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棒料切割机设计【说明书+CAD】,切割机,设计,说明书,CAD
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附录一 英语论文High Precision Finish Cutting by Dry WEDMAbstractThis paper describes the development of a new dry wire electrical discharge machining (dry-WEDM) method, which is conducted in a gas atmosphere without using dielectric liquid to improve the accuracy of finish cutting. In dry-WEDM, the vibration of the wire electrode is minute due to the negligibly small process reaction force. In addition, as the gap distance is narrower than that in conventional WEDM using dielectric liquid, and there is no corrosion of the workpiece, high accuracy in finish cutting can be realized in dry-WEDM. However, some drawbacks of dry-WEDM include lower material removal rate compared to conventional WEDM and streaks are more likely to be generated over the finished surface. Increasing the wire winding speed and decreasing the actual depth of cut are effective to resolve these drawbacks.Keywords: WEDM, dielectric, Finish cutting, Dry process1 INTRODUCTIONDry-electrical discharge machining (dry-EDM) is a new EDM process, which is conducted in a gas atmosphere without using dielectric liquid. Die-sinking EDM in dry condition was first attempted by Kunieda et al. I to discontinue the use of EDM working oil in consideration of environmental preservation, human health and prevention of fire hazards. They found other advantages of dry-die-sinking EDM such as; 1) significantly low tool wear ratio, 2) thinner white layer and lower residual stress, and 3) narrower discharge gap length.Kunieda et al. 2 found that when the EDM gap is filled with dielectric liquid, a considerably large process reaction force is applied to the tool electrode at the moment dielectric breakdown occurs. This is because a bubble is generated due to the evaporation and dissociation of the dielectric liquid, and because rapid expansion of the bubble is prevented by the influence of the inertia and viscosity of the dielectric liquid, resulting in extremely high pressure inside the bubble. In contrast, the process reaction force was found to be negligibly small when a discharge occurs in a gap filled with air instead of liquid.It is also known that an electrostatic force is applied between the tool electrode and workpiece 34 mainly during the discharge delay time in which an open voltage is applied between them. When the discharge energy is small, the influence of the electrostatic force cannot be ignored in comparison with the above-mentioned reaction force due to the expansion of the bubble. Obara et al. 4 pointed out that, since the electric permittivity of water is eighty-two times higher than that of air, the electrostatic force in conventional wire EDM (WEDM) using deionized water as the dielectric liquid is greater than when air is used as the dielectric fluid.Since WEDM uses as tool electrode a thin and flexible wire, the wire electrode is subject to deformation and vibration due to the above-mentioned forces, resulting in unfavorable geometrical error of the machined surface. This fact motivated Furudate et al. 5 to investigate the fundamental characteristics of finish cutting conducted in air. They found that dry-WEDM produces excellent straightness of the finished surface but material removal rate is lower than conventional WEDM. The present study aims to clarify the characteristics of dry-WEDM in further detail and propose methods to improve dry-WEDM.2 PRINCIPLEThe new dry-WEDM method developed in the present work basically eliminates the use of dielectric liquid. Hence both the reaction force and electrostatic force are negligibly small compared to those in conventional WEDM using deionized water, resulting in considerably better accuracy in finish cutting. Furthermore, dry-WEDM is free from the serious problem of electrolytic corrosion caused by electrolytic current flowing through water encountered in conventional WEDM.Tanimura et al. 6 proposed a new EDM process using water mist, which requires no tank for the working liquid and hence can easily be combined with other machining processes. They also pointed out that mist-EDMMIEDM enables non-electrolytic machining even when electrically conductive water is used as the working liquid. They were however not able to find other characteristics that are superior to those in conventional EDM, although dry-EDM has many advantages such as, extremely low tool wear ratio, higher precision, narrower gap, smaller process reaction force, and smaller heat affected zone.3 EXPERIMENTAL METHODGround flat surface of carbon steel or tool steel was finish-cut by conventional and dry-WEDM, and material removal rate, straightness, surface roughness, waviness and gap length were compared. With conventional WEDM, water, whose electric conductivity was adjusted moderately, was jetted from the upper and lower nozzles. With dry-WEDM, no water was supplied and cutting was performed in atmosphere. To obtain material removal rate, the removed volume was divided by the machining time. The removed volume can be obtained by integrating the product between the actual depth of cut and the fed distance of the wire electrode with the distance along the wire from the bottom to the top surface of the workpiece.Straightness was obtained by measuring the profile of the finished surface parallel to the wire using a surface roughness-measuring instrument. Surface roughness was measured also parallel to the wire. In this study, attention was paid to the waviness measured in the direction perpendicular to the wire, because, in WEDM, unfavorable streaks are in some cases generated parallel to the wire as shown in Figure l(a).Since the depth of streaks is in the same order as surface roughness, it has been very difficult to evaluate the waviness caused by the streaks. Normally the waviness is measured perpendicular to the streaks as shown in Figure l(b), and surface roughness, which is composed of relatively high frequency components, is cut-off by a low-pass filter to extract the waviness. However, since the frequencies in surface roughness are similar to those involved in the waviness, it is difficult to separate the waviness from the measured profile. We thereby proposed a new method for measuring the waviness as shown in Figure l(c). In this method, since the profile is measured along the line inclined at a small angle8 from the wire axis direction, only the frequencies of the waviness are decreased, whereas those in surface roughness are unchanged. This enables the waviness to be separated easily from the surface roughness using a low-pass filter.Figure 2 shows the measured waviness of a surface finished by dry-WEDM. From the profile measured parallel to the wire, it was found that the straightness of the surface is excellent. However, when the line of measurement is inclined by 0.5 , the waviness became recognizable. As the angle of inclination 8 increases, the frequency involved in the profile rises because the number of streaks crossed by the line of measurement increases. Based on this result, we decided to evaluate the waviness from the profile measured with 8 =I .The gap length is considered nearly equal to the distance between the preset position of the wire side surface and workpiece surface after finish-cutting measured at the points closest to the top or bottom surfaces of workpiece, because the amplitude of the wire vibration is almost zero at these points.4 COMPARISON OF MACHINING CHARACTERISTICS WITH CONVENTIONAL WEDM4.1 StraightnessStarting from a flat surface preprocessed by grinding, finish-cutting with a depth of cut of 5p m was repeated until the straightness measured became invariable. The working conditions are shown in Table 1. Figure 3 shows the difference in straightness between conventional and dry-WEDM. It is clear that the straightness is better in dry-WEDM than in conventional WEDM. Under the conditions used in this experiment, all the surfaces finished were concave.4.2 Surface roughnessFigure4shows a comparison of surface roughness obtained from the same experiment in the previous section. It was found that the surface roughness is better in dry-WEDM than in conventional WEDM. This is because since there is no dielectric liquid in the working gap in dry-WEDM, the discharge column expands easily, increasing its diameter more quickly. Thus the lower current density than conventional WEDM results in a shallower discharge craters, leading to better surface roughness.4.3 Gap le Figure 5 shows ngth the difference in the gap length. The gap length in dry-WEDM is remarkably more or less zero and, in some cases, is even minus. Kunieda et al.l and Yoshida et al. 7 reported that the gap length in dry-die-sinking EDM is narrower than that in conventional die-sinking EDM, because the dielectric strength of the working liquid in the discharge gap of conventional EDM is much lower than that of a clean working liquid before use due to the debris particles floating in the liquid during the process. In dry-die-sinking EDM, however, the debris particles are blown away from the working gap by the gas flow which is supplied into the working gap through the hollow space of a pipe electrode. In dry-WEDM in the present work, although no gas was supplied into the discharge gap, debris particles do not float in the gap because the density of debris particles is much higher than that of air and the viscosity of air is extremely lower than that of dielectric liquid.Figure 6 shows the cross sections through the middle of the work pieces, which were corner-cut at an angle of 15 . The surfaces were finished by conventional and dry-WEDM. The working conditions used were the same as in Table 1 except for the wire electrode diameter of 200 p m. The discharge current was 110A. It is clear that the corner radius obtained by dry-WEDM is smaller than that of conventional WEDM owing to the narrower gap length. Furthermore, over-cut can be seen in conventional WEDM but not in dry-WEDM due to the smaller distortion and vibration of the wire in dry-WEDM.4.4 Material removal rateFigure 7 shows a comparison of the material removal rate between conventional and dry-WEDM obtained under the same conditions as in Table 1. The material removal rate of dry-WEDM is considerably lower than that of conventional WEDM. This is because the frequent occurrence of short-circuiting due to the narrower gap length in dry-WEDM causes unfavorable repetition of the turning back and forth of the wire electrode in the feed direction. Consequently, dry-WEDM requires better frequency response in wire feed control to obtain the same removal efficiency as conventional WEDM. Yoshida et a1.7 demonstrated that the material removal rate of dry-die-sinking EDM can be improved to almost equal to that of conventional die-sinking EDM by utilizing a piezoelectric actuator for supplementary gap control.4.5 WavinessFigure 8 shows profiles of the finished surfaces. From the profiles measured parallel to the wire ( 8 =O ), the straightness of dry-WEDM was found to be better than that of conventional WEDM. From the profiles measured in the direction 8 =I , more streaks were however seen generated over the dry-WEDMed surface than the conventionally WEDMed surface. This is because the wire feed turns back and forth frequently due to short-circuiting in dry-WEDM.5 IMPROVEMENT OF MACH I N I N G CHARACTERISTICS5.1 Wire winding speedIt is well known that discharge locations should be distributed randomly over the working surface in order to obtain a stable machining state 8. From this point of view, the dry-WEDM process described in the previous section is unstable. It was observed that discharge locations were localized on the wire electrode and the area of localization moved over the workpiece surface with the wire at the same velocity as the wire winding speed. Because of the insufficient cooling of the working gap due to the absence of working liquid and the high thermal resistance and small heat capacity of the thin wire electrode, the surface temperature of the wire tends to increase, resulting in a local reduction of dielectric breakdown strength. Hence, the influence of wire winding speed was investigated.Before finish-cut, the position of the workpiece surface, which was preprocessed by grinding, was detected by touching the surface with the wire, and the position where the wire touched the surface was defined as zero. Then the wire position was offset toward the workpiece by 5 p m. This means that the depth of the wire side surface was 5 p m. Finish-cut was then started. Figure 9 shows the influence of the wire winding speed on the material removal rate and straightness. The working conditions used in this experiment are shown in Table 2. The higher the wire winding speed, the higher the material removal rate and the better the straightness will be. The localization of discharge locations was not recognized at higher wire winding speeds, suggesting that the increase in the winding speed results in decreased wire surface temperature.5.2 Air pressureIn dry-die-sinking EDM 17, a high-pressure gas flow is supplied into the working gap through a thin-walled pipe electrode to cool the gap and flush molten workpiece material out of the gap. Hence, we investigated the machining characteristics when compressed air is supplied into the working gap. Compressed air was jetted from the upper and lower nozzles, which are normally used for supplying dielectric liquid in conventional EDM. The working conditions used were the same as in Table 2. The wire winding speed was 250mm/s, which was the maximum speed of the WEDM machine used.Figure 10 shows the influence of the pressure of the compressed air on the material removal rate and straightness. It was found that the material removal rate is higher when the air pressure is increased. Unfortunately, the high-velocity airflow deteriorated the straightness. Figure 11 shows the influence of air pressure on the actual depth of cut measured and gap length. Zero Mpa means that the finish-cut was performed in atmosphere. Since the preset depth of the wire side surface was 5 p m, the gap length can be obtained by subtracting 5 p m from the actual depth of cut. The actual depth of cut decreases with increasing air pressure, because air flow with a higher velocity blows the debris particles out of the gap more effectively, resulting in a shorter gap length. The minus gap length at 0.2MPa indicates that discharge occurs even between the wire and workpiece, both of which are more or less touching each other.Additional finish-cut was conducted under the following two conditions: preset depth of wire side surface of Op m in atmosphere, and preset depth of wire side surface of 10 p m with air pressure of 0.2MPa. Including these results, all the data shown in Figure 10 and Figure 11 were plotted together in Figure 12 to show the dependence of the material removal rate and waviness on the actual depth of cut. It was found that, despite the air pressure and preset depth of the wire side surface, the material removal rate is higher and waviness is smaller when the actual depth of cut is shallower. When the actual depth of cut was smaller than 1 . 5m, there were no visible streaks over the finished surface.6 CONCLUSIONSComparisons of machining characteristics between conventional and dry-WEDM showed that dry-WEDM offers advantages such as better straightness, surface roughness, gap length, accuracy in corner-cut, and electrolytic corrosion-free. It was also found that dry-WEDM has poorer material removal rate and waviness.To resolve these drawbacks, influences of the wire winding speed, pressure of air supplied into the working gap, and preset depth of the wire side surface were investigated. It was found that, under the conditions tested in the present work, the material removal rate and waviness can be improved by increasing the wire winding speed and decreasing the actual depth of cut.附录二 汉语翻译高精度完成切割干电火花线切割机 摘要 本文介绍了开发新的干丝电火花加工（干式电火花线切割加工）方法，这是进行气体加工中，而不使用液体介质，以改善准确性完成切割。干床，振动的导线电极分钟由微乎其微小过程反应部队。此外，由于间距窄于常规电火花线切割机使用液体介质，没有腐蚀工件，精度高，在完成切割，才能实现在干切割。然而，一些弊端干切割包括更低的材料去除率相对传统电火花线切割机床和条纹更可能是产生了成品表面。增加绕线速度和减少的实际切削深度是有效的解决这些弊端。 关键词：线切割，电介质，完全切割，干法 1导言干式电火花加工（干电火花）是一种新的电火花加工过程中，这是进行气体的加工中，而不使用液体介质。模具电火花沉没在干旱条件下第一次尝试国枝等人。 一停止使用石油加工工作中考虑环境的保护，人类健康和预防火灾隐患。他们发现其他优点干死沉电火花如; 1 ）显着刀具的磨损率低， 2 ）薄白层，降低残余应力，和3 ）窄放电间隙长度。 国枝等人 2 发现，当电火花填补与液体介质，相当大的过程反应应用于工具电极此刻介质击穿发生。这是因为泡沫产生的原因是蒸发和分离介质的液体，并且由于迅速扩大的泡沫是预防的影响的惯性和粘度液体介质，造成极高的泡沫压力。与此相反，这一过程反应被认为是微乎其微小放电时发生在一个空白充满空气而不是液体。 人们还知道，静电之间的适用工具电极和工件 3 4 主要是在放电延迟时间在一个开放的电压应用于它们之间。当放电能量小，上述反应由于扩大泡沫，相比静电的影响力不能忽视。小原等人 4 指出，由于水的电力介电常数为82倍以上的空气，在传统的静电武力线切割机（线切割）使用去离子水为介质液体大于当空气被用作介质流体。 由于电火花线切割机电极使用的工具和灵活的薄丝，由于上述丝电极是受变形和振动，这一事实促使造成不利的几何误差的加工表面等。 5 调查的基本特征进行完成切割空气。他们发现，干式电火花线切割加工生产出优质的直线，但成品表面材料去除率低于常规电火花线切割机。本研究的目的是阐明干式电火花线切割加工的特点，干式电火花线切割加工中进一步详细，并提出方法，以改善干切割。 2原理 新的干式电火花线切割加工方法，在目前的工作基本上消除了使用介质的液体。因此，既反应和静电微乎其微，在使用传统的电火花线切割机床去离子水，从而大大改善准确性完成切割。此外，干切割是免费的严重问题引起的电解腐蚀电流流经电解水过程中遇到的常规电火花线切割机。 谷村等 6 提出了一种新的电火花加工过程中使用水雾，不需要别的工作液体，因此可以很容易地与其它工艺加工。他们还指出，雾使非电解加工即使导电水作为工作液。但他们无法找到其他特点，是优于传统的电火花加工，尽管干式电火花加工具有许多优点，如极低的刀具磨损率，精度高，范围较窄的差距，更小的工艺反应，和更小的热影响。 3实验方法 平整地面的表面是完成碳钢或工具钢，减少了常规和干床，和材料去除率，平直度，表面粗糙度，波纹度和差距长度进行了比较。与传统的线切割，水，其电导率适度调整，是乘飞机从上部和下部的喷嘴。与干式电火花线切割机床，没有水供应和切割是在大气中。要获得材料去除率，已删除的体积除以加工时间。拆除的数量，可通过集成的产品之间的实际切削深度和美联储距离电极导线的距离沿线的电线从底部到顶部表面的工件。 直线度测量，得到的形象成品表面平行线使用的表面粗糙度测量仪。表面粗糙度测量也是平行线。在这项研究中，注意波纹测量方向垂直线，因为在电火花线切割机床，不利的条纹，在某些情况下产生的平行线所显示的图1 （ a ）条。 由于深入的条纹是在相同的命令，表面粗糙度，已经很难评价波纹所造成的划痕。通常的波纹度测量垂直条纹显示图1 （ b ）和表面粗糙度，这是相对组成的高频成分，是切断了低通滤波器来提取波纹。然而，由于频率的表面粗糙度类似于参与波纹，这是从实测资料很难分开的波纹。因此，我们提出了一个新的测量方法波纹图所示的L （ c ）项。在此方法中，因为个人资料是衡量线沿线倾向于在一个小角8电线轴方向，只有频率的波纹度降低，而在表面粗糙度不变。这使波纹分开很容易从表面粗糙度使用一个低通滤波器。 图2显示了测量波纹表面完成干切割。从剖面测量平行线，结果发现，直线的表面非常出色。然而，当线的测量倾向于0.5的项目，成为公认的波纹。随着倾角的增加，频率参与的形象上升，因为一些条纹交叉线的测量增加。基于这一结果，我们决定评估波纹从剖面测量 长度的差距被认为是几乎相等的距离预设立场线一侧表面和工件表面后完成切割测量点最接近的顶部或底部表面的工件，由于在这些点振幅线振动几乎为零。 4比较加工特征与常规电火花线切割机 4.1直线 从一个平面上预处理研磨，抛光切割与切削深度的5p米重复，直到成为衡量直线不变。工作条件表1所示。图3显示了不同的直线之间的传统和干切割。很显然，直线是更好地干比常规电火花线切割机床的条件下使用本实验中，所有的表面完成了凹。 4.2表面粗糙度 图4显示了在上一节比较表面粗糙度得到同样的实验。结果发现，表面粗糙度好干比常规
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