Carbide Drills Research Articles

Tool wear monitoring in drilling of high-strength compacted graphite cast irons

Machining is such a complex system that any foreseen result is practically impossible. However, research always helps to further understand the process, which contributes to providing positive results. Tool wear is always difficult to foresee, but it can be measured and related to several output parameters. In each individual application, there will be the best parameter that most reliably represents the tool wear. In the present investigation, the hole quality parameters (roughness and cylindricity), power consumption, electrical consumption of the machine tool and the acoustic emission signals were recorded and correlated to the tool condition in order to find the best output parameter for tool wear monitoring during the drilling of compact graphite cast irons. Two high-strength grades of compacted graphite cast irons (both CGI 500 with changes in the matrix and graphitic structure) were machined and compared to the standard grade (CGI 450) usually used in the manufacturing of engines using TiAlN-coated carbide drills at a constant cutting condition. The results showed that the best output parameter to monitor the tool wear was the electric current signal.

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

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

Analytical and experimental investigation of the parameters in drilling flax/poly(lactic acid) bio-composite laminates

Understanding the influences of drilling parameters on machinability characteristics of NFRCs is of value to both academia and manufacturing industries. The present work investigates drilling-induced delamination and hole quality of fully biodegradable flax/poly(lactic acid) composites in response to cutting speed, feed rate, drill diameter, and drill material. Among various types of drilling-induced damages, exit-ply delamination is found to be the most destructive damage and cutting thrust force is identified as the main reason. The experimental results revealed that thrust force is highly dependent on drilling parameters where feed rate and drill material were found to be the most influential parameter on it. The choice of drill bit in terms of diameter and material has a considerable effect on the machinability. Drilling with HSS drills resulted in nearly 60% lower thrust force and better hole quality compared to that with carbide drills. While the size of delamination damage in the samples drilled at the lowest feed (0.02 mm/rev) sounds to be unrelated to cutting forces, the overall trend confirms that decreasing the value of thrust force leads to lowering delamination damages. Hence, an effective strategy in avoiding such undesirable defects is calculating the critical thrust force below which delamination is negligible. An analytical model is developed based on the theory of virtual work to determine the critical thrust force at delamination onset. Through validating with experimental data, the proposed model agrees better with a more accurate prediction than existing models.

Sustainable drilling performance optimization for Nano SiC reinforced Al matrix composites

ABSTRACT Metal Matrix Composites (MMC) reinforced by nanoparticles are competent materials, appropriate for functional and structural applications. Green manufacturing is a style for mechanized that minimizes dissipate and contamination. The pollution prevention resolves in manufacturing industries to expand and execute various environmentally-friendly strategies. The primary purpose of green machining is to hold up future generations by attaining process sustainability. In the present investigation, cryogenic machining (CM) of Nanoscaled SiC reinforced Aluminum (Al) matrix composites gives experimental outcomes and also the correlation of its performance with dry machining (DM) and Minimum Quantity Lubrication (MQL). The drilling tests are organized using a vertical machining center (VMC), which is directed by computer numeric control (CNC) employing carbide drills of 10 mm dia with cutting point angles of 90, 118, and 135 degrees. Experiments have planned as per the response surface methodology (RSM) based on Box-Behnken design (BBD). Teaching–Learning-Based Optimization (TLBO) is implemented to optimize the drilling criteria such as the speed of the spindle, feed rate, weight % of nano SiC, and cutting angle. Subsequently, Scanning Electron Microscope (SEM) is utilized to inspect the subsurface of the machined specimen.

Micro-drilling of straight and inclined holes on thermal barrier coated Inconel 718 for turbine blade cooling

ABSTRACT Thermal barrier coatings (TBC) are widely used on turbine blades working at high-temperature condition. Drilling different angled cooling holes on these blades is essential to minimize the severe heat load experienced and to improve their service life. In this study, mechanical micro-drilling is proposed to check the feasibility of the process and study the basic characteristics of thrust signal. The drilling experiments were performed on TBC Inconel 718 to drill micro-holes at different inclinations using 600-μm TiAlN-coated carbide drill under dry environment. Drilling performance is assessed in terms of the number of holes produced before drill breakage, drilling thrust, fluctuation of thrust signal, and tool wear. The longest tool life was observed while drilling at the combination of lower spindle speed and drill feed for both straight and inclined holes. However, the life of drill while drilling inclined holes was found to be lesser than that of the straight holes and spindle speed is found to be a statistically significant parameter affecting the drilling thrust. Two different drill wear mechanisms, namely, abrasion and adhesion were observed during drilling. Finally, during the drill failure phase, a large fluctuation in thrust signal was observed followed by the drill breakage.

Measurement of bit-rock interface temperature and wear rate of the tungsten carbide drill bit during rotary drilling

Rock drilling is an essential operation in mining industries. Temperature at the bit-rock interface plays a major role in the wear rate of the drill bit. This paper primarily focuses on the wear rate of tungsten carbide (WC) drill bit and the interrelationship between temperature and wear rate during rotary drilling operations conducted using a computer numerical control (CNC) machine. The interrelationship between the temperature and wear rate was studied with regard to three types of rock samples, i.e., fine-grained sandstone (FG) of uniaxial compressive strength (UCS) that is 17.83 MPa, medium-grained sandstone (MG) of UCS that is 13.70 MPa, and fine-grained sandstone pink (FGP) of UCS that is 51.67 MPa. Wear rate of the drill bit has been measured using controlled parameters, i.e., drill bit diameter (6, 8, 10, 12, and 16 mm), spindle speed (250, 300, 350, 400, and 450 rpm), and penetration rate (2, 4, 6, 8, and 10 mm/min), respectively. Further, a fully instrumented laboratory drilling set-up was utilized. The weight of each bit was measured after the bit reached 30 mm depth in each type of the rock sample. Furthermore, effects of the bit-rock interface temperature and operational parameters on wear rate of the drill bits were examined. The results show that the wear rate of drill bits increased with an increase in temperature for all the bit-rock combinations considered. This is due to the silica content of the rock sample, which leads to an increase in the frictional heat between the bit-rock interfaces. However, in case of medium-grained sandstone, the weight percentage (wt%) of SiO2 is around 7.23 wt%, which presents a very low wear rate coefficient of 6.33×10−2 mg/(N·m). Moreover, the temperature rise during drilling is also minimum, i.e., around 74 °C, in comparison to that of fine-grained sandstone and fine-grained sandstone pink. In addition, this paper develops the relationship between temperature and wear rate characteristics by employing simple linear regression analysis.

Verification of Johnson-Cook parameters of ferritic stainless steel by drilling process: experimental and finite element simulations

Ferritic stainless steels contain 16%–30% chromium and about 0.05%–0.25% carbon in their compositions. As the carbon and chromium content is high, precipitation of carbide particles provides high strength but also causes brittleness. Ferritic stainless steels are of moderate formability with an excellent corrosion resistance and relatively inexpensive. In this study, the predetermined JC model parameters of the AISI 430 ferritic steels have been verified by comparing the experimental drilling process and drilling simulations. Firstly, the drilling experiments of 430 steel with the uncoated tungsten carbide drill have been performed at three different feed rates and cutting speeds. Then, the pre-determined JC parameters have been adapted into a simulation software running with the finite element method and after the drilling simulations have been operated under the same drilling conditions. By comparing the experimental and numerical data based on the thrust force (Fz), a deviation of 4.83% has been calculated and the validity of the material's JC parameters has been demonstrated.

Optimization of Process Parameters in Drilling of Cast Iron Materials with Carbide Drills

Takım aşınmalarının, parça üretim maliyeti ve üretim verimliliğine doğrudan etkisi mevcuttur. Takımlarda meydana gelen aşınmalar, üretim kalitesini doğrudan etkileyen bir faktördür. Bu çalışmada, farklı matkap çapları ve kesme parametrelerinin takım aşınmasına etkisi araştırılmıştır. Deneyler, farklı çapta matkaplar ve farklı kesme parametreleri ile 9 farklı kombinasyonda 20 tekrar seklinde yapılmıştır. Deneysel çalışmada imalat sektöründe sıkça kullanılan 6,8 mm, 9 mm ve 9,6 mm çapa sahip yekpare karbür matkap uçlar kullanılmıştır. İş parçası olarak üretimde sıkça kullanılmakta olan GG25 ve GGG40 standartlı dökme demir malzemeler belirlenmiştir. Taguchi tekniği kullanılarak en yüksek takım ömrü değerlerini veren optimum kontrol faktörleri belirlenmiştir. Ayrıca her deneyden sonra matkap uçlarındaki aşınma durumları ve tipleri takım ölçme ve ayarlama makinası yardımı ile tespit edilmiştir. GGG40 malzemenin GG25 standartlı malzemeye göre, matkap ucunda daha çok aşınmaya sebebiyet verdiği ve matkap ucunun çapı arttıkça aşınma miktarlarında da arttığı belirlenmiştir.

Machinability properties of Al–7Si, Al–7Si–4Zn and Al–7Si–4Zn–3Cu alloys

Al–7Si, Al–7Si–4Zn, Al–7Si–4Zn–3Cu alloys were produced by permanent mold casting method to investigate the effects of copper and zinc additions on the machinability properties of Al–7Si alloy. The structural and mechanical properties of the produced alloys were investigated with conventional methods. Machinability properties of these alloys were determined by turning, and they were associated with structural and mechanical properties of the alloys. Machinability experiments were carried out in CNC vertical machining center under dry cutting conditions using uncoated carbide drill and constant cutting speed (120 m/min), feed (0.15 mm/rev) and depth of cut (15 mm) values. The microstructure of Al–7Si binary alloy was observed to be composed of aluminum-rich α phase, primary silicon crystals and eutectic Al–Si phase. The addition of 4% Zn to the Al–7Si alloy did not form a different phase in the microstructure. However, Al2Cu intermetallic phase was formed by addition of 3% Cu. While the hardness and tensile strength of the alloy increased, elongation to fracture significantly reduced. As a result of machinability experiments, it was observed that the minimum thrust force and surface roughness occurred in Al–7Si–4Zn–3Cu alloy, while the maximum built-up edge was observed during drilling of Al–7Si and Al–7Si–4Zn alloys. Microhardness value of machined surface in Al–7Si alloy was found to be the minimum while the maximum Al–7Si–4Zn–3Cu alloy was observed.

Influence of Adhesive Strength, Fatigue Strength and Contact Mechanics on the Drilling Performance of Diamond Coating.

Adhesive strength of the coating significantly affects the lifetime of the coating. However, it is still inevitable for the coating, even with strong adhesive strength, to peel off from the substrate after working for a while. In this work, fatigue and wear behaviors were employed to analyze the effect on the mechanics of coating and contribute to a fundamental understanding of peeling of the coating. A small-size Co-cemented tungsten carbide drill bit was selected as the examined substrate to fabricate the diamond coating. Roughening pretreatment with a diamond slurry combined with ultrasonic vibration was performed for the substrate surface to enhance adhesive strength. Meanwhile, a diamond coating without roughening pretreatment was also fabricated for comparison. The lifetime and quality of the coating were evaluated by the drilling test. Although the diamond coating could grow on the substrates with and without roughening pretreatment, the diamond coating with roughening pretreatment possessed a higher lifetime and stronger wear resistance than that without roughening pretreatment. We found that both substrates with and without roughening pretreatment exhibited a coarse surface, whereas the roughening pretreatment could remove the original machined surface of the substrate and thus make the near surface with numerous integrated crystalline grains become the new topmost surface. This increased the contact area and surface energy of the interface, leading to the improvement of adhesive strength. Finally, fatigue strength and contact mechanics were studied to trace the changes in the stress of the diamond coating in the whole process of drilling from a theoretical point of view. We suggest that fatigue strength and contact mechanics may play vital roles on the durability and peeling of the coating.

Experimental influence of twist angle and cryogenic gas on quality of drilled hole in carbon fiber reinforced plastic composites

The considerable body of literature on the effect of moisture on the mechanical properties of composites has shown that there is a disinclination to use coolant fluids within the composite industry. Tool geometry and cryogenic liquid cooling also have a significant impact on carbon fiber–reinforced plastic machining capabilities. In this paper, the two issues mentioned are improving the drilled hole quality and reducing the amount of CO2 released into the air to protect the environment. The experimental characteristics using a carbide drill with three levels of twist angle of flute and a gas mixture of CO2–N2 were investigated. To verify hole quality, the diameter, the delamination, the uncut fiber area, and the surface roughness were analyzed. With the goal of reducing the amount of CO2 released into the atmosphere, a list of experiments was proceeded in the dry, the air, gas CO2, and a gas mixture of CO2–N2. The thrust force and the temperature were observed. Based on the experiment results, the high helix tool was more advantageous than the triple tool and low helix tool. The difference in the effect of CO2 and CO2–N2 was not significant with the triple tool and the low helix tool; however, the performance of the CO2–N2 gas mixture showed a positive effect on the high helix tool.

Evaluation of minimum quantity lubrication and minimum quantity cooling lubrication performance in hard drilling of Hardox 500 steel using Al2O3 nanofluid

The work in this study presents an experimental evaluation on minimum quantity cooling lubrication based on the Ranque–Hilsch vortex tube and minimum quantity lubrication performance in hard drilling of Hardox 500 steel (49–50 HRC) using coated carbide drills. Al2O3 nanoparticles are suspended in the based fluids including water-based emulsion and rice bran oil to enhance the cooling and lubricating effects. The response variables, consisting of drilling thrust force, surface roughness, surface profile and microstructure, and tool wear, are studied, and the analysis of variance is used for evaluating the input machining parameters under minimum quantity lubrication and minimum quantity cooling lubrication conditions. The results of this article indicate that minimum quantity cooling lubrication using Al2O3 nanofluid provides the better machining performance and gives out better surface quality and lower thrust force compared to minimum quantity lubrication with/without nanofluid and minimum quantity cooling lubrication with pure fluid. Also, based on the optimization results, the validation experiments are conducted to study more on drilling thrust force, chip morphology, and tool wear.

Performance Analysis of Various Characteristics on Dry Drilling Hole Quality Of 17-4 PH Stainless Steel with Solid Carbide Drill Bits

17-4 PH stainless steel is one of the most imperative grades of precipitation hardened aerospace grade stainless steel particularly used in aircraft, marine vessels, nuclear industries, turbine blades, food processing equipments and oil & gas industry. It belongs to the class of difficult to cut material because of its unique properties such as high strength, high hardness and toughness including good corrosion resistance. The present study deals with comparative analysis of hole quality, surface roughness and chip characteristics when drilling 17-4 PH stainless steel with uncoated and coated solid carbide drill bits. Dry drilling operation was carried out at two different feed of 0.10 mm/rev and 0.15 mm/rev with a constant spindle speed of 2000 RPM. Results indicated that surface finish and burr thickness could not be improved, while remarkable reduction in hole diameter and delamination factor was noted for the coated solid carbide drill bit compared to its uncoated counterparts for different machining conditions.

An investigation of hole quality during drilling of carbon fibre reinforced plastic and titanium (Ti6Al4V) using tungsten carbide drills

Drilling through Carbon Fibre Reinforced Plastic (CFRP) and Titanium alloy (Ti6Al4V) in a stack is crucial for mechanical assembly of aircraft and automotive parts. This paper presents an investigation of drilled CFRP/Ti stacks hole quality in comparison to when the materials were drilled separately and individually (CFRP-only and Ti-only). The drilling trials were conducted through CFRP/Ti stacks, CFRP-only and Ti-only using carbide drills (6.1 mm diameter) at a cutting speed of 50 m/min and a feed rate of 0.05 mm/rev. The quality of the drilled holes was evaluated with respect to the hole diameters, delamination and pull-out of CFRP as well as Ti burr. It was found that drilling CFRP/Ti stacks resulted in severe Ti adhesion on the cutting edges, which caused oversized drilled holes. CFRP delamination and pull-out was found to increase by 22%−62% and 170%−530% during drilling of CFRP/Ti stacks in comparison to those produced by drilling of CFRP-only. The high damage to CFRP when drilling CFRP/Ti stacks compared to drilling CFRP-only was mainly due to sharp Ti chips, which evacuated through the CFRP plate. Furthermore, it was found that Ti burr which formed at the hole exit increased as tool wear increased. This study suggested that the hole quality and tool life when drilling CFRP/Ti stacks can be improved by improving the evacuation of Ti chip and by reducing the adhesion of Ti on the cutting edges.

Drilling process and resulting surface properties of Inconel 718 alloy fabricated by Selective Laser Melting Additive Manufacturing

Abstract One of the challenges is to produce holes with expected dimensional accuracy in metal additive manufacturing. Although post-processing is usually carried out for the additively manufactured components but improving the quality of the holes produced through additive manufacturing seems to be requirement. Otherwise, it is difficult to obtain expected quality for the holes in metal components. Therefore, this study focuses on drilling operation of Inconel 718 alloy fabricated by selective laser melting additive manufacturing. Specimens fabricated by selective laser melting (SLM) were drilled using carbide drill bit under various drilling conditions including cutting speed and feed values. The measured outputs were surface quality of drilled hole, surface topography, surface and subsurface microhardness, and microstructure. Obtained results were compared with the results from wrought Inconel 718. This study showed that drilling process helps to improve the surface quality of additively manufactured Inconel 718 by reducing the surface roughness. Besides, increased feed rate results in work hardening effect on the hole surface and eventually microhardness of surface and subsurface increases notably.

Effect of drilling parameters on Delamination of Kevlar laminate

Abstract Components made up of composite materials are usually assembled by riveted or bolted joints. As a result, one of the most frequently utilized machining operations on composite laminates is drilling. Various parameters were identified that affect the material deformation, such as delamination and fuzzing while working with composites. In this experimentation work, the effect of these parameters on the drilling operation was investigated for Kevlar laminates with 200 GSM thickness and using solid carbide drill bits of o4 mm, o5 mm and o6 mm, while focusing on the measurement of the maximum delamination of the laminate for various values of cutting speed and feed rate. The delamination caused during drilling was observed and studied, and also the degree of delamination was noted. In such a manner, the delamination effect and drilling parameters, which cause the minimum delamination, were identified. The results were analysed by using two factor ANOVA without replication

Surface roughness analysis in the drilling of carbon fiber/epoxy composite laminates using hybrid Taguchi-Response experimental design

The carbon fiber reinforced polymer composite has made a substantial impact on the manufacturing sectors owing to its excellent mechanical, thermal and corrosion resisting properties. The surface roughness mainly depends on the machining parameters while drilling of carbon fiber reinforced polymer composite laminates. The study concentrates on the impact of uncoated and titanium nitride coated solid carbide drills on minimizing the roughness that is generated while making holes in bi-directional carbon fiber reinforced polymer composite by optimizing the drilling constraints [spindle speed (A), feed rate (B), point angle (C) and drill diameter (D)]. Experimental studies are carried out using Taguchi L27 orthogonal array. The investigation discloses that the drill diameter is one of the most influencing cutting parameters followed by spindle speed and feed rate. The response surface methodology is chosen as a tool for predicting and optimizing the process parameters. The investigation also discloses that the experimental and the predicted results of surface roughness are closely matching with each other. The surface morphology illustrates that titanium nitride coated solid carbide drills minimize the surface roughness compare to that of uncoated solid carbide drills.

Quantifying Coronal Primary Tooth Discoloration Caused by Different Pulpotomy Materials.

Introduction: Bioceramic materials, gray and white mineral trioxide aggregate (GMTA, WMTA), have been shown to have high rates of success in various endodontic applications. A major drawback is their tendency to discolor teeth. Biodentine (BD), a recenlty developed bioceramic material, has been claimed not to discolor teeth. The aim of this study was to compare tooth discoloration after applying different pulpotomy base materials (BD, GMTA and WMTA). Methods: Forty human fully developed primary incisors teeth were used in this study. Coronal access was achieved by a Tungsten Carbide drill, and the pulp chambers were accessed and chemo-mechanically debrided. Each material was placed in the pulp chamber, up to the cervical sectioning level. All specimens were incubated at 37°C and 100% humidity for 14 weeks and have been evaluated before the study and weekly. Color was assessed according to the CIE L*a*b* color space system. Results: The ΔE (delta E) of all experimental groups (GMTA, WMTA and BD) were significantly different from the control group at all time points. Color changes in the GMTA and WMTA groups showed significantly higher discoloration compared to BD group in the cervical part of the crown, since week 1. WMTA group showed significant discoloration in the cervical part as of week 1, and gradually increased over time. BD group showed no significant discoloration over time. GMTA group showed the most significant discoloration at week 1 and week 14 (P<0.05). Conclusions: both GMTA and WMTA pulpotomy materials may discolor tooth structure over time in an extracted primary anterior tooth model. When choosing bioceramic pulpotomy material, BD may be preferable, mainly in esthetic area.

An analysis on the effect of machining parameters on surface quality during dry machining of Ti-6Al-4V alloy

Abstract Nowadays Titanium and its alloy materials are highly preferred for the parts of aircraft structures due to their unique properties such as good corrosive resistant and higher strength to weight ratio is sustained even at increased temperature. Even though these alloy materials are wicked for its low thermal conductivity and categorized as hard to machine alloys. Drilling of titanium alloys is a critical machining process in the fields such as medical, automobile and defence applications. In this alloy Ti–6Al–4V alloy is generally used for parts that need higher reliability therefore, surface finish and various failure to the adjacent surface layers of machined areas must to be resolved as per the customer requirement. This research work focuses on experimental study and optimization of machining parameter during dry drilling of titanium alloy (grade 5). An 8 mm diameter and 120 degree point angle solid carbide drill bits are used to carry out the experiments. The range of drilling spindle speed chosen for the experiment was between 20 to 50 m/min also feed rates were 0.05, 0.1, 0.15, and 0.2 mm/rev. Experimental analysis was done by focusing on surface roughness, circularity, hole diameter and exit burr for maintaining good quality hole. A Portable surface roughness measuring device was utilised to find surface roughness in the direction of feed on work piece material. Circularity and diameter of the machined hole was found by co-ordinate measuring machine (Contura-G2-Zeiss). From this experimental investigation it is found that feed has higher significance on surface finish when compared to drilling speed but when considering the circularity error speed has higher significance. Optimization and validation of experimental results was done by using the application of Taguchi’sdesign of experiments with signal to noise ratio graph and ANOVA

Effect of Drilling Process Parameters on Surface Roughness of LM6/B4C Composites

Metal matrix composites are a new course of materials with superior properties to those of the components. Such materials ' machining is distinct from that of traditional materials. So the optimization of machining process parameters becomes inevitable. By applying Taguchi's Signal-to-Noise ratio method, this paper examines the effects of drilling process parameter such as feed, spindle speed, drill material and percentage reinforcement on the drilled hole’s surface roughness. Variance analysis was used to evaluate each system parameter's contribution to surface roughness. The composites were manufactured by stir casting technique using aluminium alloy (LM6) as matrix material and boron carbide particulates at 3%, 6% and 9% by weight as material for the reinforcement. There are four factors investigated each at three levels, so 34 which implies 81 experiments has to be conducted, but by using Design of Experiments approach 27 experiments were conducted using L27 orthogonal array The minimum surface roughness measured for the hole was 1.08 μm at combination of 3000 rpm spindle speed, 50 mm/min feed rate, 3% reinforcement and Carbide drill.