigation focuses on the drill geometry as candidate parameter that influence drilling forces and drilling-induced damage. The four different drill geometries (solid and hollow in shape) are used for drilling in composite materials. The cutting mechanism of these drill geometries is substantially different, and therefore influences the drilling-induced damage. The experimental results suggest a strong relationship between the drill point geometry and the drilling-induced damage.

Optimization of the Process Parameters for Drilling of Metal Matrix Composites (MMC) Using Taguchi Analysis

Drilling of MMCs is considerably difficult due to the presence of extremely hard reinforcement which causes rapid tool wear and influences the cutting forces and quality characteristics. The present investigation aims at studying the effect of drilling parameters (cutting speed, feed rate and the drill point geometry) on the output responses such as, thrust force (TF), specific cutting pressure (SCP) and surface roughness (SR). Taguchi’s technique has been applied to obtain an optimal setting for drilling process parameters for optimizing the output quality characteristics.

Compressive Behavior of Glass Fiber Reinforced Plastic Laminates with Drilled Hole

The polymer matrix composites (PMCs) are increasingly being used in structural applications owing to their superior mechanical properties. The in-service performance of composite materials requires them to perform under a variety of loading environments. Although a lot of research work has been done towards the mechanical characterization of PMCs, a lot remains to be done in special cases such as characterization of glass fiber reinforced plastics (GFRP) laminates with drilled hole. It is an established fact that drilling in composite laminates causes damage around the drilled hole and the damage influences the mechanical behavior of GFRP laminates under different loading conditions. The present investigation aims at studying the compressive behavior of GFRP laminates with drilled holes. The holes have been drilled at various input parameters (cutting speed, feed rate and drill point geometry) and the effect of these parameters on the compressive behavior of the GFRP laminates has been investigated using statistically designed experiments. It has been found that the drilling parameters significantly affect the compressive behaviour of laminates with drilled holes.