Comparison of the measurement performance of high precision multi-axis metal cutting machine tools

High precision manufacturers continuously seek out disruptive technologies to improve the quality, cost, and delivery of their products. With the advancement of machine tool and measurement technology many companies are ready to capitalise on the opportunity of on-machine measurement (OMM). Coupled with business case, manufacturing engineers are now questioning whether OMM can soon eliminate the need for post-process inspection systems. Metrologists will however argue that the machining environment is too hostile and that there are numerous process variables which need consideration before traceable measurement on-the-machine can be achieved. In this paper we test the measurement capability of five new multi-axis machine tools enabled as OMM systems via on-machine probing. All systems are tested under various operating conditions in order to better understand the effects of potentially significant variables. This investigation has found that key process variables such as machine tool warm-up and tool-change cycles can have an effect on machine tool measurement repeatability. New data presented here is important to many manufacturers whom are considering utilising their high precision multi-axis machine tools for both the creation and verification of their products.

Industrial challenges in grinding

This keynote paper aims at analyzing relevant industrial demands for grinding research. The chosen focus is to understand what are the main research challenges in the extensive industrial use of the process. Since the automotive applications are the most important driving forces for grinding development, the paper starts with an analysis on the main trends in more efficient engines and the changes in their components that will affect the grinding performance. A view from 23 machine tool builders is also presented based on a survey made in interviews and during the EMO and IMTS machine tool shows. Case studies received by the STC G members were used to show how research centers and industries are collaborating. A view from the authors and the final conclusions show hot topics for future grinding research. (C) 2009 CIRP.

Mechanistic approach to predict real machining time for milling free-form geometries applying high feed rate

An accurate estimate of machining time is very important for predicting delivery time, manufacturing costs, and also to help production process planning. Most commercial CAM software systems estimate the machining time in milling operations simply by dividing the entire tool path length by the programmed feed rate. This time estimate differs drastically from the real process time because the feed rate is not always constant due to machine and computer numerical controlled (CNC) limitations. This study presents a practical mechanistic method for milling time estimation when machining free-form geometries. The method considers a variable called machine response time (MRT) which characterizes the real CNC machine`s capacity to move in high feed rates in free-form geometries. MRT is a global performance feature which can be obtained for any type of CNC machine configuration by carrying out a simple test. For validating the methodology, a workpiece was used to generate NC programs for five different types of CNC machines. A practical industrial case study was also carried out to validate the method. The results indicated that MRT, and consequently, the real machining time, depends on the CNC machine`s potential: furthermore, the greater MRT, the larger the difference between predicted milling time and real milling time. The proposed method achieved an error range from 0.3% to 12% of the real machining time, whereas the CAM estimation achieved from 211% to 1244% error. The MRT-based process is also suggested as an instrument for helping in machine tool benchmarking.

Requalificação de uma máquina-ferramenta

Dissertação de mestrado integrado em Engenharia Mecânica

Máquina-ferramenta CNC para gravação: desenvolvimento de protótipo de baixo-custo

Dissertação de mestrado em Engenharia Mecatrónica

Hohlkugelkomposit - Charakterisierung thermischer und mechanischer Eigenschaften eines neuen Leichtbauwerkstoffes

Hollow-sphere-composit, syntactical foam, filler, reactive resin system, light-weight-construction, machine tool construction, robot, test methods, thermal and mechanical properties

Monitoimipystysorvin NC- ohjelmoinnin kehittäminen CAM käyttöönotolla

Diplomityön tavoitteena oli tehostaa venttiilipesien koneistuksessa käytettävän monitoimipystysorvin NC - ohjelmointia CAM - ohjelman käyttöönotolla. Tutkimus on osa laajempaa kokonaisuutta liittyen koneistusalihankinnan kehittämiseen ja yrityksen kilpailukyvyn ylläpitoon ja parantamiseen liiketoiminta-alueella, jolla on tällä hetkellä hyvät kasvunäkymät. Tavoite rajattiin yritykseen jo aiemmin hankitun WinCAM - ohjelman päivittämiseen ja hyödyntämiseen monitoimipystysorvin NC - ohjelmoinnissa. Tutkimuksen käytännön tavoitteena oli selvittää CAM - ohjelmoinnin käyttömahdollisuudet, sekä luoda CAM - ohjelmistoon pohjautuva, räätälöity NC - ohjelmointikonsepti pilottikohteeseen. Tutkimuksen kokeellisen osuuden muodostivat tällöin nykyisen tuotannon ongelmakohtien löytäminen, koneen ohjelmointitarpeiden kartoitus,sekä menetelmäkehitys. Tutkimuksen päämääränä oli tuotannon tasolla käytettävä järjestelmä, jolla koneen ohjelmointi olisi mahdollista myös vähemmällä konekohtaisella kokemuksella. Nykyisen toimintatavan ongelmina olivat yhtenäisen NC - ohjelmointikäytännön puute, niin valmiiden ohjelmien käytössä kuin uusienkin ohjelmien tekemisessä. Tähän olivat syynä NC - ohjauksen heikko käytettävyys erityisesti sorvauksen osalta. Nämä tekijät yhdistettynä monitoimityöstökoneessa tarvittavaan koordinaatiston hallintaan vaikeuttivat ohjelmointia. Työntekijäkohtaiset erot NC - ohjelmien käytössä, sekä laadultaan vaihtelevat valuaihiot aiheuttivat tuotannon läpäisyaikaan merkittävää vaihtelua. Siten myös koneen kuormituksen säätely oli vaikeaa. Uuden ohjelmointikonseptin toteutuksessa pidettiin etusijalla hyvää käytettävyyttä, sekä uuden menetelmän aukotonta liittymistä olemassa oleviin tuotantojärjestelmiin. Ohjelmointikonseptin toteutuksessa, osaperheestä haettiin selkeästi parametroitaviksi soveltuvat työvaiheet, jotka voitiin hallita yleiskäyttöisillä aliohjelmilla. Tuotteiden muidengeometrioiden hallintaan laadittiin geometriakirjasto, jota voitiin käyttää tavanomaisen graafisen ohjelmoinnin pohjana. Vanhaa toimintatapaa ja diplomityön aikana kehitettyä CAM - ohjelmointijärjestelmää vertailtiin perustuen NC - ohjelmien tehokkuuteen, jota tarkasteltiin saman työvaiheen työstöaikaan perustuen. Tämän lisäksi tärkeän tuloksen muodostavat myös kvalitatiivisetseikat, jotka liittyvät ohjelmointiympäristön käytettävyyteen. CAM - ohjelmoinnin kehittäminen ja käyttöönotto pilottikohteessa sujui pääosin hyvin ja laaditunsuunnitelman mukaisesti. Aiemmin hankalasti ohjelmoitavat työvaiheet, kuten erilaisten laippatasopintojen ja reikäpiirien ohjelmointi muutettiin makrokäyttöön soveltuviksi. Sorvauksessa ongelmia aiheuttaneen tiivistelilan koneistukseen sovellettiin graafista ohjelmointia. Koko tuotannon mittakaavassa NC - ohjelmoinninosuus oli kuitenkin vähäinen, mistä johtuen koneen tuottavuuteen ei tutkimuksenajanjaksolla voitu vaikuttaa. Sen sijaan tuotannon sujuvuuteen oleellisesti vaikuttavaa työtekijöiden 'hiljaisen tiedon' määrää voitiin vähentää vakioimalla ohjelmointia ja siirtämällä tehokkaiksi havaitut menetelmät ohjelmointijärjestelmään.

The Effect of Operational Disturbances on Reliability and Operation Time Distribution of NCmachine Tools in FMS

This thesis concentrates on studying the operational disturbance behavior of machine tools integrated into FMS. Operational disturbances are short term failures of machine tools which are especially disruptive to unattended or unmanned operation of FMS. The main objective was to examine the effect of operational disturbances on reliability and operation time distribution for machine tools. The theoretical part of the thesis covers the fimdamentals of FMS relating to the subject of this study. The concept of FMS, its benefits and operator's role in FMS operation are reviewed. The importance of reliability is presented. The terms describing the operation time of machine tools are formed by adopting standards and references. The concept of failure and indicators describing reliability and operational performance for machine tools in FMSs are presented. The empirical part of the thesis describes the research methodology which is a combination of automated (ADC) and manual data collection. By using this methodology it is possible to have a complete view of the operation time distribution for studied machine tools. Data collection was carried out in four FMSs consisting of a total of 17 machine tools. Each FMS's basic features and the signals of ADC are described. The indicators describing the reliability and operation time distribution of machine tools were calculated according to collected data. The results showed that operational disturbances have a significant influence on machine tool reliability and operational performance. On average, an operational disturbance occurs every 8,6 hours of operation time and has a down time of 0,53 hours. Operational disturbances cause a 9,4% loss in operation time which is twice the amount of losses caused by technical failures (4,3%). Operational disturbances have a decreasing influence on the utilization rate. A poor operational disturbance behavior decreases the utilization rate. It was found that the features of a part family to be machined and the method technology related to it are defining the operational disturbance behavior of the machine tool. Main causes for operational disturbances were related to material quality variations, tool maintenance, NC program errors, ATC and machine tool control. Operator's role was emphasized. It was found that failure recording activity of the operators correlates with the utilization rate. The more precisely the operators record the failure, the higher is the utilization rate. Also the FMS organizations which record failures more precisely have fewer operational disturbances.

A modified contour error controller for a high speed XY table

This article deals with a contour error controller (CEC) applied in a high speed biaxial table. It works simultaneously with the table axes controllers, helping them. In the early stages of the investigation, it was observed that its main problem is imprecision when tracking non-linear contours at high speeds. The objectives of this work are to show that this problem is caused by the lack of exactness of the contour error mathematical model and to propose modifications in it. An additional term is included, resulting in a more accurate value of the contour error, enabling the use of this type of motion controller at higher feedrate. The response results from simulated and experimental tests are compared with those of common PID and non-corrected CEC in order to analyse the effectiveness of this controller over the system. The main conclusions are that the proposed contour error mathematical model is simple, accurate, almost insensible to the feedrate and that a 20:1 reduction of the integral absolute contour error is possible.

Permutation entropy based real-time chatter detection using audio signal in turning process

Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting tool. With increase in depth of cut, the cutting regime changes from chatter-free cutting to one with chatter. In this paper, we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measurement to detect the onset of chatter from the time series using sound signal recorded with a unidirectional microphone. PE can efficiently distinguish the regular and complex nature of any signal and extract information about the dynamics of the process by indicating sudden change in its value. Under situations where the data sets are huge and there is no time for preprocessing and fine-tuning, PE can effectively detect dynamical changes of the system. This makes PE an ideal choice for online detection of chatter, which is not possible with other conventional nonlinear methods. In the present study, the variation of PE under two cutting conditions is analyzed. Abrupt variation in the value of PE with increase in depth of cut indicates the onset of chatter vibrations. The results are verified using frequency spectra of the signals and the nonlinear measure, normalized coarse-grained information rate (NCIR).

Influencia de la comunidad de clústers en las relaciones estratégicas comunitarias y el marketing compartido

Un clúster es entendido por la gran mayoría como un gran conglomerado de empresas que giran en torno a un objetivo, en su gran mayoría económico. Su intención es competir con otros conglomerados en cuanto a precios y cantidades, ya que de manera individual no podrían. En consecuencia, esta unión se utiliza en un principio para crear ventajas tanto competitivas como comparativas en contra de la competencia, lo cual genera un valor a esta unión, con el fin de producir fidelidad en el cliente y recordación de todos los productos que tal unión brinde. Según estudios realizados por diversos autores, en muchas ocasiones, los clúster no se crean con una finalidad económica, sino como desarrollo de un perfil comunitario que ayude a la sociedad y las organizaciones que la componen. La base de las relaciones se centra en la comunicación y en las diversas técnicas que existen en ese ámbito para asegurar la sostenibilidad de la organización. Dentro de estas relaciones, se le da un reconocimiento a la educación y la cultura en donde se encuentra ubicado el clúster, ya que las estrategias que se implementen se relacionan directamente con las necesidades de los clientes, generando en el pensamiento de la comunidad la perdurabilidad y sostenibilidad como efecto del desarrollo social.

Mechanistic approach to predict real machining time for milling free-form geometries applying high feed rate

An accurate estimate of machining time is very important for predicting delivery time, manufacturing costs, and also to help production process planning. Most commercial CAM software systems estimate the machining time in milling operations simply by dividing the entire tool path length by the programmed feed rate. This time estimate differs drastically from the real process time because the feed rate is not always constant due to machine and computer numerical controlled (CNC) limitations. This study presents a practical mechanistic method for milling time estimation when machining free-form geometries. The method considers a variable called machine response time (MRT) which characterizes the real CNC machine's capacity to move in high feed rates in free-form geometries. MRT is a global performance feature which can be obtained for any type of CNC machine configuration by carrying out a simple test. For validating the methodology, a workpiece was used to generate NC programs for five different types of CNC machines. A practical industrial case study was also carried out to validate the method. The results indicated that MRT, and consequently, the real machining time, depends on the CNC machine's potential: furthermore, the greater MRT, the larger the difference between predicted milling time and real milling time. The proposed method achieved an error range from 0.3% to 12% of the real machining time, whereas the CAM estimation achieved from 211% to 1244% error. The MRT-based process is also suggested as an instrument for helping in machine tool benchmarking.

Monitoring in precision metal drilling process using multi-sensors and neural network

This paper presents a new method to estimate hole diameters and surface roughness in precision drilling processes, using coupons taken from a sandwich plate composed of a titanium alloy plate (Ti6Al4V) glued onto an aluminum alloy plate (AA 2024T3). The proposed method uses signals acquired during the cutting process by a multisensor system installed on the machine tool. These signals are mathematically treated and then used as input for an artificial neural network. After training, the neural network system is qualified to estimate the surface roughness and hole diameter based on the signals and cutting process parameters. To evaluate the system, the estimated data were compared with experimental measurements and the errors were calculated. The results proved the efficiency of the proposed method, which yielded very low or even negligible errors of the tolerances used in most industrial drilling processes. This pioneering method opens up a new field of research, showing a promising potential for development and application as an alternative monitoring method for drilling processes. © 2012 Springer-Verlag London Limited.

Estimação do diâmetro e rugosidade em um processo de furação utilizando multi sensores e redes neurais artificiais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da predição da circularidade e rugosidade de peças retificadas utilizando as redes neurais artificiais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)