X-Y數(shù)控工作臺及其控制系統(tǒng)設計【說明書+CAD】

X-Y數(shù)控工作臺及其控制系統(tǒng)設計【說明書+CAD】,說明書+CAD,X-Y數(shù)控工作臺及其控制系統(tǒng)設計【說明書+CAD】,數(shù)控,工作臺,及其,控制系統(tǒng),設計,說明書,仿單,cad 附錄一 英語論文 High Precision Finish Cutting by Dry WEDM Abstract This 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 process 1 INTRODUCTION Dry-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 [3][4] 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 PRINCIPLE The 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 METHOD Ground 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 WEDM 4.1 Straightness Starting 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 roughness Figure4shows 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 rate Figure 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 Waviness Figure 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 CHARACTERISTICS 5.1 Wire winding speed It 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 pressure In dry-die-sinking EDM [1][7], 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 CONCLUSIONS Comparisons 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. 附錄二 漢語翻譯 高精度完成切割干電火花線切割機 摘要 本文介紹了開發(fā)新的干絲電火花加工（干式電火花線切割加工）方法，這是進行氣體加工中，而不使用液體介質，以改善準確性完成切割。干床，振動的導線電極分鐘由 微乎其微小過程反應部隊。此外，由于間距窄于常規(guī)電火花線切割機使用液體介質，沒有腐蝕工件，精度高，在完成切割，才能實現(xiàn)在干切割。然而，一些弊端干切割包括更低的材料去除率相對傳統(tǒng)電火花線切割機床和條紋更可能是產生了成品表面。增加繞線速度和減少的實際切削深度是有效的解決這些弊端。 關鍵詞：線切割，電介質，完全切割，干法 1導言 干式電火花加工（干電火花）是一種新的電火花加工過程中，這是進行氣體的加工中，而不使用液體介質。模具電火花沉沒在干旱條件下第一次嘗試國枝等人。 [一]停止使用石油加工工作中考慮環(huán)境的保護，人類健康和預防火災隱患。他們發(fā)現(xiàn)其他優(yōu)點干死沉電火花如; 1 ）顯著刀具的磨損率低， 2 ）薄白層，降低殘余應力，和3 ）窄放電間隙長度。 國枝等人[ 2 ]發(fā)現(xiàn)，當電火花填補與液體介質，相當大的過程反應應用于工具電極此刻介質擊穿發(fā)生。這是因為泡沫產生的原因是蒸發(fā)和分離介質的液體，并且由于迅速擴大的泡沫是預防的影響的慣性和粘度液體介質，造成極高的泡沫壓力。與此相反，這一過程反應被認為是微乎其微小放電時發(fā)生在一個空白充滿空氣而不是液體。 人們還知道，靜電之間的適用工具電極和工件[ 3 ] [ 4 ]主要是在放電延遲時間在一個開放的電壓應用于它們之間。當放電能量小，上述反應由于擴大泡沫，相比靜電的影響力不能忽視。小原等人[ 4 ]指出，由于水的電力介電常數(shù)為82倍以上的空氣，在傳統(tǒng)的靜電武力線切割機（線切割）使用去離子水為介質液體大于當空氣被用作介質流體。 由于電火花線切割機電極使用的工具和靈活的薄絲，由于上述絲電極是受變形和振動，這一事實促使造成不利的幾何誤差的加工表面等。 [ 5 ]調查的基本特征進行完成切割空氣。他們發(fā)現(xiàn)，干式電火花線切割加工生產出優(yōu)質的直線，但成品表面材料去除率低于常規(guī)電火花線切割機。本研究的目的是闡明干式電火花線切割加工的特點，干式電火花線切割加工中進一步詳細，并提出方法，以改善干切割。 2原理 新的干式電火花線切割加工方法，在目前的工作基本上消除了使用介質的液體。因此，既反應和靜電微乎其微，在使用傳統(tǒng)的電火花線切割機床去離子水，從而大大改善準確性完成切割。此外，干切割是免費的嚴重問題引起的電解腐蝕電流流經電解水過程中遇到的常規(guī)電火花線切割機。 谷村等[ 6 ]提出了一種新的電火花加工過程中使用水霧，不需要別的工作液體，因此可以很容易地與其它工藝加工。他們還指出，霧使非電解加工即使導電水作為工作液。但他們無法找到其他特點，是優(yōu)于傳統(tǒng)的電火花加工，盡管干式電火花加工具有許多優(yōu)點，如極低的刀具磨損率，精度高，范圍較窄的差距，更小的工藝反應，和更小的熱影響。 3實驗方法 平整地面的表面是完成碳鋼或工具鋼，減少了常規(guī)和干床，和材料去除率，平直度，表面粗糙度，波紋度和差距長度進行了比較。與傳統(tǒng)的線切割，水，其電導率適度調整，是乘飛機從上部和下部的噴嘴。與干式電火花線切割機床，沒有水供應和切割是在大氣中。要獲得材料去除率，已刪除的體積除以加工時間。拆除的數(shù)量，可通過集成的產品之間的實際切削深度和美聯(lián)儲距離電極導線的距離沿線的電線從底部到頂部表面的工件。 直線度測量，得到的形象成品表面平行線使用的表面粗糙度測量儀。表面粗糙度測量也是平行線。在這項研究中，注意波紋測量方向垂直線，因為在電火花線切割機床，不利的條紋，在某些情況下產生的平行線所顯示的圖1 （ a ）條。 由于深入的條紋是在相同的命令，表面粗糙度，已經很難評價波紋所造成的劃痕。通常的波紋度測量垂直條紋顯示圖1 （ b ）和表面粗糙度，這是相對組成的高頻成分，是切斷了低通濾波器來提取波紋。然而，由于頻率的表面粗糙度類似于參與波紋，這是從實測資料很難分開的波紋。因此，我們提出了一個新的測量方法波紋圖所示的L （ c ）項。在此方法中，因為個人資料是衡量線沿線傾向于在一個小角8電線軸方向，只有頻率的波紋度降低，而在表面粗糙度不變。這使波紋分開很容易從表面粗糙度使用一個低通濾波器。 圖2顯示了測量波紋表面完成干切割。從剖面測量平行線，結果發(fā)現(xiàn)，直線的表面非常出色。然而，當線的測量傾向于0.5的項目，成為公認的波紋。隨著傾角的增加，頻率參與的形象上升，因為一些條紋交叉線的測量增加?；谶@一結果，我們決定評估波紋從剖面測量 長度的差距被認為是幾乎相等的距離預設立場線一側表面和工件表面后完成切割測量點最接近的頂部或底部表面的工件，由于在這些點振幅線振動幾乎為零。 4比較加工特征與常規(guī)電火花線切割機 4.1直線 從一個平面上預處理研磨，拋光切割與切削深度的5p米重復，直到成為衡量直線不變。工作條件表1所示。圖3顯示了不同的直線之間的傳統(tǒng)和干切割。很顯然，直線是更好地干比常規(guī)電火花線切割機床的條件下使用本實驗中，所有的表面完成了凹。 4.2表面粗糙度 圖4顯示了在上一節(jié)比較表面粗糙度得到同樣的實驗。結果發(fā)現(xiàn)，表面粗糙度好干比常規(guī)電火花線切割機床。這是因為沒有液體介質中的工作差距干電火花線切割機，放電柱擴展容易，增加其直徑更迅速。因此，較低的電流密度放電比傳統(tǒng)的切割產生的凹坑較淺，從而更好的表面粗糙度。 4.3間隙長度 圖5顯示的不同長度的差距。長度或的差距在干切割明顯或多或少零，而且在某些情況下，甚至負。國枝等人[ L ]和吉田等人[ 7 ]報道，干死沉電火花窄長度差距比常規(guī)死沉電火花，因為絕緣強度工作液中的放電間隙常規(guī)電火花加工是遠遠低于一個清潔工作液體在使用前由于碎片微粒漂浮在液體的過程中。干死沉電火花加工，然而，碎片粒子吹離工作差距的氣流是供應到工作的差距通過空間的空心管電極。干切割工作，雖然沒有天然氣供應的放電間隙，碎片粒子不浮動的差距，因為碎片粒子密度明顯高于空氣和粘度的空氣極度低于介質液體。 圖6顯示截面通過中間片的工作，這是角上被淘汰的夾角為15 。表面是完成常規(guī)和干切割。使用的工作條件除外表1電極絲直徑200米， p放電電流為110A是一樣的。清楚的是，由于窄間隙長度刀尖圓弧半徑得到了干切割小于常規(guī)電火花線切割機。此外，由于規(guī)模較小的失真和振動的電線干切割，在切割中可以看出常規(guī)切割而不是在干式電火花線切割機床。 4.4材料去除率 圖7顯示了材料去除率之間的傳統(tǒng)和干切割獲得同樣的條件下的比較，在表1 。干切割材料去除率大大低于常規(guī)電火花線切割機。這是因為由于窄間隙長度的干切割原因不利重復走回頭路的來回線電極頻繁發(fā)生的短路。因此，干式電火花線切割機床，在送絲控制需要更好的頻率響應，常規(guī)電火花線切割機以取得同樣的去除率。吉田等格A1 。 [ 7 ]表明，干死沉電火花材料去除率可改善幾乎相當于常規(guī)死沉的電火花加工利用壓電驅動器用于補充差距控制。 4.5波紋度 圖8顯示簡介成品表面。從剖面測量平行線（ 8 = 0 “ ） ，該直線干切割被發(fā)現(xiàn)優(yōu)于常規(guī)電火花線切割機。從剖面測量方向8 =我” ，但更多的人看到條紋產生在干WEDMed面比傳統(tǒng)WEDMed表面。這是因為送絲輪流來回經常會因短路干切割。 5.1繞線速度 眾所周知，履行地點應是隨機分布的工作表面，以獲得穩(wěn)定的加工狀態(tài)[ 8 ] 。從這個角度來看，干切割過程中所描述的前一節(jié)是不穩(wěn)定的。有人指出，履行地點本地化的線電極和本地化領域的移動工件表面的線在同一速度為繞線速度。由于沒有足夠的冷卻工作差距，由于缺乏工作液和高耐熱性和熱容量小的細導線電極，表面溫度的線呈上升趨勢，導致在一個地方減少的介電擊穿強度。因此，它們是繞線速度的影響。 之前完成的，工件表面的位置，這是預處理研磨，檢測接觸表面的鐵絲網，以及位置線觸及表面被定義為0 。然后鋼絲位置抵消對工件的5個P米這意味著，深度線一側表面先是5個P完成切割，然后開始。圖9顯示的影響，繞線速度對材料去除率和直線的工作條件，本實驗中使用的是列于表2 。繞線速度越高，較高的材料去除率和更好的直線將。本地化的履行地點不承認較高繞線速度，這表明增加的結果清盤速度下降線表面溫度。 5.2空氣壓力 干死沉電火花加工[ 1 ] [ 7 ] ，高壓氣體流量供應到工作的差距通過薄壁管電極冷卻液差距和沖洗出的工件材料的差距。因此，我們研究加工特征時壓縮空氣供應到工作的差距。壓縮空氣乘飛機從上部和下部的噴嘴，它通常用于液體介質提供常規(guī)電火花加工。使用的工作條件是一樣的表2 。該繞線速度250毫米/ s ，這是最高切割機的使用。 圖10顯示的影響，壓縮空氣的壓力的材料去除率和直線。結果發(fā)現(xiàn)，材料去除率較高時，空氣壓力增大。不幸的是，高速氣流惡化直線。圖11顯示的影響，空氣壓力的實際切削深度測量和差距長度。零MPa意味著完成切割的氣氛中進行。由于預置深度線一側表面是5時，這一差距長度可減去5時從實際切削深度。實際切削深度增加而減小，空氣壓力，因為空氣流通，以更高的速度沖擊出的碎片粒子的差距更有效，因此在較短的時間差距。負缺口長度在0.2表明，即使發(fā)生放電之間的鐵絲網和工件，這兩方面都或多或少地觸摸對方。 附加完成