The primary barrier to the production of better machined parts is machine tool error. Present day applications are requiring closer machine part tolerances. The errors in dimensional part accuracy derive from the machine, in this case, a vertical two axis CNC lathe. A two axis vertical lathe can be utilized to produce a variety of parts ranging from cylindrical features to spherical features. A vertical lathe requires a spindle to rotate the work at speeds reaching 3000rpm, while simultaneously requiring the machine tool to be positioned in such a manner to remove material and produce an accurate part. For this to be possible, the machine tool must be precisely controlled in order to produce the correct contours on the part. There are many sources of errors to be considered in the two axis vertical lathe. Each axis of importance contains six degrees of freedom. The machine has linear displacement, angular, spindle thermal drift, straightness, parallelism, orthogonal, machine tool offset and roundness error. These error components must be measured in order to determine the resultant error. The characterization of the machine addresses thermal behavior and geometric errors. This thesis presents the approach of determining the machine tool errors and using these errors to transform the actual tool path closer to the nominal tool path via compensation schemes. One of these schemes uses a laser interferometer in conjunction with a homogenous transformation matrix to construct the compensated path for a circular arc, facing and turning. The other scheme uses a ball bar system to directly construct the compensated tool path for a circular arc. Test parts were created to verify the improvement of the part accuracy using the compensated tool paths.

Machine tools need to be tested to check they behave correctly while machining. A bigger production (capacity), improving the accuracy in final products (quality) or reducing costs are some of the main goals. Reducing the maintenance of the machines, their nonproductive time and a higher quality of the final parts, have a strong influence in the costs. Even machines built to the same specification present different properties and behaviours, which leads into a reduction of the flexibility when it comes to move operations among them. This study is focused on the measurement and modelling of four machine tools (M1, M2, M3 and M4), with same specifications, from the static point of view. Methods used to measure all these properties are the circular tests under loaded conditions, with the device Loaded Double Ball Bar (LDBB), which measures positional accuracy and static stiffness. Different pressures (0.5, 1, 3, 5, 6, 7 bar) and locations for the LDBB have been used.   After the tests were performed, all the machines shown good properties with the detail of M4, which had a lower stiffness than the other three ones due to its table attachments. / Maskinverktyg måste testas för att kontrollera att de beter sig korrekt vid bearbetning. En större produktion (kapacitet), förbättra noggrannheten i slutprodukterna (kvalitet) eller sänka kostnaderna är några av huvudmålen. Att minska underhållet av maskinerna, deras icke-produktiva tid och en högre kvalitet på de slutliga delarna har ett starkt inflytande i kostnaderna. Även maskiner konstruerade för samma specifikation presenterar olika egenskaper och beteenden, vilket leder till en minskning av flexibiliteten när det gäller att flytta verksamheten bland dem. Denna studie är inriktad på mätning och modellering av fyra verktygsmaskiner (M1, M2, M3 och M4), med samma specifikationer, ur statisk synvinkel. Metoder som används för att mäta alla dessa egenskaper är de cirkulära testerna under laddade förhållanden, med enheten Loaded Double Ball Bar (LDBB), som mäter positionsnoggrannhet och statisk styvhet. Olika tryck (0,5, 1, 3, 5, 6, 7 bar) och platser för LDBB har använts.   Efter testerna visade alla maskiner goda egenskaper med detaljerna i M4, som hade en lägre styvhet än de andra tre på grund av dess bordsfästanordningar.

Comprehensive knowledge and information about the static and dynamic behaviour of machine tools, cutting processes and their interaction is essential for machining system design, simulation, control and robust operation in safe conditions. The very complex system of a machine tool, fixture and cutting tools during the machining of a part is almost impossible to model analytically with sufficient accuracy. In combination with increasing demands for precision and efficiency in machining call for new control strategies for machining systems. These strategies need to be based on the identification of the static and dynamic stability under both the operational and off-operational conditions. To achieve this it is necessary to monitor and analyze the real system at the factory floor in full production. Design information and operational data can then be linked together to make a realistic digital model of a given machining system. Information from such a model can then be used as input in machining simulation software to find the root causes of instability. The work presented in this thesis deals with the static and dynamic capability of machining systems. The main focus is on the operational stability of the machining system and structural behaviour of only the machine tool, as well. When the accuracy of a machining system is measured by traditional techniques, effects from neither the static stiffness nor the cutting process are taken into account. This limits the applicability of these techniques for realistic evaluation of a machining system’s accuracy. The research presented in this thesis takes a different approach by introducing the concept of operational dynamic parameters. The concept of operational dynamic parameters entails an interaction between the structural elements of the machining systems and the process parameters. According to this concept, the absolute criterion of damping is used to evaluate the dynamic behaviour of a machining system. In contrast to the traditional theory, this methodology allows to determine the machining system's dynamic stability, in real time under operating conditions. This framework also includes an evaluation of the static deformations of a machine tool.  In this context, a novel concept of elastically linked system is introduced to account for the representation of the cutting force trough an elastic link that closes the force loop. In addition to the elastic link which behaves as a static element, a dynamic non-contact link has been introduced. The purpose is to study the non-linear effects introduced by variations of contact conditions in joints due to rotational speed. / QC 20111123

There is an increasing trend in manufacturing industry for producing complex and delicate parts. As a result, the importance of having a deeper understanding of machine systems, in order toget higher accuracy of machined parts, arises. This leads to an increasing demand of testingmachine accuracy under operational condition. There are methods that has been investigated in order to test under operational condition. However, the studies were mostly focused on thestatic, quasi-static and dynamic states separately and comparison were not investigated. This thesis aims at presenting a comparative study of static and quasi-static compliance on machine tool under loaded conditions, to investigate how the stiffness changes from static toquasi-static state, and also the potential factors that would lead to this result. A 5-axis machine tool- Hermle C50U machine is used in order to perform the measurements.The method chosen for the measurements includes circular tests under loaded conditions utilizinga loaded double ball bar device. Three LVDTs are used for the measurements, in order to detect the deflection along the circular trajectory. The main parameter that undergoes study is the effect of the applied feed rate. After the measurements, the data is analyzed using MAT-LAB and the average deflections for both states are compared. In general, the results show that there is no significant difference between the two states, despite the observed different shape ofdeflection. / Det finns en ökande trend inom tillverkningsindustrin för tillverkning av komplexa och känsliga delar. Som ett resultat uppstår vikten av att ha en djupare förståelse för maskinsystem, för att få högre noggrannhet hos bearbetade delar. Detta leder till en ökande efterfrågan på att testamaskinens noggrannhet under driftsförhållanden. Det finns metoder som har undersökts för att testa under driftskondition. Studierna var dock mest inriktade på de statiska, kvasistatiska och dynamiska tillstånden separat och jämförelsen undersöktes inte. Denna avhandling syftar till att presentera en jämförande studie av statisk och kvasi-statisk överensstämmelse på maskinverktyg under belastade förhållanden, för att undersöka hur styvheten förändras från statiskt till kvasi-statiskt tillstånd, och även de potentiella faktorer som skulle leda till detta resultat. Ett 5-axligt verktygsmaskin- Hermle C50U-maskin används för att utföra mätningarna.Metoden som valts för mätningarna inkluderar cirkulära tester under belastade förhållanden med användning av en laddad dubbelkulstångsanordning. Tre LVDT används för mätningarna för att detektera nedböjningen längs cirkelbanan. Huvudparametern som genomgår studier är effekten av den applicerade matningshastigheten. Efter mätningarna analyseras data med MATLAB och de genomsnittliga avböjningarna för båda tillstånden jämförs. I allmänhet visar resultaten att det inte finns någon signifikant skillnad mellan de två tillstånden, trots den observerade olika avböjningsformen.