Coating characterization of TiN & TiAIN on burr formation in drilling pragmatic investigation

Burrs are source of dimensional errors, jamming and misalignment in the assembly process. They may cause short circuits in electrical components and may reduce the fatigue life of the part. Furthermore, burrs can be a safety hazard to personnel because they are usually sharp. This scientific research investigates the characterization of 8 mm diameter, 120° point angle of coated drill tool in burr formation. The exit burrs were investigated using two different types of popular coatings, namely TiN and TiAlN. The effect of cutting speed and feed rate of the tool in burr formation onto the workpiece are discussed. In this study, the exit burr height was measured using optical microscope. Moderately harder material, 304L series stainless steel was used in the evaluation of the super coatings. The experiments were conducted using CNC HAAS Milling Machine. These experiments can be classified as hard drilling based on the experimental values and machining conditions

Study of the generation of microburrs in the process of drilling and its subsequent elimination by deburring, of tubes cylindrical aluminium AA6065-T9

Enllaç a la versió editorial: http://scitation.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1181&Issue=1Creation of microburrs drilling constitute a potencial danger because their detachment can modificate the correct operation of a mechanism. The burrs must be eliminated completely in the case of pistons brake, ensuring a high productivity and a low cost. In this work has been studied the mechanism for the creation of microburrs in thru holes drilled (phi2, 02 mm) of a aluminium alloy piston AA6065-T9 in order to various parameters such as the type of drill bit, feedrate, cutting speed and lubrication, imposing a minimum feedrate of 450 mm/min not to reduce the current production. Creation of microburrs drilling is inevitable and several deburring processes have been analyzed for their total elimination. After a few first essays, It has been determined that in order that the deburring are effective must be worked with minimal and known position burrr drillings.Peer ReviewedPostprint (author’s final draft

Optimization for drilling process of metal-composite aeronautical structures

Metal-composite laminates and joints are applied in aircraft manufacturing and maintenance (repairing) using aluminum alloys (AA) and glass fiber-reinforced polymer (GFRP). In these applications, drilling has a prominent place due to its vast application in aeronautical structures’ mechanical joints. Thus, this study presents the influence of uncoated carbide drills (85C, 86C, H10N), cutting speeds (vc = 20, 40, and 60 m min−1), and feed rates (f = 0.05, 0.15, and 0.25 mm rev−1) on delamination factor, thrust force ( Ft), and burr formation in dry drilling metal-composite laminates and joints (AA2024/GFRP/AA2024). Experiments were performed, analyzed, and optimized using the Box–Behnken statistical design. Microscopic digital images for delamination evaluation, piezoelectric dynamometer for thrust force acquisition, and burr analysis were considered. The major finding was that the thrust force during drilling depends significantly on the feed rate. Another significant factor was the influence of the drill type (combined or not with feed rate). In fact, it was verified that the feed rate and the drill type were the most significant parameters on the delamination factor, while the feed rate was the most relevant on thrust force. The cutting speed did not affect significantly thrust force and delamination factor at exit (FdaS). However, the combination f × vc was significant in delamination factor at entrance (FdaE). Based on the optimized input parameters, they presented lower values for delamination factors (FdaE=1.18 and FdaS=1.33) and thrust force ( Ft=67.3N). These values were obtained by drilling the metal-composite laminates with 85C-tool, 0.05 mm rev−1 feed rate, and 20 m min−1 cutting speed. However, the burrs at the hole output of AA2024 were considered unsatisfactory for this specific condition, which implies additional investigation

Development of a high-speed high-precision micro-groove cutting process

A high-speed, high-precision chip formation-based micro-groove cutting process has been developed for cutting grooves in metals with nearly arbitrarily shaped cross-sections, which have widths and depths of a few hundred nanometers to a few microns, and lengths of tens of millimeters. A flexible tool, consisting of a single-point cutting geometry mounted on the end of a small cantilever, is moved along a workpiece surface while a constant cantilever deflection is maintained to apply a cutting load. Depth of cut for a given tool shape is determined by cutting load and workpiece material properties. A major advantage of the flexible tool concept is increased depth of cut precision. Furthermore, the use of a flexible tool enables the process to be robust against machine tool registration error, guide misalignment, and component inertial deflections. The process was implemented by fitting a 5-axis micro-scale machine tool with a specially constructed micro-groove cutting assembly. Early, experiments using diamond-coated AFM probes as tools demonstrated process viability up to cutting speeds of 25 mm/min and chip formation at the sub-micron scale. However, AFM probe geometries proved too fragile for this demanding application. High quality tools with improved cutting geometries were designed and fabricated via focused ion beam machining of single-crystal diamond tool blanks, and tool edge radii of 50 - 64 nm were achieved. The improved tools enabled well-formed rectangular grooves to be cut in aluminum at up to 400 mm/min with widths of 300 nm to 1.05 microns and depths up to 2 microns. Complex compound v-shaped grooves were also produced. Virtually no tool wear (less than 20 nm) was observed over a cutting distance of 122.4 mm. Small amounts of side burr formation occurred during steady-state cutting, and exit burr formation occurred when a tool exited from a workpiece. Parallel 1.05 micron wide grooves were controllably cut as close as 1.0 micron apart, and machining of intersecting grooves was successfully demonstrated. To better understand process mechanics including chip formation, side burr formation, and exit burr formation at the small size scale involved, a 3D finite element model of the process was developed. Validation with experimental results showed that on average the model predicted side burr height to within 2.8%, chip curl to within 4.1%, and chip thickness to within 25.4%. An important finding is that side burr formation is primarily caused ahead of a tool by expansion of material compressed after starting to flow around a tool rather than becoming part of a chip. Also, three exit burrs, two on the sides of a groove and one on the bottom of a groove, are formed when a thin membrane of material forms ahead of a tool and then ruptures as the tool exits a workpiece. Finally, conclusions about the process are drawn and recommendations for future work are presented

Maintenance Actions to Address Fatigue Cracking in Steel Bridge Structures: Proposed Guidelines and Commentary

This document provides guidelines for the maintenance actions to address fatigue cracking and details at risk of constraint-induced fracture (CIF) in steel bridges. It is a synthesis of best practices from published literature, project reports, past and ongoing research projects, as well as input from industry professionals gathered through a web-based survey. Intended to be a very practical reference text, it is written with everyone in mind from a maintenance contractor to an asset manager and design engineer, providing detailed descriptions of the driving causes of fatigue cracking and CIF in steel bridges and accepted methods for repair or retrofit. A number of case studies are discussed giving context for the different detail susceptibilities and utilizing a mixture of real-world and rendered images to illustrate the problems and solutions. For each case, a suggested sequence of steps is also provided as a ‘‘how-to.’

Improvement deburring consistency of fuel nozzle parts

RÉSUMÉ: L'objectif de cette étude est d'améliorer la qualité produite par l'ébavurage des pièces de tourbillon d’air. Ces pièces de haute précision sont habituellement ébavurées de façon manuelle par un humain. Comme première étape vers l'amélioration de ces ébavurages, l'analyse des causes fondamentales a été réalisée. Puis les conditions actuelles des pièces ont été étudiées par des expériences utilisant la méthode de Taguchi. L’analyse de la variance a été menée sur les données recueillies pour illustrer la significativité des facteurs des plans d’expériences et de leur contribution. La formation de bavures sur les pièces a été étudiée, trois régions principales ont été analysées. Le modèle cyclique de formation de bavures a été observé à l'état d'équilibre de la formation de bavures. L'amélioration du profil de bavure a été réalisée suivant deux méthodes : 1) le liquide de refroidissement à travers les trous d’huile du foret et 2) en position verticale du perçage. Le procédé d’ébavurage avec des abrasifs magnétiques a été évalué comme une alternative possible pour l'ébavurage manuel. Les échantillons ont été traités sous deux conditions : 1) pas de préparation en sortie de trou après perçage et 2) sortie de trou préparée. Les échantillons dont leurs arrêtes (sorties de trou) ont été préparées, ont montré une amélioration significative en terme de régularité.----------ABSTRACT: This study is about improving the deburring consistency of air-swirlers. The parts are high precision critical components of hot section of aircraft engine, which have key role in stabilizing the combustion flames via providing turbulent air-fuel mixture for the combustion chamber. The product needs to meet high standards including edge quality and surface finish. These small in process parts are deburred manually due to their size, complex geometry, restricted access and adjacent critical surfaces to the edges. The title of the research was selected through investigations, cost estimation and prioritization of deburring issues within Pratt and Whitney Canada. In order to tackle the issue, a comprehensive study was conducted on state of the parts. The investigation aimed to lay a basis of comparison to evaluate the further improvement approaches. The parts were investigated through experiments, designed based on Taguchi method. For designing the experiments, root cause and fault tree analysis was performed first. Then the preliminary experiments were employed to define the level of affecting parameters. The designed experiments were conducted on four different in process parts. The data was analyzed using STATISTICA software. Based on the results, the areas, which required further investigation, were identified and feasible improvement strategies were proposed. The complementary experiments comprise two main topics: burr control and alternative deburring process. In order to improve the burr characteristics of the parts, burr formation study was conducted. The parts were assessed during various manufacturing cycles. Burr formation pattern was identified on the parts. Based on observation it was concluded that the pattern could be attributed to the temporary degradation of tool properties due to elevated temperature cutting during short time intervals. Hence, the temperature of the cutting tool was measured during production via thermal sensors. With respect to validation of hypothesis two main strategies were proposed in order to provide proper and homogenous cooling to reduce the tool temperature during the cut: Coolant thru design drill and vertical position for production. Both approaches revealed significant results. The burr height decreased and burr profile improved using both methods