Rotordynamics of an Improved Face-grinding Spindle: Rotational Stiffness of Thrust Bearing Increases Radial Stiffness of Spindle

The support is a key factor affecting performance of face-grinding spindle. However, advantage of traditional rolling element bearing is not highlighted when it is for large-size face grinding. This technical brief aims to develop a combined support for the face-grinding spindle consisting of a water-lubricated hydrostatic thrust bearing and two types of radial rolling bearings, and the flexible rotor dynamics of the spindle with the combined support is analyzed using the modified transfer matrix method. The results show that the rotational stiffness of water-lubricated hydrostatic thrust bearing can increase the radial stiffness of the face-grinding spindle, so the small-size rolling bearings can be utilized as the radial support for the spindle by aid of such rotational stiffness. A comparative study of comprehensive performance between the spindle supported by rolling bearings and the replacement spindle designed with our proposed combined support shows that the proposed one has technical advantage of large axial load-carrying capacity, low frictional power loss, low temperature rise and etc.

Peculiarities of the Grinding Process of a Gear Hob Helical Rake Face

This paper presents a study regarding the gear hob’s rake face grinding possibilities and its consequences. A simple theoretical lined surface is considered. The mathematical model of the reciprocate meshing of surfaces was applied. It was proven that the proposed form of the rake face cannot be obtained because an undercut of inacceptable extent occurs. It is also proven and sustained by CAD modeling that using a simplified, flat grinding disk, the undercut is avoided, but the phenomenon of transection appears.

Research on Surface Quality by Ultrasonic Vibration-Assisted Face Grinding of Cemented Carbide

Cemented carbide has huge applications in industrial production, but its high mechanical properties also increase the difficulty of processing. In this work, ultrasonic vibration-assisted grinding technology is used for the precision manufacturing of cemented carbide. The influence of the dynamic trajectory of the grains on the material removal process is analyzed. The morphology and roughness of the processed surface are measured and studied. It was observed that in the conventional grinding, the blade pattern is obvious with some defects on the surface. While in the ultrasonic vibration-assisted grinding, the material surface is mainly distributed with pits and small protrusions, and there is no obvious blade pattern. According to the roughness test, the roughness of ultrasonic vibration-assisted grinding is better than that of conventional grinding, and the increase in amplitude has a significant effect on the improvement of roughness. When the amplitude increases from 3μm to 9μm, the surface roughness is improved about 38.1%. The research of ultrasonic vibration-assisted grinding should be of great importance for promote the high-efficiency and high-quality processing and special applications of cemented carbide.

The Prospects of Abrasive Treatment of Tough-To-Machine Materials

In current conditions, great attention is paid to the quality of parts, which is in many ways determined by finishing operations of mechanical treatment, with surface grinding being the most widespread. Grinding process efficiency, abrasive tool wear intensity, machined surface quality and other features of grinding process depend on properties of the environment, where the cutting process takes place. Forced changing of conditions of this environment is one of the ways to control and optimize the grinding process, which can be reached due to finding new technological decisions. One of the most promising directions to solve this problem is the process of face grinding with discontinuous grinding tool and supply of cooling fluid or air in the cutting zone directly. Carried analysis of features of face grinding has shown that heat density can be decreased by the usage by grooved wheels with vortex air cooling or by supply of cooling-lubricant technological fluid. Obtained dependences of temperature field of part surface during grinding establish the influence of the length of working shoulders and grooves, vortex tubes number, outflow rate, temperature and flow rate of cold vortex flow of air. These data provide conscious control over the process of discontinuous face grinding by changing wheel grain size and grinding speed.