1,721,066 research outputs found
Improving Laser Microcutting Quality of AZ31 Mg Alloy by Submerged Cutting for Manufacturing of Biodegradable Stents
No full textCardiovascular stents are typically produced by laser microcutting of tubular precursors. The cutting edge quality is a key factor for the correct interaction between the human body and the inserted biomedical device. The reduction or elimination of dross during process is desired for increased productivity in manufacturing. Laser cutting with the aid of submersion liquid can improve the cut edge quality, which can be exploited also in the case of manufacturing of biodegradable stents in Mg alloys. In this work, submersion cutting of AZ31 Mg alloy with a pulsed green fibre laser is demonstrated. Three different submersion liquids, namely pure water, ethanol-water solution and paraffin based lubricant oil were used and compared to dry cutting condition. The impact on quality was quantified by the amount of deposited dross and complete cut penetration. The results show that surface dross can be remarkable reduced by the correct selection of submersion liquid and laser processing parameters
Uncertainty in 3D Micro Measurement with Focus Variation Microscopy
No full textMicro manufacturing is important for new product applications. As such, due to its size, micro tolerance verification is a challenging task. Optical metrology instruments provide solutions for this task due to their flexibility in accessing the part surface. In addition, it can capture big data in shorter time compared to the tactile (contact) instruments as well as eliminating the risk of damaging the part surface. A fundamental aspect in geometric measurement is traceability, which strictly relates to measurement uncertainty. Only by quantifying uncertainty, measurement results are reliable and comparable each other. Moreover, uncertainty estimation in geometric metrology is not easy since it is “taskspecific” with respect to what is currently measured. In this paper, the importance of measurement uncertainty and its available estimation methods are briefly presented. The implementation of a simulation method to estimate the task specific measurement uncertainty is presented and discussed with a case study
Microtool Wear Measurement and Assessment
No full textWear is an unavoidable phenomenon in tooling. Many studies have been conducted to try to reduce it. In the case of microtools, the problem of wear is even more difficult to approach. Microtools wear mechanics and characteristics are not well known yet. In this work, we will focus on the microtool wear measurement and characterization as a first step necessary to the study of how microtool wear happens during machining. A couple of algorithms will be proposed for the automatic calculation of flank wear land and face crater wear. However, specific measurements on microtools will show if these wear indicators are not suitable for microtools
Test for Evaluating the Performance of Micro Milling Processes
No full textThe growing interest of several industrial fields (biomedical, medical, electronic, defence, aerospace, etc) on miniaturized components leads to an increased interest on micro cutting processes. When approaching these processes, phenomena that can be neglected in macro scale become predominant. For this reason material microstructure, material and geometry of the tool, machine-tool and process parameters must be correctly defined. Another aspect of interest in micro scale cutting is the definition of tests for qualifying the process performance. The present paper aims to propose a testing procedure for evaluating the performance of a micromilling process considering the machine-tool, tool-holder, tool and workpiece fixtures chain. This procedure is based on a series of micro channels realized by consecutive steps. A case of study is reported. The results allows to better understand the performances of the process and of the chain composed by the machine-tool, the tool-holder and the tool
Performance of Micro End Milling Force Prediction on Aluminum 6061-T6 with 3D FE Simulation
No full textMicro-milling is a rather complicated process to simulate due to the complexities involved, such as the geometrical, mechanical, tribological, thermal and chemical aspects. They all lead to the generation of cutting forces and consequent material removal in micro scale which have some straight difference in respect to macro cutting. So far, not many 3D FEM have been presented along with their experimental validation results in micro milling. This study discusses the performance of 3D force prediction of a Finite Element model of micro end-mill cutting on Aluminum 6061-T6, implemented in AdvantEdge®. FE shows some important advantages, i.e. can easily deal with any kind of tool geometry and any side effects affecting chip formation such as thermal aspects and material properties changes. On the other hand, due to the small chip size of micro milling, extremely fine meshes and related automatic remeshing techniques are required thus increasing the computation efforts: the simulation of even a partial cutter engagement requires several hours/days of computation with the available power on to-date computing servers. In order to evaluate whether these efforts are worthy, compared to other modelling techniques, the performance of the FEM prediction were compared with the performance of a state-of-art mechanistic model, capable of including minimum chip thickness aspects as well effective rake angle effects and capable of providing force prediction with less computational time. The simulated cutting forces with the two models are then compared with experimental results and a supporting discussion is provided. Tolerable correlations between the forces profile shapes were observed. In terms of force magnitude, the predictions were overestimating the real values, also considering the results provided by the mechanistic model and to cope with that some further development area of the model are identified
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cutting Force Prediction in Micro Orthogonal Cutting by an Analytical-Numerical Coupled Model
No full textThe slip-line field model developed by Waldorf [1] for the macroscale is suitable to predict cutting forces when a large ploughing action occurs, as in micromachining, since it takes into account a rounded-edge tool. The present study considers the procedure that was developed in a past work of the same authors [2] to adjust the slip-line model for a specific target material by means of a restricted set of experiments. The aim of this paper is to improve this procedure by coupling analytical and numerical modeling and to make the calibration phase independent from cutting experiments. The prediction performance of the analytical-numerical coupled model is evaluated by an objective comparison between the predicted cutting and thrust forces and the forces acquired in the experimental campaign carried out on C38500 brass (CuZn39Pb3)
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