Advances in Science and Technology Vol. 132

Abstract: The generation of the surface topography in machining is a complex process whereby the dynamics of the machine-tool and the kinematics of the cutting process are combined. The purpose of developing a surface topography simulation model in turning is to predict the combined effect of the tool geometry, process parameters, and relative tool-workpiece vibration. The simulations demonstrate that a single vibration frequency can generate multiple wavelengths on the workpiece profile. The correlation between machine-tool vibrations and surface topography is applied to accurately diagnose the machine defect that results in poor surface quality in a cylindrical turning process.

Abstract: The Forming Limit Curve (FLC) shows the limit combinations of principal strains on the sheet surface that can be successfully achieved before necking appears. Above the FLC, Atkins in 1996 proposed the existence of an unstable region where localized necking develops before reaching at the Fracture Forming Limit (FFL). Only the methodology for the evaluation of the FLC is covered in an international standard ISO 12004-2, where the basis of the tests consists of stretching of a previously clamped sheet blank over a Marciniak or Nakazima punch, providing an almost linear strain path in the sheet surface of the specimen. On the contrary, in single-point incremental forming (SPIF) processes, the hemispherical-shaped tools usually employed are relatively small compared to the general dimension of the specimen, producing a highly nonlinear strain path derived from both the incremental nature of the process and the severe curvature imposed by the small radii of the punches used in the forming process.Many authors have observed fracture strains in SPIFed samples well above the FFL obtained with Nakazima tests under the ISO 12004-2 standard. At the macroscopic level, the reason for this behaviour has been explained mainly based on the effect of bending and the difference in the stress triaxiality level, among others. This research analyzes the initiation of ductile fracture in Nakazima and SPIF specimens under a scanning electron microscope to elucidate the reasons of those differences at the microscopic level.

Abstract: Soft robotics presents itself as a new path to adopt in several applications in the industry. The area of soft robotics aims to equip robots for unpredictable needs, providing them with capabilities that are based not on control systems, but on the properties of materials and the morphology of their bodies. This work aims the creation of a soft robotics application, more specifically a soft gripper. The development of an original concept of a soft material handler (soft gripper) is intended, capable of performing the stipulated handling functions, through certain actuation mechanisms, meeting the requirements and constraints presented in the next sub-section. The final solution is based on an improvement procedure supported on structural Finite Element (FE) analyses. Cost analysis and prototype construction/validation finalize the evaluation. The gripper was designed, a prototype was executed, and tests were carried out to prove correct operation. These tests were successful showing the project as suitable for a real production environment.

Abstract: Automation of welding with robotic arms has become an inevitable trend in modern manufacturing technologies. This process can be automated by using a "click and go" in which the robot will weld a line where the spot is described or by using an in-line tracking algorithm in which the robot will choose the spot where to weld the line in each layer. This paper presents a simple methodology for the reconstruction of the weld joint and the classification of the joint geometry to serve as a first step to the automatic determination of the robot trajectory. The weld joint has been reconstructed using a laser profilometer placed as a tool on the robot. Spurious data has been removed by signal processing. The joint has been reconstructed three-dimensionally. The classification of the joint profiles was generated using an algorithm based on signal processing and artificial intelligence. This algorithm has been tested for the classification of V-joints (bevel-bevel) and single bevel joints.

Abstract: Despite environmental general conscience, heavy use of paper is still one fact in nowadays factories. The shorter the manufacturing production, the greater the tendency to employ paper to support quality tracking of pieces; using it to register measurements or nonconformities. This tendency increases drastically in some manufactures like aerospace, where typical production ratios vary between 9 and 18 subassemblies per month. The current work presents an automatic speech recognition system, meant to replace paper by a digitalized version of the manual writing task. The work presents (i) industrial use cases with benefits and requirements; (ii) the system architecture, including several tested free Automatic Speech Recognition modules, their analysis; and (iii) some open-source supporting modules that improves its functionality. The work concludes presenting several tests, showing the system performance against different kind of industrial noises, low to high quality microphones and users with different dialects.

Abstract: The digitization of processes in the context of Smart Manufacturing enables the control and monitoring of production processes. Visual inspection of parts is a process where the surface finish of machined parts is evaluated. For this purpose, manual inspection units have been traditionally used to evaluate the validity of the parts. This manual inspection process requires the operator to position the lens to obtain the images, which supposes an inefficient and non-repeatable process producing a considerable waste of production time. In order to design a more competitive process in the context of Smart Manufacturing, we fully automate in this paper an industrial borescopy unit by implementing closed-loop stepper motors, sensors, and microcontrollers. In addition, a web server has been programmed where operators monitor and upload ISO codes depending on the inspected part. This web server is connected to the microcontroller and the borescope positioning camera for automatic imaging. Therefore, the visual part inspection unit has been digitized and provided with connectivity and intelligence as the cyber physical system of the Smart Manufacturing.

Abstract: Additive Manufacturing (AM) production of plastic parts has experienced a continuous increase during the past decades. Simultaneously, advanced societies have become deeply concerned about the use of plastics and their impact on natural environments. As a result, there is a growing interest in recycled plastic as a feedstock material in additive manufacturing machines. However, the commercialization of recycled plastic filament introduces additional production and distribution steps. An alternative approach would avoid these steps by mixing recycled particles (obtained from local waste) with brand-new particles and using the resultant blend with Fused Particle Fabrication (FPF) machines, but some alimentary plastics, like Polyethylene Terephthalate (PET) have printability issues that hamper their direct use in AM. Present work analyses the feasibility of extruding blends composed of Polyethylene Terephthalate Glycol (PETG) spherical pellets and recycled Polyethylene Terephthalate (rPET) flakes so that local prosumers could give a second use to their own wasted water bottles. Additionally, tensile, and flexural specimens were analyzed for combinations of different rPET particle sizes and PETG/rPET blends (100%PETG, 30%rPET/70%PETG, 50%rPET/50%PETG, and 70%rPET/30%PETG). The experimental program included relaxation tests from which the relaxation modulus, E(t), was obtained. The results showed that the addition of PETG combined with a modification that insufflates pressurized air into the pellets inlet would permit to print blends up to a 70% rPET. It has also been found that an increase in the percentage of rPET causes a slight increase in the relaxation modulus of the test specimen. Finally, the viscoelasticity ratio remains nearly constant among the different blends whereas particle size has been found to have an influence on the results.

Abstract: Flexible and adaptive systems for handling and transporting materials within companies and warehouses are increasingly being studied in order to respond to the variability of production and the market. Following this trend, the authors, seeking a simplified design and control, proposed a novel under-actuated modular surface that exploits the friction forces generated by idler rotors inside the modules, for object manipulation. On this subject, the paper concerns the design of two novel measurement set-ups for the determination of parameters fundamental to the single module functioning and the validation of its analytical model. In particular, the test benches are designed to collect the friction forces exchanged between the device rotor and the object moving on top of it, simulating a normal working condition of the surface. The first set-up is specifically dedicated to identify the friction coefficients in the two main directions of the rotor, i.e. along the axis of rotation and in the perpendicular direction. While the second set-up is focused on the validation of the analytical model, thanks to the simultaneous measurement of the two in-plane friction forces caused by the object moving in different directions with respect to the rotor axis. The article describes the operating principles of the test benches and the analytical models for interpreting the data. In addition, some results concerning friction coefficients are introduced. These verify the basic operating assumptions and therefore evidence the module functioning and the quality of the novel test benches, opening their use also for similar transport devices.

Abstract: Models for Manufacturing (MfM) is a methodology currently under development with a novel approach to applying Ontology-Based Engineering concepts to manufacturing. MfM is based in a 3-Layer Model (3LM) framework: a Data layer that collects all the information, e.g. in databases, an Ontology layer for ontological definition containing the domain knowledge, and a Service layer comprising all necessary software services. The Ontology layer is the core of the 3LM framework and is made up of 4 models: Scope, Data, Behaviour, and Semantic models. The 3LM framework is supported by user-friendly modelling tools and guarantees independence between the 3 layers. This work aims to evaluate the MfM methodology through the development of a real use case based on previous work by the authors: an experimental test plan to study sheet metal formability in hole-flanging operations by Single-Point Incremental Forming (SPIF). The test plan includes the definition of the main geometrical parameters of the specimens, the generation of the forming tool paths and G-code for a CNC machine, the evaluation of the manufactured parts and the analysis of the material formability. The paper presents the definition of the Ontology layer for the developed use case using various graphical modelling tools and a simple implementation of Data and Service layers as well as the interfaces between the 3 layers. The conclusions of the work highlight the strengths and weaknesses of the application developed and point out the main lines of future development of the MfM methodology.

Abstract: Pocketing is one of the most important operations in the machining of complex parts. This milling process usually consumes a large part of the total machining time, especially if an extensive quantity of material is involved, determining the efficiency of the process. This paper studies the influence of the machining strategy and cutting conditions, and the geometry of the pocket on the machining time and cost when milling AW2007 aluminum alloy. For that purpose, a combined methodology based on experimental tests and CAM simulation is proposed. Cost analysis, which represents the main novelty of the research, takes into consideration, properly, the cutting time required to complete the pocket, the tool life, the tool change time and some economic factors such as power and tool costs. Spiral, curvilinear, parallel and zig-zag machining paths, along with seven different pocket geometries, are considered. Parallel and curvilinear milling trajectories have been found as the most cost-effective strategies. The efficiency of the parallel strategy increases with respect to the others as the geometry of the pocket becomes less compact, i.e., it is defined with a higher shape factor. According to the experimental tests and cost results, the machining operation should be performed with the highest feed rate, axial depth and cutting speed of the experimented values, 0.2 mm/tooth, 10 mm and 200 mm/min, respectively.