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In the drilling process, unwanted materials which extend beyond the work-piece surface are called burr. The main objective is to find out optimum drilling condition which minimize the burr height and burr thickness. For this purpose, an experimental study has been performed on aluminium alloys using an HSS twist drill according to L27 experimental run. For this experiment the input process parameters spindle speed, feed rate and depth inside backup support and for the response parameters burr height and burr thickness have been considered. The response surface methodology-based regression equation has been developed for burr height and burr thickness using this experimental dataset and compared with the experimental result that shows a close matching. The effect of the input process parameters i.e. spindles speed; feed rate and depth inside backup support are presented in contour plots to understand the effect of them. Finally, optimum drilling process has been obtained by using Biogeography Based Optimisation (BBO) technique to minimize the burr height and burr thickness. From BBO optimization it cleared that minimum burr height is found at a speed of 320 rpm, feed of 0.08 mm/rev and depth inside backup support of 0.20 mm, also minimum burr thickness is produced at a speed of 125 rpm, feed of 0.9395 mm/rev and depth inside backup support of 0.56 mm.

This paper presents a new burr formation model for predicting drilling burr sizes in consideration of tool wear. A new force model is established by combining the drilling thrust force with the ploughing force caused by tool wear. The traditional drilling burr formation model is modified by using the new force model to determine burr heights and thicknesses in terms of tool wear percentage. A series of drilling experiments are carried out on two commonly used aerospace aluminiums to validate and calibrate the model. A close agreement between simulation and experiment is achieved showing that burr height and thickness increase with the increase in tool wear, and at 50% of tool wear, the maximum burr height could triple and the maximum burr thickness could double.

Drilling of composite materials is a common manufacturing process which is widely used in various applications such as aircraft and automobile assemblies. Usually, drilling of composite materials is very challenging because of their high strength, non-homogeneous and anisotropic properties. Several undesirable failures such as deflection of workpiece, delamination and burr formation occur at exit side of machined surface due to lack of support under workpiece while drilling of the material. Therefore, it is necessary to develop cost-effective techniques to suppress drilling damages. The backup support technique is an important approach to prevent damages while machining at various machining parameters, tool geometries and with other machining strategies. This review paper summarizes the principle of the technique and its effectiveness on various composites towards suppressing material damages. The backup methods are categorized under active backup force, passive backup support, stack acts as backup and fabricated backing support technique. The above methods are reviewed with respect to tool geometry/material, drilling parameters and other machining strategies to bring out the importance of backup support and its influence on quality of machined surface.

Miniature/micro-drilling of holes is increasingly utilized in manufacturing. While non-conventional machining methods (laser and spark erosion) were applied successfully for micro-drilling, mechanical drilling still of interest to industry due to its unmatched geometrical accuracy. However, tool wear and burr formation would hinder the economics of mechanical drilling supremacy. Hence, the need for understanding of tool wear, burr formation and cutting forces progression with process variables is a step towards comprehensive modelling of micro-drilling mechanics and subsequent enhanced process economics. The current research details experimental trials involving mechanical drilling of steel 1008/CR4 using twin-fluted twist drills of diameters 0.5, 1 and 1.5 mm. Full factorial design of experiments was utilized, and analysis of variance was accomplished to study the effects of feed rate and tool diameter (each of them at 3 levels) on tool flank wear and drilled hole quality. Entry and exit burr heights were increased by 80–150% when tool diameter and feed rate were two times higher. Progression of tool flank wear and usage of bigger tool diameter conversely reduced hole surface roughness. In addition, tool flank wear was increased when reducing of feed rate and using larger tool diameter. Catastrophic failure of 0.5-mm-diameter tool was noticed (after drilling of 46 holes at high feed rate level and after drilling of 97 holes at low feed levels) due to chip packing/jamming in the insufficient flute area.

Burrs, being one of the most undesired obstructions generated during machining, affects work piece quality negatively in many aspects. Although deburring removes burrs, this extra process is time consuming, costly and might affect dimensional accuracy. This study investigates mechanisms, effects and variations on burr formation in most common machining processes such as drilling, milling, turning and grinding based on the information available in literature. The problems related to burrs as well as ways and methods to remove burr and control or minimize burr formation has critically discussed. Burrs can be minimised by selecting proper tool geometry, tool materials, coolant, machining parameters, work piece material, process planning and tool path design. As there is no method that can eliminate burr formation, thus deburring is essential to eliminate burrs after machining. Manual tools, abrasive blasting, abrasive flow, magnetic abrasive finishing, centrifugal barrel finishing, thermal melting and electrochemical effect are most commonly used for deburring depending on material, size and precision of parts.

Use of conventional drilling process have been utilized by academia and industry alike for making holes in difficult to machine materials like titanium alloys. However nowadays helical hole milling process has been adopted due to the advantages it brings in. This work therefore aims to evaluate the traditional drilling process against the newer helical milling process for hole making in titanium alloy. The evaluation was carried out considering the thrust force, surface roughness, hole diameter and machining temperature. The morphology of chips generated and the burr formation were also investigated. The comparison of thrust force and machining temperature were found to be lower for the holes processed using helical milling process. The finish of the machined hole surfaces was better when helical milling process was used. Additionally, helical milling of holes resulted in relatively diametrically accurate and burr free holes. The preliminary results obtained show that helical milling process can be a promising alternative to traditional drilling process for machining difficult-to-machine material like titanium alloy provided the productivity of the process can be improved.

In precision manufacturing, especially in making of holes on the parts during drilling process for precision assembling of parts facing problems with burr formation. Drilling is one of the finishing operations in the production cycle, removal of burrs during drilling process is a time consuming and non-value added process to the manufacturing sector. In this paper, we developed an analytical models for thrust force, torque and burr size with variable clearance angle of drill bit geometry especially for Aluminium alloys used for automotive applications. An analytical model results were obtained by writing a code in MATLAB @ 2010 software for aluminium alloy series such as Al 6061, Al 2014 and Al 7075. In an economic front, de-veloped mathematical models are benefitted to reduce experimentation, these results reveal that at the beginning of the drilled hole due to indentation of chisel edge, more thrust and torque was identified, beyond that suddenly thrust force was lowered, cutting forces by the lip edges were increased from beginning of the process to progress of drilling process. The proposed model approach is helpful to the budding entrepreneurs in the related areas to select optimal combination of drilling parameters to attain multiple performance characteristics of responses especially in burr size to prevent the post finishing operations up to certain extent.

A novel analytical model to describe entrance burr formation when drilling ductile metals as a function of tool geometry (point/helix angles, diameter), operating parameters (cutting speed, feed rate) and workpiece material properties, was initially formulated. The model was further developed to account for interlayer burr dimensions when drilling CFRP-metallic stack arrangements. Data from validation trials performed on Ti–6Al–4V, AA7010 and AA2024 workpieces together with their associated CFRP stack assemblies over 4 different combinations of cutting speed and feed rate showed that the predicted sizes of entrance and interlayer burrs were all accurate to within 20% of the experimentally measured results.

The process of drilling is commonly employed in the processes involving the complex manufacturing processes. Burr exists in almost all these process whether it be drilling, milling or any kind other kind of manufacturing operations. The burrs that are generated on any of the component (part) may lead to several unwanted effects: practically like not having any proper contact between the members that are the carriers of currents and also the irregular arrangements between the contacted surfaces of the components. Burrs could also be injurious while performing some machining operations since they can be responsible for creating the wear of groove of the cutting edges. Subsequently, it is necessary to understand those elements that influences the arrangement of burrs at the exit of the openings in drilling operations in order to decrease the burr size at the site of their generation. The central target of this review research work is to complete the previous several years in this significant theme. The paper remember the conversation for the burr development in different drilling procedure improvement, impacted by the cutting conditions and the drill geometry during penetrating of different sorts of work materials, utilizing turn drills. The drilling improvement is performed to decide the ideal benefits of cutting pace, feed, point edge and lip angle of clearance for a predefined drill distance across that at the same time limit burr size, to be specific, burr height (tallness) and thickness of the burrs.

Burr formation during machining process is a vital role in the assembly lines, even though it is a non value added process but also care should be taken while machining due to non avoiding output generated at the end of material removal process. At present almost all manufacturing sectors faces lot of problems due to these issues and invest more money towards deburring still advanced manufacturing methods available. So, complete burr removal is not possible and only thing is reducing utmost by applying better optimizing techniques, to develop good mechanization methods, selecting optimum process parameters and their conditions. The aim this paper deals about research methods implemented by earlier authors on burr formation especially in drilling. The reason why the present authors selected the drilling is number of automotive and aircraft engineers struggling during structural building works because of these burrs wherever precise measurement needed. In this connection, the authors concentrate their study on previous researcher works related to investigations on experimentation, developing new theoretical mechanisms to minimize burrs, adapt a new technologies available to modify drill bit geometries such that improvement in the minimization of burrs. Finally found that research contributions by changing their drill bit geometry and cutting process parameters have been focused on utilizing the methodologies, changing time to time. In analyzing the performance characteristics with that of input process parameters, several mathematical and empirical models were developed by many researchers so far in their works. Efforts have been made in the direction of optimization of process parameters in drilling for minimizing burr size.

This paper investigates burr generation while drilling of mild steel grade 350. The influences of feed, speed and point angle on burr height, thrust force, torque and chip ratio are investigated to correlate with burr height. It was found that, the burr height reduces gradually with the rise of speed at minimum feed and point angle. At maximum feed and point angle, initially the height rises with speed and then reduces as speed rises further. The maximum burr is 720 μm at 584 rpm. At maximum point angle and speed, the height rises initially and then reduces as the feed rises where the trend is opposite at minimum feed and speed. The maximum burr is 1223.15 μm at 0.25 mm/rev feed. The variation of burr height with point angle is similar to that with the variation of feed. The maximum burr is 1230 μm at 125°point angle. The trends of thrust forces, torques and chip ration with the variation of different parameters are not similar to that of burr height in most of the cases. The complex interaction between strain hardening and thermal softening plays the main role in burr formation for the considered material. Refereed/Peer-reviewed

In this paper, the tool wear mechanism in low-frequency vibration-assisted drilling (LF-VAD) of carbon fiber reinforced polymer (CFRP)/Ti6Al4V stacks has been proposed using variably machining parameters. Based on the kinematics analysis, the effect of vibration amplitude on the chip formation, uncut chip thickness, chip radian, and axial velocity was presented. Subsequently, the effect of LF-VAD on the cutting temperature, tool wear, delamination, and geometrical accuracy was presented for different vibration amplitude. The LF-VAD with the utilization of minimum quantity lubricant (MQL) resulted in a successful drilling process of 50 holes, with a 63 % reduction of the cutting temperature. For the rake face, LF-VAD reduced the adhered height of Ti6Al4V by 80 % at low cutting speed and reduced the crater depth by 33 % at the high cutting speed. On the other hand, LF-VAD reduced the flank wear land by 53 %. Furthermore, LF-VAD showed a significant enhancement on the CFRP delamination, geometrical accuracy, and burr formation.

Millions of holes are produced in many industries where efficient drilling is considered the key factor in their success. High-quality holes are possible with the proper selection of drilling process parameters, appropriate tools, and machine setup. This paper deals with the effects of drilling parameters such as spindle speed and feed rate on the chips analysis and the hole quality like surface roughness, hole size, circularity, and burr formation. Al7075-T6 alloy, commonly used in the aerospace industry, was used for the drilling process, and the dry drilling experiments were performed using high-speed steel drill bits. Results have shown that surface roughness decreased with the increase in spindle speed and increased with the increase in the feed rate. The hole size increased with the high spindle speed, whereas the impact of spindle speed on circularity error was found insignificant. Furthermore, short and segmented chips were achieved at a high feed rate and low spindle speed. The percentage contribution of each input parameter on the output drilling parameters was evaluated using analysis of variance (ANOVA).

Presently a-days precision manufacturing has picked up its significance in all assembling industries. The best product dimensions at low cost with minimum time become a measure of concern. The drilling process imparts more than 30% of all the metal removing operations done on a job or assembly. The burr is a plastically deformed material, generated during drilling is unnecessary output and reduces the product acceptability, often lowers the surface quality of the product requires deburring which increases the cost of product. Burr is caused due to improper machining, tooling and environmental parameters. Total elimination of burrs during drilling process is a difficult task but using proper process parameters it can be minimized. In the present experimental study, the optimization of process parameters for minimization of burr formation in drilling process has been carried out for Al6082 plate. The tool type (coated/uncoated), spindle speed, feed rate, and drill diameters were used as the process parameters. Taguchi’s L18 orthogonal has been applied for DOE and drilling of Al6082 plates has been performed using ply-board as a backup support and without using any backup support on CNC drilling machine. The burr height and surface roughness were analyzed and optimized using S/N ratio and ANOVA and the optimum combinations for burr height and surface roughness has been found from S/N plots. The most influencing factors for burr height and surface roughness have been found from ANOVA tables.

This article discuss the effects of heat treatment and lubrication modes on the machinability of an A356 alloy (Al-Si-Mg); the alloy is studied as-received, with solution heat-treated alloy (SHT) as well as with an alloy that is solution heat-treated and then aged at 155, 180 and 220 °C. In the course of machinability evaluation, several criteria including cutting force, surface roughness, tool wears and burr analysis (chip) were studied. The results and analysis in this work indicated that the selected machinability criteria are important and necessary to effectively evaluate the machinability of A356 alloys. The machinability of both materials and tools were estimated in terms of cutting force, chip thickness ratio and burr formation, flank wear and roughness. The effects of different cutting parameters (cutting speed and feed rate) and lubrication modes (dry, mist and wet) on the machinability of the A356 cast alloy were also examined. The influence of heat treatments on the burr formation and surface quality was clearly revealed by the experimental results. Experimental work revealed that cutting forces were influenced significantly by aging and cutting speed. However, the different aging at 155, 180, and 220 °C and the cutting speed significantly affected the machinability of the A356 cast alloy. The results obtained show that a better drilling performance in terms of surface quality occurs at a high feed rate, with dry drilling and artificial aging at T6.

In this study, the technique of drilling at stepped feed rate is suggested as a new method for reducing the burr size at the exit of a hole in Al-5005, without prolonging the drilling time. The hole was divided into two regions, which were drilled at different feed rates. As a reference for comparison analysis, Al-5005 was drilled at constant drilling parameters. The smallest burr size with constant drilling parameters was obtained at 140° point angle, 0.1 mm × rev−1 feed rate, and 400 rpm spindle speed. The parameters that mainly effect the burr size were determined to be point angle, feed rate and the spindle speed, respectively. The same material was drilled employing the method of stepped feed rate, where the first region of the hole was drilled at 140° point angle, feed rates of 0.1, 0.2, and 0.3 mm × rev−1, and spindle speeds of 400, 800, and 1200 rpm. The second region was drilled with a feed rate that was automatically adjusted by the CNC machine to be one tenth of the feed rate in the first region, without removing the drill bit from the hole. It was observed that, using the stepped feed rate method, the burr height and burr thickness were diminished by 35 % and 25 %, respectively, compared to constant drilling parameters.

Burr formation is a problem in drilling process as it not only affects quality of products but also increases processing time and operating cost. At the current, burr formation is still unavoidable, and more studies should be performed in order to gain better understandings. As the drilling progresses, the drill is continuously deteriorated, leading to increasing drilling forces and burr heights. In this study, burr heights formed on S50C and SS400 steel at the exit of 4 mm thick workpieces were compared as well as peak forces during drilling process using 8 mm HSS drills. The feed rates were set at 0.01 and 0.03 mm/rev, and the cutting speeds at 25 and 30 m/min. In each condition, 100 workpieces were drilled consecutively and was repeated twice. It was found that the steel type affected the drilling force and burr height. The steel with higher hardness, i.e. S50C, was associated with the higher drilling force especially at later workpieces. The peak force during the drilling process was between 400-650 N and 380-510 N for S50C and SS400, respectively. However, the steel with higher hardness had shorter burr heights; i.e., the burr height occurred on S50C and SS400 was between 0.49-1.31 mm and 0.44-1.97 mm, respectively. For S50C, mathematical relationships can be found between the wear developed on the HSS drill bit and the peak and average drilling forces with promising R 2 values between 0.8230-0.9738.

Helical milling is a hole-making process which can be applied to achieve high-quality finished boreholes in hardened steels. Due to the drilling process limitations, which are intensified when applied in hardened steels, the helical milling process can be applied on hole-making tasks in moulds and dies industry, since milling have been widely applied in moulds and dies machining to replace high-cost operations like grinding and electrical discharge machining. However, to succeed in achieving high-quality boreholes in hardened parts, which presents high added value due to previous operations, tool wear in the helical milling of hardened steels should be more investigated. In the present study, dry helical milling tool life tests were conducted in AISI H13 hardened steel parts, varying the cutting velocity. The flank wear on frontal cutting edges was progressively measured through optical microscopy, and SEM/EDS was performed in frontal and peripheral worn cutting edges. The wear occurred progressively in the flank of the frontal cutting edges with adhesion and oxidation as main wear mechanisms. In the peripheral edges, coating loss, and adhesion of workpiece material in the tool clearance surface were observed, besides fracture in the tool nose flank with the highest cutting velocity. A nested ANOVA was performed to evaluate the burr height in the borehole exit. The tool life stage was statistically significant in the burr height. published

Fibre metal laminates (FMLs) are a special type of hybrid materials, which consist of sheets of metallic alloys and prepregs of composite layers stacked together in an alternating sequence and bonded together either mechanically using micro hooks or thermally using adhesive epoxies. The present paper contributes to the current literature by studying the effects of three types of cutting tool coatings namely TiAlN, AlTiN/TiAlN and TiN on the surface roughness and burr formation of holes drilled in an FML commercially known as GLARE®. While the cutting tool geometry is fixed, the study is also conducted for a range of drilling conditions by varying the spindle speed and the feed rate. The obtained results indicate that the spindle speed and the type of cutting tool coating had the most significant influence on the achieved surface roughness metrics, while tool coating had the most significant effect on burr height and burr root thickness. The most important outcome for practitioners is that the best results in terms of minimum roughness and burr formation were obtained for the TiN coated drills. However, such drills outperform the other two types of tools, i.e. with TiAlN and AlTiN/TiAlN coatings, only when used for short series of hole drilling due to rapid tool deterioration.

In this study, a carbon fiber-reinforced thermoplastic (CFRTP) laminate has been drilled and the drill-hole quality was evaluated. Drill-holes were introduced into the laminate by two 5.9 mm diameter step drills to simulate low and high quality machining processes. Defects from manufacturing of the laminate as well as resulting from the machining process were identified and classified by different imaging techniques on representative images. It became obvious, that burr formation is the dominant but not exclusive type of damage in drilled CFRTP in contrast to delamination in case of CFRP. Subsequently, 4-point-flexure and tensile tests have been performed with initial and differently drilled samples to characterize the starting material as well as to determine the influence of the different drill-hole qualities on the mechanical performance and failure behavior. These tests showed that there is no critical influence of the drill-hole quality on the open-hole tensile and flexure strength of the applied CFRTP.

Interlayer burr formation in drilling of stacked aerospace materials is a common problem in aircraft assembly operations. Burrs formed at the interface of the stacked sheets need to be removed, and the deburring is a nonvalue but time and costs waste operation, particularly in automatic drilling and riveting assembly. This article presents an analytical model of the interlayer gap formation to predict the interlayer burr height, and drilling experiments were developed to understand the difference between the interlayer burr height and the interlayer gap. The impact of cutting force, spindle rational speed and feed rate was taken into consideration. Specific conclusions regarding the influence of the interlayer gap on burr formation were presented.

Machining Glass fibre aluminium reinforced epoxy (GLARE) is cumbersome due to distinctively different mechanical and thermal properties of its constituents, which makes it challenging to achieve damage-free holes with the acceptable surface quality. The proposed work focuses on the study of the machinability of thin (~2.5 mm) GLARE laminate. Drilling trials were conducted to analyse the effect of feed rate and spindle speed on the cutting forces and hole quality. The resulting hole quality metrics (surface roughness, hole size, circularity error, burr formation and delamination) were assessed using surface profilometry and optical scanning techniques. A three dimensional (3D) finite-element (FE) model of drilling GLARE laminate was also developed using ABAQUS/Explicit to help understand the mechanism of drilling GLARE. The homogenised ply-level response of GLARE laminate was considered in the FE model to predict cutting forces in the drilling process.