Carbide Twist Drills Research Articles

SURFACE ROUGHNESS ANALYSIS IN DRILLING OF GFRP COMPOSITES BY TUNGSTEN CARBIDE TOOL

Nonlaminated composites having superior mechanical properties than laminated composites is widely used in ballistic applications. Since literature on the machinability of nonlaminated composites is scarce, an investigation was carried out to study the hole quality in drilling thick nonlaminated Glass Fiber Reinforced Plastic (GFRP) composite rods using coated tungsten carbide twist drill. The GFRP composite rods were made by pultrusion method with high fiber weight fraction. The surface roughness of the drilled holes was measured using surface roughness tester. Taguchi’s orthogonal array and analysis of variance (ANOVA) were employed to study the influence of process parameters such as feed and spindle speed on surface roughness. The optimum level of process parameters towards minimum surface roughness of the drilled hole walls was obtained to achieve defect controlled drilling of pultruded GFRP composite rods. Correlation for surface roughness with process parameters was established using a statistical software MINITAB 16. The influence of feed and speed on surface roughness was insignificant. The optimal process parameter levels within the range examined was identified as 0.15 mm/rev feed and 750 rpm speed for drilling pultruded GFRP composite rods using 10 mm diameter twist drill. The influence of process parameters on hole quality in nonlaminated composite rods differs with drill geometry and also differs from the influence of process parameters on hole quality in laminated composites.

Microstructure-based 3D Finite Element Model for Micro Drilling Carbon Steels

It is well recognized that microstructure controls the physical properties and thermo-mechanical behaviour of a material. The complexity of the microstructure often makes it very difficult to simulate the material behavior in cutting processes using analytical or numerical modeling techniques. This paper presents a three-dimensional finite element approach to incorporate microstructure into micro cutting simulation based on the concept of a representative volume element (RVE) and constitutive material modeling. For this purpose, the Lagrangian formulation proposed in the implicit FE code Deform 3DTM was applied. Micro drilling tests with solid carbide twist drills in different diameters (d = 100μm - 1mm) were performed on ferritic-pearlitic carbon steels C05, C45 and C75 for the verification of the developed 3D multiphase FE computation model. The microstructure-based 3D FE model was successfully validated regarding chip formation, feed force, and torque. A realistic prediction of size effects identified in micro drilling tests could also be obtained.

Study of the Damage of Drills in Dry Drilling of NM360 Steels

According to the characteristics of NM360, a contrast experiment for drilling performance in YG8 cemented carbide twist drill, high-speed steel twist drill and factories used in coating the ordinary high-speed steel twist drill has been done. Using microscope to observe the damage of drills, we found that form this experiment some causation in tool invalidation that tool breakage is main factor for the high-speed steel drill bits, brittle fracture is main factor for carbide drill bits. Brittle carbide cutting tools, feed speed too much impact load is too large, causing the blade fracture. As the tool edge wedge angle is too small, poor edge strength, easy chipping, edge wedge angle can not be too small.

Influence of Cutting Parameters on Torque in Drilling of Al-15%SiC-4% Graphite Metal Matrix Composites

Hybrid Metal Matrix composite consists of at least three constituents. Machining of metal matrix composite (MMC) is difficult due to the presence of hard abrasive particles. To make the composite prone to easy machining graphite is added. Machining is a material removal process and therefore is important for the final fabrication stage prior to application. This paper discusses the influence of cutting parameter on Torque in drilling of hybrid metal matrix composites. The experiments are conducted to study the effect of spindle speed and feed rate on torque using TiN coated solid carbide twist drill of 4mm, 8mm and 12mm under dry machining condition. The influence of parameters are discussed and studied in detail.

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.

Thermal Aspects in Deep Hole Drilling of Aluminium Cast Alloy Using Twist Drills and MQL

The deep hole drilling process with solid carbide twist drills is an efficient alternative to the classic single-lip deep hole drilling, due to the generally higher feed rates possible and the consequently higher productivity. Furthermore the minimum quantity lubrication (MQL) can be applied, in order to reduce the production costs and implement an environmentally friendly process. Because of the significantly reduced cooling performance when using MQL, a higher heat loading results for the tool and the workpiece. This paper presents the investigations of the temperature distribution in the workpiece and the heat balance of the deep hole drilling process.

A new 3D multiphase FE model for micro cutting ferritic–pearlitic carbon steels

A new three-dimensional multiphase finite element computation model is proposed for the simulation of micro drilling two-phase ferritic–pearlitic carbon steels in order to understand the cutting, ploughing, tribological and heat transfer mechanisms at the microscale. Based on the Split-Hopkinson-Pressure-Bar technique, a constitutive material law has been developed to model the thermo-mechanical material behaviour including the effect of the microstructure. Micro drilling tests using solid carbide twist drills with different diameters (d=50μm to 1mm) were performed on ferrite–pearlite two-phase steel AISI 1045 for the verification of the developed 3D FE computation model regarding chip formation, feed force, and torque.

Parameter-Design and Experimental Study on Small-Diameter Solid Carbide Deep-Hole Twist Drill

Base on the conventional twist drill, the new type of solid carbide twist drill which the length-to-diameter radio (L/D) is about 12 was developed with improved parameters of drill point and flute geometry. Study of intensity and rigidity of drill was performed by using analysis software ANSYS Workbench for the theoretical support and technical guidance for the design of twist drill. Tests were carried out to compare the new drills with the competitive drills in terms of tool life, chip breaking, and chip disposal. The results obtained from tests indicated that the new type twist drills have similar cutting capability compare to the competitor’s drills.

A study aimed at minimizing delamination during drilling of CFRP composites

The aim of this study is to present the methodology of Taguchi optimization technique for minimizing the delamination at the entrance of holes in high speed drilling of carbon fiber-reinforced plastics (CFRPs). The drilling process parameters evaluated are spindle speed, feed, and point angle. The experiments were performed as per Taguchi’s L27 orthogonal array using cemented carbide (K20) twist drills. The defects observed at the entrance of drilled holes of CFRP plates were measured and the delamination factor was computed for each trial of the orthogonal array. The analysis of means (ANOM) and analysis of variance (ANOVA) were employed to determine the optimal process parameter levels and to analyze the effect of parameters on delamination factor. The confirmation tests with the optimal levels of parameters were carried out to illustrate the effectiveness of Taguchi design. The optimization results indicate that point angle is the most significant factor followed by feed and spindle speed. The results also highlight the importance of employing the higher speeds to minimize the delamination defects.

Experimental characterization of micro-drilling process using nanofluid minimum quantity lubrication

This paper discusses the experimental characterization of the micro-drilling process with the nanofluid minimum quantity lubrication (MQL). The miniaturized drilling machine tool system is developed, and then a series of micro-drilling experiments are conducted in the cases of compressed air lubrication, pure MQL and nanofluid MQL. For the nanofluid MQL, nano-diamond particles having the diameter of 30 nm are used with the base fluids of paraffin and vegetable oils. For the micro-drilling process, an uncoated carbide twist drill having the diameter of 200 μm is used for making holes in the aluminum 6061 workpiece. The experimental results show that the nanofluid MQL significantly increases the number of drilled holes and reduces the drilling torques and thrust forces. In addition, the nanofluid MQL effectively eliminates remaining chips and burrs to enhance the quality of drilled holes.

A study of drilling uni-directional carbon/epoxy composites

A study of drilling uni-directional carbon/epoxy (C/E) composite, a difficult-to-machine material, has been carried out to reveal the formation mechanism of drilling-induced surface damages. A theoretical analysis is reported, which shows that the drilling damages mostly occur in the areas where the fibre orientation angle is in the range of 0°–90°, especially in the vicinity of 6°. To minimise the damages, drilling tools with electroplated diamond abrasives are used to drill the C/E composite. Experimental results with these drills show that the thrust force decreased by 30%–50% while drilling damages at the exit side are also significantly reduced when comparing to drilling with traditional carbide twist drills.

Drilling Force and Temperature of Bone by Surgical Drill

Drilling force and temperature of tibia at the high speed drilling for improving the design of surgical drills are very important. In this paper we describe experiments using pig tibia bones, measuring the drilling force and temperature of a new design of drill bit and compare the results against a twist drill. The result shows that the drilling force and temperature are affected by the feed rate and drilling speed, which vary with the drilling depth into the bone. The new surgical drill with three top cutting edges can achieve lower temperature below 47oC and lower drilling force than with the stainless steel twist drill and carbide twist drill.

Drilling Force of SiC Particle Reinforced Aluminum-Matrix Composites with Ultrasonic Vibration

In recent years, particle reinforced metal matrix composites (PRMMCs）has been widely applied because of its excellent mechanical performances. But the machining is very difficult due to the rigidity of reinforced phase in it, thus the popularization of PRMMCs is restricted much. Here, a method of ultrasonic vibration drilling is presented to the hole-making of Aluminum-matrix composites based on cutting force analysis between common and vibration machining. In virtue of the self-developed ultrasonic drilling equipment, experiments of common and ultrasonic vibration drilling are performed on SiC particle reinforced Aluminum-matrix composites with different content of SiC by using two types of tungsten carbide twist drill. Since the tool life can be represented directly by drilling force, especially the torque, the study of drilling force is very important for the surface roughness, the design and life of drill. Drilling force and its variation in the machining process are analyzed by comparison of common and vibration drilling. It shows that the eviction of drilling chips can be meliorated to some extent, and the drilling torque can be reduced about 30% during the ultrasonic vibration drilling process.

Delamination analysis in high speed drilling of carbon fiber reinforced plastics (CFRP) using artificial neural network model

The carbon fiber reinforced plastics (CFRP) are highly promising materials for the applications in aeronautical and aerospace industries. The delamination is a major problem associated with the drilling fiber reinforced composite materials, which reduce the structural integrity of the material. The present work focuses on the analysis of delamination behavior as a function of drilling process parameters at the entrance of the CFRP plates. The delamination analysis in high speed drilling is performed by developing an artificial neural network (ANN) model with spindle speed, feed rate and point angle as the affecting parameters. A multilayer feed forward ANN architecture, trained using error-back propagation training algorithm (EBPTA) is employed for this purpose. Drilling experiments are conducted as per full factorial design using cemented carbide (grade K20) twist drills that serve as input–output patterns for ANN training. The ANN model so developed is validated by presenting training and new testing input patterns. The validated ANN model is then used to generate the direct and interaction effect plots to analyze the delamination behavior. The simulation results illustrate the effectiveness of the ANN models to analyze the effects of drilling process parameters on delamination factor. The analysis also demonstrates the advantage of employing higher speed in controlling the delamination during drilling.

Cutting edge preparation to improve drilling tools for HPC processes

High material removal rate, high cutting parameters and, hence, high resultant forces are characteristics of high performance cutting. Due to these greater requirements on cutting tool material with respect to its strength and wear resistance, as well as the applied coating, the cutting edge design also gains in importance. By cutting edge preparation, the process reliability can be enhanced through a reduced chipping and a defined rounding along the cutting edge. In this research, the abrasive water jet blasting process was used to prepare different cutting edge designs of carbide twist drills prior to coating. Based on the results of drilling tests using high performance cutting conditions, it was determined that the high performance process can be effectively optimized with respect to workpiece quality and tool life by selectively varying the microscopic cutting edge form.

Machining characteristic study of friction drilling on AISI 304 stainless steel

A no-chip drilling process was formed by thermal friction principle in which it had the most important features such as no pollution, short machining time, and long tool life. After the friction drilling operation had been conducted, a thin plate (workpiece) was formed into a bush with a thickness of 3 times larger than that of the workpiece. The bush can provide a longer area of contact which can fit a shaft firmly. The bush can also be taped to create an internal screw without welding a nut. The main purpose of this study was to develop a new type of thermal friction drill with a sintered carbide in which it can be grinded and processed to the necessary geometric shape. It then can be applied to drill the Austenite stainless steel (AISI 304). The Taguchi method was applied to explore how the different parameters such as drill shape and friction angle, friction contact area ratio, feed rate, and drilling speed would affect the response parameter. The optimal drilling condition was A 1 (friction angle = 30°), B 1 (friction contact area ratio = 50%), C 2 (feed rate = 100 mm/min), D 3 (drilling speed = 90 m/min) and then four drilling confirmatory runs were conducted to obtain an average surface roughness Ra = 0.96 μm. This Ra value is the smallest one compared with all the Ra values from L 18 arrays. Therefore, the confirmatory experimental runs were verified. After the optimal drilling parameters of friction drilling were obtained, the optimal geometric shape and friction contact area ratio of the friction drill was selected to conduct experiments. The performance of the friction drill was compared with the Tungsten carbide (WC) twist drill. The results showed WC twist drill damaged seriously after three drilling runs. However, the friction drill can normally process the AISI 304 material after 60 runs and only showed little wear of the drill. Therefore, the friction drill has a better performance than WC twist drill. A good quality hole surface which is like a mirror could be obtained.

Analysis of parametric influence on delamination in high-speed drilling of carbon fiber reinforced plastic composites

In this paper, the effects of process parameters on delamination during high-speed drilling of carbon fiber reinforced plastic (CFRP) composite are presented. The damage caused at the entrance of the drilled hole is characterized by delamination factor, which is evaluated by considering cutting speed, feed rate and point angle as affecting process parameters. The drilling experiments using cemented carbide (K20) twist drills were performed based on full factorial design of experiments with three levels defined for each of the process parameters. The computed values of delamination factor are empirically related to process parameters by developing a second order non-linear regression model based on response surface methodology (RSM). The effects of cutting speed, feed rate and point angle on delamination factor were analyzed using the models by generating response surface plots. The investigations reveal that the delamination tendency decrease with increase in cutting speed. The study also suggests low values of feed rate and point angle combination for reducing the damage. The details of model development and model adequacy test by analysis of variance (ANOVA) are presented in this paper.

Tool length influence on wear behaviour of twisted carbide drills

The drilling of holes with an l/d-ratio greater than 12 is responsible for a significant amount of the overall production time and therefore has a high impact on the productivity. In the past gun drills were used for those higher l/d-ratios, providing good surface qualities and straight holes. However the productivity of gun drills compared to solid carbide twist drills is very low, due to the limited feed rate. With the use of solid carbide twist drills with l/d-ratios up to 40 and overall lengths up to 350 mm production time can be reduced extensively. Solid carbide twist drills can furthermore be used on standard machine tools. Former drilling tests show that the tool life of these drilling tools decreases abundantly clear with an increasing tool length. This paper presents the influence of the drill length and the dynamic behaviour of the drilling process on the wear behaviour of the drilling tool.

Wear of Twist Drills in ZrO<sub>2</sub>/CePO<sub>4</sub> Composite Machining

Machinable ZrO2/CePO4 composite was fabricated. ZrO2/CePO4 and mild steel materials were machined with tungsten-cobalt carbide twist drills. The material removal characteristic was analyzed by consideration of tool wear in different stock removals. Wear of twist drills was observed with SEM. Wear widths on major flank were measured with microscope. The experimental results show when ZrO2/CePO4 was drilled, wear widths on flank were much bigger comparing to mild steel drilling processes. The wear of twist drills occurred on major flank, minor flank and on chisel edge. Wear on minor flank is a unique characteristic in drilling of ZrO2/CePO4 ceramics. There exist obvious scratch remarks on tool wear. The tool wear results from abrasive wear, adhesive wear and oxidation wear.

Effects of MQL on Drilling (1st Report)

The paper deals with the effects of an MQL (Minimum Quantity of Liburication) process on drilling of 0.5% carbon steel. In drilling, discharge of chips from a hole drilled, tool wear, accuracy and surface roughness of the hole are the biggest problems, especially in deep drilling. MQL process gives fairly good results about these problems if suitable cutting conditions are selected. However the mechanisms have not been clarified yet. In this study, drilling tests with different lubrications, i.e. dry, MQL and wet, were carried out on the steel using solid carbide twist drills having two through holes. Tool life, cutting forces, profile and surface roughness of inside wall of drilled hole, enlargement and cylindricity of drilled holes were examined. Results obtained were as follows. (a) The longest tool life and the best quality of the drilled hole were obtained in MQL process. (b) Diameters of drilled holes in MQL process were larger than those in other process, while cylindricity of the hole in MQL process is better than that in other process. (c) The maximum torque in MQL process is smaller than that in other process.