Search results

The purpose of this paper is to present the results of an investigation on the straightness, flatness and circularity achievable on two direct RT methods: direct metal laser sintering (DMLS) and stereolithography (SLA).

The steps included manufacturing of samples in eight custom designs with widely used geometric features, intelligent sampling of measurement data, and estimation of corresponding form tolerance by the least square method (LSM). The region elimination adaptive search‐based sampling method involved selecting additional sampling points around the maximum deviation in both positive and negative directions from the corresponding reference feature. The LSM solutions, which are commonly used in metrology, are used to estimate the form tolerances considering the best points along with initial measurement data points.

Application of the region elimination search‐based sampling method enables form tolerance estimation from a limited number of sample measurements. The study of the DMLS and SLA processes suggested that form accuracy of SLA samples are relatively poor, though their dimensional accuracy is much better than DMLS.

This paper was focused on estimating the form tolerances based on limited number of measurement data using region elimination search‐based sampling technique. It was assumed that build process parameters suggested by the material and RP systems vendors gives optimum results, presently it does not cover the effect of geometry and other causes of errors on form accuracy.

There are two major applications of this investigation and the corresponding knowledge base: evaluating the process capabilities of different rapid tooling processes for comparison and for selecting an appropriate process; and allocating tolerance based on manufacturability considerations, so that the designs are compatible with the process, leading to fewer iterations. A similar approach can be used for updating the capabilities of an improved process as well as include newer processes to develop a comprehensive database of RT process capabilities.

In most of the previous benchmarking studies, a given RT process is compared with conventional practice or a limited number of other RT processes, the capabilities in terms of dimensional accuracy, form tolerance, and surface properties (surface finish, wear, and scratch resistance) have not been studied very well. To the best of authors' knowledge, no efforts have been made to estimate form tolerances of the parts or tooling produced by rapid prototyping and tooling processes. Application of the region elimination search‐based sampling technique enables estimation of form tolerances that saves costly experimentations. It appears to be completely new in the rapid prototyping and tooling domain.

The purpose of this paper is to show how an ultra‐precision manufacturing process (flycutting) can be improved through interferometry.

The paper presents a theoretical model of the machine tool cutting system and then uses interferometer measurements to validate the results. The model is then used to show some general findings relating process conditions to workpiece quality.

A realistic cutting model can predict the workpiece flatness with excellent accuracy and closely match interferometer measurements. The process parameters in precision flycutting should be chosen such that the flycutting tool is in contact with the workpiece for an integer number of vibration cycles. The machine tool stiffness and structural damping will affect the workpiece quality, but the most significant improvements are made through thoughtful selection of the flycutter spindle speed as it relates to the machine dynamics.

This paper presents a math model that accurately matches results obtained by experimental verification and extensive testing. Interferometry is shown to be an extremely useful tool in optimizing the process conditions in a flycutting manufacturing operation. Furthermore, the results are of general use to practitioners using flycutting in a variety of industrial applications.

The purpose of this paper is to report experimental investigations performed to analyze the effect of process parameters on the shape accuracy of selective laser sintered (SLS) parts.

The effect of process parameters, namely build orientation, laser power, scan speed, cylinder diameter and build chamber temperature has been studied on shape accuracy by using geometric tolerances such as cylindricity and flatness. Central composite design (CCD) is used to plan the experiments and a second order regression model has been developed to predict flatness and cylindricity. The significance of process variables on flatness and cylindricity has been evaluated using analysis of variance technique.

It is observed that interaction effects are more dominant than individual effects. In case of cylindricity, it is found that the interaction between the scan speed and orientation is the dominant factor next to the orientation and quadratic effect of the geometry. In case of flatness, the interaction between build chamber temperature and scan speed is the dominant factor.

The empirical models presented in this paper work within the range of values used for the experiments and most of these models need to be redeveloped for use with other materials.

The empirical models developed in this work would be useful in deciding the process parameters for parts with improved geometrical tolerances. The optimum parameters identified from the empirical model are found to yield accurate parts with minimum shape error.

The paper establishes the interactions between this build orientation, geometry and process parameters on the shape accuracy of SLS process.

The purpose of this paper is to develop a numerical approach inspired by Geometrical Product Specifications (GPS) standards for the assessment of geometrical defects appearing during Additive Manufacturing (AM) by Laser Beam Melting (LBM).

The study is based on finite element (FE) simulations of thermal distortions, then an assessment of flatness defects (warping induced by the high-residual stresses appearing during the manufacturing) from the deformed surfaces provided by simulation, and finally the correction of the calculated flatness defects from preliminary comparison between simulated and experimental data.

For an elementary geometrical feature (a wall), it was possible to identify the variation in the flatness defect as a function of the dimensions. For a complex geometry exhibiting a significant flatness defect, it was possible to improve the geometric quality using the numerical tool.

To the best of the author’s knowledge, this work is the first attempt using a numerical approach inspired by GPS standards to identify variations in thermal distortions caused by LBM, which is an initial step toward optimization. This paper is mainly focused on flatness defect assessment, even though the approach is potentially applicable for all types of geometrical defects (shape, orientation or position defects).

The study opens prospects for the optimization of complex parts elaborated using LBM, based on the minimization of the geometric defects caused by thermal distortions.

The prospects in terms of shape optimization will extend the potential to benefit from the new possibilities offered by LBM additive manufacturing.

Unlike the usual approach, the proposed methodology does not require any artifacts or comparisons with the computer-aided-design (CAD) model for geometrical distortion assessment. The present approach opens up the possibility of performing metrology from FE simulation results, which is particularly promising in the AM field.

BGAs are a new type of surface mountable component. Successful industrial implementation of BGA assembly on electronic boards needs specific studies, evaluations and qualification. The methodology used in Bull is presented, along with an analysis of the different BGA types. Implementation and qualification results are provided.

The purpose of this paper is to verify the feasibility and reliability of mineral casting applied in high-precision printed circuit board (PCB) drilling machine. The mechanical properties of machine frame are quantified to provide a solution for machine tool industry to seek a perfect substance competing with classic materials such as cast iron and granite.

The optimal design of machine frame is performed via the CAD system combined with finite element analysis (FEA). The mechanical properties of the frame elements are evaluated by a series of mechanical experiments: static performance is quantified by flatness tests, dynamic behavior is estimated by experimental and numerical models, respectively. Meanwhile, the performance of the frame element with traditional materials is examined experimentally.

Mineral casting parts can be successfully applied to PCB drilling machine to meet high accuracy requirements. The characteristic of mineral casing gives the most possibilities in structural design. The frame parts show good static/dynamic behaviors by structural optimization processes. Especially, the machine frame with mineral casting gains a great weight reduction compared with traditional materials.

The application of mineral casting in PCB drilling machine offers greater design flexibility and innovative system solutions. The combination of FEA is convincing to achieve optimal structure and ideal weight to maximize the economic and technical benefits. Moreover, lightweight design of machine structural components achieves not only higher kinematic/dynamic precision but also considerable cost reduction.

In the process of cold rolled strip, there is tight coupling between flatness control and gauge control. The variation of the roll gap caused by the change of bending force will lead to the change of rolling force. Furthermore, it can cause a deep impact on the control accuracy of strip exit thickness and exit crown. The purpose of this paper is to improve the accuracy of the bending force preset value for cold rolled strip.

In this paper, the bending force preset control strategy with considering of rolling force was proposed for the first time and the preset objective function of bending force was established on the basis of the two-objective optimization of bending force and rolling force. Meanwhile, the multi-objective intelligent algorithm – INSGA-II – was used to solve the objective function.

The proposed bending force multi-objective preset model has been tested in a 1,450 mm tandem cold rolling line. The analyzed results of field data show that the deviations of strip exit thickness and exit crown are reduced effectively by using the improved model, and at the same time, more reasonable bending force preset values are obtained, which can enhance the accuracy of flatness preset control.

A preset model of bending force with considering flatness and gauge is proposed in this paper and the multi-objective function of bending force preset is established on the basis of the two-objective optimization of bending force and rolling force. The value lies in proposing a new decoupling method of rolling force and bending force.

This paper aims to investigate the quality of printed surfaces and manufacturing tolerances by comparing the cylindrical cavities machined in parts obtained by fused deposition modeling (FDM) with the holes manufactured during the printing process itself. The comparison focuses on the results of roughness and tolerances, intending to obtain practical references when making assemblies.

The experimental approach focuses on the comparison of the results of roughness and tolerances of two manufacturing strategies: geometric volumes with a through-hole and the through-hole machined in volumes that were initially printed without the hole. Throughout the study, both alternates are explained to make appropriate recommendations.

The study shows the best combinations of technological parameters, both machining and three-dimensional printing, which have been decisive for obtaining successful results. These conclusive results allow enunciating recommendations for use in the industrial environment.

This paper fulfills an identified need to study the dimensional accuracy of the geometries obtained by additive manufacturing, as no experimental evidence has been found of studies that directly address the problem of the FDM-printed part with geometric and dimensional tolerances and desirable surface quality for assembly.

The purpose of this paper is to present a study of the stereolithography apparatus SLA 250‐50 motivated by the introduction of the new epoxy resin AccuGen™.

Several process variables are examined using a Box‐Behnken design and optimization techniques are employed to determine their optimal settings.

The results indicate operating conditions at which high levels of performance can be achieved.

The results reported in this research are process specific, however, the methodology employed can be readily applied to different rapid prototyping processes.

Effective utilization of the SL process.

Quantitative understanding of the process capability in relation to key process variables.