The difficulties of the assessment of tool life in CNC milling

In the manufacturing process, tool life is an important parameter in milling operations. The main objective of this paper is to explain how difficult is it to assess how much work a tool has undertaken before it must be changed. A number of ways of expressing tool life are currently used, including the conventional method based upon one of several configurations of the Taylor Tool Life Equation. These usually express tool life in terms of known material properties together with primary machining variables like speed, feed and depth of cut. Other approaches are based upon the extrapolation of a tool wear curve and considerations of the volume of metal removed. This initial investigation adopts an approach that is based upon a series of experiments, which produce data indicating the changes in machined feature form and dimension. For this study, a new test piece was designed in order to allow the indirect assessment of the tool flank wear by utilising a Coordinate Measuring Machine to accurately measure the workpieces. This work is intended to indicate how difficult it is to actually apply the existing methods to manage tool wear. The aim is to engineer a better way and to establish a methodology of measuring what the tool is actually doing in real time using the machine controller

The development of a process charge expert system for a Basic Oxygen Steelmaking plant.

In an integrated steelworks the Basic Oxygen Steelmaking (BOS) process is required for the refining of molten iron from a blast furnace to produce steel. The development of an expert diagnostic system is considered in the context of the initial phase of BOS operation, the loading and operation of the BOS vessel. In this part of the steelmaking process the BOS vessel is charged with the molten iron, scrap metal and fluxes which are there to facilitate the capture of impurities by forming slag. The nature of the elements added requires knowledge of the steelmaking process, the actual state of the contents of the vessel and the available process management options. The expert system produced to oversee this process exhibits the capability of dealing with both continuous and batch data, combining the two together to aid effective decision making and management. Fuzzy inference is used in the main diagnostic system due to the large rule base required to diagnose faults and infer a process state. The operation of the system and its use by the process operators and the application of this approach into other areas of the steelworks is considered in this paper

An investigation into the recycling of Ti-6Al-4V powder used within SLM to improve sustainability

This paper considers the steps to be taken in investigating the effects of recycling Ti-6Al-4V powders for Selective Laser Melting (SLM). A research methodology is presented that shall allow for investigation in to the change in powder characteristics through repeated use, and will provide the basis for eventual determination of any effect that these changes have on the chemical, mechanical and metallurgical properties of laser melted parts. An in depth understanding of the link between powder and part characteristics is essential for SLM, and measuring powder characteristics after building production parts may prove to be an important marker for part quality. Initial powder characterisation testing was conducted on powder that had been recycled up to five times. The results showed a trend towards increased Particle Size Diameter (PSD) through repeated recycling, with a reduction in the number of fine particles. Additionally, a roughening of the powder surface was observed, with a reduction in the sphericity of powder particles. Chemical composition tests on the powder to determine changes in interstitial oxygen and nitrogen showed negligible change through repeated recycling

Product change management: the through-life impact of diverging designs within product fleets

The designs of high-value, long-life products such as aircraft, trains and industrial plant continually evolve, both at the time of manufacture but also during their operating lives. Such products are invariably managed in complex multi-stakeholder environments where the product change process spans a number of organisations. It is clearly important that regulatory systems are able to monitor that the design integrity established when a product is first created is maintained through-life. The purpose of this paper is to assess the challenges to maintaining design integrity throughout the product lifecycle. Discussions with a number of organisations undertaken by the authors have indicated that managing product information in the context of the product change process continues to be problematic. There is a fundamental need to improve the alignment between through-life design management processes, information technology and the management models used to guide decision making. To quantify the challenges currently being experienced a mathematical model has been developed to support investigations into the level and impact of design changes that have been reported by engineers in industry

Development and application of a process diagnostic system for the desulphurisation process

In an increasingly competitive steel industry, with ever-stricter grade requirements for sulphur, the requirement for improved control and efficiency is increasingly important to reduce process costs. This paper describes an online system that has been developed and implemented at Tata Steel Port Talbot Works, to monitor and report on the desulphurisation process. The aim of the system is to generate an objective report on the process, to highlight all process deviations and issues, and facilitate diagnosis. This diagnosis will improve process control and process efficiency. The desulphurisation process typically uses lime and magnesium to facilitate the removal of sulphur from the hot metal and into the slag where this is removed by a rabble. The process, with a start Hot Metal Sulphur of 0.045 (wt.%) and Aim Sulphur of 0.008 (wt.%) typically uses approximately 100kg magnesium and 300kg lime for a 300T ladle. The main focus of this system has been the development of linguistic outputs. The outputs have been optimised to provide concise and interoperable information to assist the operators to quickly understand the current state of the process. The system has been designed to monitor three areas regarding the desulphurisation process; model setup, process deviation and sample availability. A report is generated every morning, for use by shift and plant managers, highlighting every deviation in the process over the past 24 hours and diagnosis of the exact cause where possible. The report is compiled on an exception basis, only highlighting treatments providing there has been an issue or deviation from expected material usage

Assessing the challenges of managing product design change through-life

Whole-life support for complex products requires coordinated action. Existing shortcomings of the design change management process currently operated within key UK engineering sectors are identified and discussed. The challenges that must be met in order to better satisfy the need for accurate product information across an integrated supply chain are presented. The role that information technology must play in achieving greater efficiency is developed. Recommendations are made in the form of 10 requirements to guide future design change management strategies. It is intended that implementation of these requirements will enable and improve the provision of product-related information so that it more accurately reflects the current configured status of the products. The aim is to facilitate and support enhanced product maintenance, effectiveness and utilisation

Tidal Steam Turbine blade fault diagnosis using time-frequency analyses

Tidal Stream Turbines are developing renewable energy devices, for which proof of concept commercial devices are been deployed. The optimisation of such devices is supported by research activities. Operation within selected marine environments will lead to extreme dynamic loading and other problems. Further, such environments emphasise the need for condition monitoring and prognostics to support difficult maintenance activities. This paper considers flow and structural simulation research and condition monitoring evaluations. In particular, reduced turbine blade functionality will result in reduced energy production, long down times and potential damage to other critical turbine sub-assemblies. Local sea conditions and cyclic tidal variations along with shorter timescale dynamic fluctuations lead to the consideration of time-frequency methods. This paper initially reports on simulation and scale-model experimental testing of blade-structure interactions observed in the total axial thrust signal. The assessment is then extended to monitoring turbine blade and rotor condition, via drive shaft torque measurements. Parametric models are utilised and reported and a motor-drive train-generator test rig is described. The parametric models allow the generation of realistic time series used to drive this test rig and hence to evaluate the applicability of various time-frequency algorithms to the diagnosis of blade faults

Performance and condition monitoring of tidal stream turbines

Research within the Cardiff Marine Energy Research Group (CMERG) has considered the integrated mathematical modelling of Tidal Stream Turbines (TST). The modelling studies are briefly reviewed. This paper concentrates on the experimental validation testing of small TST models in a water flume facility. The dataset of results, and in particular the measured axial thrust signals are analysed via timefrequency methods. For the 0.5 m diameter TST the recorded angular velocity typically varies by ± 2.5% during the 90 second test durations. Modelling results confirm the expectations for the thrust signal spectrums, for both optimum and deliberately offset blade results. A discussion of the need to consider operating conditions, condition monitoring sub-system refinements and the direction of prognostic methods development, is provided