Jefferson de Oliveira Gomes

Analysis of high-speed milling dynamic stability through sound pressure, machining force and tool displacement measurements

High-speed milling is a manufacturing process that has great economical potential owing to high material removal rate, accuracy and quality of machined workpieces. However, chatter might arise especially in situations where there is lack of dynamic stiffness of the system composed by the machine tool, the cutting tool and the workpiece. This work analyses the dynamic stability of the high-speed end milling process. The evaluation of stability is based on sound pressure, machining force and tool displacements measured during the process. In order to investigate the transition from stable cutting to cutting with chatter, the experimentally measured tool displacements are used as input data into a computer simulation to estimate the chip thickness variation during the process. It was found that for unstable cuts, the tool shaft motions are elliptical, process dynamics are dominated by power at the chatter frequency and other vibration modes of the system can resonate with the harmonics of the chatter frequency. Through the computational simulation of the estimated chip thickness variation, it was possible to observe the transition from stable cutting to cutting with chatter, the phase differences between undulations left by subsequent teeth and their consequences in machining forces.

Applying a Benchmarking Methodology to Empower a Virtual Organisation

This paper describes an experience applying a benchmarking methodology in a Virtual Organisation (VO) called Virfebras. A peculiar characteristic of Virfebras is that enterprises’ members are competitors, but entrepreneurs are convinced that they have to work co-operatively in order to achieve common business-related goals.

Evaluation of Technological Trends and Demands of the Manufacturing Industry to a Center of R&D&I

The manufacturing industry is fairly representative in the Brazilian economy. The research activities in technology, development and innovation promoted by technology centers are of great importance to boost the competitiveness of this segment. In this context, this work aims presenting the development of the strategic planning for a Center of R&D&I (Research & Development & Innovation), looking 20 years ahead, on a macro level, creating a master plan which summarizes the future focus areas of competence for technology research, development and innovation, coping with manufacturing trends, using a participative workshop approach. Thus, it is expected that this center offer integrated technological solutions with high added value that promote the development and competitiveness of the manufacturing industry, in the prospects for medium and long term. In order to achieve the project objectives taking the principle of strategic planning was followed. On the one hand, focus was placed on the internal perspective analyzing the current status of the Center. On the other hand, the environment of the Center (external perspective) was analyzed. Matching the analysis results regarding both perspectives future competence areas were derived, according to global technological trends as well as national and local industrial demand. Thus, the competencies required to be developed by a technology center to meet the manufacturing industry over the next twenty years would be derived.

Combining Collaborative Networks and Knowledge Management: The SENAI Case

This work describes a practical case combining collaborative networks and knowledge management, at SENAI environment. SENAI was founded in 1942 to support the Brazilian industry through professional and technological education, and services. In 2011 SENAI started implementing a national program targeting the industrial competitiveness all over the country. Such an ambitious program relies upon several key elements and this work is focused on the most strategic one: culture. Logically such a challenge requires the combined effort of many actors and instruments as well. Those reported in this work are collaborative (technical) networks and knowledge management. On the one hand, the framework adopted to support the development of such networks is presented. On the other hand, knowledge management concepts and mechanisms were introduced in the scenario aiming at improving and catalyzing the results achieved by those networks.

Surface Finish Assessment of Polishing Process of Tool Steels by Abrasion, Using Diamond and Alumina Particles

The present work investigates the surface finishing of two mould tool steels (WNr 1.2738~P20 and WNr 1. 4305) after polishing by conventional method and automatic laboratory equipment. These steels are employed in the fabrication of polymer injection moulds due to its good machinability, homogeneous microstructure and hardness. The polishing process was performed in laboratory by manual and automated processes. The surface finishing was measured by mechanical and optical methods. In the manual polishing, SiC paper grit 320, 600 and 1200 was used. Final polishing was carried out with polishing cloth containing 0.3 μm alumina suspension or 6 μm and 1 μm diamond suspension. Alternately, polishing of steel specimens in the specially developed laboratory automatic equipment was performed using a large rotating disc at 140 rpm, nominal pressures of 0.013 Pa, 0.139 Pa and 0.244 Pa and diamond paste with particle size 1 μm. Surface finish of specimens were compared as a function of the particle size and polishing time by three methods: the roughness parameter Rz (mean of maximum roughness depth) using a stylus probe, light reflectance with an integrating sphere connected to a spectrophotometer, and reflected diffuse light intensity analysis of a He-Ne laser. Specimen surface images were also obtained by an optical microscope to compare the topography after polishing. From the plot of roughness measurements versus particle size and intensity of diffuse light versus particle size, it was observed that both roughness parameter Rz and the intensity of diffuse light decreased linearly with the abrasive particle size for the manual polishing method. The method of light reflectance measurements shows an approximately constant value of 55 % for all particle size. Therefore, the better methods to assess surface finish of tool steels are the roughness parameter Rz and the intensity of diffuse light by laser method. For the automatic polishing, the results show that there is an optimized time for minimum roughness which is 5 minute. Other relevant aspects of surface finish by particle abrasion are also discussed.

Assessing the heterogeneity of residual stress for complementing the fatigue performance comprehension

The residual stress analysis is a well-established method for predicting fatigue failures of mechanical components. Within industrial constraints, the X-ray diffraction is a technique usually applied to measuring a small spot of the workpiece surface. This punctual and averaged outcome does not allow the proper representation of the residual stress. The objective of this study is to define a feasible method for assessing the heterogeneity of the surface residual stress state. The proposal is based on the theoretical relationship between the deviation of the residual macrostress and the intensity of the microstress. Steel shot peened gears were produced and their microstresses were assessed by means of the diffraction profiles broadening. The reference database was composed of topography measurements, metallographic analyses and residual macrostress maps. The stress heterogeneity was reasonably correlated to the intensity of the Gauss integral breadth. Applied to ground parts, the correlation’s parameter filled a comprehension gap between the measured residual stress intensity and observed contact fatigue failures. Using the same data from the macro residual stress measurement, the method proved to be feasibly applied. Moreover, by providing a deviation perspective to the residual stress state, the heterogeneity assessment enhances the analysis of a fatigue failure.

Remanufacturing versus Manufacturing – Analysis of Requirements and Constraints for a Study Case: Control Arm of a Suspension System

In order to attend to the requirements of the market many efforts have been centered on technical and economical performance together with environmental evaluations of the product. Nevertheless, few attempted an approach that integrates decision making criteria with the consumer expectations. The present paper proposes the voice of the client as a fourth factor to support decision making, rendering these decision more precise and sustainable. An approach was developed for choosing between a new product and a remanufactured product. A multi-criteria decision analysis is applied to the results, together with a sensitivity analysis with the purpose of aggregating to the results limitations and opportunities for decision making, apart from, basically, having a better awareness of the problem.

Sustainable Layout Planning Requirements by Integration of Discrete Event Simulation Analysis (DES) with Life Cycle Assessment (LCA)

Discrete Event Simulation (DES) provides computational models with different scenarios in which it is possible to check waste and capacity-constrained resources to generate comparative results. However, these analyses are guided by questions such as cost and production time without regard for wastes that impact on the environment. This paper examines how a tool of Life Cycle Assessment (LCA) can supplement DES in performing analyses of production systems taking into account environmental impacts, such as energy consumption and greenhouse emission. These ideas are demonstrated by a case study developed in an automotive company. The results ratify the importance of global projects with local solutions, even for layout planning.

Selection of Additive Manufacturing Technologies Using Decision Methods

The use of Rapid Prototyping technologies is becoming increasingly popular due to the reduction of machinery prices. Consequently, more and more industries now have the opportunity to apply such processes to improve their product development cycles. The term Rapid Prototyping was commercially introduced to highlight the first application, the quickly production of prototypes into the product development process. Improvements were done in the quality of the equipments and the variety of materials. Furthermore, new processes were introduced into the market, which enlarged the application’s range of Rapid Prototyping technologies. As a consequence, new terms were also used to describe the final application of such technologies as Rapid Manufacturing (RM); Rapid Tooling (RT), which indicates the use of such technologies to produce moulds and tooling, etc. However, as important as to identify the technical limits of the each technology, it is needed to balance the characteristics of each process in order to decide which one fulfills the product requirements the best way. And this should be done systematically using a decision method. The decision method, in turn, should be able to evaluate the relative weights of product requirements related to the process capabilities. It is not just a matter of manufacturing process substitution. It is possible – and desirable in case of RM – to modify designing and product development processes too. This chapter is divided into two sections. The first part considers prototyping applications, where the requirements of the part to be produced are not too severe. In this case, available process capabilities should be used to satisfy costumer’s needs, usually at the lowest manufacturing cost and delivery time possible. The second section is intended to those who are concerned in Rapid Manufacturing Applications. Rapid Manufacturing means that the parts will be produced as end product, thus, the product requirements are more rigorous then prototyping applications.

Influence of Worn Tool on Polishability and Wear Resistance of VP20ISO Mold Steel

The aim of this study was to evaluate the influence of tool flank wear on polishability and wear resistance of mold steel. Two surfaces of Villares VP20ISO steel were machined, one was roughed with worn tools (VB>0.3 mm) and another one with new tools (0.05 mm<VB<0.1 mm), followed by the finishing process of both surfaces by machining with new tools. The surface residual stresses were then measured using the X-ray diffraction method. Surfaces were etched down to different depths in order to monitor the residual stresses in the total affected depth of workpiece deformed layer. The results show that the cutting and passive forces provided the major differences between two machining conditions. The micro-hardness in the cross section did not show significant differences. Moreover, the residual stress measurements showed that after the finishing process, the surface roughed with new tools exhibited 100 MPa compressive stresses at 35 mm below the surface, while the surface roughed with worn tools provided a valley of tensile stress from the surface. Tests conducted on a pin-on-disk tribometer showed that the wear rates of the surface roughed with new tools were lower than the one roughed with worn tools and, after the polishing process, that the surface finishing of the surface roughed with new tools was better.