Abstract: This paper investigates the effects of the cutting tool edge radius on the cutting forces and stability lobes in micro-milling. The investigation is conducted based on recently developed models for prediction of micro-milling cutting forces and stability lobes. The developed models consider the nonlinearities of the micro-milling process, such as nonlinear cutting forces due to cutting velocity dependencies, edge radius effect and run-out presence. A number of finite element analyses (FEA) are performed to obtain the cutting forces in orthogonal cutting which are used for determining the micro-milling cutting forces. The chip morphology obtained for different tool edge radii using FEA is presented. It is observed that at large tool edge radii the influence of the ploughing effect become more significant factor on the chip morphology. The results related to micro-milling cutting forces and stability lobes show that by enlarging the tool edge radius the micro-milling cutting forces increase while the stability limits decrease.
Abstract: Miniature end mills with sizes in the order of 1 mm in diameter are used in several industries for generation of small features with high precision. As in case of standard size end mills, chatter stability can be an important problem in these applications as well, and it is the focus of this paper. Dynamics and stability analyses need frequency response function (FRF) of the tool. There are several practical problems in measuring miniature tool FRFs. First of all, it is not possible to excite the tool tip using an impact hammer due to the small size. In addition, miniature tools have very high natural frequencies which are difficult to excite and measure. An indirect measurement approach for miniature milling tool dynamics is used. Another important problem with miniature tools is the detection of chatter. Although stability diagrams can be used for selection of stable conditions, cutting tests proved that chatter detection for miniature tools is very challenging.
Abstract: Over the last three decades, researchers have responded to the demands of industry to manufacture mechanical components with geometrical tolerance, dimensional tolerance, and surface finishing in nanometer levels. The new lapgrinding process developed in Brazil utilizes lapping kinematics and a flat grinding wheel dressed with a single-point diamond dresser in agreement with overlap factor (Ud) theory. In the present work, the influences of different Ud values on dressing (Ud = 1, 3 e 5) and grain size of the grinding wheel made of silicon carbide (SiC = 800, 600 e 300 mesh) are analyzed on surface finishing of stainless steel AISI 420 flat workpieces submitted to the lapgrinding process. The best results, obtained after 10 minutes of machining, were: average surface roughness (Ra) 1.92 nm; 1.19 µm flatness deviation of 25.4 mm diameter workpieces and mirrored surface finishing. Given the surface quality achieved, the lapgrinding process can be included among the ultra-precision finishing processes and, depending on the application, the steps of lapping followed by polishing can be replaced by the proposed abrasive process.
Abstract: The rise of high speed manufacturing gave birth to high capabilities machine tools; meanwhile the constraints have increased. To face these challenges, several simulation solutions have been proposed. They cover many aspects of the manufacturing process such as CNC controller behavior, cutting forces estimation or geometric errors. However, most of them center on a specific view of the machining process. In contrast, combined multiphysics and multiscale approaches are beneficial, in particular for surface integrity improvements purposes. This paper discusses the interest of using simulation approaches at different levels. The first target is to analyze existing parameterizations. Then, a comparison of several parameters tuning extends the space of acceptable solution and provides new enhancements. Finally, a simulation method for form defect of machined surfaces identification is introduced. Several simulation solutions developed in the laboratory are taken as illustrative examples.
Abstract: Rough end mill tools with serrated cutting edges profile are extensively used for removing a bulk of material and suppressing the chatter vibrations during milling operations. The serrated profile of cutting edge has phase shift from one flute to the next and interfere with the regeneration of waviness of the cut surface. In this research, serrated cutting edges are analytically defined and geometrically modeled as a NURBS curve. In addition; the chip load on the serrated cutting edges is calculated by a newly proposed algorithm. The validity of the algorithm is investigated by applying solid modeling techniques using ACIS 3D solid Modeler. In order to validate the results, several experiments were performed by utilizing serrated end mill. Verification of simulated and experimental results shows that the developed algorithm can be effectively implemented to simulate the cutting force for any geometry of milling tools as well as serrated end mills.
Abstract: The focus of CAM systems is on effectively creating cutting tool paths. However, collision risk is very high on multi axes machines when performing non-cutting traverse moves. If available, CAM systems offer limited setting options for non-cutting tool moves. In this paper an approach is presented that allows to automatically generating non-cutting tool paths. Process planners will not only be released from developing and simulating time-consuming multi axes traverse moves. The automatically calculated traverse moves will also machine-specifically optimized with respect to various optimization criteria.
Abstract: This work presents some contributions for optimization of the 2 ½ D pocket machining. The machining strategy considered is divided in internal machining and corners machining. The internal machining is carried through equidistant paths to the contour (offset) made by using Voronoi’s Diagram and the corner machining follows the same principle. As the Voronoi Diagram is parametric, the spaces between the paths can change. Thus, the best situation of spacing between paths can be determined to optimize the process. By using Dynamic Programming, the best combination of dimensions of the available tools can also be identified to remove the material of the pocket in smaller time.
Abstract: The electrical discharge machining (EDM) is a process widely used in machining of complex geometries and hardened materials, conditions that often are not met by conventional machining processes. In EDM the electrode reproduces its image or geometry on the part and this image is obtained by chip removing process, which is given by high frequency electrical discharges, causing the melting and vaporization of electrically conductive materials. Due to this mechanism of material removal, the surface is subjected to high thermal loads, which heavily influences the surface quality of obtained parts. For the characterization of these surfaces must be considered the surface topography and the metallurgical changes of the subsurface layer, since both characteristics influence the functionality of the machined parts. In addition, several variables related to the EDM process have influence on the characteristics of the generated surface. This work presents a study of the influence of EDM process on the surface quality of square cavities. It was evaluated different regions of the cavities, such as side wall, bottom and corners. The results showed significant differences between the analyzed regions.
Abstract: Electrochemical machining (ECM) is the controlled removal of material by anodic dissolution in an electrolytic cell in which the workpiece is the anode and the tool is the cathode. The ECM presents the advantages: three-dimensional surfaces with complicated profiles can be easily machined in a single operation, irrespective of the hardness and strength of the material. ECM offers a higher rate of metal removal as compared to traditional and nontraditional methods, especially when high machining currents are employed. There is no wear of the tool, which permits repeatable production. This work shows a study of development of a prototype of electrochemical machining (ECM) developed at the Federal University of Uberlândia Minas Gerais-Brazil. A state-of-the-art ECM system is the art of assemblage of facilities including a proper ECM machine, a power supply, a process parameter control system, and an electrolyte preparation, feed and purification system. With the prototype developed, the material removal rate (MRR) was studied. The MRR was influenced by tool feed rate and type of electrolyte.
Abstract: This paper shows a study of correlation between EDM´s parameters with the level of superficial defects development, which can lead to premature failure of die cast mold machined by EDM. The correlation of parameters was determined through experimental matrix that uses the DOE methodology (Design of Experiment). In order to evaluate the surfaces of some machined samples a stereo optical microscopy, SEM (the scanning electron microscope) and a micro hardness profile machine were used. The results show that in the worst machining condition, which is caused by association of long electric discharge pulse time-on and graphite machine-electrode, it is possible to minimize the amount of surface defects, without applying a subsequent machining process such as polishing, just using the reduced time-on´s electric discharge pulse, copper electrode and dielectric fluid with base of hydrocarbon.