极性效应在微细电火花反拷加工中的应用

研究了极性效应对微细电火花加工的影响,讨论了微细电火花加工中碳黑膜的生成条件及其对微细电极的保护作用.针对微细电火花反拷加工中电极损耗较大的问题,采取了粗精结合的加工策略,提高了工件的加工精度和表面质量.     

削边电极深小孔微细电火花间隙流场仿真研究

深小孔加工是微细电火花加工的重要应用领域之一.采用削边电极加工是提高深小孔加工深径比的有效工艺手段之一.通过间隙流场仿真结合工艺实验,解释了削边电极深小孔加工提高深径比和加工速度的原因.     

激波电火花复合微细孔加工试验研究

提出了一种新的复合微细电火花加工方法，通过工件的微幅激振改善加工条件，提高放电加工脉冲利用率和微细孔加工的深径比。介绍了实验装置的构成，并给出了初步试验结果。     

激波电火花复合微细孔加工试验研究

提出了一种新复合微细电火花加工方法，通过工件的微幅激振改善加工条件，提高放电加工脉冲利用率和微细孔加工的深径比。介绍了实验装置的构成，并给出了初步试验结果。     

微细电火花伺服扫描加工实验研究

进行微细电火花三维扫描加工时,由于电极损耗相对严重,导致形位公差难以保证和加工效率较低。该研究分析了电火花加工常规的电极损耗补偿方法,提出了基于放电间隙伺服控制进行电极损耗实时补偿的微细电火花三维扫描加工方法。辅助以电极电接触感知工件平面和加工原点,三维结构加工实验显示,采用间隙伺服控制进行电极损耗实时补偿有利于提高扫描加工微三维结构的形位精度和加工效率。     

微细电火花小孔加工过程仿真

微细电火花小孔加工过程中存在的电极损耗问题,严重影响了孔的加工精度.以单脉冲放电理论为基础,改进了微细电火花小孔加工过程的仿真模型,对工具与工件加工形状的变化过程进行了仿真研究.与实验结果相比,模型能较好地预测电极损耗及其对工件形状精度的影响,从而为进一步研究电极离线补偿提供了一种经济、可行的方法.     

基于混粉内冲液的微细电火花深小孔加工

电火花深小孔加工常采用管电极内冲液的方式促进电蚀产物排出,以提高加工速度、深小孔的加工质量和深径比。以自来水为工作液开展实验,首先通过正交试验确定深小孔加工的最优参数;然后在工作液中分别混入不同磨料,对比分析不同磨料对深小孔加工效果的影响。结果发现：添加半导体磨料有利于提高加工效率、减小孔的锥度并降低孔壁表面粗糙度值,而添加绝缘体磨料有利于降低电极损耗;混粉浓度和磨料粒径对加工效率、电极损耗、孔径及孔壁表面粗糙度均有明显影响;射流磨料对工件产生磨蚀效果并在孔壁表面留下刮痕,可减少或去除电火花加工表面的重铸层。     

微喷部件阵列孔电火花加工工艺试验研究

比较各种微细阵列孔的电火花加工方法,分析了单电极加工微细阵列孔方法的优点。以去离子水作为工作液,在已研制成功的微喷部件阵列孔电火花加工机床上进行单电极加工微细阵列孔的工艺试验,研究电源参数对微细阵列孔的孔径一致性、加工效率及电极损耗的影响规律。优化微细阵列孔加工的电参数,实现稳定的一次性加工256个直径小于50μm、偏差小于2μm的微细阵列孔。     

微细电解铣削加工技术研究进展及展望

微细电解铣削加工技术具有工具电极无损耗、加工柔性高、与工件材料硬度无关等特点,在金属微结构器件制造领域展现出极具诱惑力的应用前景。通过综合国内外文献资料,按照不同的电解液供给方式介绍微细电解铣削加工技术的研究进展,分析微细电解铣削加工相关技术研究中存在的不足,并展望该领域的未来发展趋势。     

微细电火花加工损耗补偿的研究

针对三维微细结构的微细电火花加工,应用等损耗理论,采用分层加工的方法,建立了单道单层加工时底面形状随电极损耗而变化的轮廓模型,在此基础上,提出电极损耗适时补偿的方法.实验测定了钨电极加工不锈钢的损耗率,应用适时补偿方法加工得到的单层单道窄槽的尺寸精度良好.     

High aspect ratio micro-hole drilling aided with ultrasonic vibration and planetary movement of electrode by micro-EDM

When a micro-hole is drilled deeply by EDM, the viscous resistance in the narrow discharge gap causes difficulty in the removal of debris and bubbles from the working area, leading to frequent occurrences of abnormal discharges and resulting in extensive electrode wear. This paper presents a new method of drilling high aspect ratio micro-holes by EDM, in which the planetary movement of an electrode, with enhancement from ultrasonic vibration, provides an unevenly distributed gap for the debris and bubbles to escape from the discharge zone easily. Micro-holes with aspect ratio of 29 have been drilled.     

High Aspect Ratio and Complex Shaped Blind Micro Holes by Micro EDM

It is difficult to drill high aspect ratio through holes and complex shaped blind holes using micro EDM. The debris concentration in the narrow discharge gap causes abnormal discharges leading to excessive electrode wear and lower machining precision. In micro EDM, the electrode size is too small for internal flushing. This paper presents a new approach for effective self-flushing using planetary movement. Through micro holes with an aspect ratio of 18 have been drilled. This approach is also demonstrated by drilling blind noncircular micro holes with sharp corners and edges. The process performance characteristics are analyzed under different machining conditions.     

Efficiency improvement in electrical discharge machining (EDM) of constant section cavity based on experimental study and numerical calculations

Electrode jump motion is applied to most of the electrical discharge machining (EDM) machine to remove debris from machining gap. The time consumption of one consecutive-pulse discharge process between two adjacent electrode jump motions is named electrode machining time. If the two parameters can be timely adjusted to the optimal values during machining, the efficiency will be obviously improved. However, the complicated flow field of the machining gap that contains kerosene, debris, and bubbles makes it difficult to determine the optimal values of electrode machining time and jump height. This research proposes a strategy to solve this problem. By detecting the voltage and current signals between electrode and workpiece, the normal discharge frequency and abnormal discharge ratio were calculated to determine the optimal electrode machining time. Then, the optimal electrode jump height was calculated through a model which simulates the gap flow field in EDM. Experimental results show that the proposing strategy evidently improves the EDM efficiency.     

混气电火花加工气泡形成机理及实验研究

为了研究混气电火花加工中微气泡的形成机理,建立了微气泡数学模型。分析发现,微气泡的大小与气泡内外的压力差有关,压力越大,气泡直径越小。选择不同的混气压力进行了对比试验,结果表明:极间混入气体后改变了原有的放电状态,加工效率略有降低,电极绝对损耗变小,表面粗糙度值下降;随着混气压力的增加,放电间隙减小,增大了电蚀产物从极间排出的难度,加工效率继续降低,电极损耗基本不变,表面粗糙度值略有下降。     

Simulation model of debris and bubble movement in consecutive-pulse discharge of electrical discharge machining

Debris concentration and bubble volume fraction in the bottom gap between the electrode and workpiece affect the state of consecutive-pulse discharge and the efficiency of electrical discharge machining (EDM). Thus, the mechanisms of debris and bubble movement during consecutive-pulse discharge should be elucidated. However, these mechanisms have not been fully understood because of debris and bubble movement in the machining gap are difficult to simulate and observe. This study proposes a three-dimensional model of flow field with liquid, gas, and solid phases for machining gap in EDM. The mechanisms of debris and bubble movement in the machining gap during consecutive-pulse discharge were analyzed through the model. Debris and bubble movement in consecutive-pulse discharge was observed through experiments. The results showed that the proposed simulation model is feasible. The bubble expansion is the main way that the bubbles exclude from machining gap. Much debris moves outside the machining gap following the excluded bubbles, which is the main way that the debris excludes from machining gap. The bubble expansion becomes strong with the increase of the discharge current and pulse-on time.     

A study on pulse control for small-hole electrical discharge machining

Small-hole EDM has a problem of debris evacuation from the narrow gap between the electrode and workpiece. The presence and difficulty in evacuating the debris formed during an erosion process limit the achievable aspect ratio. To address the problem of debris accumulation, a pulse generator, which is able to shut off harmful pulses and to apply high discharge energy pulses, is developed. A FPGA chip is used as the master controller for the determination of pulse discharge status and MOSFET switching. A series of experiments are carried out to examine the machining performance by shutting off harmful pulses and applying high discharge energy pulses. The experimental results show that the efficiency of small-hole drilling is improved and the aspect ratio is increased.     

电火花加工微孔深径比的理论模型实验研究

为预测和提高电火花加工微孔的深径比,对描述该深径比的理论模型开展了进一步研究。在不同条件下加工50个微孔,采用罗曼诺夫斯基准则处理微孔加工数据,并应用误差传递公式分析各主要误差对该理论模型的影响,进一步表明了微孔深径比理论模型的有效性。     

微细电加工应用技术研究

微细电加工要达到工业应用的目的,需兼顾加工效率和加工精度两方面的要求.以微细孔、微细三维结构的加工为目标,进行了微细孔电火花加工、三维微细结构电火花伺服扫描加工及微细电化学加工技术的研究开发.设计出微细电极的损耗补偿进给和导向机构,开发出三维微细结构的电火花伺服扫描加工工艺,研究了采用阵列微细电极的微细电化学加工方法.微细孔电火花加工可连续加工直径小至100 μm的孔.伺服扫描电火花加工可便捷地在小于1 mm2区域内加工出三维微细结构.提出的微细电化学加工技术路线拟将微细电解加工应用于阵列微细孔和三维微细结构的加工.     

电火花摇动加工微细阵列轴和孔的试验研究

针对微细阵列轴和孔的电火花加工,提出了利用数控电火花加工机床摇动功能的摇动加工微细阵列轴和孔的方法.此法是基于电火花反拷贝加工的原理,先用丝电极在薄平板(中间电极)上按要加工的阵列轴和孔间距或数倍间距加工阵列小孔(直径0.1 mm以上),然后用加工的薄平板(中间电极)作电极,电火花摇动加工微细阵列轴(电极),最后用此微细阵列电极加工阵列孔.进行了电火花摇动加工微细阵列电极试验,得到了单电极直径为50 μm、长径比为16的3×3阵列电极,并用此电极在70 μm厚的不锈钢板上加工出单孔直径为70 μm的3×3微细阵列孔.试验结果表明,电火花摇动加工方法可实现微细阵列轴和孔的加工.     

微小间隙火花放电的伺服控制特性实验研究

为探索微小间隙火花放电的伺服控制特性,利用高速示波器和非接触式电涡流位移传感器,采用门槛电压阈值控制方法,实验研究了微小间隙火花放电规律与主轴伺服运动特性之间的关系,得出了主轴频响和运动速度对放电率的影响规律.并利用频响达200 Hz的直线电机主轴,验证了高频响主轴伺服控制微小放电间隙的优越性.研究发现:开短路交替频率、主轴跳动幅值、开短路率大小及比例可作为放电效果的评价指标;深度效应将造成一个特定深度的加工状态破坏点.这些结果为优化主轴机构和伺服控制策略提供了依据.