Applied Mechanics and Materials Vols. 809-810

Abstract: The use of hydrostatic guideways in CNC machine-tools is very common as a result of their low friction coefficient. The major problem of hydrostatic guideways represents the recovery of the fluid used in guideways, where the fluid should be protected against mechanical impurities and then led towards the hydraulic aggregate. The floating support described in this paper resolves the collection of fluid by using a closed circuit, without exposing the fluid to mehanical impurities and to a gravitational collecting.

Abstract: The gears are some of the most used mechanical transmission due to the advantages its provide: constant transmission ratio, high power transmitted, high efficiency, small size, silent operation, precision kinematic, etc. This causes the wheel to be one of the most valuable machine elements both in terms of accuracy and processing technology as well. From the technological point of view due to high precision and productivity, one of the most methods used is processing with gear hob cutter. Although the tool profile does not depend on the number of teeth on the wheel, but only its module, large diversity of gear requires the design of gear hob cutters tailored to existing needs. As it is known the gear hob cutters are complicated and expensive gear cutting tools, both due to the manufacturing process and in terms of design, requiring a significant amount of calculations, high effort from the designer and consequently results in a large cycle of design. For this reason, the literature and in various websites, there are many studies and research information to optimize the design process and increase accuracy of gear hob cutters.

Abstract: Very large variety of constructions are among granular materials mixers. This is a result of different needs from industry. The paper presents the mixers available in industrial practice. Analysis of mixers construction has been performed and their applications have been specify.

Abstract: Precision of the machining centers is influenced by many factors among which are mechanical vibrations that occur in the machine-tool-part-device system. Evaluation of vibration level for five axes machining centers is a very important issue considering structural and functional complexity of these equipments. The paper presents researches performed at University of Oradea to evaluate vibration of TMA-AL 550 five axes machining center, equipped with a two rotating axes table, during the machining process. There have been used two methods: evaluation of the dynamic behavior of the spindle using a laser vibrometer and evaluation of mechanical vibrations of the five axes machining center using triaxial accelerometers. Measurement data had been processed using spectral analysis and time-frequency parameters, revealing frequency domains which can cause high amplitudes of vibration. Results also show that the measured vibration levels are not exceeding the accepted limits.

Abstract: In the paper a research methodology was developed and used to determine the rigidity in transversal direction of modular fixture structures. The paper presents experimental results regarding the total deformation of modular structure consisting of ”narrow” modules from modular kits. The research conducted showed the different evolution of deformation curves in the case of modular structure, with different shape and different sizes of modules, in the case of similar loads. The experimental results indicate displacements of the entire modular structure alongside the base plate and, also, tilting. The measured deviations of modules from fixture structure may cause "dimensional"/ position deviations (linear displacement of the measurement base) and deviations of shape and orientation-position (angular displacement of the measurement base) of the workpiece during severe machining conditions.

Abstract: Fixtures are use to ensure the orientation and position of workpiece and cutting tools in machining systems. Drill bush guide / holder or are part of a specific category of elements and mechanisms, found in the fixtures structure: elements for size adjustment and guidance for cutting tools. These drill guide bush/ holder are used for guidance of drills, in order to ensure a certain position of the tool regarding the certain reference elements of the workpiece, or to increase the stiffness of drills, when the tool diameter is reduce, or when the surface of the machined workpiece is inclined. The drill bushes are placed in the fixture body, directly or through drill bush guide plates/ drill bush support plates. The characteristic feature of these bush plates is the console length. Sometimes, the bush guide plates can have large lengths that affect the dynamic stability. The bush guide plates are dynamically excited by the direct contact with the drill of the bush. If the natural frequency of vibration of the plate is equal or higher than the excitation frequency of the machining process, then the resonance phenomenon can appear.

Abstract: This research paper presents the analysis of the superficial layer wear of the moving metallic components in a screw compressor, depending on the presence of metal particles in the oil resulted from friction, wear and fatigue processes. The data presented are useful for the analysis of the structural modifications that occur and develop during the operation of a screw compressor, with the possibility to predict a failure. The study of the structural changes can be made by various nondestructive testing methods, namely by analyzing the oil at certain time intervals/hours of operation of the compressor

Abstract: This paper approach the study of the dynamic behaviour of a real gear with asymmetric teeth which will replace the current gear with symmetrical teeth. Research approach is founded on two questions: How does the error of the flank's tooth form influence the dynamic behaviour of a gear How is the dynamic behaviour influenced by the configuration of a gear with asymmetric teeth compared with a gear with symmetric teeth, with comparable accuracy

Abstract: This paper presents theoretical and experimental research regarding a temperature control system of electric furnaces with thermostatic heat treatment which agreed parameters determined based on PID (proportional-integrative-derivative) control laws predictive control allows this type of restricted thermal heat treatment applied pieces with complex configurations made of medium or high alloyed steels to obtain a structure and mechanical properties invariant mass in the whole piece, with trace constituents evenly distributed and without residual stress in part, the realization of these heat treatments can be done by custom management process workpiece heating furnace heat treatment, heat treatment allows simultaneous varied on different portions of the piece in order to obtain structural and mechanical properties.

Abstract: The actives surfaces of screw compressors are helical surfaces, cylindrical and uniform pitch. The generation of helical surfaces can be done using tools bordered by revolution surfaces (as end mill cutter, or disk cutter). The shaping of generating tools is based on fundamentals theorem of the enveloping surfaces. This paper consists to propose a graphic solution, using specific tools of the design environment AUTOCAD, to problem concerning the shaping end mill tool which generates the helical flute of male rotor component of screw compressor. The algorithm has been developed based on a complementary theorem - "The theorem of substituting circles family".