Effects of drill microgeometry and cooling supply in the surface integrity (original) (raw)
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Analysis of drilling surface microgeometry
The improving quality of hole boring, primarily by tool innovation activities, allows us to use drilling as a finishing technology. It is well known that the attainment of a perfect chip-forming ability poses an enormous technical challenge to developers. In order to succeed in this challenge, in practice it is not enough to reach a sufficient cutting condition be sides the right combination of the construction-geometry-coating triple. However, any chip forming disorder will significantly influence the quality of the machined surface. The wear resistance of the surfaces and their adequate functional behavior are definitely linked to surface quality parameters. It is well known that the lifetime of parts and their functional behavior and reliability depend, besides shape and bore accuracy, on the deviation of the microgeometry of the machined surface (waviness (W) and roughness (R)): on surface quality in a broader sense. For an accurate evaluation of the surface profile, typical descriptive parameters have to be analyzed in a complex manner. It is not enough to deal with the roughness (R) profile, but the unfiltered (P) profile should rather be focussed on. I.
Effect of machining parameters on hole quality of micro drilling for brass
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This paper present the effect of drilling parameter such as spindle speed, feed rate and drilling tool size on material removal rate (MRR), surface roughness, dimensional accuracy and burr. In this work, a study on optimum drilling parameter for HSS drilling tool in micro-drilling processes in order to find the best drilling parameter for brass as a workpiece material. Micro drilling experiment with 0.5 mm to 1.0 mm drill sizes were performed by changing the spindle speed and feed at three different levels. The results were analyzed using microscope and surface roughness device. Comparatives analysis has been done between surface roughness, MRR and accuracy of drilled holes by experimentation. From the result, the surface roughness are mostly influenced by spindle speed and feed rate. As the spindle and feed rate increases, the surface roughness will decrease. The tool diameter gives less influence on the value of surface roughness. The value of MRR is decreased when the tool diameter, spindle speed and feedrate are decreases. As drilling tool diameter, feedrate and spindle speed increase the dimensional accuracy of drilled hole will decrease. The increment of spindle speed and feed rate value mostly will affect the tool wear and size of burr on the edge of drilled holes.
Advances in Mechanical Engineering, 2011
This work evaluates the hole quality on AISI H13 hardened steel using high-speed drilling. Specimens were machined with new and worn out drills with 8.6 mm diameter and (TiAl)N coating. Two levels of cutting speed and three levels of cooling/lubrication systems (flooded, minimum lubrication quantity, and dry) were used. The hole quality is evaluated on surface roughness (Ra) parameter, diameter error, circularity, and cylindricity error. A statistical analysis of the results shows that the cooling/lubrication system significantly affects the hole quality for all measured variables. This analysis indicates that dry machining produces the worst results. Higher cutting speeds not only prove beneficial to diameter error and circularity errors, but also show no significant difference on surface roughness and cylindricity errors. The effects of the interaction between the cooling/lubrication systems, tool wear, and cutting speed indicate that only cylindricity error is influenced. Thus, the conclusion is that the best hole quality is produced with a higher cutting speed using flooded or minimum lubrication quantity independent of drill wear.
Effect of the Cutting Edge Preparation on the Surface Integrity after Dry Drilling
Procedia CIRP, 2014
Nowadays, cutting edge preparation is a widely applied tool improvement method, especially when concerns tool's life. However, the effects of the tool treatments on the generated hole surface are still an ongoing investigation. The machined hole is subject to severe contact with the tool, in particular the drill corner and guide, providing an increase of friction and thus, heat generation. Consequently, the surface integrity suffers several alterations. Therefore, this study aims to understand the effect of the cutting edge preparation on the surface integrity of holes. Experiments performed with carbide tools, coated with TiAlN and three configurations of tools (sharpened, polished with abrasive brushes and treated with drag finishing surface treatment) during dry drilling, showed that the tool condition has an important effect on the surface roughness, temperature and subsurface plastic deformation.
Experimental Assessment of Hole Quality and Tool Condition in the Machining of an Aerospace Alloy
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This paper deals with an experimental investigation of hole quality in Al2024-T3, which is one of the aerospace alloys used in aircraft fuselage skin due to its high level of resistance to fatigue crack propagation. The experiments are conducted with 6 mm uncoated carbide and HSS drill bits using a CNC machine under dry conditions and different drilling parameters. The characteristics of the hole quality are investigated in terms of its perpendicularity, cylindricity, circularity and hole size. An ANOVA (analysis of variance) and Pareto charts are used to analyze the effects of the drilling parameters on the hole quality. The hole quality is also assessed using a digital microscope to observe the formation of hole burrs. Moreover, scanning electron microscopy is also used to investigate the inside-hole surface defects. Further investigations are carried out using optical microscopy to inspect the post-drilling tool condition at high drilling parameters. The results show that hole qu...
An Experimental Investigations on Machining Parameters in Micro-drilling Process
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Under various fundamental machining process Drilling is one of them. For getting holes below 1mm Micro Drilling process which is high precision process are preferred. It is used for the purpose increasing quality of special parts and items. Along with high precision it is also preferred for high spindle speed application to improve productivity and quality. It has an attractive applications like Printed circuit boards, Fuel injection nozzles, Watch parts, Camera parts, Medical needles, Aeronautics, Mobilephones, Computerset. One of the major goal in machining operation is material Removal Rate . This paper deals with how the MRR can be optimized considering the input parameters like, speed, feed and depth of hole and Investigation had done by Designing Experiment in Taguchi and Analyzing using ANNOVA and signal to noise ratio. Taguchi method not only optimize quality characteristics through the setting of design parameters, but also reduce the sensitivity of the system performance t...
Size effects of micro drilling in steel
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The main objective of this research work is to investigate size effects by downscaling the twist drilling process into the micro range (diameter: d = 50 lm to 1 mm). Therefore, experimental micro drilling tests in steel AISI 1045 (normalized and full-annealed) are performed with different cutting conditions (drill diameter, feed, cutting speed) and compared with data obtained from conventional drilling. Various size effects and its significant influence on the micro cutting process are characterized with help of the experimental results. Additionally, the formula of Victor-Kienzle is adjusted to model the feed force in micro drilling operations.
The influence of drill point geometry on tool life
Tehnički glasnik, 2018
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 pr...
An Experimental Investigation on Micro Drilling of Cold Work Steel X153CrMoV12 By EDM
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In this study, it was aimed to analyze the effects of machining parameters on the process quality by drilling holes in heat treated cold work tool steel with a hardness of 60-62 HRC using the electrical discharge machining (EDM) method and Ø2 mm diameter brass electrodes. In this context, drilling was performed using three different current values (5, 6, 7 A), three different voltage values (1, 2, 3 V), three different discharge pulse frequency Ton (23, 26, 29 µs) as well as Toff (3, 5 µs) respectively, and the effects of these machining parameters on the machining time, material removal rate (MRR), electrode wear rate (EWR), surface roughness (SR) and hardness of around the white layer were analyzed using micro, macro and analytical measurements, especially with Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). As a result of the analysis, ıt was observed that current, voltage, Ton and Toff had an effect on machining time, MRR, EWR, SR and hardness,...