Search results

This paper aims to develop a theoretical method to analyze the rotation accuracy of rotating machinery with multi-support structures. The method effectively considers the geometric errors and assembly deformation of parts.

A method composed of matrix and FEA methods is proposed to do the analysis. The deviation propagation analysis results and external loads are set as boundary conditions of the model which is built with Timoshenko beam elements to calculate the spatial pose of the rotor. The calculation is performed repeatedly as the rotation angle increased to get the rotation trajectories of concerned nodes, and further evaluation is done to get the rotation accuracy. Additionally, to get more reliable results, the bearing motion errors and stiffness are analyzed by a static model considering manufacturing errors of parts.

The feasibility of the proposed method is verified through a case study of a high-precision spindle. The method reasonably predicts the rotation accuracy of the spindle.

For rotating machinery with multi-support structures, the paper proposes a modeling method to predict the rotation accuracy, simultaneously considering geometric errors and assembly deformation of parts. This would improve the accuracy of tolerance analysis.

To meet the high stiffness requirement of bearings used in high-precision spindles, this paper aims to propose a novel kind of bearing composited by hydrostatic cavities and tilting pads with preload.

Cavities are cut on the oil seal surface of a hybrid bearing, in which the tilting pads are set up. The load of the bearing is carried by the hydrostatic cavities and tilting pads. The structural features of this compound bearing and the controlling variables of the main stiffness coefficient are presented. Two basic design principles are proposed on the basis of equal machining clearance (EMC) and equal installation clearance (EIC).

The theoretical analysis indicates that the stiffness of compound bearings under the EMC condition increases to infinity monotonously when the preload coefficient of the tilting pad tends to 1, while the stiffness under the EIC condition has a peak value. Therefore, a synthetic design principle is proposed by synthetically using the above-mentioned two principles. The applicable range of the three principles is discussed through an example.

The study about technological combination of hydrostatic cavity and tilting pad in this paper can provide suggestions for the design of a high-stiffness bearing in a precision spindle.

A NEW BALL AND ROLLER BEARING FACTORY recently placed in production at Indianapolis, Indiana, U.S.A. by the Link‐Belt Company, is claimed to be one of the most modern plants of its kind in the world. At this new plant electronically‐controlled machine tools maintain tolerances as close as 28 millionths of an inch and some 758 separate gauging operations are employed to produce one of the company's new high precision spherical roller bearings. A high degree of automation and a wide range of materials handling equipment are employed at the new plant, which has 50% greater capacity than the old one it replaces, and in the designing of which Link‐Belt's own bearing plant personnel took two years.

Thermal performances are key factors impacting the operation of angular contact ball bearings. Heat generation and transfer about angular contact ball bearings, however, have not been addressed thoroughly. So far, most researchers only considered the convection effect between bearing housings and air, whereas the cooling/lubrication operation parameters and configuration effect were not taken into account when analyzing the thermal behaviors of bearings. This paper aims to analyze the structural constraints of high-speed spindle, structural features of bearing, heat conduction and convection to study the heat generation and transfer of high-speed angular contact ball bearings.

Based on the generalized Ohm’s law, the thermal grid model of angular contact ball bearing of high-speed spindle was first established. Next Gauss–Seidel method was used to solve the equations group by Matlab, and the nodes temperature was calculated. Finally, the bearing temperature rise was tested, and the comparative analysis was made with the simulation results.

The results indicate that the simulation results of bearing temperature rise for the proposed model are in better agreement with the test values. So, the thermal grid model established is verified.

This paper shows an improved model on forecasting temperature rise of high-speed angular contact ball bearings. In modeling, the cooling/lubrication operation parameters and structural constraints are integrated. As a result, the bearing temperature variation can be forecasted more accurately, which may be beneficial to improve bearing operating accuracy and bearing service life.

A very recent addition to the machining capacity at The British Aerospace (Military Aircraft) Brough unit is the Matsuura FX‐5 high speed vertical twin pallet machining centre which was introduced last year to the UK market by Beaumont Machine Tools. The FX‐5 represents a new concept which is capable of spindle speeds of 20,000 RPM and feed rates of 15 metres per minute. For the next few months the machine will be under development and evaluation to determine the benefits and techniques of most use to the aerospace industry.

METHODS of assessing the level at which vibration becomes unacceptable in any bearing are generally based on comparison. Hoffmann have now initiated a programme to substitute comparative measurements of bearing vibration with quantitative measurements. To be able to achieve this a means of accurately calibrating vibration transducers had to be devised and a start has been made on compiling and analysing data relating to acceptable vibration characteristics or rolling bearings in a wide range of service applications.