The article discusses the technology of manufacturing low-stiff long multistage shafts made of stainless steels. A feature of this technology is the cutting of annular cooling fins on the entire surface of the shaft blank during machining and their use in thermal operations and further to finishing turning. To implement the technology, self-centering steady rests with double rollers were used during machining.
An experimental study of the possibility of using the acoustic emission signal during turning to assess the machinability of steel by cutting has been carried out. According to the results of previous studies, it has been shown that the use of the total acoustic energy of the cutting process to assess the machinability does not have sufficient resolution. The article presents the results of measurements of the acoustic emission signal in comparison with the results of measuring the tool wear during resistance tests. A group of samples of six steels with a known chemical composition and mechanical properties were used as materials. The group includes steels that differ a priori in machinability and steels whose machinability cannot be predicted in advance. Endurance tests were carried out for face turning with a tool made of highspeed steel with a variable cutting speed. The maximum height of the wear area in the direction perpendicular to the cutting edge was used as a criterion for machinability. The acquisition of the acoustic emission signal was carried out by a broadband sensor built into the tool holder with a preamplifier of 60 dB and a bandwidth of 50...1000 kHz. The integral energy characteristic of the RMS signal is used as a criterion for predicting the processability. As a result of the experiments, it was found that the use of an acoustic emission signal has a good resolution in assessing the machinability by turning steels.
The article discusses a special automatic control system for the machining process as applied to metal turning lathe. In processing, generalized information about the precision parameters of the processing system is gathered that makes affordable to integrate four control loops into its system. The first control loop stabilizes the tool post body. The second control loop stabilizes the workpiece axis during cutting. The third control loop stabilizes the cutting edge and the fourth one stabilizes the tool-workpiece.
Device for axis-stabilizing of low-rigid work pieces has been presented in the article. The method of calculation of dynamic parameters of the “work pieces-supports” subsystem is discussed. The influence on dynamic of work pieces by different variants of fixation is explored.
The article proposes a method for improving the quality of cold straightening of non-rigid shafts. The essence of the solution is to change the sequence of traditional technological operations by introducing dynamic straightening of the workpiece with subsequent application of a given depth of the deformed layer, immediately before roughing and finishing, and after them, in addition, in the process of roughing and finishing, the depth and nature of stresses are preserved. due to the exclusion and redistribution of surface stresses arising directly in the process of machining non-rigid parts, taking into account the changing dynamic characteristics of the cutting process itself. A complex functional diagram of the automatic control system has been developed. The results of straightening a non-rigid shaft, without a system and using automatic control, are presented. Decrease of processing error by 2..3 times is shown.
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