Papers by Keyword: Machining Accuracy

Abstract: In recent years, as global environmental problems have become increasingly serious, the concept of sustainable development, such as the 3Rs, has gained importance. Against this backdrop, machinery and equipment are becoming smaller, lighter, more sophisticated, and multifunctional, with highly integrated products increasingly requiring the machining and assembly of minute mechanical parts. However, the relatively large amounts of servo standby power generated by small machine tools during operation highlight the need for machining methods that reduce power consumption. In this study, we developed a novel 5-axis controlled machine tool equipped with an idling-stop function in the feed-driving system to reduce the power consumption of machining processes. Since this function stops the servo lock of the feed axis, it was unclear whether the same machining accuracy could be maintained as with the original setup. Therefore, in the present study, we measured straight cutting and endpoint areas using a laser microscope and an acceleration sensor and examined the change in machining accuracy due to the idling-stop function. It was found that when the idling-stop was turned off, vibration occurred, resulting in excessive cutting.

Abstract: While grinding with CNC cylindrical grinding machines, there are many factors that determine the precision and accuracy of the finished product. These may include dimensional accuracy, surface roughness, circularity (roundness), cylindricity, etc. But all these factors pertain to the work. The condition of the tool, in this case, the cutting edges of the grinding wheel, also greatly influence the profile and precision of the work. So, in order to maintain the precision of the work, there is a need to repeatedly and regularly maintain the cutting edges in a good cutting condition, by the process of dressing. In other words, when the swarf gets adhered to the grinding wheel, the abrasive particles can no longer perform machining with the same efficiency, due to increase in contact surface area between the abrasive particles and the work. This dissertation describes a technique that can be adopted to continuously monitor the grinding forces generated during the grinding operation, by using an in-process 2-dimensional piezoelectric force sensor, which can simultaneously measure the force and break it down into its two force components. The force sensor not only calculates the force generated, but also quantifies the force variation. By analyzing the variation in the radial and tangential force components individually, and by conducting Fourier analysis on the observed data, it is found that deterioration of the grinding wheel and the dress pattern can be continuously monitored and controlled.

Abstract: The research is to automatically testing and analyzing machining accuracy for the finished product by Pneumatic Measuring technology including the technology of data acquisition and the theory of disposition of data .To build a feasible system to analyze the machining error using Pneumatic measuring instrument to measure the parts by sensor to change the atmospheric pressure. A data acquisition card is used to gather and save the data. By programming software to write internet applications to statistical analysis for data, draw normal distribution figure, scatter diagram and histogram. To analyses the graph gains estimate the machining error and improve the performance for machine. By the experimental tests verify the feasibility and validity of the system.

Abstract: In the paper the analysis of the dimensional structure of different manufacturing process is made. There are shown that the different schemes of the designer sizes result in a different level of an optimality of a dimensional structure. At definition of number of the technological sizes as criterium of a optimality it is necessary to allow both formation of the intermediate sizes and the effect of errors compensation. The effect of errors compensation is the reason for the change of the sizes nominals and its limit deviations. The detail subjected to machining, is characterized by constructive dimensional links which reflect, eventually, its functionality. The character of the constructive dimensional links is defined by the designer who takes into account the technological features of machine tools, but not in detriment of functionality. Therefore, carrying out of the dimensional analysis on a joint of these two phases is very important with the purpose of improvement of dimensional adaptability to manufacture of made details. One of criterions of this optimality has the structural nature. The manufacturing process is considered optimum, if in the structure of all technological dimensional chaines number of the technological sizes is minimum. This condition executes if to each designer size there corresponds in a technological dimensional chain the unique technological size, and in dimensional circuits for machining allowances, each machining allowance is determined by two technological sizes or one technological size and one size on blank. For different variants of the linear dimensions are shown the way in which are changing the limit deviations of technological sizes and respectively of the constructive sizes of the equivalent details.

Abstract: In the given work it is shown, that at machining the technological dimensional structures are optimum if they are similar to the design dimensional structure of a detail. The conditions of the locating and fastening, and also some technical requirements interfere achievements of similarity. In these cases the directed change of the design dimensional structure of a detail is recommended due to recalculation of the sizes. From this point of view creation of technological process represents a compromise of mutual approche of the dimensional structures of a detail and of a technological system. Technological process may be built from operation elements, but they (the operation elements) do not have the necessary characteristics to create the dimensional structures. These characteristics are not formed during decomposition because the relevant details dimensional structure is not taken into account. The most appropriate entity as element of which may be built the technological process is a technological mounting. The mounting has a dimensional structure and includes the communication elements - the sizes up to locating surfaces Thus, the dimensional designing of technological processes results in optimality if it is possible to achieve the similarity of design and technological dimensional structures in the following order: creation of the blank's dimensional structure similar to the detail's dimensional structure; formation of optimum technological dimensional links of the first technological operations or mounting (roughing) by resizing if necessary of the blank and of the detail; formation of optimum technological dimensional links on the subsequent technological operations or mounting by resizing if necessary of the detail in progress; formation of optimum technological dimensional links on the final technological operations or mounting by resizing if necessary the detail; calculation of the minimal machining allowances; the dimensional analysis of technology with calculation of the operational sizes, their tolerances and limit deviations; formation of drawings of the blank.

Abstract: During the machining, the places of tool and work piece may change as influenced by various factors, consequently, the machined parts can not meet the needs of actual use. Therefore, before machining, various influencing factors on machining accuracy should be taken into consideration. This paper analyzed the influencing factors on machining accuracy and proposed measures to reduce machining errors and provide a guarantee for improving the machining accuracy.

Abstract: The study determines the most suitable pattern of alignment and fixing of low-rigidity shafts; it also presents factors that determine such choice. The part is fixed both by force closing and kinematic closing. A new method for machining low rigidity shafts is developed to control the elastic-deformable state of these shafts in a technological system and to produce parts with the required accuracy during turning. To implement this new developed method for low rigidity shafts, an apparatus is designed. The apparatus allows to increase the rigidity of shafts during machining by the application of axial tensile force to the workpiece. Rational prime costs of preparing technological alignment centers at the stage of production preparation are determined; knowing these costs, it is possible to select a suitable machining technology for low rigidity shafts, to produce a technology-oriented design, and to reduce the costs of machining these shafts.

Abstract: connecting rod parts except under larger dynamic load in the institutions, it is also connected with other parts, movement and direction, therefore, the part of the connecting rod connected with other parts on the machining accuracy is crucial. In this paper, analysis and study connecting rod machining process, through the improvement plan, ensure the accuracy of the important parts of the connecting rod parts and the connecting rod production and processing efficiency.

Abstract: This paper presents a mathematical method to analyze the influence of each machine tool part deformation on the machining accuracy. Taking a 3-axis machine tool as an example, this paper divides the machine tool into the cutting tool sub-system and workpiece sub-system. Taking the deformation of lower surface of the machine bed as the research target, the mathematical model of the deformation on the displacement of the cutting point was established. In order to distribute the stiffness of each part, the contribution degree of each part on the machining accuracy was analyzed. Using this mathematical model, the stiffness of each part can be distributed at the design stage of the machine tool, and the machining accuracy of the machine tool can be improved economically.

Abstract: In the process of wire electrical discharge machining, the wire electrode inevitably suffers bending deformation due to wire tension, electrostatic force, electrodynamics force, etc., and the deflection would make an clearly negative impact upon the machining accuracy, productivity and stability. In this paper, first of all, a novel modeling and simulation method is proposed for quantitatively calculating the wire deflection. Secondly, the mainly impact factors and trend of wire deflection have been concluded. Moreover, the feasibility of the model is proved by comparing with other researchers models. Eventually, the practical approaches of reducing wire deflection and improving the machining accuracy have been proposed.