Rapid prototyping (RP) techniques are being increasingly used to manufacture injection molding and die casting core and cavity sets, known as tools, and for other…
Rapid prototyping (RP) techniques are being increasingly used to manufacture injection molding and die casting core and cavity sets, known as tools, and for other tooling‐related parts, such as EDM electrodes. This paper presents a STL‐based finish machining technique for tools and parts made using RP techniques in order to achieve the tight tolerance and surface finish requirements necessary for tooling applications. Rotate, scale, translate and offset algorithms are used to pre‐process the 3D model prior to its manufacture. A machining strategy of adaptive raster milling of the surface, plus hole drilling and sharp edge contour machining, is developed to finish the parts and tools after fabrication using RP. Finally, a benchmark part was designed and fabricated using the above‐mentioned strategies and the results show the effectiveness of the developed software.
This paper presents a unique method to recognize circular holes from 3D models in the STL format. The topological information generated by this method enables…
This paper presents a unique method to recognize circular holes from 3D models in the STL format. The topological information generated by this method enables identification of holes and tool path generation for holes which should be drilled rather than milled.
A method based on a set of developed algorithms is used to identify closed loops from a STL model, identify which closed loops correspond to cylindrical holes, find hole orientations, locations and diameters, and calculate the depth for the recognized holes. The developed procedure and algorithms have been implemented in Visual C++ to illustrate the efficacy of the method.
The implementation results showed that the developed algorithms can successfully recognize circular holes of differing sizes on both simple and complex surfaces, and in any orientation. Tool paths can thus be generated from STL models to more efficiently and accurately machine circular holes.
The developed method requires that at least one simple closed loop exist for each potential hole.
A new and unique hole recognition method for use with STL models was developed. This method is useful for accurately and efficiently machining parts with circular holes from STL models as well as finish machining near‐net shape parts with circular holes created using rapid prototyping.
IS there anything magic about the shape of a wing section? Asked to sketch the profile of a wing on the back of an envelope, one would have no difficulty in representing a…
IS there anything magic about the shape of a wing section? Asked to sketch the profile of a wing on the back of an envelope, one would have no difficulty in representing a shape which would probably, for most purposes, be adequate. Assuming this generalization to be true—perhaps it is a rather rash one—one might equally well question the need for an article on aerofoil design, or indeed the need for the long and painstaking research which, over the years, has been conducted on this particular subject. But it is this same research which, in the long run, has resulted in the recognition of certain general rules relating to aerofoil geometry, which are now taken so much for granted that they would probably be embodied in one's preconceived notion of what a wing section should look like. Recently, also, rather complicated theoretical techniques have made possible the design of profiles which, if manufactured faithfully and carefully in each detail, can provide a performance which is considerably better than any more arbitrary shaping to general rules would produce. Finally, of course, one must recognize that there are exceptional conditions where the application of conventional ideas is inadvisable, and where theoretical and experimental research is needed to suggest what is more appropriate. This article will be concerned for the most part with amplifying these remarks; but, by and large, it must be admitted at the outset that we cannot point to any revolutionary discontinuities in the progress of aerofoil design such as have characterized advances in the means of aircraft propulsion, or structural design.
Part I—Constant Chord Blades 1. Summary Rotor/fuselage clearance is the most fundamental design consideration when laying out a new project, and it is essential to…
Part I—Constant Chord Blades 1. Summary Rotor/fuselage clearance is the most fundamental design consideration when laying out a new project, and it is essential to estimate this accurately at a very early stage. When centrifugal force droop stops are fitted to a rotor, the design criterion is usually the effect of a sharp‐edged down gust impinging on the rotor when it is not generating thrust; for example, whilst running‐up on the deck of an aircraft carrier. In this paper the dynamics of blade flapping motion are developed and a method for rapidly obtaining maximum gust deflexion is presented in the form of a Data Sheet (FIG. 5). This enables the maximum deflexion in a gust to be determined with no calculation. The solution obtained is exact; hitherto the only attempts to calculate gust deflexion known to the writer have developed an approximate equation of motion for the blade, and offered the Particular Integral as a sufficiently accurate solution. It is shown in Part II of this paper that this can be very misleading, and undcr‐estimates the true deflexion. In preliminary project design, the blade inertia is, of course, unknown. It is shown that this is a function of the coning angle and CL, basic only, probably the two most fundamental design parameters.
It is clear that for satisfactory service and resistance to corrosion, it is necessary not only to choose the right metal to be electrodeposited, and the right thickness…
It is clear that for satisfactory service and resistance to corrosion, it is necessary not only to choose the right metal to be electrodeposited, and the right thickness of deposit, but also to ensure that the design of the basic article to be plated is such that a reasonably uniform deposit can be achieved without too much difficulty. The more complex the shape to be plated, the higher will be the cost, either because the total weight of metal over the whole article will have to be greater in order to provide the minimum thickness in the most difficult places, or because special plating jigs and anodes will be required to achieve a uniform deposit. The designer should therefore strive to avoid deep or narrow recesses, sharp edges and corners, sharp points, and generally complex shapes; he should aim to provide relatively simple shapes without sudden changes of contour or cross‐section, and generous radii on all corners and edges, both external and re‐entrant. Ideally, the worse the throwing power of the solution to be used for electroplating, the more simple should be the shape to be plated. Fig. 1 illustrates some of the points mentioned.
Creases are marks that are created and left in a fabric during garment wear. Pressing is a process to flatten garment panels and sharpen garment edges and pleats. To…
Creases are marks that are created and left in a fabric during garment wear. Pressing is a process to flatten garment panels and sharpen garment edges and pleats. To minimize crease, the fabric should recover after pressing without creating a creased edge. Whereas, good pressing performance means the creased edge stays sharp after pressing. Good crease recovery and pressing performance appear contradictory. However, crease recovery and pressing performance are different as creases are formed during wear and pressing is carried out using pressing equipment such as iron, pressing machines, etc. The condition, i.e. temperature and humidity, under which the creases are formed in wear and pressing are very different. The latter has much higher temperature, pressure and humidity. This paper reports on an experimental investigation on the relationship between the crease recovery and pressing performance of wool and other fabrics. It was found that there are only generally weak to moderate relationships between the crease recovery as measured by the Shirley Crease Recovery Tester and the pressing performance as measured by the Siro‐Press Tester. The characteristics of wool fabrics, which have both good crease recovery and pressing performance, are identified. This study is a step towards fabric engineering.
THE trend of design in the modern aeroplane has been toward improved performance realised through external cleanness. It is apparent that the number of essential units…
THE trend of design in the modern aeroplane has been toward improved performance realised through external cleanness. It is apparent that the number of essential units comprising a modern aeroplane is nearly a minimum at the present stage of the art, and it appears also that the possibilities of further striking reductions in the drag of these units, due to change in form or shape either individually or in combination, are not great.
THE adaptation and application of the cumulative experience of practical and theoretical research to the problems of industry has led to the solving of many of its…
THE adaptation and application of the cumulative experience of practical and theoretical research to the problems of industry has led to the solving of many of its problems and the linking up of industries of very diverse natures. Materials, processes, and mechanisms have been developed in many instances to an almost perfected state, leading to an economy in power consumption, reduced production costs, greater efficiency of the unit, and increased service life. Yet the protection of materials, particularly metals, employed in industry has not revealed itself to the same extent, more because of the enormity of the field of application than lack of development in this direction.
The purpose of this paper is to examine geometrical design influence of various types of flying discs on their flight performance from the aerodynamics perspective.
The lift, drag and moment coefficients of the discs were measured experimentally using a wind tunnel. Three types of golf discs and four sets of simpler parametric discs were studied to analyze and isolate the effect of design factors on these aerodynamic characteristics. Full six degree-of-freedom simulations of the discs were performed to visualize their flight trajectories and attitudes. These simulations, combined with the experimental data, provide details on the well-known “S-shaped” ground-path traced by a flying disc.
This paper reveals two key parameters to evaluate the flight performance of a disc: its coefficient of lift-to-drag ratio (CL/CD) and, more importantly, its coefficient of pitching moment (CM). The latter influences the tendency of the disc to yaw from its intended path, and the former influences its throwing distance.
The work suggests that to optimize the flight performance of a disc, the magnitudes and gradient of its CM should be minimized and its trim-point shifted from origin, while its CL/CD should be maximized with a flatter peak.
In this paper, the design parameters and the aerodynamic characteristics of various types of flying discs are analysed, compared and discussed in depth. Recommendations of design improvements to enhance the performance of any flying disc are offered as well.
I SHOULD like first to say how much I appreciate the honour of being invited to deliver the Wright Brothers Lecture. To anyone whose work is associated in any way with the…
I SHOULD like first to say how much I appreciate the honour of being invited to deliver the Wright Brothers Lecture. To anyone whose work is associated in any way with the aeronautical sciences, it must be a source of pride and gratification to be invited to be a chief participant in one of the greatest occasions in the world of aeronautical research, an occasion designed in honour of the two great pioneers, Wilbur and Orville Wright. In my own case these feelings are shared with a feeling of humility and of my own unworthiness for the task.