工具機預估工件銑削品質可行性之研究

The Feasibility Research of Milling Surface Quality Prediction Technology

陳傑(Jay Chen)

指導教授 ： 鄭志鈞

國立中正大學/工學院/機械工程學系/碩士(2014年)

摘要

本研究是為探討工具機之動態特性、工件銑削品質，以及兩者間的相關性。本研究主要分成兩個主軸。第一部分為探討機台振動與工件銑削表面波紋之波組成，並對於兩者之訊號組成進行細部分析，進而了解各自之的特性與兩者間的相關性，最後，利用主軸至平台之振動傳遞率之方式，探討不同切削深度的切削剛性與銑削表面整體粗糙度之相關性。傳統之相關研究常以粗糙度值，Ra，此為直覺且簡單之方式以量化銑削表面，但也無法探討表面波紋特性與細節。本研究藉由輪廓儀，量測得工件表面波紋之頻譜組成，並以有系統且詳細之方式探討機台振動與工件表面波紋之頻譜的線性相關性，結果顯示，機台之振動頻譜於低頻部分與波紋頻譜有著很好的線性關係，並且，本研究亦探討於不同切削深度下機台之振動與銑削表面粗糙度值之關係，結果顯示，振動傳遞率與粗糙度值，亦有著相當高之線性相關性，因此以振動傳遞率預估粗糙度值是可行的。第二部分為提出一利用單純量測摩擦扭矩以得滾珠導螺桿預壓力之技術。實驗結果證明，馬達之85%進給驅動扭矩是來自於滾珠導螺桿之預壓扭矩，而剩下15%是由固定軸承之摩擦轉矩所造成。

關鍵字

摩擦扭矩 ； 滾珠導螺桿預壓力 ； 相關性 ； 粗糙度估測 ； 頻譜組成 ； 波紋 ； 振動 ； 銑削

並列摘要

The relation between the dynamic characteristics of the machine tool and the surface quality of the milling work piece was examined. This study could be divided into two parts. The first one is to investigate the correlation between the milling machine acceleration and the surface roughness of the work piece. The second part is to study the relation between the work piece roughness and the acceleration transmissibility between the spindle and the work table with respect to the varying cutting depth. The work piece roughness traditionally is quantified using Ra. Although Ra is easy to be implemented practically; however, many details related to the machining characteristic are neglected. In this study, the surface roughness is measured using a surface profile measurement station in such a way that the roughness can be decomposed as linear combinations of harmonic waves with different wavelengths using fast fourier transformation, i.e. the composition of surface roughness in the wave number domain. Then the vibration spectra is compared to the surface roughness wavenumber spectral to determine their correlations. Results show that the surface roughness is correlated well with the work table acceleration in the low frequency which dominates the surface roughness. Furthermore, the surface roughness quantified using Ra is positively correlated with the acceleration transmissibility. Therefore, it is concluded that predicting the machining quality using acceleration transmissibility as an index is feasible. Finally, a method of measuring the ball screw friction torque solely from the preload is proposed. Experiment results validate that 85% of the feed drive torque measured traditionally using a torque sensor is the friction torque induced by the ball screw preload while 15% is caused by the supported bearings.

並列關鍵字

Relation ； Roughness predicting ； Spectrum composition ； Friction torque ； Ballscrew ； Vibration ； Milling ； Preload

參考文獻

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