Additive manufacturing is being introduced in industry during the last years being laser cladding one of the most representative technologies. Laser cladding is usually combined with machining in ...hybrid processes in order to obtain tolerance and finishing requirements. Therefore, added material must be machined and material properties need to be evaluated for a high quality machining operation execution. In this paper, laser deposited Inconel®718 alloy machinability properties are evaluated. The work is focused on hybrid processes of laser cladding build up geometries that require final machining operations such as turning and milling for final part obtaining. Inconel®718 machining behavior is analyzed for turning and milling operations. Turning tests are carried out for different cutting speed values (60, 80, and 100 m/min), cutting speed values (0.1, 0.2, and 0.4 mm), and depth of cut values (0.1, 0.2, and 0.3 mm/rev). Milling tests are also performed for different machining parameters such as axial depth of cut (20, 15, 10, and 5 mm), radial cutting depth (0.1, 0.3, and 0.5 mm), cutting speed (depending on the average diameter for each axial cutting depth), and feed per tooth (0.05 and 0.06 mm/tooth). For both processes, the material is studied in three different states, that is, base material (heat treated), added material as deposited (i.e., without final heat treatment), and deposited and treated material (with final heat treatment). In all cases, machinability properties such as cutting forces, specific cutting energy, material roughness, and microhardness values are evaluated. Obtained study results are discussed in the last section.
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•Presentation of a small-size dataset of friction drilling experiments of two dissimilar materials.•Gap’s model using different artificial intelligence techniques: MLPs, decision ...trees and ensembles of decision stump.•Discretization of the gap is required to obtain accurate models taking into account real industrial requirements with small datasets.•Analysis of performance quality and tuning effects of the machine-learning techniques is presented.•Adaboost ensembles provide the highest accuracy and are more easily optimized than the other techniques.
Form and friction drilling techniques are now promising alternatives in light and medium boilermaking that will very probably supersede conventional drilling techniques, as rapid and economic solutions for producing nutless bolted joints. Nonetheless, given the number of cutting parameters involved, optimization of the process requires calibration of the main input parameters in relation to the desired output values. Among these values, the gap between plates determines the service life of the joint. In this paper, a suitable smart manufacturing strategy for real industrial conditions is proposed, where it is necessary to identify the most accurate machine-learning technique to process experimental datasets of a small size. The strategy is first to generate a small-size dataset under real industrial conditions, then the gap is discretized taking into account the specific industrial needs of this quality indicator for each product. Finally, the different machine learning models are tested and fine-tuned to ascertain the most accurate model at the lowest cost. The strategy is validated with a 48 condition-dataset where only feed-rate and rotation speed are used as inputs and the gap as the output. The results on this dataset showed that the Adaboost ensembles provided the highest accuracy and were more easily optimized than artificial neural networks.
In 1907, F.W Taylor—the father of production engineering—exposed the fundamentals of modern machining and defined chatter as the most obscure and delicate of all problems facing the machinist ...
The geometry of rotary aircraft engine components is usually defined by thin mechanical elements and complex surfaces that are only achievable by 5-axis machining due to either limited access or the ...design itself. Such thin-walled characteristics make these components susceptible to vibrations while machining and usually require careful manipulation of the toolpath parameters to minimize cutting forces and vibration. Moreover, the tool suppliers’ approach leans towards the feature-build design of cutter geometry to increase the productivity and quality of a machined surface. Some examples of those recent improvements for rotary aircraft engine components are barrel-shaped tools that attempt to increase the contact radius on the tool-part interface to minimize step-over while conserving the scallop height to meet roughness tolerances. This research aims to fill a gap in the current literature by proposing a stability model for barrel-shaped tools. Stability contour maps make use of a mechanistic dynamic force model for barrel-shaped tools. The force model is also capable of including tool runout and orientation angles, tilt and lead, as named in most CAM software. By simulating dynamic forces on the time domain, a contour map is presented to address unstable vibrations. Since forced vibrations and surface location error (SLE) may also appear when milling aircraft parts, SLE and surface roughness are also determined. Finally, given the complexity and number of parameters, validation of the stability maps is performed through experimental chatter tests using a thin wall component.
The machining of slots in aeronautical turbine cases and discs is an extremely delicate operation. First, these parts require materials with excellent wear, high temperature and corrosion properties, ...such as the low machinability materials of the S group. Secondly, as this is one of the last turning operations, the value of the part is already considerable and any machining error can be dramatic. Traditionally, carbide tools have been the choice due to their greater safety and precision control. However, ceramic inserts offer unquestionable advantages in terms of higher cutting speeds and lower cost per part. Nonetheless, the behaviour of these cutting tools has a much narrower application interval (i.e. optimal set of cutting parameters) than carbide inserts. Machine workers need reliability. This work analyses the performance of ceramics, specifically, whiskers reinforced alumina type ceramics in the machining of grooves on Inconel® 718. Specifically, it analyses the effects of edge rounding, wear and other cutting parameters on cutting forces, and proposes a predictive model for grooving including the above parameters (rounding, wear and feed) for the first time. The validation results gave relative errors of 1.5% in the tangential component, and 4.8% in the feed component. As a result, it can be stated that the rounding radius affects more feed components than tangential ones, being, moreover, more critical to wear. Furthermore, smaller feeds and bigger cutting edge radii delay the apparition of flank wear.
Gamma titanium aluminides (γ-TiAl) present an excellent behavior under high temperature conditions, being a feasible alternative to nickel-based superalloy components in the aeroengine sector. ...However, considered as a difficult to cut material, process cutting parameters require special study to guarantee component quality. In this work, a developed drilling mechanistic model is a useful tool in order to predict drilling force (
) and torque (
) for optimal drilling conditions. The model is a helping tool to select operational parameters for the material to cut by providing the programmer predicted drilling forces (
) and torque (
) values. This will allow the avoidance of operational parameters that will cause excessively high force and torque values that could damage quality. The model is validated for three types of Gamma-TiAl alloys. Integral hard metal end-drilling tools and different cutting parameters (feeds and cutting speeds) are tested for three different sized holes for each alloy.
The anisotropic nature of laser powder bed fusion (LPBF) parts means that the cutting force coefficients obtained by linear regression or non-linear optimization methods only work for one tool ...position relative to the workpiece. These methods must obtain a new set of coefficients for each tool position relative to the workpiece, which becomes cumbersome for surface machining with multiple tool-to-workpiece orientations, which is typical for LPBF parts. As a first step to overcome this drawback, this paper presents a new methodology for calculating cutting coefficients sensitive to material shear strength changes when the tool changes orientation. To this end, a vector inverse model based on the instantaneous contact area is presented. The shear coefficients obtained from the present model make physical sense and provide the basis for predicting cutting coefficients for multiple tool orientations from recently developed microstructure-based models. For the model verification, prismatic IN718 LPBF samples were manufactured and machined with a peripheral endmill for three tool orientations (cases). The material was characterized with SEM and EBSD, and the plastic anisotropy was verified. The coefficients obtained with the proposed model presented a high correlation (0.97) with the cutting resistance in contrast to those obtained with the linear inverse model, which establishes that the vector-based mechanistic coefficients are more appropriate for anisotropic materials. The simulated cutting forces from the coefficients obtained through the proposed model were compared with the experimental forces, observing similar patterns and levels. The coefficients obtained with the model allow average forces to be obtained with a prediction error between 5 and 15 %, depending on the percentage of instantaneous data used to estimate the mean value of the coefficients.
Ball-burnishing is presented herein as a mechanical surface treatment for improving mechanical properties after the friction stir welding process. Ball-burnishing provides good surface finish, high ...compressive residual stresses, and a hardness increase of the surface layer. These characteristics are key for the fatigue life improvement of the component, and for wear resistance due to the higher hardness. This work presents a complete analysis of surface and sub-surface hardness values focusing on the determination of each process parameter influence. Burnishing pressure, radial width, and burnishing direction influence were analyzed. The tested material was 2050 aluminum alloy with two different heat treatments (T3 and T8). The optimum parameters were established, and a complete analysis of the surface hardness was performed. Results show that burnishing is an economical and feasible mechanical treatment for the quality improvement of component surfaces.
The productivity during the machining of thin-floor components is limited due to unstable vibrations, which lead to poor surface quality and part rejection at the last stage of the manufacturing ...process. In this article, a semi-active magnetorheological damper device is designed in order to suppress chatter conditions during the milling operations of thin-floor components. To validate the performance of the magnetorheological (MR) damper device, a 1 degree of freedom experimental setup was designed to mimic the machining of thin-floor components and then, the stability boundaries were computed using the Enhance Multistage Homotopy Perturbation Method (EMHPM) together with a novel cutting force model in which the bull-nose end mill is discretized in disks. It was found that the predicted EMHPM stability lobes of the cantilever beam closely follow experimental data. The end of the paper shows that the usage of the MR damper device modifies the stability boundaries with a productivity increase by a factor of at least 3.
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