Design methodology for production systems retrofit in SMEs

Investment in the productive systems of small and medium-sized enterprises (SMEs) in the manufacturing sector is usually quite limited. For this reason, normal practice is to apply minor developments internally or upgrade equipment as it becomes obsolete to increase their productive capacity and competitiveness at a lower cost. However, the work team, mostly made up of engineers, does not usually have experience in the use of design methodologies but also they are often familiar with the functioning of various design and quality-management tools. This paper presents a clear and simple design methodology that facilitates the development of adaptations to items of equipment that might be considered one-off products. It includes a selection of design tools that are, according to the literature on the subject, the most common and best-known among engineers, and which are also best-suited to the environment of an SME. The design methodology was validated experimentally with the upgrading of a gear-rolling tester installed on the premises of an SME in the sector. The recommended techniques and tools were satisfactory applied opening the possibilities for further application of the methodology in similar machine''s upgrades in the future

Measurement procedure for application of white light scanner in the automotive sector

Advanced optical metrology systems are continuously being developed to cope with the challenges arising from large-scale, high-quality production, especially in the automotive sector. Therefore, these measuring devices are relatively new and they are ruled by very general standards. The main goal of this work is to develop a specific procedure for a white light fringe projection optical measurement equipment from a general measurement system analysis procedure used in the automotive sector (MSA-4 Reference Manual) considering the recent international regulations for the verification of this type of equipments: Technical Recommendation VDI/VDE 2634 and ISO 10360-8: 2013. Only the tests applicable to the equipment used to validate the proposed procedure, a 3D white light structured scanner SIDIO Pro from Nub3d, were analyzed

Digitalizado y reconstrucción CAD mediante ingeniería inversa de un carenado de motocicleta de competición

El trabajo desarrolla el método seguido para digitalizar y reconstruir mediante ingeniería inversa un carenado de motocicleta de competición de 125 c.c. Para ello se documenta gráficamente y acompañado de las pertinentes explicaciones las herramientas que se han ido utilizando durante todo el proceso. En la memoria se intenta seguir la línea temporal del desarrollo, con algún inciso para poder entender el porqué de las decisiones tomadas. Las especificaciones técnicas del equipo de medición, así como las distintas herramientas software utilizadas, determinan el resultado del proyecto. De ahí, que se profundice en los mejores métodos para desarrollar estas labores. Desde la forma más adecuada de posicionar el escáner a la hora de digitalizar una superficie concreta, hasta los parámetros adecuados para extraer una superficie según el resultado deseado. Como herramienta fundamental, podemos destacar la comparación del CAD reconstruido con la malla del digitalizado. Permite evaluar y analizar los resultados en la reconstrucción CAD de forma sencilla y rápida. También se analizan los usos y técnicas más comunes utilizadas en la industria. Cada día más habituales debido al abaratamiento y aumento de calidad de los equipos de medición. La utilización de estas herramientas está presente muchos de los procesos industriales. Por ejemplo en la automoción, en las fases de diseño y desarrollo de producto. Ya que se utilizan prototipos que muchas veces se realizan a mano. Por último se muestran los resultados. Por un lado el ensamblando de los CAD del carenado obtenido en el CAD del chasis de la moto. Y por otro lado se añade el anexo I, que es un resumen pieza por pieza del resultado obtenido y las dificultades que ha entrañado cada pieza en concreto.

Measuring sensors calibration in worm gear rolling testers

The ISO standard regulating gear-rolling measurement does not specify in detail the calibration and verification procedures for this type of equipment. This may be one of the reasons for the lack of reproducibility in these rolling tests. The uncertainty budget method, which is the most appropriate way to know the accuracy of this dynamic measurement, shows that the measuring sensors’ accuracy is only a part of the total measurement process uncertainty. In this work, a new calibration and verification procedure for a worm gear rolling tester is presented, based on machine tool, coordinate measuring machine and gear measuring instruments’ calibration techniques. After compensating numerically for the measuring instruments, it has been evaluated how the error components of each movement affect the meshing point, a fundamental factor to ensure a good gear transmission. The study shows that there are unintentional position variations, not detected by the measuring sensors, that have to be identified and quantified in the calibration for their later inclusion in the uncertainty budget. In this way, the measurement uncertainty could be reduced, and thus improve the reproducibility of these testers, as a preliminary stage to the development of optimized rolling measurement equipment to solve current limitations

Analysis of different camera calibration methods on a camera-projector measuring system

The accuracy of metrology equipment formed by a camera-projector pair depends directly on the calibration procedure used. This kind of equipment allows to perform the calibration by two different approaches: as a whole system or separately. The most common approach is the second one: conventional calibration. Studies show that the uncertainty of the camera parameters from its calibration propagates to the projector parameters. The objective of this study is to have a clear comprehension of the relationships between the camera and projector parameters and of how uncertainty is propagated. This will be done by using a camera previously calibrated by Tsai, Zhang or Direct Linear Calibration (DLC) methods, followed by the calibration of the projector using DLC

A New Methodology for Kinematic Parameter Identification in Laser Trackers

In recent years, there has been an increasing interest in measurement systems such as laser trackers (LT) for the verification of large-scale parts in the aeronautic, spatial or naval sectors because of their advantages in terms of portability, flexibility, high speed in data acquisition, accuracy, and reliability. These systems present systematic errors caused by geometrical misalignments, environmental conditions, mechanical wear and tear and other unpredictable variables. Different standards such as the ASME B89.4.19 and the VDI 2617-10 suggest tests to calculate the geometric errors of the LT. In this work, we present an alternative calibration method based on a new errors model. The LT can be considered as an open kinematic chain, so it is possible to shape a kinematic model of the LT. Once the kinematic model has been set, the error model is defined. The model has been validated with synthetic data. Then, experimental tests based on the measurement of a mesh of reflectors placed at suitable places for different locations of the LT have been performed to ensure the reliability of the method proposed. A sensitivity analysis shows the best experimental setup to perform a calibration test. The calibration results have been validated with nominal data

Surface Roughness Evolution Model for Finishing Using an Abrasive Tool on a Robot

The polishing process is the final step in the manufacturing workflow for many parts and tools. While previous tasks have evolved technically, the finishing of freeform surfaces is still effected mostly by hand. Many parts are rejected because no control of the process is possible. The main problems are geometrical shape deviations and no repeatability of the process. A new methodology has been developed for the passes of the abrasive on the polished part. This research focusses on the feasibility of robotic polishing and the development of a new evolution model pertaining to the surface roughness for an abrasive tool mounted on a spherical robot. The polishing principle is mechanic and based on dry friction. The tool is multilayered with a compressive foamed core. The combination of rotational and translational movement requires the creation of a model that can predict the footprint on the polished surface. The mathematical model developed for the evolution model permits for making a prediction of the final surface quality in the function of the programmed polishing parameters. Furthermore, the model described allows for setting up polishing parameters in order to reach a desired final roughness with less than 15% deviation. Repeatability is assured and polishing time is reduced down to 1/5 of manually effected procedures

Design and mechanical evaluation of a capacitive sensor-based indexed platform for verification of Portable Coordinate Measuring Instruments

During the last years, the use of Portable Coordinate Measuring Machines (PCMMs) in industry has increased considerably, mostly due to their flexibility for accomplishing in-line measuring tasks as well as their reduced costs and operational advantages as compared to traditional coordinate measuring machines (CMMs). However, their operation has a significant drawback derived from the techniques applied in the verification and optimization procedures of their kinematic parameters. These techniques are based on the capture of data with the measuring instrument from a calibrated gauge object, fixed successively in various positions so that most of the instrument measuring volume is covered, which results in time-consuming, tedious and expensive verification procedures. In this work the mechanical design of an indexed metrology platform (IMP) is presented. The aim of the IMP is to increase the final accuracy and to radically simplify the calibration, identification and verification of geometrical parameter procedures of PCMMs. The IMP allows us to fix the calibrated gauge object and move the measuring instrument in such a way that it is possible to cover most of the instrument working volume, reducing the time and operator fatigue to carry out these types of procedures

Analysis of the initial thermal stabilization and air turbulences effects on Laser Tracker measurements

During the several last years, Laser Trackers have become more common as a measurement tool in the manufacture and assembly of large components such as aircraft wings and ship hulls, as well as for error mapping in coordinate measuring machines and machine tools. Most of these processes cannot be developed in a controlled metrological laboratory but must be implemented directly on a shop floor. Therefore, the process of stabilization of the Laser Tracker has been studied in several experimental tests, and it has been observed that the warm-up time suggested by the manufacturer is not enough. During the first hours of the measurement process two types of thermal errors significantly affect the measurements, causing inaccuracies of between 20 and 80 µm, depending on the equipment used and the positions of the measured points. These thermal errors are systematic and repeatable; therefore they can be estimated and compensated for each measurement system. Because environmental conditions on a shop floor cannot be controlled, once the Laser Tracker is stabilized, the effects of ambient air in measurements have also been studied, focusing on the effect of turbulent flows on the beam path. It has been observed that this turbulence may cause radial distance drifts on the order of micrometers, deflection of the beam trajectory and signal loss