The development of a tool to promote sustainability in casting processes

The drive of the manufacturing industry towards productivity, quality and profitability has been supported in the last century by the availability of relatively cheap and abundant energy sources with limited focus on the minimisation of energy and material waste. However, in the last decades, more and more stringent regulations aimed at reducing pollution and consumption of resources have been introduced worldwide and in particular in Europe. Consequently, a highly mature and competitive industry like foundry is expecting challenges that an endeavour towards sustainability can turn into significant opportunities for the future. A tool to undertake a systematic analysis of energy and material flows in the casting process is being developed. An overview of the computer program architecture is presented and its output has been validated against real-world data collected from foundries

A proposed configuration for a stepped specimen to be used in the systematic evaluation of factors influencing warpage in metallic alloys being used for cryogenic wind tunnel models

A proposed configuration for a stepped specimen to be used in the system evaluation of mechanisms that can introduce warpage or dimensional changes in metallic alloys used for cryogenic wind tunnel models is described. Considerations for selecting a standard specimen are presented along with results obtained from an investigation carried out for VASCOMAX 200 maraging steel. Details of the machining and measurement techniques utilized in the investigation are presented. Initial results from the sample of VASCOMAX 200 show that the configuration and measuring techniques are capable of giving quantitative results

Comparison of Volumetric Analysis Methods for Machine Tools with Rotary Axes

Confidence in the ability of a production machine to meet manufacturing tolerances requires a full understanding of the accuracy of the machine. However, the definition of “the accuracy of the machine” is open to interpretation. Historically, this has been in terms of linear positioning accuracy of an axis with no regard for the other errors of the machine. Industry awareness of the three-dimensional positioning accuracy of a machine over its working envelope has slowly developed to an extent that people are aware that “volumetric accuracy” gives a better estimation of machine performance. However, at present there is no common standard for volumetric errors of machine tools, although several researchers have developed models to predict the effect of the combined errors. The error model for machines with three Cartesian axes has been well addressed, for example by the use of homogenous transformation matrices. Intuitively, the number of error sources increases with the number of axes present on the machine. The effect of the individual axis geometric errors can become increasingly significant as the chain of dependent axes is extended. Measurement of the “volumetric error” or its constituents is often restricted to a subset of the errors of the Cartesian axes by solely relying on a laser interferometer for measurement. This leads to a volumetric accuracy figure that neglects the misalignment errors of rotary axes. In more advanced models the accuracy of the rotary axes are considered as a separate geometric problem whose volumetric accuracy is then added to the volumetric accuracy of the Cartesian axes. This paper considers the geometric errors of some typical machine configurations with both Cartesian and non-Cartesian axes and uses case studies to emphasise the importance of measurement of all the error constituents. Furthermore, it shows the misrepresentation when modelling a five-axis machine as a three-plus-two error problem. A method by which the five-axis model can be analysed to better represent the machine performance is introduced. Consideration is also given for thermal and non-rigid influences on the machine volumetric accuracy analysis, both in terms of the uncertainty of the model and the uncertainty during the measurement. The magnitude of these errors can be unexpectedly high and needs to be carefully considered whenever testing volumetric accuracy, with additional tests being recommended

Automatic Modeling for Modular Reconfigurable Robotic Systems: Theory and Practice

A modular reconfigurable robot consists of a collection of individual link and joint components that can be assembled into a number of different robot ge-ometries. Compared to a conventional industrial robot with fixed geometry, such a system can provide flexibility to the user to cope with a wide spectru

Surface roughness detector Patent

Roughness detector for recording surface pattern of irregularitie

Optimized normal and distance matching for heterogeneous object modeling

This paper presents a new optimization methodology of material blending for heterogeneous object modeling by matching the material governing features for designing a heterogeneous object. The proposed method establishes point-to-point correspondence represented by a set of connecting lines between two material directrices. To blend the material features between the directrices, a heuristic optimization method developed with the objective is to maximize the sum of the inner products of the unit normals at the end points of the connecting lines and minimize the sum of the lengths of connecting lines. The geometric features with material information are matched to generate non-self-intersecting and non-twisted connecting surfaces. By subdividing the connecting lines into equal number of segments, a series of intermediate piecewise curves are generated to represent the material metamorphosis between the governing material features. Alternatively, a dynamic programming approach developed in our earlier work is presented for comparison purposes. Result and computational efficiency of the proposed heuristic method is also compared with earlier techniques in the literature. Computer interface implementation and illustrative examples are also presented in this paper

Constant scallop height tool path generation

Journal ArticleAn approach for the automatic generation of constant scallop height tool paths is presented. An example is shown generated from a B-spline model, although it can be used with many types of sculptured surfaces. The approach utilizes surface subdivision techniques and a new algorithm for tool path generation. The new algorithm is based on computer graphics shading algorithms and on methods from graph theory. A tool path with a constant scallop height renders minimum waste tool moves and hence results in much better machine time. Since neither numerical methods nor high order derivatives are required by the algorithm, it provides an efficient and robust method for tool path computation. Besides, the new algorithm is capable of producing tool paths whose milling directions are based on local surface geometry

Reconstruction of freeform surfaces for metrology

The application of freeform surfaces has increased since their complex shapes closely express a product's functional specifications and their machining is obtained with higher accuracy. In particular, optical surfaces exhibit enhanced performance especially when they take aspheric forms or more complex forms with multi-undulations. This study is mainly focused on the reconstruction of complex shapes such as freeform optical surfaces, and on the characterization of their form. The computer graphics community has proposed various algorithms for constructing a mesh based on the cloud of sample points. The mesh is a piecewise linear approximation of the surface and an interpolation of the point set. The mesh can further be processed for fitting parametric surfaces (Polyworks® or Geomagic®). The metrology community investigates direct fitting approaches. If the surface mathematical model is given, fitting is a straight forward task. Nonetheless, if the surface model is unknown, fitting is only possible through the association of polynomial Spline parametric surfaces. In this paper, a comparative study carried out on methods proposed by the computer graphics community will be presented to elucidate the advantages of these approaches. We stress the importance of the pre-processing phase as well as the significance of initial conditions. We further emphasize the importance of the meshing phase by stating that a proper mesh has two major advantages. First, it organizes the initially unstructured point set and it provides an insight of orientation, neighbourhood and curvature, and infers information on both its geometry and topology. Second, it conveys a better segmentation of the space, leading to a correct patching and association of parametric surfaces.EMR

Analysis of KrF excimer laser beam modification resulting from ablation under closed thick film flowing filtered water

The application of closed thick film liquid to immerse the ablation etching mechanism of an excimer laser poses interesting possibilities concerning debris control, modification of machined feature topography and modification of ablation rate. Further more, these parameters have been shown to be dependant on flow velocity; hence offering further user control of machining characteristics. However the impact of this technique requires investigation. This contribution offers comparison of the calculated ablation pressure and the effect on feature surface characteristics given for laser ablation of bisphenol A polycarbonate using KrF excimer laser radiation in ambient air against laser ablation of the same substrate under closed thick film flowing filtered water immersion. Also, the impact of such immersion equipment on the optical performance of the micromachining centre used is quantified and reviewed. The pressure is calculated to have risen some 53% when using the liquid immersed ablation technique. This increase in pressure is proposed to have promoted the frequency of surface Plasmons and asperities with a surface area less than 16 µm2. The focal length of the optical system was accurately predicted to be increased by 2.958 mm when using the equipment composed of a 5 mm thick ultraviolet grade fused silica window covering a 1.5 mm thick film of filtered water flowing at 1.85 m/s. This equipment was predicted to have increased the optical depth of focus via reduction in the angle of convergence of the two defining image rays, yet the perceived focus, measured by mean feature wall angle as a discrete indication, was found to be 25% smaller when using the closed thick film flowing filtered water immersion technique than when laser ablating in ambient air. A compressed plume interaction is proposed as a contributing factor in this change