Advanced Materials Research Vols. 690-693

Abstract: A novel non-circular grinding technique which utilizes two grinding wheels of different diameters is proposed for the locomotive camshaft with concave curves. The larger grinding wheel is used for rough machining to increase grinding efficiency and the smaller is used for finish machining to form the cam profile accurately. Based on the analysis of motion law of grinding carriage and headstock, the speed and acceleration curves are reconstructed by three different methods to optimize kinematic characteristics of cam non-circular grinding. Simulation and experimental results show that the profile accuracy and surface quality can be improved effectively through kinematic optimization by reconstructing the acceleration curves with cosine curves.

Abstract: This document explains the details of electric spindle thermal characteristics experiments. The temperature distribution, shaft deformation and the stress of temperature sensitive points are tested. Thermal characteristics are gathered about the different cooling strategies and different spindle speeds in the experiments results analysis. Choosing reasonable cooling strategy can use to design spindle cooling system. Thermal stress test can obtain accurate data at temperature sensitive points. The stress analysis can be used to reflect spindle deformation.

Abstract: Our previous work presented a method for estimating the time constant of grinding system in infeed period. To monitor the precision cylindrical plunge grinding process in dwell period, an estimation of the time constant of grinding system in the dwell period, using acoustic emission signal, is presented in this paper. Acoustic emission signals generated during precision grinding are sensitivity and present challenges for accurate and reliable process monitoring. Experiments demonstrate the results of the acoustic emission sensing approach in estimating the time constant in the dwell period of cylindrical plunge grinding.

Abstract: The text takes Z-Axis of precision machine tool as study object, and proceed the thermal character's experiment of Z-Axis feed system in different working condition (different Cooling strategy, different Feeding speed, load or not). The data of experiment shows the higher of the feed speed, the more heat is generated. Position accuracy can be increase by apply the right load and load is nearly none business with temperature rise. Cooling strategy is nearly none business with temperature rise and may cause the discretization of position accuracy.

Abstract: Overcut or speed impact exists in high-speed interpolation of consecutive tiny segments. Because the remaining distance of the current segment does not exactly equal to an interpolation cycle required distance. Taking processing accuracy as a precondition, a new inflection point processing method is proposed to solve this problem. With different solutions of different angles, this method realizes the tiny line continuous processing with high processing quality. And this method needs a small amount of calculation with strong real-time. Error analysis is done and it can meet machining accuracy requirements. Now this method has been applied to engineering practice.

Abstract: The influence of current harmonics on high-speed permanent magnet motor is analyzed in this paper. The several aspects influence of current harmonics are analyzed in detail such as on the stator core losses, copper losses, as well as additional losses, the rotor losses, the electromagnetic torque etc. The necessity of suppressing current harmonics for high-speed motor stable and reliable running and the key issues of high-speed motor control system stable operation is stated.

Abstract: This paper explains a set of tests necessary for ensuring spindle performance focus on the rotating sensitive direction of spindle. It is found that the original signals of spindle dynamic rotation could be separated and reconstructed to spindle dynamic signal and random signal according to their different frequency components. The asynchronous error and synchronization error of spindle dynamic rotation in radial direction and axial direction could be computed from spindle dynamic signal. The distribution trend of spindle dynamic errors is studied, it is found without considering the shift speed of machine tool spindle and the natural frequency of machine tool, the distribution of spindle dynamic errors presented a trend of rising with the rotation speed increasing.

Abstract: Power ultrasonic honing is an advanced precision grinding technology, with ultrasonic vibration applied on the oilstone surface. The high frequency vibration of oilstone make cutting fluid appear cavitation effect, which make acoustic field of power ultrasonic honing present instability and complex, and even appear chatter and noise. In this paper, the cavitation mechanism of power ultrasonic honing is explained, and the oilstone radiated pressure are obtained. Furthermore, the dynamics and radiated pressure model of cavitation bubble in the grinding area is established and analysed. Finally, the pressure of oilstone surface is measured by ultrasonic sound intensity measuring instrument. It shows that the acoustic pressure radiated from oilstone with theoretical calculations and simulations are one order higher than cavitational threshold value of cutting fluid, ultrasonic cavitation occurs. Cavitation bubbles have been nonlinear vibration with high frequency, great amplitude and up to 107 Pa orders pressure, which seriously affect the workpiece processing quality and oilstone life. Comparisons between theoretical analysis and experimental verification have shown a satisfactory agreement.

Abstract: After analyzing the characteristics of each type of dynamic secondary cooling control methods, the combination use of on-line thermal model control and effective casting speed computer dynamic control method was adopted in CISDI dynamic secondary cooling control. On the basis, the transient heat-transfer mathematic model was developed, the determination methods of strand target surface temperature and real time cooling water were proposed, and the design idea of effective casting speed computer dynamic control method was introduced. Considering the probably unreliability of heat transfer difference calculation and inadaptability of heat transfer boundary conditions when too low, too high casting speed or speed variation rate, the on-line thermal model control method was used when the casting speed between 0.8m/min and 1.4 m/min and casting speed variation rate within 0.1m/(min·s), in other cases, effective casting speed computer dynamic control method was adopted.

Abstract: Hot strip cooling temperature and its cooling rate is get by strip cooling system and coiling temperature of hot rolled strip is an important parameter on its performance index. It presents laminar cooling system of the 700 mm hot strip mill and the mill rolling process is present, the laminar cooling system is analyzed on the rolling theory and techniques. The laminar cooling system and its problems are present. The improvement programs of laminar cooling system are present, The control system of laminar cooling system is present combining feed-forward main control and feed-backward self-learning control, and measuring instruments is reinstall and water valves is improved. It could be a reference for the similar mill units and new building rolling mills.