METHOD OF SELECTING THE OPERATION PARAMETERS OF ELECTRIC SPINDLE WITH AEROSTATIC SUPPORTS FOR SEPARATION OF SEMICONDUCTOR PLATES TO CRYSTALS. PARTS 2–3

The article presents the results of studies of the shaft oscillation processes of a precision horizontal highspeed electric spindle with aerostatic radial and axial supports, used at Planar OJSC in equipment for separation of semiconductor plates into crystals. The studies were carried out using the developed mathematical models that take into account the design features of these electric spindles, including the cantilever mounting of the cutting tool, the imbalance of the diamond disc with the mandrel and the mass ratio of the main components of the electric spindle, as well as the results of their full-scale tests. Based on the analysis of the data obtained, regularities are shown that connect the amplitude values of the oscillations of the electric spindle shaft with the imbalance of the diamond disc with the mandrel and the rotational speed of the electric spindle, which made it possible to propose engineering dependences for choosing the permissible values of the imbalance and rational, from the standpoint of resonance conditions and permissible shaft oscillations, rotational speed of the electric spindle. Recommendations have been developed for the creation of a system for monitoring and active control of the parameters and functioning of the electric spindle in the process of separating semiconductor plates into crystals, which make it possible to use the resonant mode of radial oscillations to improve cutting conditions, excluding direct contact of the working surfaces of aerostatic supports, their seizure and loss of performance of the electric spindle. The article presents a method of selecting the operation parameters of a high-speed precision horizontal electric spindle with aerostatic radial and axial supports and a cantilever mounting of a diamond cutting disc. It is based on the analysis of the simulation results of shaft forced oscillations and data on the shaft oscillations during the operation of the electric spindle with different rotation frequencies and imbalances. The results obtained can be used to monitor shaft oscillations during the operation of the electric spindle, while the high operation efficiency of which is achieved by adaptive control of rotation frequencies taking into account the amplitudes of these oscillations.

Safe technologies for cutting reinforced concrete structures by means of diamond tools

The advantages and the need to improve the safety of work when using modern diamond technologies for cutting concrete and reinforced concrete structures which are common during the dismantling and reconstruction of civil objects are shown. Improved organizational, structural and technological schemes of cutting these structures with diamond disc and wire saws with remote control are reasonably proposed. Preliminary fastening of cut elements on independent spatial scaffolding with screw jacks is a distinctive feature of the proposed schemes. In case of reconstruction by means of a device or an increase of the size of openings in load-bearing reinforced concrete and stone walls, a preliminary installation and commissioning of reinforcement steel frames provided for by the project are proposed, on them – guides of diamond disc, chain or wire saws and only then – cutting of reinforced concrete with its forced canting outside the working area for recycling.

Prevalence of Different Types of Apical Root Canal Morphology and their Treatment Recommendations in an Institute

Introduction: Canals can be of different shapes in cross section including round canals, oval canals, long oval canals or ribbon shaped canals. Recesses of nonround canals may not be included in the round preparation created by rotary instruments and thus they remain unprepared. The aim of this study included determination of shape and taper of the apical root canal based on diameter at different levels. Methods: This was a cross sectional study which used convenient sampling technique to determine the sample size. Seventy extracted teeth were sectioned horizontally at one, two and three millimeter from the apex using the diamond disc which was observed under trinocular research microscope for the determination of diameter of root canal under 10x magnification. Results: The most common canal configuration was oval. The taper of the canals was 25% in mesial root and 20% in distal in bucco-lingual orientation and 14% in mesial root and 15% in distal in mesio-distal orientation. Conclusions: The most prevalent canal configuration in this study was non round, however, most of the rotary instruments tend to prepare root canals into round shape making their use questionable. The taper of the root canals was found to be higher in our study than what most of the shaping instruments have to offer. So it would be advisable to consider this fact while selecting instruments and preparing these non-round canals as far as the Nepalese subpopulation is considered.