Materials Science Forum Vols. 836-837

Abstract: Inorder to analyze the influence of the grinding wheel parameters on the spiralgroove parameters in the grinding process of spiral groove, this paper analyses indetail the influence of grinding wheel radius, fillet radius and grinding wheelcone angle on the rake angle and the opening angle of the spiral groove basedon the spiral groove mathematical model of the end mill. And two polynomial werefitted between the grinding wheel fillet and the rake angle of spiral groove. Studieshave shown that: when the wheel attitude angle remains unchanged, the fillet ofgrinding wheel influence the rake angleand opening angle of spiral groove significantly; the cone angle of grindingwheel affects the opening angle largely; the radius and cone angle of grindingwheel have the weak influence on the rake angle of spiral groove.

Abstract: The titanium alloy thin-walled structure has been widely used in aircraft construction as one of the main load-bearing components. However, it is difficult to ensure the machining accuracy because of the machining difficulties of materials and structures. This paper takes titanium alloy (Ti6Al4V) thin-walled web as the research object and analyzes the factors of milling deformation. Based on the analysis, the milling process of the titanium alloy thin-walled structure is optimized, including the decrease of cutting force and the increase of processing system rigidity. Furthermore, a reasonable milling scheme is put forward.

Abstract: AFRP(Aramid Fiber Reinforced Plastics) is widely used in the aerospace and automotive while there are many problems in machining AFRP such as furry, delamination, burns and so on. Milling experiments of AFRP have been conducted to study the influence of different helix angle (0°, 30°, 60°) and cutting tools (traditional end mill, multiple flute end mill and compression end mill) on cutting force and machined surface quality. The results indicated that the cutting force has been reduced and the surface quality has been improved with the increase of helix angle. The cutting tool structure can make greater influence on machined surface quality than the cutting parameters. A cutting tool with the structure of multiple flute or herringbone cutting edge could reduce the axial cutting force. However the cutting force is too small to cut off fibers when using a multiple flute end mill. A good processing surface can be achieved while cutting with a compression end mill or a tool with big helix angle.

Abstract: High speed milling is one of the most commonly used machining processes in many fields of the industry. It is regarded as a simple and fast solution to achieve a high material removal rate, which allows an important production of parts. Unbalance is a problem in any machining process but becomes a considerable problem when reaching high speed machining. The vibrations due to an unbalanced tool or tool holder can result in a poor surface quality and a damaged tool. The damping of the vibrations can be achieved with a specially designed tool showing an anti-vibration clearance angle. This paper shows the influence of the anti-vibration clearance angle by a computational model and a set of experiments to see if it can reduce or suppress the vibrations due to unbalance in high speed milling.

Abstract: High-speed milling tests were performed on vol. (5%-8%) TiC_p/TC4 composite in the speed range of 50-250 m/min using PCD tools to nvestigate the cutting temperature and the cutting forces. The results showed that radial depth of cut and cutting speed were the two significant influences that affected the cutting forces based on the Taguchi prediction. Increasing radial depth of cut and feed rate will increase the cutting force while increasing cutting speed will decrease the cutting force. Cutting force increased less than 5% when the reinforcement volume fraction in the composites increased from 0% to 8%. Radial depth of cut was the only significant influence factor on the cutting temperature. Cutting temperature increased with the increasing radial depth of cut, feed rate or cutting speed. The cutting temperature for the titanium composites was 40-90 °C higher than that for the TC4 matrix. However, the cutting temperature decreased by 4% when the reinforcement's volume fraction increased from 5% to 8%.

Abstract: This paper is aimed at evaluating the micro-machinability of the Ti-6Al-4V titanium alloy made by the means of two different Additive Manufacturing (AM) technologies. AM comprises promising technologies, widely used especially to produce parts made of difficult-to-cut materials, such as the titanium alloys. Titanium alloys represent one of the most widely used materials in the biomedical field, thanks to the high biocompatibility and excellent mechanical characteristics. Even if near-net-shape parts can be produced through AM, semi-finishing and/or finishing machining operations may be necessary to obtain the required surface finish and geometrical tolerances. Micro-milling technique is a soliciting solution for this kind of application due to its high flexibility, elevated material removal rate and direct contact between the tool geometry and work piece. Nevertheless, there are deficiencies in the literature regarding the study of micro-machinability of materials produced by means of AM technologies. In this paper, the micro-machinability of the Ti-6Al-4V alloy obtained by two different AM technologies, namely Electron Beam Melting (EBM) and Direct Metal Laser Sintering (DMLS), was studied and compared in order to assess the influence of the material as-delivered condition. Micro-milling tests were conducted on a high-precision 5-axis Kugler™ micro-milling centre under dry cutting conditions, by using uncoated, two fluted, flat-end-square, tungsten carbide tools with a diameter of 300 microns. The full immersion slotting strategy was chosen under full factorial design of experiments with two factors (cutting speed and feed per tooth). The micro-machinability was evaluated in terms of burr formation, surface integrity (surface topography and surface defects), tool damage and microstructure alterations.

Abstract: Recently the demands for miniature component of varying materials have been rapidly increasing in aerospace industry. Carbon fiber reinforced plastics is widely used as functional or structural material due to its superior material properties. It also is one of the difficult to machine materials because of the poor machinability. This paper presents an experimental study on micro milling of carbon fiber reinforced plastics with self-developed polycrystalline diamond tool. Cutting force and specific cutting energy are analyzed. The minimum chip thickness and carbon fiber diameter are found to have great effect on the cutting force signature peak. Tool wear mechanism of polycrystalline diamond tool also is investigated.

Abstract: Fabrication of microchannels on titanium alloy with micro-milling is a tough challenge due to the difficultly to remove the burrs formed in machining process. A novel method to gelatinize workpiece surface to control the generation of burr as well as the optimization of cutting parameters are investigated in this paper. Differences existed between the process of micro-milling and that of traditional milling can be accounted for size effect. Influences of feed per tooth, depth of cut and spindle speed on the formation of burr were taken into consideration respectively by single factor method. The topographies of the machined surface with micro-milling were observed and measured by optical microscope. Results showed that the dimensions of burrs increased with the rise of depth of cut. However, it decreased initially, then increased later with the augment of feed per tooth. Sacrifice layer with PMMA was coated and gelatinized on the workpiece surface, which could restrain the plastic deformation of materials during titanium alloy micro-milling. The experimental results presented that the dimensions of burr could reduce greatly by the proposed PMMA coating method compared to materials without coating.

Abstract: Helical point micro-drill is characterized by a continuous helical flank instead of the piecewise planar flank, and its improved drilling performance is validated compared with planar drill point by some researchers. In this study, to analyze the effect of geometry parameters of helical point drill on the drilling performance, the micro-drills with different point angles, web thicknesses and helix angles of the flute are fabricated on a 6-axis CNC tool grinder, and a serial of micro-drilling experiments involving these drills on 1Cr18Ni9Ti austenitic stainless steel are carried out. In experiments, the drilling forces are measured and exit burrs are observed. Within a certain range of geometry parameters, thrust force increases with the increase of point angle and web thickness, and the decrease of the helix angle of the flute. The point angle is the main contributory factor for the thrust force followed by web thickness, while helix angle has a moderate effect on the force. Furthermore, poisson burr and rollover burr are generated with different point angles. Based on the results, a good selection of the helical point drill geometry parameters with small point angle, big helix angle and small web thickness are proposed to improve the micro-drilling performance.

Abstract: For the problem of the non standard cutter shape cutting edge not smooth transition connection and flank face of cutting tool grinding precision difference, the influence of wheel deformation is analyzed to different grinding linear speed, and the grinding wheel deformation error compensation grinding method is studied in this work. The grinding of annular milling cutter with double-circular-arc is processed in five axis CNC tool grinder. Finally the machining precision of annular milling cutter with double-circular-arc is tested by the tool test center, the result show that the wheel grinding method based on compensation of grinding can realize smooth transition in different parts of cutting edge belt of annular milling cutter with double-circular-arc and flank grinding precision is ensured.