This thesis addresses a comprehensive approach to understanding the time-varying thermal errors in machine tools. Errors in machine tools are generally classified as being time or spatial dependent. Thermal errors are strongly dependent on the continuously changing operating conditions of a machine and its surrounding environment. Uniform temperature rises or stable temperature gradients, which produce time-invariant thermal errors, are considered to be rare in ordinary shop floor environments. Difficulties in analysing time-varying thermal errors are that, first of all, the temperature distribution within the components of a machine should be evaluated, and secondly, the distribution is continuously changing with time. These difficulties can be overcome by introducing a point-wise description method with three thermal parameters. From the theoretical analysis of simple machine elements such as bars, beams and cylinders, and extensive finite-element simulation data for a straightedge subject to room temperature variations, three thermal parameters, i. e. time-delay, time-constant and gain, were identified to obtain a precise description of the thermal deformation of a point of a machine body. Time-delay is dependent largely on thermal diffusivity, and the heat transfer mechanism. The time-constant is governed by heat capacity, heat transfer mechanism and body size. Gain, on the other hand, is determined by the thermal expansion coefficient, heat transfer mechanism and mechanical constraint. The three thermal parameters, in turn, imply that thermal deformation of a point in a body can be described by a simple first- order differential equation. Regarding their dependence on the heat transfer mechanism, a more refined description requires a time-varying linear first-order differential equation. Such an equation can be applied to each point of interest of a machine body. The final form of modelling, using the parameters, is a state-space equation gathering the governing equations for the points of interest. By adopting the point-wise discrete modelling method, we can overcome the difficulty of the spatial distribution of the temperature. Indeed, the calibration of a machine tool is usually performed at discrete points. The completion of this approach was made by presenting the methods by which the three thermal parameters can be evaluated. The first method employs analytical tools based on simplifying assumptions about the shape and boundary conditions of machine components. The second method was to apply numerical techniques to complex machine components. Because there are many drawbacks in theoretical approaches, experimental techniques are essential to complement them. The three thermal parameters can be easily identified using popular parameter identification techniques which can be applied to time-varying cases by their recursive forms. The techniques described were applied to modelling the thermal errors in a single-point diamond turning research machine. It was found that the dominant error component was spindle axial growth. The predictive model for the time-constant was shown to be in agreement with both the machine and with the scaled physical model rig.

On-machine inspection (OMI) via on-machine probing (OMP) is a technology that has the potential to provide a step change in the manufacturing of high precision products. Bringing product inspection closer to the machining process is very attractive proposition for many manufacturers who demand ever better quality, process control and efficiency from their manufacturing systems. However, there is a shortness of understanding, experience, and knowledge with regards to efficiently implementing OMI on industrially-based multi-axis machine tools. Coupled with the risks associated to this disruptive technology, these are major obstacles preventing OMI from being confidently adopted in many high precision manufacturing environments. The research pursued in this thesis investigates the concept of enabling high precision machine tools as measurement devices and focuses upon the question of: “How can traceable on-machine inspection be enabled and sustained in an industrial environment?” As highlighted by the literature and state-of-the-art review, much research and development focuses on the technology surrounding particular aspects of machine tool metrology and measurement whether this is theory, hardware, software, or simulation. Little research has been performed in terms of confirming the viability of industrial OMI and the systematic and holistic application of existing and new technology to enable optimal intervention. This EngD research has contributed towards the use of industrial machine tools as traceable measurement systems. Through the test cases performed, the novel concepts proposed, and solutions tested, a series of fundamental questions have been addressed. Thus, providing new knowledge and use to future researchers, engineers, consultants and manufacturing professionals.