铣削加工透波性Si3N4陶瓷表面质量研究

为了探索透波性Si3N4陶瓷铣削中加工表面创成机理及加工工艺参数对其影响规律,对加工表面形貌和边缘破损特征,以及加工参数与切削力、表面粗糙度、边缘破损的映射关系等开展了试验研究。首先对加工表面形貌进行了分析,由于存在陶瓷粉末去除和破碎性颗粒去除两种形式,造成加工表面形貌结构一种体现为变化平缓,而另一种包含微裂纹、层状结构体等,且存在凹坑、沟槽等缺陷。其次研究了边缘破损形式及产生机理,当刀具运动到出口棱边处,刀尖应力集中处将产生微裂纹,并向工件侧面扩展,从而在加工表面和加工侧面诱导形成边缘破损。最后基于均匀设计试验,分析了工艺条件对加工性能的影响。结果表明:随着切削深度从0. 2增加到0. 5 mm和切削宽度从1增加到4 mm时,x轴切削力呈耦合增长,y轴切削力呈二次方增长;当切削深度和切削宽度分别为0. 2 mm和1 mm、进给速度为500 mm/min时,加工表面粗糙度值最小;转速为2 000 r/min、切削深度和切削宽度最小时,边缘破损幅值最小。此结果可为提高透波性Si3N4陶瓷铣削加工质量提供技术支撑。

Effect of Milling on the Surface Quality of Wave-transmitting Si3N4 Ceramics

To investigate on the surface generation mechanism and the influence of milling process of the wave-transmitting Si₃N₄ ceramics,experimental study on the surface topography and edge chipping characteristics,as well as the mapping relationship between machining parameters and cutting force,surface roughness and edge chipping had been carried out.Firstly,the surface morphology of the machined surface had been analyzed.Due to the existence of ceramics powder removal and broken particle removal,the surface topography was characterized by gentle change,while the other contains micro-cracks,layered structures,etc.And there were defects such as pits and grooves.Secondly,the edge chipping shape and its mechanism had been studied. When the tool moves to the edge of the exit,micro-cracks would be generated at the stress concentration of the tool tip and spread to the side of the workpiece,thus causing edge chipping on the machined surface and the side.Finally,the influence of process conditions on the processing performance has been analyzed based on the uniform design experiments.The experimental results show that with the cutting depth increases from 0.2 mm to 0.5 mm and the cutting width increases from 1 mm to 4 mm, the cutting force of the x-axis is coupled growth, and that of of the y-axis increases quadratically.The machining surface roughness value is minimum when the cutting depth is 0.2 mm,the cutting width is 1mm and the feed speed is 500 mm/min,respectively.As the rotation speed is 2 000 r/min, the edge chipping amplitude is the smallest when the cutting depth and the cutting width are the smallest.Machining process control can be implemented to improve the milling surface integrity of the wave-transmitting Si₃N₄ ceramics.