【作者】 李明毅；

【导师】 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械工程， 2023， 硕士

【摘要】 碳纤维增强聚醚醚酮(CF/PEEK)具备良好的力学性能、抗辐射性、尺寸稳定性和热稳定性,被广泛应用于航空航天、汽车、电子产品和医疗器械领域。该材料常见的成型方式有注塑成型、热压成型、3D打印成型以及微编织成型等,材料成型后,在各种应用场合不可避免要进行切割、制孔等二次加工,但是由于其硬度较高,抗剥离性能较差等特点,采用传统机械加工的方式进行制孔对刀具要求较高,且容易造成材料的报废,因此采用电火花加工这种非接触式加工对该材料进行制孔是更为有效的手段。放电状态检测和脉冲电源是电火花加工时的核心技术与设备,对电火花加工过程有着十分重要的影响。本文以单脉冲放电的形式研究了CF/PEEK利用电火花加工的可行性,将该材料单脉冲放电波形与不锈钢单脉冲放电波形进行对比,得出该材料能利用电火花加工进行制孔的结论。探究了碳纤维各向异性对CF/PEEK电火花加工过程的影响,分别让工具电极垂直碳纤维和平行碳纤维时对该材料进行加工,比较两个加工方向加工得到的孔的表面质量、加工效率以及电极损耗的各自特点。利用单因素实验明确了脉冲宽度、脉冲间隙、电流、电容和伺服进给速度对该材料电火花加工过程加工效率和电极相对损耗的影响规律。最后对该材料实际加工过程的典型放电波形进行了采集并整理分类,总结了该材料利用电火花加工进行制孔的加工特点和存在的问题,并对本文放电状态检测和脉冲电源的设计提出了要求。设计了同时利用间隙电压和电流信号的放电状态检测方案,完成了该方案所需的硬件电路设计。设计了具备多能量等级的可控式RC脉冲电源,并在电源中加入了脉冲清扫和单脉冲放电的功能,完成了脉冲电源所需的硬件电路设计。搭建了基于FPGA的电源控制系统,主要包含放电状态识别模块、串口通信模块、脉冲清扫控制模块、NMOS控制模块等六个部分。为了实现对放电状态的实时掌握以及对脉冲电源参数的改变和功能的切换,利用Labview软件完成了与脉冲电源配套的上位机设计。采用单脉冲放电的形式对放电状态检测的准确率进行了验证,结果表明该状态检测系统的准确率达到了96%。利用设计的脉冲电源对CF/PEEK展开小孔加工实验,将实验结果与原机床脉冲电源加工结果进行对比,结果表明用新脉冲电源加工得到的小孔表面质量较原脉冲电源有了较大的提高。工具电极垂直碳纤维加工时,极限深径比相较于原电源提高了90.85%,正常放电的比例提高了36.6%,短路和拉弧所占的比例降低了24.1%,材料去除率增加了82.6%,电极相对损耗降低了23.19%。工具电极平行碳纤维加工时,极限深径比相较于原电源提高了79.95%,正常放电的比例提高了26%,短路和拉弧所占的比例降低了5%,材料去除率增加了103%,电极相对损耗降低了17.83%。实验表明本文设计的放电状态检测方法和脉冲电源系统达到了预期目标,符合设计要求。更多还原

【Abstract】 Carbon fiber reinforced polyether ether ketone(CF/PEEK)has good mechanical properties,radiation resistance,dimensional stability and thermal stability,and is widely used in aerospace,automotive,electronic products and medical instruments.The common molding methods of the material are injection molding,hot pressing molding,3D printing molding and micro-braided molding,etc.After the material molding,it is inevitable to carry out secondary processing such as cutting and hole making in various applications.However,due to its high hardness,poor stripping resistance and other characteristics,the traditional machining method is used to make holes with higher tool requirements.It is easy to scrap the material,so it is more effective to use the non-contact EDM to make holes in the material.Discharge state detection and pulse power supply are the core technology and equipment of EDM,which have very important influence on EDM process.In this thesis,the feasibility of using EDM for CF/PEEK is studied in the form of monopulse discharge.The monopulse discharge waveform of CF/PEEK is compared with that of stainless steel,and it is concluded that the material can be used for hole making by EDM.The effects of carbon fiber anisotropy on CF/PEEK EDM processing were investigated,and the material was processed when the tool electrode was perpendicular to the carbon fiber and parallel to the carbon fiber respectively.The surface quality,processing efficiency and electrode loss of the holes were compared in the two machining directions.The effects of pulse width,pulse gap,current,capacitance and servo feed speed on the machining efficiency and electrode relative loss in EDM were determined by single factor experiment.Finally,the typical discharge waveform of the actual processing of the material is collected and sorted out,and the machining characteristics and existing problems of the material are summarized,and the requirements for the discharge state detection and the design of the pulse power supply are put forward.A discharge state detection scheme using gap voltage and current signal is designed,and the hardware circuit design is completed.A controllable RC pulse power supply with multiple energy levels is designed,and pulse cleaning and single pulse discharge are added to the power supply,and the hardware circuit design is completed.The power control system based on FPGA is built,including discharge status identification module,serial communication module,pulse cleaning control module,NMOS control module and other six parts.In order to master the discharge state in real time,change the parameters and switch the functions of the pulse power supply,the upper computer matching with the pulse power supply is designed by using Labview software.The accuracy of discharge state detection is verified by using the form of single pulse discharge,and the results show that the accuracy of the system reaches 96%.The small hole machining experiment of CF/PEEK was carried out with the designed pulse power supply,and the experimental results were compared with those of the original machine tool pulse power supply.The results show that the surface quality of the small hole machined by the new pulse power supply is greatly improved compared with the original pulse power supply.When the tool electrode was processed vertically,the limit depth-diameter ratio increased by 90.85%,the proportion of normal discharge increased by 36.6%,the proportion of short circuit and arc pulling decreased by 24.1%,the material removal rate increased by 82.6%,and the relative electrode loss decreased by23.19%.When the tool electrode is processed parallel to carbon fiber,the limit depth-diameter ratio is increased by 79.95%,the proportion of normal discharge is increased by 26%,the proportion of short circuit and arc pulling is reduced by 5%,the material removal rate is increased by 103%,and the relative electrode loss is reduced by17.83%.The experimental results show that the discharge state detection method and pulse power system designed in this paper achieve the expected goal and meet the design requirements.更多还原