Heiji Yasui

Studies on cylindrical traverse grinding in high depth of cut. (3rd report). The generated process and a preventive measure of grinding burn.

This paper deals with the generated process and a preventive measure of the burning in the cylindrical traverse grinding of the high depth of cut. The experiment was carried out to examine the surface layer, the hardness and the surface configuration at the burning position of the workpiece. And also, the change of wheel configuration and the loading in the grinding process were investigated. The main conclusions obtained are as follows: (1) The workpiece burn occurs darkly at the starting position of traverse grinding, but disappears as the grinding proceeds. The reason why burning occurs is considered that spark-out grinding can not be done due to the shrinkage of workpiece diameter which is expanded by the generated grinding heat. (2) The workpiece burn exerts a bad influence on the dimensional accuracy and the machining properties. However, careful attention should be paid to the thermal damage even when no visual burning is observed. (3) The loading closely relates to the occurrence of workpiece burn. (4) The wheel dressed to the stepped configuration with the same width as the traverse feed has a good grinding performance in high depth of cut grinding and prevents the workpiece burn.

On the Wear Characteristic of Grinding Wheel in High-depth of Cut Wet Grinding (Part 1)

以上,湿式高切込み研削における砥石の損耗形態および砥石の損耗に及ぼす理論削除率の影響を調べた結果をまとめると次のようになる.(1)乾式の場合と比較して湿式高切込み研削では目づまりがかなり少なくなる.(2)ソリュブルを使用した場合の湿式高切込み研削では,湿式にすることによる切れ刃の破壊強度の低下が砥石の損耗特性に大きく影響することが考えられる.(3)不水油を使用した方がソリュブルを使用するよりも砥石の損耗速度はかなり小さくなる.(4)理論削除率がある程度以上の範囲では,理論削除率が増加するにつれて砥石の損耗速度は急速に増大するようになる.また,理論削除率と実削除率との比も小さくなる.その結果,研削比も小さくなる.(5)ある理論削除率以上の範囲では,理論削除率を増加しても実削除率は増加しなくなる.

Microstructure and Transitional Behavior of Dressed Abrasive Cutting Edges

The microstructure of dressed abrasive cutting edges and the transitional behavior of the cutting edges in the initial stage in grinding are investigated by observing directly dressed abrasive cutting edges in detail and by pursuing the behavior of the particular cutting edges in grinding. The relation between the transitional behavior of the cutting edges and the grinding force in the initial stage in grinding is examined by measuring the variations of the cutting edge ratio and the grinding force in grinding.The conclusions obtained in this study are as follows : (1) The surface roughness of dressed abrasive cutting edges is approximately flat though the dressed streak is observed on the surface. Accordingly the microunevenness reported previously cannot be found on the surface.(2) A lot of nondirectional microcracks are observed on the surface. Therefore the surface structure is fragile and the fragile layer is easily removed by the replica operation and in grinding. The microunevenness exists under the fragile layer and is appeared after the fragile layer is removed.(3) The grinding force and the cutting edge ratio are high in the initial stage in grinding. From these results, it is considered that the flatness of the dressed cutting edges influences the high grinding force in the initial stage with some reason.

Adjustment of Effective Cutting Edge Spacings by New Dressing Method

The role of the effective cutting edge spacing on the grinding performance is studied and a new dressing method is devised for this purpose.By this new device, it becomes possible to adjust the spacings of the effective cutting edge on the working surface of the grinding wheels, and therefore, to investigate the effect of spacing on the grinding performance. In order to examine the effect, redresslife tests were carried out and also the radial wheel wear, the surface roughness of the workpiece are measured. Moreover, from the microscopic point of view the effective cutting edge spacing and the cutting edge ratio in the grinding process are examined.The main conclusions obtained in this study are as follows:1) Within the range of this study, the longer is the effective cutting edge spacing, the better grinding performance is obtained and the performance is improved about ten times in some cases.2) For the life time value of the effective cutting edge spacing and the cutting edge ratio, the former tends to increase while the latter to decrease, as the initial effective cutting edge spacing becomes longer. Therefore, the redress life of the grinding wheel is found to be influenced not only by the cutting edge ratio as previously predicted but also by the effective cutting edge spacing, which is indicated in this study.