【作者】 张凯；

【导师】 张立强；

【作者基本信息】 上海工程技术大学 ， 机械制造及其自动化， 2016， 硕士

【摘要】 随着我国航天事业的蓬勃发展,大型筒段薄壁类工件被越来越多的加工生产,因此,如何提高该类工件的加工质量也就成了人们越来越重视的问题。航天类部件普遍都有着质量小的要求,因此该类工件的材质大多为密度较小的铝质合金。然而,由于铝合金材质类工件的自身刚性小,因此其在加工过程中非常容易因切削作用力、装夹作用力以及工件内部的残余应力等作用而发生加工变形,从而产生加工误差,影响工件的加工精度,最终无法保证工件的等厚度加工目标。因此,为了保证工件的加工精度,实现等厚度加工目标,需要在工件的加工过程中对加工变形进行控制以及对加工变形所引起的加工误差进行主动补偿。本文以航空用难滚弯筒段薄壁件为研究对象,以提高工件的加工精度,保证最终的工件等厚度为目标,以优化厚度补偿加工工艺为主线,开展了工件厚度测量、厚度补偿加工以及提高补偿加工的加工刀路精度等方面的研究,完成的主要工作内容有:(1)为了保证工件的等厚度加工,需要在工件的加工工艺中包含厚度补偿加工工艺,对因加工变形所导致的加工误差进行补偿。在进行厚度补偿加工前需要首先获得加工刀位点处的工件实际厚度,从而根据实际厚度来确定补偿加工的加工量。目前,工件实际厚度值的获取方式主要是依靠工人手持厚度测量仪器来进行厚度测量,而这种人工测量方式难以保证厚度测量精度,同时测量效率也非常低,从而无法保证整个工件的加工精度与加工效率。针对人工测量方式的不足,本文提出了一种由数控系统控制的,能够实现刀位点位置处工件厚度测量的原位厚度测量系统,从而代替人工测量方式,提高测量精度与测量效率。(2)依据本文所提出的原位厚度测量系统,提出了一种厚度补偿加工工艺。该加工工艺首先根据工件被加工部位的形状特征来确定实际厚度测量点的位置及数量,然后利用本文所提出的原位厚度测量系统测量得到工件在实际厚度测量点处的厚度值,进而由测得的厚度值插值获取所有刀位点处的工件实际厚度,并将实际厚度与理想厚度进行比较得到每个刀位点处的厚度补偿加工量,进行补偿加工。最后,利用五轴设备对所提出的厚度补偿加工工艺进行了加工试验验证,验证结果表明该补偿加工工艺能够有效的保证工件的加工质量,实现等厚加工目标。(3)在利用五轴设备进行联动加工时,两个加工刀位点之间会由于机床旋转轴的运动而出现沿进给方向以及垂直于进给方向两种类型的非线性加工误差,从而降低工件的加工质量,阻碍等厚度加工目标的实现。目前,各研究人员主要针对沿进给方向的非线性误差进行了研究控制,而对垂直于进给方向的非线性加工误差却未能给予足够的重视。因此,针对厚度补偿加工过程中所出现的垂直于进给方向的非线性加工误差,本文提出了一种误差控制方法,即首先建立了旋转轴的运动学模型,进而利用所建立的模型对误差的产生过程进行了分析,并在分析的基础上提出了误差控制方法。最后,对该误差控制方法进行了仿真以及加工试验验证,验证表明该控制策略能够有效的提高工件加工精度,保证等厚加工目标的实现。更多还原

【Abstract】 With the rapid development of aerospace industry in our country, thin-walled cylinder aluminum alloy part is widely used in aerospace, and people pay much attention to how to improve the machining precision of this kind of part. Because the rigid of thin-walled part is weak, it is easily to be deformation by the reason of cutting force, clamp force and the residual stress in processing. In order to ensure the machining precision, it is necessary to control the deformation or to compensate the value of deformation. In this dissertation, my research mainly involves the thickness measuring technology, thickness compensation technology and improve the precision of thickness compensation. The works mainly include:(1) In order to achieve the target of equal thickness, it is need to have the thickness compensation processing. Before thickness compensation, it first to obtain the actual thickness of workpiece and then have the value of compensation. Now, the actual thickness of workpiece was obtained by manual measurement, but this measurement manner will introduce more artificial error and difficult to measure the machining precision and have a low efficiency. In order to overcome these weaknesses, a in-situ thickness measurement system which controlled by numerical control system was introduced in this article and it can replace the manual measurement and ensure the machining efficiency.(2) According to the in-situ thickness measurement system which introduced by this paper, a more optimization thickness compensation technology was introduced. Firstly, the actual thickness measurement points could be gained by the feature of workpiece, and the actual thickness of these points can achieved by the in-situ thickness measurement system, then the actual thickness of every cutting location point can achieved by interpolation and the value of thickness compensation of every cutting location point can be obtained at the end. Finally, the thickness compensation technology was verified by five-axis machining equipment and the experimental results showed that this thickness compensation technology can guarantee the machining quality effective.(3) In five-axis machining, two types of non-linearity which along the direction of feed and vertical to the direction of feed will appeared in the middle of two cutter locations, and non-linearity will reduce the machining quality. Now, researchers mainly aimed at the first kind of non-linear error but neglect the second. In terms of the non-linearity error in the thickness compensation which vertical to the cutting direction, the article introduced an error control method. First, the kinematic model of rotary axes was established. Secondly, the process of error occurring was analyzed by the model. Then, the error control method was achieved. Finally, the error control method was verified by simulation.更多还原