Papers by Keyword: Geometrical Accuracy

Abstract: Abstract. This study aims to investigate wire electrical discharge machining of copper alloys. Extensive research was done to design an optimum cutting method with adequate wire balance to achieve the requisite surface smoothness and geometrical dimensional correctness. Parameters were used in this work to simulate the process pulse-on time, pulse-off time, peak current, servo feed-rate, servo-volt, wire-feed rate, wire tension, and water pressure. For each given treatment requirement, the primary impacting elements are highlighted. The results are the best standard settings that have been designed to satisfy the client’s varied developing needs. A low pulse achieves superior surface polish on time and a high pulse off time. According to the (ANOVA) findings, the most significant cutting parameter is the pulse on-time (Ton), which affects surface roughness by (42.922)%, followed by pulse off time (Toff), which affects surface roughness by (24.860)%, and servo feed (SF), which affects surface roughness by (6.850)%. The impact of the process variables was wire tension on response characteristics, dimensional deviation, cutting rate, and surface roughness.

Abstract: This paper presents a study of design of a motorcycle headlight fairing for single point incremental forming by employing a simplified design guideline in conjunction with a finite element simulation of the forming process. Comparison with the experimental formed motorcycle headlight fairing is performed based on a detailed analysis of geometric accuracy of the formed parts. The study may serve as a demonstration of capabilities of single point incremental forming with respect to dimensional accuracy when forming complex parts.

Abstract: The paper discusses the problems on accurate assembly of large-sized cylinder segments by illustrating an example of the geokhod assembly. The mathematical expressions for determining deviations of sector profile from the nominal circle of the shell depending on the radius of sector, its tolerances and the location of supports. The influence of the distance between the supports on the profile deviation is shown. Solutions to minimize the profile deviation are given.

Abstract: The technology of part manufacturing by means of 3D printing is currently the essential tool in fast production of prototypes and significantly participates in shortening the development an innovation time of the product. In manufacturing by means of a 3D printer as well as in any other manufacturing technology, the precision of the end product is affected by a variety of factors and effects that shall be familiarised with in order to provide high dimensional and shape precision.The research specified in this post is focused on dimensional and shape precision analysis of part manufacturing using the Selective Laser Melting method (SLM). This technology manufactures a prototype by selectively melting metallic powder layer by layer by means of a laser. A CAD model of a specific shape was designed for the purpose of the analysis. An orientation of this part was designed by means of SLM 280HL workspace with regard to minimisation of the internal stress. The part itself was made of AlSi12 material and printed on this machine. The part was afterwards digitised by means of Atos II 3D optical scanner. The data obtained by digitising were compared to the nominal CAD model. The comparison was a basis for the evaluation of the resulting dimensional and shape precision of a prototype manufactured by means of this technology.

Abstract: Domestic CNC machine tool and NC machine tools abroad's main gap is accuracy stabilization rather than accuracy. Accuracy stabilization test is done on some three-axis vertical machining center aiming at the status. Laser interferometer is used to test X, Y, Z axis's positioning accuracy, repeat positioning accuracy and reverse gap. The test is done taking 80 days as the period. The accuracy test results is analyzed. From the positioning accuracy, repeat positioning accuracy and reverse gap curves we can see that, because of the factors of machine's use and temperature's change, X, Y, Z axis's positioning accuracy changes violently, repeat positioning accuracy and reverse gap change a little.

Abstract: This paper deals with Incremental Sheet Forming (ISF) a sheet metal forming process that knew a wide development in the last years. A lot of experimental and simulative researches have been conducted in this field with different aims: to study the sheet formability and part feasibility; to define models able to forecast the final sheet thickness; to understand how the sheet deforms and how formability limits can be defined. Another very important issue is related with the tool path optimization. In fact, the process is characterized by high springback which causes dimensional defects. When IF is performed by a robot, the capabilities of the technology is improved in terms of obtainable shapes (it is possible to use the 6 degrees of freedom of the robot), but the shape errors seem to be higher due to the lower robot stiffness in comparison with CNC machine. In this work the comparison between two different ISF configurations, tool mounted on a CNC machine or tool mounted on a robot, is reported. A suitable geometry was investigated working different sheet material types and sheet thicknesses. The results in terms of geometrical accuracy and sheet deformation have been analyzed in order to define advantages and disadvantages of these two techniques. An analysis on the process forces has been carried out too.

Abstract: In the case of turning workpieces having high aspect ratios, i.e. length divided by diameter, it is not so easy to obtain high cylindricity because of the elastic deformations due to the thrust forces taking place under operations. In this paper, the generating mechanism of geometrical errors is discussed and its suppressing method is proposed. That is, applying previously established controlling method of thrust forces to turning cylinders with high aspect ratios, it is confirmed that geometrical errors of workpieces due to the action of thrust forces can be suppressed.

Abstract: Many models [1-3] have been proposed to study the infeed grinding of Si wafers and to understand its effects on the surface generation. However, most exiting models are based on 2D/3D kinematical analysis of the wheel or its cutting edges, thus unable to suggest the behavior at the interface of wheel/substrate including effects of the elastic deformation and the cutting path density. In this paper, a new grinding model of capable to incorporate the machine tool stiffness and the substrate contact rigidity has been developed. By taking the effect of cutting path density into account, this model is able to give a better explanation of interference between the cutting edge and substrate, and the geometrical profile generated in an infeed grinding scheme.