A Ground Surface Roughness Model Considering Grit and Vibration Variances

考慮磨粒與振動變異效應之表面粗糙度模式建立

張煌權(Huang-Cheng Chang) ； 王俊志(Jiunn-Jyh Junz Wang)

《中國機械工程學刊》 40卷5期 (2019/10) Pp. 491-497

摘要

By combining the kinematic grit and spindle vibration effects, an analytical ground surface roughness model representing their individual effects on the ground surface was developed. In this model, the surface profile is treated as the superposition of variances of the kinematic grit and vibration profiles. By summing the variance of the two profiles, the root-mean-square ground surface roughness can be estimated. The transmitting factor, which defines the amount of power transmitted from spindle vibration to the ground surface, was derived from the dynamic grinding system and is related to the stiffness of the process, namely the workpiece cutting stiffness and wheel contact stiffness. An experimental procedure for identifying the stiffness in the process was also developed. Due to its analytical nature, the model estimates the ground surface roughness as well as allowing for the analysis of the contribution and effects of the grinding conditions, machine vibration and stiffness within the process. Procedures for identifying the process parameters were developed and a series of experiments with varying parameters were performed in order to validate the model. Discussions regarding the grinding conditions for the surface roughness based on experimental and model analysis results are presented. The model predictions and experimental results support the finding that a greater grinding depth and width increases the grinding force and hence deteriorates the ground surface. Furthermore, although a greater feed of the workpiece results in a larger grinding force and spindle vibrations, it also increases the cutting stiffness and thus reduces the transmitting factor of the spindle vibration, diminishing its adverse effects on the ground surface roughness.

關鍵字

grinding ； surface roughness ； spindle vibration ； grit kinematic effect ； process variance

並列摘要

通過結合磨粒運動和主軸振動效應，建立了反應磨粒與主軸震動對表面粗糙影響的解析模型。在考慮振動效應之磨削表面粗糙度模式中，均方根表粗度之平方可表示為磨粒隨砂輪轉動及振動之軌跡變異數相加。從動態磨削系統得出的傳遞因子定義了從主軸振動傳遞到表面的功率，與製程剛性有關，即工件的切削剛性和砂輪的接觸剛性。由於本模型的分析性質，本模型可用於估計表面粗糙度，並分析磨削條件、機床振動和加工過程中剛性的貢獻和影響。本文建立一參數識別程序，並進行了一系列參數變化的實驗，以驗證模型，根據實驗和模型分析結果，討論表面粗糙度的磨削條件。模型預測和實驗結果表明，磨削深度和磨削寬度越大，磨削力越大，磨削質量越差。此外，雖然較大的工件進給會導致較大的磨削力和主軸振動，但也會增加切削剛性，從而降低主軸振動的傳遞因子，減少其對表面粗糙度的不利影響。