Dissertations / Theses on the topic 'Lobe diagrams'

This diploma thesis deals with the design of a two-axis multi-spindle lathe carriage. In the first part, there is made a research, and its aim is to find possible variants of design solutions. After the best rated variant was selected, the thesis further continues with the necessary technical calculations of the main design nodes such as a synchronous servomotor, ball screw, linear guide and bearing. The design itself was carried out with regard to calculations and the resulting model was examined in terms of dynamic stability. The subject of examination was to find the natural frequencies of the assembly and to determine the amplitudes of the oscillations which arise from the harmonic excitation force. Finally, Lobe diagrams for grooving and longitudinal turning operations were drawn.

Chatter vibration is a common problem for the manufacturing industry that limits the productivity, accuracy and surface quality of machined parts. This study is focused on the out of process methods, such as Stability Lobe Diagrams (SLD), that ensure the selection of the optimal cutting parameters in which the machining process is stable. Previous studies have found that the dynamic properties of the spindle change with the rotational speed. This fact can also affect the accuracy of the SLD predictions, since, the traditional structural dynamic tests such as the Experimental Modal Analysis (EMA) are carried out at static state. An alternative method for the calculation of speed - dependant SLD using a Contactless Excitation Response System (CERS) was proposed. The modal characteristics, such as natural frequencies and damping ratio were determined by EMA tests carried out at idle state whereas CERS measurements were performed at increasing rotational speeds up to 14000 rpm. Subsequently, the SLD at static and dynamic state were computed. Finally, it was concluded that there was not a significant variation of the dynamic properties and SLD prediction with spindle speed at the tested speed range (0 rev/min to 14000 rev/min).
Chatter är ett vanligt problem inom tillverkningsindustrin som begränsar produktiviteten och minskar noggrannheten och kvalitén på bearbetade ytor. Denna studie fokuserar på processkilda metoder, till exempel stabilitetsdiagram (SLD), vilka säkerställer valet av optimala skärparametrar för en stabil skärprocess. Tidigare studier har visat att spindelns dynamiska egenskaper är beroende av rotationshastigheten. Detta påverkar även noggrannheten vid skattningen av SLD eftersom traditionella strukturdynamiska tester, som experimentell modalanalys (EMA), utförs under statiskt tillstånd. En alternativ metod för bestämning av hastighetsberoende SLD med hjälp av ett beröringsfritt excitering- och svarssystem (CERS) föreslås. De modala egenskaperna, som till exempel egenfrekvens och dämpning, bestämdes med hjälp av EMA med stillastående spindel medan mätningar med CERS utfördes med ökad rotationshastighet upp till 14000 varv/min. Efter detta beräknades SLD för de båda fallen. Till sist drogs slutsatsen att testerna inte påvisade någon större skillnad, vare sig dynamiska egenskaper eller SLD skattning, för spindelhastigheter inom det testade intervallet (0 till 14000 varv/min).

La millora de la productivitat i la qualitat són indubtablement dues de les principals exigències del sector productiu modern i factors clau per la competitivitat i la supervivència. Dins aquest sector,la fabricació per arrancada de material juga encara avui en dia un paper protagonista tot i l'aparició de noves tècniques de conformat per addició.Indústries com l'aeronàutica, l'automobilística,la del motlle o l'energètica, depenen en bona part de les prestacions de les màquines-eina. Aquesta Tesi aborda dos aspectes rellevants quan es tracta de millorar de la productivitat i la qualitat del sector productiu: el problema del fimbrament, més conegut per la denominació anglosaxona chatter,i la monitorització de la rugositat superficial en el mecanitzat a alta velocitat.
Productivity and quality improvement are undoubtedly two of the main demands of the
modern manufacturing sector and key factors for competitiveness and survival. Within this sector, material removal processes play, still nowadays, a principal role despite the emergence of additive manufacturing techniques. Industries such as aerospace, automotive, molds and dies or energy largely depend on machine tools performance for improved productivity and quality. This Thesis is focused on two important aspects when it comes to improving productivity and quality of the manufacturing sector: chatter problem, and surface roughness monitoring in high speed milling.

The diploma work deals with a mathematical description of vibration and its generation when machining. Moreover, some techniques of modal parameters measurement in the theoretical part are included. The practical part is designed and based on the measured natural frequencies of the machine with specific tool and materials. In conclusion, a lobe diagram stability for semiautomatic lathe SPN 12 CNC and selected machining operation is specified by means of apparatus.

In theoretical part, this master´s thesis deals with vibrations in cutting machine and description of creation of self-excited vibrations theory. In practical part, there is problem of chatter in cutting machine solved with using simulation program Adams and computing program MATLAB. Gradually, Multi body system of cutting machine and model of cutting tool with features flexible body are analyzed. At the end all both models were used to create complex model of the cutting machine .

Drosophila larvae present unique opportunity for anatomical and functional mapping of their nervous system because of features such as numerical simplicity of neurons its nervous system is composed of, and ability to exhibit quantifiable behaviors such as chemotaxis. Here, we mapped entire antennal lobe of larval Drosophila with one of its circuits responsible for controlling sensorimotor transformation in lateral horn (LH) (higher brain) through a single brain descending neuron using electron microscopic 3D reconstruction. In antennal lobe, we reported a canonical circuit with uniglomerular projection neurons (uPNs), working to relay gain-controlled ORN activity to higher brain centers like Mushroom body and lateral horn. We also found a parallel circuit with multiglomerular projection neurons (mPNs) and hierarchically organized local neurons (LNs) selectively integrating signal from multiple ORNs at the first synapse with LN-LN connectivity putatively implementing gain control mechanism that can potentially switch from computing distinguished odor signals through panglomerular inhibition to allowing system to respond to faint aversive odor in an environment rich with strong appetitive odors. We also reconstructed and studied one of the olfactory connected circuits in the LH that was found to be influencing chemotaxis behavior in larva through a single brain descending neuron, PVM027. We found that this neuron was responsible in controlling stop response of chemotaxis behavior. EM reconstruction revealed its connection with variety of motor systems and SEZ descending neurons in the VNC. Connections were revealed with the peristaltic wave propagation circuit of larva, and PVM027 was found to be implementing stop by terminating and ceasing the origin of forward peristaltic waves.
Las larvas de Drosophila ofrecen una oportunidad única para el mapeo anatómico y funcional de su sistema nervioso debido a propiedades como la simplicidad numérica de neuronas que componen su sistema nervioso y su habilidad de exhibir comportamientos cuantificables como la quimiotaxis. En este estudio hemos mapeado el lóbulo antenal de la larva de Drosophila con uno de sus circuitos responsable de controlar la transformación sensorial-motora en el asta lateral (LH) (cerebro superior) a través de una sola neurona descendiente usando la reconstrucción 3D para microscopia electrónica. Hemos presentado, en el lóbulo antenal, un circuito canónico con proyecciones neuronales uniglomerulares (uPNs) responsables de transmitir aumentos controlados de actividad desde sus ORN* hasta centros superiores del cerebro como el cuerpo fungiforme y el asta lateral del protocerebro. Hemos descubierto también un circuito paralelo formado por neuronas con proyecciones multiglomerulares (mPNs) y neuronas locales (Lns), organizadas jerárquicamente, que integran selectivamente señales desde múltiples ORNs a nivel de primera sinapsis con conectividad LN-LN implementando aparentemente un mecanismo de aumento de control que potencialmente puede intercambiar señales olfativas distintas computacionalmente a través de inhibición panglomerular permitiendo al sistema responder a olores vagamente aversivos en un ambiente rico en fuertes olores apetitosos. También hemos reconstruido y estudiado uno de los circuitos olfativos que conectan con el LH conocido por influenciar la quimiotaxis de la larva a través de un sola neurona cerebral descendiente, la PVM027. Hemos descubierto que dicha neurona es la responsable de controlar la respuesta stop en el comportamiento de quimiotaxis. La reconstrucción por EM revela su conexión con una variedad de sistemas motores así como neuronas descendientes SEZ en el VNC. Observamos dichas conexiones gracias al circuito de propagación de onda peristáltica de la larva, y descubrimos que la PVM027 implementa la señal de stop terminando e interrumpiendo el origen de la onda peristáltica.

Diplomová práce se zabývá analýzou produktivity a efektivity řezného procesu frézování. Pro zjištění kritické hloubky třísky byla analyzována reálná frézka. Model frézky byl vytvořen v programu Autodesk Inventor. Analýza řezného procesu probíhala v programu Ansys Workbench. Výsledky byly použity pro sestavení stabilitních diagramů. Po vyhodnocení výsledků byly navrženy dva přístupy pro zefektivnění procesu frézování. Vliv těchto změn na produktivitu řezného procesu byl ověřen porovnáním výsledků s předchozí analýzou.

This diploma thesis is concerning about summarizing and describing types of vibrations, their causes and influences to the machining. The stable conditions of machining were pointed out. The experiment was conducted in which the frequency response function of specific milling machine was measured. Than the stability lobe diagram was constructed.

Predmet istraživanja prikazanih u okviru doktorske diseracije su samopobudne vibracije pri obradi glodanjem. Na osnovu detaljne analize zakonitosti nastanka samopobudnih vibracija uspostavljena je određena paralela između glodanja i mikrogkodanja, za slučajeve kada je dubina rezanja veća od radijusa rezne ivice alata. Za tako usvojene pretpostavke, razvijeni su modeli unapređene numeričke simulacije procesa glodanja i mikroglodanja. Razvijeni modeli su svestrano verifikovani, s jedne strane, u segmentima gde postoje podaci u literaturi; poređenjem sa rezultatima drugih autora, a sa druge strane poređenjem sa sopstvenim eksperimentalnim ispitivanjima. Za eksperimentalno definisanje granične dubine rezanja pri glodanju predložena je inovativna metoda tangenti, a pri mikroglodanju, imajući u vidu raspoloživu mernu opremu, metoda hrapavosti obrađene površine. Matematički modeli i eksperimentalne metode su verifikovani pri obradi tri karakteristične vrste materijala i na dva obradna sistema pri glodanju, odnosno jednom materijalu i jednom obradnom sistemu pri mikroglodanju. Rezultati istraživanja su prezentovani kroz dvanaest poglavlja čiji sadržaj se navodi u nastavku.U prvom, uvodnom poglavlju, ukazano je na značaj istraživanja samopobudnih vibracija pri makro i mikroglodanju. Prikazana je i aktuelnost istraživanja analizom broja naučnih radova koji se bave problematikom samopobudnih vibracija u periodu od poslednjih dvadeset pet godina.Kroz drugo poglavlje detaljno su prikazana dosadašnja istraživanja samopobudnih vibracija pri makroglodanju, dok su u trećem poglavlju prikazana istraživanja samopobudnih vibracija pri mikroglodanju. Izvršena je analiza uticajnih parametri na graničnu dubinu rezanja, koja predstavlja osnovni pokazatelj dinamičke stabilnosti kako makro, tako i mikroobradnih sistema.Na osnovu saznanja prikazanih u okviru drugog i trećeg poglavlja u četvrtom poglavlju su definisani ciljevi i hipoteze istraživanja.Matematičke metode za definisanje karte stabilnosti obradnog sistema, prikazane su u petom poglavlju. Prikazana su dva matematička modela za definisanje karte stabilnosti pri makroglodanju, model srednjeg ugla kontakta alata u zahvatu i model Furijeovih redova. Prezentovana je numerička simulacija procesa obrade glodanjem, namenjena prvenstveno za simulaciju sila rezanja. Polazeći od prethodno prikazane ideje u okviru ovog poglavlja je razvijena nova matematička metoda predikcije granične dubine rezanja - unapređena numerička simulacija procesa glodanja.U okviru šestog poglavlja prikazane su eksperimentalne metode identifikacije vibracija mašina alatki, odnosno eksperimentalno određivanje modalnih parametara obradnih sistema kao i metode detekcije samopobudnih vibracija pri glodanju. U cilju definisanja granične dubine rezanja, prikazana je metoda frekventne analize vibracija pri glodanju, kao metoda koja se često koristi u savremenim eksperimentalnim istraživanjima. Međutim, i matematičke i eksperimentalne metode analize vibracija pri glodanju imaju određena ograničenja. Polazeći od prethodnog, razvijena je inovativna metoda tangenti, bazirana na ranije korišćenoj metodi u okviru Laboratorije za mašine alatke Instituta za proizvodno mašinstvo FTN u Novom Sadu, i primeni savremenih mernih sistema. Pored toga, u ovom poglavlju je eksperimentalno potvrđen uticaj samopobudnih vibracija na kvalitet obrađene površine i geometrijsku tačnost obratka.Metodologija sprezanja matematički i eksperimentalno definisanih funkcija frekventnog odziva elemenata mašine alatke prikazana je u sedmom poglavlju. Prezentovane su jednačine sprezanja pomerajnih odziva matematmički definisanih funkcija frekventnog odziva alata i držača alata, bazirane na Ojlerovoj teoriji grede, sa eksperimentalno definisanom funkcijom frekventnog odziva sklopa glavnog vretena mašine alatke.U okviru osmog poglavlja razvijen je matematički model sila rezanja pri mikroglodanju. Predloženi model sila rezanja, koji uzima u obzir silu trenja između leđne površine alata i obrađene površine, implementiran je u unapređenu numeričku simulaciju glodanja čime je omogućena njena primena za definisanje graničnih dubina rezanja pri mikroglodanju.Verifikacija razvijenih numeričkih i eksperimentalnih metoda za ispitivanje vibracija pri makroglodanju je prikazana u devetom poglavlju. Sproveden je niz eksperimentalnih ispitivanja, pri kojima su određivane granične dubine glodanja pri obradi tri različita materijala obratka (Al7075, 42CrMo4 i Ti-6Al-4V) na dva obradna sistema. Na osnovu ovih ispitivanjima izvršena je verifikacija unapređene numeričke simulacije glodanja i inovativne metode tangenti.U desetom poglavlju prikazana je verifikacija metoda analize samopobudnih vibracija pri mikroglodanju. Primenom metodologije sprezanja pomerajnih odziva, definisani su modalni parametri obradnog sistema za mikroobradu, potrebni za definisanje graničnih dubina rezanja, tj. karte stabilnosti, unapređenom numeričkom simulacijom mikroglodanja. Karta stabilnosti definisana razvijenom unapređenom numeričkom simulacijom, verifikovana je eksperimentalno i poređenjem sa literaturnim izvorima.U jedanaestom poglavlju data su zaključna razmatranja, kritički osvrt na ostvarene rezultate, i pravci budućih istraživanja.Dvanaesto poglavlje prikazuje pregled korišćene literature, koju čini 218 referenci većim delom citirane u samom radu, a u zasebnom poglavlju dati su prilozi.
The subject of research presented in the doctoral dissertation are self-excited vibrations in milling. Based on a detailed analysis of the self-excited vibrations occurrence, a certain parallel has been established between macro and micromilling, for cases when the depth of cut is greater than the cutting edge radius of the tool. For such adopted assumptions, models of advanced numerical simulation of macro and micromilling processes were developed. The developed models were comprehensively verified, on the one hand, by comparison with the results of other authors, and on the other hand by comparison with own experimental results. An innovative tangent method has been proposed for the experimental definition of the cutting depth limit in milling, and the method of machined surface roughness has been proposed for micromilling, having in mind the available measuring equipment. Mathematical models and experimental methods were verified by machining three characteristic types of materials on two machining systems in macromilling, and one material on one machining system in micromilling. The results of the research are presented through twelve chapters, the content of which is listed below.In the first, introductory chapter, the importance of the research of self - excited vibrations in macro and micromilling is pointed out. The topicality of the research is also presented by analyzing the number of scientific papers dealing with the issue of self - excited vibrations in the period of the last twenty - five years.The second chapter presents in detail the previous research on self-excited vibrations during macromilling, while the third chapter presents research on self-excited vibrations during micromilling. An analysis of the influential parameters on the cutting depth limit was performed, which is a basic indicator of the dynamic stability of both macro and micromachining systems.Based on the findings presented in the second and third chapters, the fourth chapter defines the goals and hypotheses of the research.Mathematical methods for defining the stability lobe diagram of the machining system are presented in the fifth chapter. Two mathematical models for defining the stability lobe diagram for macromachining are presented, the model of the tool’s mean contact angle and the model of Fourier series. Numerical simulation of the milling process is presented, intended primarily for the simulation of cutting forces. Starting from the previously presented idea, a new mathematical method for predicting the cutting depth limit has been developed within this chapter - an improved numerical simulation of the milling process.In the sixth chapter, experimental methods of machine tools vibration identification are presented, ie experimental determination of machining systems modal parameters as well as methods of self - excited vibrations detection during milling. In order to define the cutting depth limit, the method of vibrations frequency analysis during milling is presented, as a method that is often used in modern experimental research. However, both mathematical and experimental methods of milling vibration analysis have certain limitations. Starting from the previous one, an innovative tangent method was developed, based on the previously developed method, used within the Laboratory for Machine Tools, Institute of Production Engineering Facultz of Technical Sciences in Novi Sad, and the application of modern measuring systems. In addition, in this chapter, the influence of self - excited vibrations on the machined surface quality and the geometric accuracy of the workpiece is experimentally confirmed.The methodology of machine tool elements mathematically and experimentally defined frequency response functions coupling is presented in the seventh chapter. The displacement responses coupling equations of mathematically defined tools and tool holders FRF's (based on Euler 's beam theory) with the experimentally defined FRF of the machine tool main spindle assembly are presented.Within the eighth chapter, a mathematical model of cutting forces in micromilling was developed. The proposed cutting forces model, which takes into account the friction force between the reliefe tool surface and the machined surface, is implemented in an advanced numerical micromilling simulation, which enables its application to define cutting depth limit in micromilling.Verification of the developed numerical and experimental methods for vibrations analysis during macromachining is presented in the ninth chapter. A series of experimental tests were performed, during which the cutting depth limits were determined during the milling of three different workpiece materials (Al7075, 42CrMo4 and Ti-6Al-4V) on two machining systems.In the tenth chapter, the verification of the methods of analysis of self-excited vibrations during micromilling is presented. Using the methodology of coupling displacement responses, the modal parameters of the machining system for micromachining are defined, needed to define the cutting depth limits, ie. stability lobe diagram, by advanced numerical micromilling simulation The stability lobe diagram, defined by the developed advanced numerical simulation, was verified experimentally and by comparison with literature sources.The eleventh chapter provides concluding remarks, a critical review of the achieved results, and directions for future research.The twelfth chapter presents an overview of the used literature, which consists of 218 references, mostly cited in the paper itself.

Cette these decrit la synthese de reseaux lineaires de dipoles couples electromagnetiquement (dipoles c. E. M. ) avec prise en compte des couplages. Cette synthese est ensuite appliquee a la realisation d'un diagramme de rayonnement forme du type depression spherique

碩士
中原大學
機械工程研究所
102
Through this study, the actual milling experiment to capture the vibration acceleration, time domain and frequency domain analysis of vibration changes flutter occurs, the signal changes by transient analysis and spectrum analysis dual threshold formulate chatter judgment rule, while taking advantage of cutting stability diagram auxiliary determine whether the cutting conditions in the region chatter to improve the accuracy of judgment. In terms of inhibition of chatter, chatter suppression in order to allow more efficient, is to establish a stable figure in cutting chatter direct identification method for inhibiting the cutting speed to make a one-time suppress chatter. Research has also established a two-way data transfer controller capture module, to achieve real-time monitoring and control functions via TCP / IP protocol. The method of development, in addition to PLC is compiled, the research to Visual C # to establish the overall monitoring system in Visual C ++ environment, can be CNC controller data transmission, recording real-time vibration signal and cutting unusual information, draw cutting stability graph model and online chatter real-time monitoring and other functions.According to experimental results, show that the system can quickly and accurately find and make immediate chatter suppression.

碩士
國立臺灣科技大學
機械工程系
103
Cutting is one of machinery manufacturing and processing methods, as advances in technology, metal processing technology, has been toward high-precision machining. However, the set of milling operations, often dependent on practical experience as a set of cutting parameters, in order to reduce tool wear. But empirically selection parameter, usually more subjective, and likely to cause the tool and machine damage. Chatter is a kind arising from a failure caused by the cutting parameters, chatter has many adverse effects, such as poor surface, accuracy errors, serious noise and increase tool wear, even damage processing equipment and reduce the material removal rate, resulting in processing time, material and energy costs relative increase, in order to improve the above problems, to study how the economy and establish an effective process parameters based on, in order to reduce tool wear, and increase costs production efficiency, it is also a very important issue currently. In this study, flank wear as a benchmark to determine the tool life of Taylor tool life equation, and estimates that when the flank wear reach 300 μm, the tool can be cut much time, uses MetalMax software to get Stability Lobe Diagram, and finally uses MATLAB to combine the results of both obtained. From the experimental results that, cutting speed was the strongest in tool life, and followed by feed rate, and cutting depth was weakest, it can increase the overall increase in feed material removal rate, less wear effect. Therefore, the feed rate can be added to increase the overall material removal rate, less wear effects but increase the cutting speed will make the tool life greatly reduced, on the other hand, in a high speed region, which allows the cutting depth of 0.3 mm, at low speed 170 rpm about cutting depth can be infinitely raised without causing chatter.

碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
108
With the rapid advancement of industrial technology, the improvement of processing efficiency has gradually becoming the mainstream trend. However, the assembly quality, material properties and tool geometry of the machine will lead to the stability of processing. In the past, it was only possible to rely on experience for processing, and this processing was hard to handle the current changing and complex processing conditions now, so the processing through the prediction of the cutting force model and the chatter prediction technology can obtain stable cutting parameters to avoid the unstable speed range for better surface roughness of the workpiece. In view of the fact, this study was mainly carried out in different wear states of cutting tools, the experiments such as the following: cutting force prediction system, chatter stability system and dynamic cutting monitoring system. Firstly, prediction of cutting force used NACHI high speed steel and Alloy 7075-T6, and researched cutting force and cutting coefficients under the different tool wear conditions, the cutting force is estimated by dynamic cutting, and the cutting force coefficients is calculated by linear regression during tool wear. The cutting forces of X direction grew 25% to 32%, and the cutting forces of Y direction grew 3% to 6%. Second, the chatter stability prediction system was divided into dynamic rigidity experiment and milling stability curve, the prediction of chatter stability applied analysis of frequency response data by dynamic rigidity experiments and cutting force coefficients. The preliminary determination of the corresponding cutting force coefficients was helpful for the prediction of the chatter stability, and this stability model constructed relationship between the spindle speed and cutting depth by regenerative chatter theory and frequency response function, the experimental results shew that the prediction accuracy was about 80%. Lastly, the dynamic cutting system for monitoring tool chatter used G-sensor and microphone to measure the resonant frequency of cutting, then it used the vibration value and frequency to know cutting chatter. The dynamic cutting monitoring system can know whether the machine was unstable machining state during processing, the success rate of verification was about 95%.

Cutting movement is still one of the main means to obtain the desired machined surface. As the most representative cutting method in subtractive manufacturing, milling is widely used in industrial production. However, the chatter induced by the dynamic interaction between machine tool and process not only reduces the accuracy of the machined workpiece, but also increases the tool wear and affects the rotary accuracy of the spindle. The stability lobe diagram can provide stable machining parameters for the technicians, and it is currently an effective way to avoid chatter. In fact, the dynamic interaction between the machine tool and process is very complicated, which involves the machine tool, milling tool, workpiece and fixture. The induced mechanism of chatter depends on different machining scenarios and is not entirely dependent on the vibration modes of milling tool. Therefore, it is important to obtain stable machining parameters and to know the dynamic surface location error distribution, which can ensure machining quality and improve machining efficiency. In this dissertation, two methods for constructing stability lobe diagram are first introduced, and then two machining scales, macro milling and micro milling, are studied. For the macro-milling scale, the dynamic response of the in-process workpiece with time-varying modal parameters during the material removal process is analyzed. The stability lobe diagrams for thin-walled workpiece and general workpiece with continuous radial immersion milling are established respectively. Besides, the cumulative surface location error distribution is also studied and verified for the general workpiece. For the micro-milling scale, the dynamics at the micro-milling tool point is obtained by means of the receptance coupling substructure analysis method. The stability lobe diagram and surface location error distribution are analyzed under different restricted/free tool overhang lengths. The relationship between measurement results and burrs is further explained by cutting experiments, and the difference between the two milling scales is compared in the end.