JP3739473B2 - Control device for wire electric discharge machine - Google Patents

Control device for wire electric discharge machine Download PDF

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JP3739473B2
JP3739473B2 JP05452796A JP5452796A JP3739473B2 JP 3739473 B2 JP3739473 B2 JP 3739473B2 JP 05452796 A JP05452796 A JP 05452796A JP 5452796 A JP5452796 A JP 5452796A JP 3739473 B2 JP3739473 B2 JP 3739473B2
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machining
output
wire electrode
wire
workpiece
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JPH09248717A (en
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尚武 毛利
久 山田
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Description

【０００１】
【発明の属する技術分野】
本発明はワイヤ放電加工装置の高精度化に係り、ワイヤ電極の振動を抑制して、加工精度を改善するワイヤ放電加工機の制御装置に関するものである。
【０００２】
【従来の技術】
図６は従来のワイヤ放電加工機の一例を示すものである。図において、１はワイヤ電極、２は被加工物、３は上部および下部でワイヤ電極１を案内する一組のワイヤガイド、４は被加工物２を載置するテーブル、５ａ、５ｂは電極１と被加工物２との相対位置を位置決めするＸ軸およびＹ軸駆動モータ、６はＸ軸およびＹ軸駆動モータ５ａ、５ｂを制御する軸駆動制御装置、７はワイヤ電極１と被加工物２との加工間隙３に放電電流パルスを供給する加工用電源、８は加工用電源７のスイッチング動作を制御する加工用電源制御回路、９は極間における加工電圧を検出する電圧検出回路、１０は軸駆動制御装置６および加工用電源制御回路８に軸移動指令および加工条件パラメータを送出するＮＣ装置、１１はＮＣプログラムである。図７は加工用電源装置の一例を示す図であり、７０１は加工電流を極間に供給するための直流電源、７０２は加工用電源制御回路によりオン、オフ制御されるスイッチング素子、７０３は極間に流れる電流値を制限する制限抵抗器、７０４はコンデンサであり、極間に並列に接続される。
【０００３】
次に動作について説明する。ＮＣ装置１０にはＮＣプログラム１１または操作盤（図示せず）から加工経路情報および加工電気条件パラメータが入力される。入力された加工電気条件パラメータに関しては加工用電源制御回路８に出力される。加工用電源制御回路８はこのパラメータに基づき、所定の電流ピーク、パルス幅、休止時間を持った駆動信号を発生し加工用電源７を制御する。加工用電源７はこの駆動信号によって駆動され、所定の電流パルスが被加工物２の上部および下部でワイヤガイド３により保持されたワイヤ電極１と被加工物２との加工間隙に供給されるとともに、加工間隙に一般には水または水系の加工液が供給されることによって放電加工が行われる。図８は極間波形を示す図であり、図８（ａ）は加工電圧、（ｂ）は加工電流を示しており、図７におけるスイッチ素子７０２がオンした後、放電が開始されるまで加工間隙電圧は（ａ）のように直流電源７０１の電圧Ｅ１まで上昇し、放電開始とともに加工間隙電圧はアーク電位まで低下し、（ｂ）に示したように所定時間ＴＯＮの間スイッチ素子７０２がオンの状態を継続し、加工間隙に直流電源７０１の電圧Ｅ１、制限抵抗器７０３、コンデンサ７０４の定数等で決定される加工電流が供給される。その後にスイッチ素子７０２がオフし、所定時間ＴＯＦＦだけオフ時間が継続され、再びスイッチ素子７０２がオンされる以上の動作を繰り返す。上記のようにワイヤ電極と被加工物間に放電を発生させると同時に、加工経路情報に基づき駆動制御装置６に位置決め指令を出力し、Ｘ軸駆動モータ５ａおよびＹ軸駆動モータ５ｂによりテーブル４の位置決め制御をおこなうことにより所望の形状が加工される。
【０００４】
【発明が解決しようとする課題】
従来の放電加工装置は上記のように構成されており、加工用電極に剛性のないワイヤを使用しているため、加工中のワイヤ電極振動の発生が原因で太鼓形状になったり、加工形状角部での形状誤差の原因となっている。こうした問題に対して特開昭５４−１０９６９８ではワイヤ電極の振動数に合わせて休止時間を設定し、加工屑の排除をよくして加工精度を上げる技術が開示されているが、具体的に振動を抑制する技術についての記述はない。また、特開昭５３−２４６９９、５４−９０６９１、５５−１３７８４０等に高周波振動を与えてワイヤ振動を抑制する技術が開示されているが、振動モードを変化させたり、加工屑の排除の効果を目的としたものである。また、特開昭５４−１２０４９５では実際にワイヤ電極振動を測定する技術について開示されているが、複雑な検出装置が必要となる。
【０００５】
本発明は以上の問題点を解決するためになされたもので、ワイヤ放電加工装置において、安価で、かつワイヤ電極の振動挙動を的確に検出する振動検出装置を実現し、さらに、ワイヤ電極の振動挙動からワイヤ電極の振動を抑制して加工精度の向上を図ることを目的とする。
【０００６】
【課題を解決するための手段】
【０００７】
第１の発明におけるワイヤ放電加工機の制御装置は、ワイヤ状電極の走行を案内支持する複数のガイド間を張力付加状態で走行するワイヤ状電極と所望の形状の加工される被加工物とで形成される加工間隙の状態を検出し、前記加工間隙に供給する加工パルスを制御するワイヤ放電加工機の制御装置において、前記加工間隙の電圧を検出する電圧検出手段と、前記電圧検出手段の出力信号から前記複数のガイド間における前記ワイヤ電極の固有振動に基づいた所定周波数帯域を通過させるバンドパスフィルター（帯域フィルター）と、前記バンドバスフィルターの出力を微分する微分器と、前記微分器の出力を、所定の比較電位と比較する比較器と、を備え、前記比較器の出力に基づいて前記ワイヤ電極が被加工物から離れる際に加工電流の供給を停止するように加工パルスを制御するものである。
【０００９】
【発明の実施の形態】
実施の形態１．
この発明の実施の形態１を図について説明する。図１はこの発明の実施の形態１を説明するためのワイヤ放電加工機を示す接続図である。ワイヤ放電加工機の全体の構成および加工用電源装置については、それぞれ図７および図８に示された従来例と同様であるので説明を省略する。
【００１０】
図１はこの発明の実施例１の制御回路の詳細を示す図である。図において、１０１は接触子、１０２および１０３は分圧抵抗であり、ワイヤ電極の電位を分圧抵抗１０２と１０３の抵抗値の比により所定の電圧値に変換して検出する。１０４はローパスフィルタであり、１０５の可変抵抗器、１０６のコンデンサから構成され、ローパスフィルタ１０４の入力端は分圧抵抗１０２および１０３に接続されている。１０７はハイパスフィルターであり、１０８のコンデンサ、１０９の可変抵抗器から構成され、ハイパスフィルター１０７の入力端はローパスフィルタ１０４の出力端に接続される。ローパスフィルタ１０４およびハイパスフィルタ１０７からバンドパスフィルター１１０が構成され、可変抵抗器１０５および１０９を所定の値に設定してパスバンドを設定する。さらに、１１１はコンパレータ、１１２は図７に示すスイッチング素子７０２のスイッチングを制御するパルス発振器、１１３はインバータ回路であり、コンパレータの入力端の一方はバンドパスフィルタ１１０の出力端と接続され、他方は所定の電位に保持され、さらに出力端はインバータ回路１１３の入力端に接続されている。１１４はＮＡＮＤ回路、１１５はＡＮＤ回路であり、ＮＡＮＤ回路の一方の入力端はインバータ回路１１３の出力、もう一方はパルス発振器の出力端１１２ａに接続されており、出力端１１２ａには加工電流ＯＮ時間ＴＯＮの信号のみが出力される。ＮＡＮＤ回路１１４の出力端はＡＮＤ回路１１５の一方の入力端に接続され、ＡＮＤ回路１１５の一方の入力端はパルス発振器の出力端１１２ｂに接続されており、出力端１１２ｂにはスイッチング素子７０２のスイッチング制御信号が出力され、ＡＮＤ回路１１５の出力端はスイッチング素子に接続されている。
【００１１】
次に、実施の形態１の制御回路の動作について、図を用いて説明する。図２は図１の各部の出力信号の一例を示す図であり、２０１はバンドパスフィルター１１０の入力信号波形、つまり極間電圧波形であり、２０２はバンドパスフィルター１１０の出力波形、２０３はコンパレータ１１１の出力波形、２０４はＴＯＮつまりパルス発振器１１２ａの出力波形、２０５は発振停止信号、２０６はパルス発振器１１２ｂの出力波形、２０７はＡＮＤ回路１１５の出力波形である。
【００１２】
ここで、バンドパスフィルター１１０の出力信号２０２の意味を図３を用いて説明する。図はワイヤ電極１が被加工物を加工する際のワイヤ電極の振動の挙動であり、荒加工、つまり溝を加工する例である。ワイヤ電極の振動は一般には図に示すような１次、２次、３次・・・・といった高次の振動モードの重ねあわせで形成される。さらにワイヤ電極が振動することによって、ワイヤ電極と工作物間の距離がある程度縮まるまで接近する際に放電が開始し、逆にある程度離れた際に放電が終了するといった現象が繰り返されて放電が継続することがわかっている。したがって、ワイヤ電極１が被加工物２に近づくほど放電頻度が高くなり無負荷時間Ｔｄが短くなることで極間電圧は低下し、逆にワイヤ電極１が被加工物２から遠ざかって放電頻度が低くなれば無負荷時間Ｔｄが長くなることで極間電圧は高くなることになる。特に被加工物２がワイヤガイド３の中央にあれば、そのワイヤ電極と工作物の距離は１次の振動モードに最も影響されると考えられる。その１次の振動モードの周波数はワイヤガイド間の距離ｚ、ワイヤ張力Ｔ、ワイヤ電極の材質および線径から決まる線密度ｍから求めることができる固有振動数に近い値であり、２次はその倍、ｎ次はｎ倍となる。１次の固有振動数ｐは式１で与えられる。
【数１】

Figure 0003739473
したがって、上式で求めた１次の固有振動数近傍、かつ、大きくても２次の固有振動数までの周波数域を通過させるバンドパスフィルタを構成するように可変抵抗器１０５、可変抵抗器１０９のパラメータを設定して２次の固有振動数帯域以上を除去することでワイヤ振動波形に近い信号を出力できる。同様にして、ワイヤガイド３と被加工物２の位置関係によりワイヤ電極１の振動検出に最適なモードを選択し、それ以外のモード近傍の周波数帯域以外を除去するようにすればよい。
【００１３】
次に、コンパレータ出力２０３はバンドパスフィルター１１０の出力信号２０２が基準電位Ｖｃより高い場合に”１”が出力される。つまり、ワイヤ電極１と被加工物との相対的な距離に相当する所定のＶｃを決定することで、ワイヤ電極１が被加工物２に所定距離近接したことを検出できる。パルス発振器１１２からは所定のパルスＯＮ時間ＴＯＮが１１２ａから２０４の様に出力されるとＮＡＮＤ回路１１４の出力に２０５のような発振停止信号が出力される。この信号と、２０６に示すパルス発振器１１２ｂの出力波形より、両者のＡＮＤ信号が２０７のように出力される。つまり、ワイヤ電極が所定距離より被加工物に接近している期間はＴＯＮ時間のスイッチング素子７０２は停止するため放電による外力が作用せず、ワイヤ電極の振動振幅は増大しないことになり、ワイヤ電極の振動が効率よく抑制される。
【００１４】
実施の形態２．
この発明の実施の形態２を図について説明する。図４はこの発明の実施の形態２の制御回路の詳細を示す接続図である。図において、接触子１０１、分圧抵抗１０２、１０３、バンドパスフィルタ１１０、パルス発振器１１２は実施例１の図１に示されたものと同様であるので説明を省略する。４０１は微分回路であり、４０２のコンデンサ、４０３の抵抗器、４０４のオペアンプから構成されており、４０５はコンパレータ、４０６はインバータ回路であり、コンパレータの入力端の一方は微分回路４０１の出力端と接続され、他方は所定の電位Ｖｃに保持され、さらに出力端はインバータ回路４０６の入力端に接続されている。４０７はＮＡＮＤ回路、４０８はＡＮＤ回路であり、ＮＡＮＤ回路４０７の一方の入力端はインバータ回路４０６の出力、もう一方はパルス発振器の出力端１１２ａに接続されており、出力端１１２ａには加工電流ＯＮ時間ＴＯＮの信号のみが出力される。ＮＡＮＤ回路４０７の出力端はＡＮＤ回路４０８の一方の入力端に接続され、ＡＮＤ回路４０８の一方の入力端はパルス発振器の出力端１１２ｂに接続されており、出力端１１２ｂにはスイッチング素子７０２のスイッチング制御信号が出力され、ＡＮＤ回路４０８の出力端はスイッチング素子に接続されている。
【００１５】
次にこの制御回路の動作について図を用いて説明する。図５は図４の各部の出力信号の一例を示す図であり、５０１はバンドパスフィルター１１０の入力信号波形、つまり極間電圧波形であり、５０２はバンドパスフィルター１１０の出力波形、５０３は微分回路４０１の出力波形、５０４はコンパレータ４０５の出力波形、５０５はＴＯＮつまりパルス発振器１１２ａの出力波形、５０６は発振停止信号、５０７はパルス発振器１１２ｂの出力波形、５０８はＡＮＤ回路４０８の出力波形である。バンドパスフィルター１０５の出力信号５０２およびパルス発振器１１２ｂの出力信号５０５は実施の形態１における図３と同様であるので説明を省略する。
【００１６】
図５における微分回路４０１では、ハイパスフィルター１０７の出力信号の値が減少する際に＋電位が出力され、逆に出力信号５０２の値が増加する際に−電位が出力される。さらに、コンパレータ４０５の比較電圧を微分回路４０１から出力される負電位と０Ｖの間の所定の負電位に比較電位を設定することによって、ハイパスフィルター１０５の出力信号の値が増加する際に”０”が出力され、それ以外に”１”が出力される。すなわち、コンパレータ４０５の出力信号には、ワイヤ電極１が工作物２に接近する際および停止している際には”１”が出力され、逆にワイヤ電極１が工作物２から離れる際”０”が出力される。その結果、実施の形態１と同様に本実施の形態の制御回路はワイヤ電極１が工作物２から離れる際にＴＯＮ時間のスイッチングを停止するように動作する。したがって、ワイヤ電極１が工作物２から離れる場合に放電が発生しないため、ワイヤ電極１に作用する放電反発力はワイヤ電極の振動を抑制する方向のみ働くこととなり、ワイヤ電極の振動を抑制することができる。
【００１７】
【発明の効果】
【００１９】
本発明によれば、ワイヤ状電極の走行を案内支持する複数のガイド間を張力付加状態で走行するワイヤ状電極と所望の形状の加工される被加工物とで形成される加工間隙の状態を検出し、加工間隙に供給する加工パルスを制御するワイヤ放電加工機の制御装置において、加工間隙の電圧を検出する電圧検出手段と、電圧検出手段の出力信号から複数のガイド間におけるワイヤ電極の固有振動に基づいた所定周波数帯域を通過させるバンドパスフィルター（帯域フィルター）と、バンドバスフィルターの出力を微分する微分器と、微分器の出力を、所定の比較電位と比較する比較器と、を備え、比較器の出力に基づいてワイヤ電極が被加工物から離れる際に加工電流の供給を停止するように加工パルスを制御するので、ワイヤ電極の振幅が所定の大きさ以上になった際に放電電流の供給を停止することにより、ワイヤ電極の振動の増大を抑制することができ、太鼓精度、角部の形状精度等の加工精度を向上させることができる。
【図面の簡単な説明】
【図１】実施の形態１の制御回路を示す接続図である。
【図２】実施の形態１の制御回路の動作を示すタイミングチャートである。
【図３】実施の形態１のワイヤ電極の振動モードを説明する図である。
【図４】実施の形態２の制御回路を示す接続図である。
【図５】実施の形態２の制御回路の動作を示すタイミングチャートである。
【図６】従来例を説明するためのワイヤ放電加工機を示すブロック図である。
【図７】従来の加工用電源装置の一例を示す接続図である。
【図８】従来のワイヤ放電加工機の極間波形を示す図である。
【符号の説明】
１・・・ワイヤ電極、２・・・被加工物、３・・・ワイヤガイド、
７・・・加工用電源、８・・・加工用電源制御回路、
１０１・・・接触子、１０２・・・分圧抵抗、１０３・・・分圧抵抗、
１１０・・・バンドパスフィルター、１１１・・・コンパレータ
４０１・・・微分回路、４０５・・・コンパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an increase in accuracy of a wire electric discharge machining apparatus, and relates to a control apparatus for a wire electric discharge machine that improves the machining accuracy by suppressing vibration of a wire electrode.
[0002]
[Prior art]
FIG. 6 shows an example of a conventional wire electric discharge machine. In the figure, 1 is a wire electrode, 2 is a workpiece, 3 is a set of wire guides for guiding the wire electrode 1 in the upper and lower portions, 4 is a table on which the workpiece 2 is placed, 5a and 5b are electrodes 1 X-axis and Y-axis drive motors for positioning relative positions of the workpiece 2 and the workpiece 2, 6 is an axis drive controller for controlling the X-axis and Y-axis drive motors 5 a and 5 b, and 7 is the wire electrode 1 and the workpiece 2. A machining power supply for supplying a discharge current pulse to the machining gap 3, 8 a machining power control circuit for controlling the switching operation of the machining power supply 7, 9 a voltage detection circuit for detecting a machining voltage between the electrodes, 10 An NC device 11 for sending an axis movement command and machining condition parameters to the shaft drive control device 6 and the machining power control circuit 8 is an NC program. FIG. 7 is a diagram showing an example of a machining power supply device, in which 701 is a DC power supply for supplying machining current between the electrodes, 702 is a switching element that is on / off controlled by a machining power supply control circuit, and 703 is a pole. A limiting resistor 704 for limiting the value of the current flowing between them is a capacitor, which is connected in parallel between the poles.
[0003]
Next, the operation will be described. Machining path information and machining electrical condition parameters are input to the NC device 10 from the NC program 11 or an operation panel (not shown). The input machining electrical condition parameter is output to the machining power control circuit 8. Based on this parameter, the machining power supply control circuit 8 generates a drive signal having a predetermined current peak, pulse width, and pause time, and controls the machining power supply 7. The machining power supply 7 is driven by this drive signal, and a predetermined current pulse is supplied to the machining gap between the wire electrode 1 and the workpiece 2 held by the wire guide 3 above and below the workpiece 2. In general, electric discharge machining is performed by supplying water or an aqueous machining fluid to the machining gap. FIG. 8 is a diagram showing a waveform between electrodes, FIG. 8A shows a machining voltage, FIG. 8B shows a machining current, and machining is performed until the discharge is started after the switch element 702 in FIG. 7 is turned on. The gap voltage rises to the voltage E1 of the DC power supply 701 as shown in (a), and the machining gap voltage falls to the arc potential as discharge starts, and the switch element 702 is turned on for a predetermined time TON as shown in (b). Then, the machining current determined by the voltage E1 of the DC power source 701, the constants of the limiting resistor 703, the capacitor 704, and the like is supplied to the machining gap. After that, the switch element 702 is turned off, the off time is continued for a predetermined time TOFF, and the operation above the switch element 702 is turned on again is repeated. As described above, a discharge is generated between the wire electrode and the workpiece, and at the same time, a positioning command is output to the drive control device 6 based on the machining path information. A desired shape is processed by performing positioning control.
[0004]
[Problems to be solved by the invention]
The conventional electric discharge machining apparatus is configured as described above, and uses a non-rigid wire as the machining electrode. This is the cause of the shape error in the part. In order to deal with such problems, Japanese Patent Laid-Open No. 54-109698 discloses a technique for setting a pause time in accordance with the frequency of the wire electrode to improve the processing accuracy by improving the removal of processing waste. There is no description of the technology that suppresses this. Further, Japanese Patent Application Laid-Open Nos. 53-24699, 54-90691, 55-137840, etc. disclose a technique for suppressing wire vibration by applying high-frequency vibration, but the effect of changing the vibration mode or eliminating machining wastes is disclosed. It is intended. Japanese Patent Laid-Open No. 54-120495 discloses a technique for actually measuring wire electrode vibration, but a complicated detection device is required.
[0005]
The present invention has been made to solve the above-described problems. In the wire electric discharge machining apparatus, an inexpensive vibration detection apparatus that accurately detects the vibration behavior of the wire electrode is realized, and further, the vibration of the wire electrode is realized. The object is to improve the machining accuracy by suppressing the vibration of the wire electrode from the behavior.
[0006]
[Means for Solving the Problems]
[0007]
According to a first aspect of the present invention, there is provided a control device for a wire electric discharge machine comprising: a wire electrode that travels in a tensioned state between a plurality of guides that guide and support the travel of the wire electrode; and a workpiece to be machined in a desired shape. In a control device of a wire electric discharge machine that detects a state of a machining gap to be formed and controls a machining pulse supplied to the machining gap, a voltage detection means for detecting a voltage of the machining gap, and an output of the voltage detection means A band-pass filter (band filter) that passes a predetermined frequency band based on the natural vibration of the wire electrode between the plurality of guides from a signal, a differentiator that differentiates the output of the band-pass filter, and an output of the differentiator and and a comparator for comparing a predetermined comparison voltage, the wire electrode based on the output of the comparator has a machining current when away from the workpiece And controls the machining pulse to stop feeding.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a connection diagram showing a wire electric discharge machine for explaining Embodiment 1 of the present invention. The overall configuration of the wire electric discharge machine and the machining power supply device are the same as those of the conventional example shown in FIGS.
[0010]
FIG. 1 is a diagram showing details of a control circuit according to Embodiment 1 of the present invention. In the figure, reference numeral 101 denotes a contact, and reference numerals 102 and 103 denote voltage dividing resistors, which are detected by converting the potential of the wire electrode into a predetermined voltage value by the ratio of the resistance values of the voltage dividing resistors 102 and 103. Reference numeral 104 denotes a low-pass filter, which includes a variable resistor 105 and a capacitor 106, and an input terminal of the low-pass filter 104 is connected to the voltage dividing resistors 102 and 103. Reference numeral 107 denotes a high-pass filter, which includes a capacitor 108 and a variable resistor 109, and an input terminal of the high-pass filter 107 is connected to an output terminal of the low-pass filter 104. The low pass filter 104 and the high pass filter 107 constitute a band pass filter 110, and the variable resistors 105 and 109 are set to predetermined values to set the pass band. Further, 111 is a comparator, 112 is a pulse oscillator that controls the switching of the switching element 702 shown in FIG. 7, 113 is an inverter circuit, one of the input terminals of the comparator is connected to the output terminal of the bandpass filter 110, and the other is The output terminal is held at a predetermined potential, and the output terminal is connected to the input terminal of the inverter circuit 113. 114 is a NAND circuit, and 115 is an AND circuit. One input terminal of the NAND circuit is connected to the output terminal of the inverter circuit 113, and the other terminal is connected to the output terminal 112a of the pulse oscillator. Only the TON signal is output. The output terminal of the NAND circuit 114 is connected to one input terminal of the AND circuit 115, one input terminal of the AND circuit 115 is connected to the output terminal 112b of the pulse oscillator, and the switching terminal 702 is connected to the output terminal 112b. A control signal is output, and the output terminal of the AND circuit 115 is connected to a switching element.
[0011]
Next, the operation of the control circuit according to the first embodiment will be described with reference to the drawings. 2 is a diagram showing an example of the output signal of each part of FIG. 1, where 201 is an input signal waveform of the bandpass filter 110, that is, an inter-electrode voltage waveform, 202 is an output waveform of the bandpass filter 110, and 203 is a comparator. 111, TON, that is, an output waveform of the pulse oscillator 112a, 205, an oscillation stop signal, 206, an output waveform of the pulse oscillator 112b, and 207, an output waveform of the AND circuit 115.
[0012]
Here, the meaning of the output signal 202 of the band pass filter 110 will be described with reference to FIG. The figure shows the behavior of the vibration of the wire electrode when the wire electrode 1 processes the workpiece, and is an example of roughing, that is, processing a groove. The vibration of the wire electrode is generally formed by superposing higher-order vibration modes such as the first, second, third,. Furthermore, when the wire electrode vibrates, the discharge starts when the distance between the wire electrode and the workpiece approaches until the distance is reduced to some extent, and on the contrary, the discharge ends when the distance is left to some extent. I know you will. Accordingly, the closer the wire electrode 1 is to the workpiece 2, the higher the discharge frequency and the shorter the no-load time Td, so that the voltage between the electrodes decreases, and conversely, the wire electrode 1 moves away from the workpiece 2 and the discharge frequency increases. If it becomes lower, the no-load time Td becomes longer and the voltage between the electrodes becomes higher. In particular, if the workpiece 2 is at the center of the wire guide 3, it is considered that the distance between the wire electrode and the workpiece is most affected by the primary vibration mode. The frequency of the primary vibration mode is a value close to the natural frequency that can be obtained from the line density m determined from the distance z between the wire guides, the wire tension T, the material of the wire electrode, and the wire diameter. The nth order is n times. The primary natural frequency p is given by Equation 1.
[Expression 1]
Figure 0003739473
Therefore, the variable resistor 105 and the variable resistor 109 are configured so as to constitute a band-pass filter that passes the frequency range up to the second-order natural frequency in the vicinity of the first-order natural frequency obtained by the above equation. A signal close to the wire vibration waveform can be output by setting the parameter of and removing the second or higher natural frequency band or more. Similarly, an optimum mode for vibration detection of the wire electrode 1 may be selected based on the positional relationship between the wire guide 3 and the workpiece 2, and other than the frequency bands near the other modes may be removed.
[0013]
Next, the comparator output 203 is “1” when the output signal 202 of the bandpass filter 110 is higher than the reference potential Vc. That is, it is possible to detect that the wire electrode 1 has approached the workpiece 2 by a predetermined distance by determining a predetermined Vc corresponding to the relative distance between the wire electrode 1 and the workpiece. When a predetermined pulse ON time TON is output from the pulse oscillator 112 as indicated by 112a to 204, an oscillation stop signal such as 205 is output to the output of the NAND circuit 114. From this signal and the output waveform of the pulse oscillator 112b shown at 206, the AND signal of both is output as shown at 207. That is, during the period in which the wire electrode is closer to the workpiece than the predetermined distance, the switching element 702 in the TON time is stopped, so that no external force due to the discharge acts and the vibration amplitude of the wire electrode does not increase. Is effectively suppressed.
[0014]
Embodiment 2. FIG.
Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 4 is a connection diagram showing details of the control circuit according to the second embodiment of the present invention. In the figure, the contact 101, the voltage dividing resistors 102 and 103, the band pass filter 110, and the pulse oscillator 112 are the same as those shown in FIG. Reference numeral 401 denotes a differentiation circuit, which includes a capacitor 402, a resistor 403, and an operational amplifier 404. Reference numeral 405 denotes a comparator. Reference numeral 406 denotes an inverter circuit. One input terminal of the comparator is an output terminal of the differentiation circuit 401. The other end is held at a predetermined potential Vc, and the output end is connected to the input end of the inverter circuit 406. Reference numeral 407 denotes a NAND circuit, and reference numeral 408 denotes an AND circuit. One input terminal of the NAND circuit 407 is connected to the output terminal of the inverter circuit 406, and the other terminal is connected to the output terminal 112a of the pulse oscillator. Only the signal of time TON is output. The output terminal of the NAND circuit 407 is connected to one input terminal of the AND circuit 408, one input terminal of the AND circuit 408 is connected to the output terminal 112b of the pulse oscillator, and a switching element 702 is connected to the output terminal 112b. A control signal is output, and the output terminal of the AND circuit 408 is connected to the switching element.
[0015]
Next, the operation of this control circuit will be described with reference to the drawings. FIG. 5 is a diagram showing an example of the output signal of each part of FIG. 4, wherein 501 is an input signal waveform of the bandpass filter 110, that is, an inter-electrode voltage waveform, 502 is an output waveform of the bandpass filter 110, and 503 is a differential. The output waveform of the circuit 401, 504 is the output waveform of the comparator 405, 505 is the output waveform of TON, that is, the pulse oscillator 112a, 506 is the oscillation stop signal, 507 is the output waveform of the pulse oscillator 112b, and 508 is the output waveform of the AND circuit 408. . The output signal 502 of the bandpass filter 105 and the output signal 505 of the pulse oscillator 112b are the same as those in FIG.
[0016]
In the differentiating circuit 401 in FIG. 5, a positive potential is output when the value of the output signal of the high pass filter 107 decreases, and a negative potential is output when the value of the output signal 502 increases. Further, when the comparison voltage of the comparator 405 is set to a predetermined negative potential between the negative potential output from the differentiation circuit 401 and 0 V, the value of the output signal of the high-pass filter 105 is increased to “0”. "Is output and" 1 "is output in addition. That is, the output signal of the comparator 405 is “1” when the wire electrode 1 approaches the workpiece 2 and is stopped, and conversely “0” when the wire electrode 1 leaves the workpiece 2. "Is output. As a result, like the first embodiment, the control circuit of the present embodiment operates so as to stop the switching of the TON time when the wire electrode 1 leaves the workpiece 2. Accordingly, since no discharge is generated when the wire electrode 1 is separated from the workpiece 2, the discharge repulsive force acting on the wire electrode 1 works only in the direction of suppressing the vibration of the wire electrode, thereby suppressing the vibration of the wire electrode. Can do.
[0017]
【The invention's effect】
[0019]
According to the present invention, the state of a machining gap formed by a wire-like electrode that travels in a tensioned state between a plurality of guides that guide and support the travel of the wire-like electrode and a workpiece to be machined in a desired shape. In a control device of a wire electric discharge machine that detects and controls a machining pulse supplied to a machining gap, a voltage detection means for detecting a machining gap voltage, and a wire electrode unique between a plurality of guides from an output signal of the voltage detection means A band-pass filter (band filter) that passes a predetermined frequency band based on vibration, a differentiator that differentiates the output of the band-pass filter, and a comparator that compares the output of the differentiator with a predetermined comparison potential since the wire electrode based on the output of the comparator controls the machining pulse so as to stop supplying the machining current when away from the workpiece, the amplitude of the wire electrode a predetermined By stopping the supply of the discharge current when it becomes more than the size, it is possible to suppress an increase in vibration of the wire electrode, it is possible to improve the processing accuracy of such drums accuracy, shape accuracy of corners.
[Brief description of the drawings]
FIG. 1 is a connection diagram illustrating a control circuit according to a first embodiment.
FIG. 2 is a timing chart showing the operation of the control circuit according to the first embodiment.
FIG. 3 is a diagram illustrating a vibration mode of the wire electrode according to the first embodiment.
FIG. 4 is a connection diagram illustrating a control circuit according to a second embodiment.
FIG. 5 is a timing chart showing the operation of the control circuit according to the second embodiment.
FIG. 6 is a block diagram showing a wire electric discharge machine for explaining a conventional example.
FIG. 7 is a connection diagram illustrating an example of a conventional processing power supply device.
FIG. 8 is a diagram showing a waveform between electrodes of a conventional wire electric discharge machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Wire electrode, 2 ... Workpiece, 3 ... Wire guide,
7 ... Power supply for machining, 8 ... Power supply control circuit for machining,
101 ... Contact, 102 ... Partial resistance, 103 ... Partial resistance,
110: Band pass filter, 111: Comparator 401: Differentiation circuit, 405: Comparator

Claims (1)

ワイヤ状電極の走行を案内支持する複数のガイド間を張力付加状態で走行するワイヤ状電極と所望の形状の加工される被加工物とで形成される加工間隙の状態を検出し、前記加工間隙に供給する加工パルスを制御するワイヤ放電加工機の制御装置において、A state of a machining gap formed by a wire electrode running with tension applied between a plurality of guides for guiding and supporting the running of the wire electrode and a workpiece to be machined in a desired shape is detected, and the machining gap is detected. In the control device of the wire electric discharge machine that controls the machining pulse supplied to
前記加工間隙の電圧を検出する電圧検出手段と、Voltage detecting means for detecting the voltage of the machining gap;
前記電圧検出手段の出力信号から前記複数のガイド間における前記ワイヤ電極の固有振動に基づいた所定周波数帯域を通過させるバンドパスフィルター（帯域フィルター）と、A band pass filter (band filter) that passes a predetermined frequency band based on the natural vibration of the wire electrode between the plurality of guides from the output signal of the voltage detection means;
前記バンドバスフィルターの出力を微分する微分器と、A differentiator for differentiating the output of the band-pass filter;
前記微分器の出力を、所定の比較電位と比較する比較器と、A comparator for comparing the output of the differentiator with a predetermined comparison potential;
を備え、前記比較器の出力に基づいて前記ワイヤ電極が被加工物から離れる際に加工電流の供給を停止するように加工パルスを制御することを特徴とするワイヤ放電加工機の制御装置。And controlling a machining pulse so as to stop the supply of machining current when the wire electrode leaves the workpiece based on the output of the comparator.
JP05452796A 1996-03-12 1996-03-12 Control device for wire electric discharge machine Expired - Lifetime JP3739473B2 (en)

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DE19753812C2 (en) 1997-12-04 2000-05-18 Agie Sa Method and device for electrical discharge machining
EP1004385B1 (en) 1998-05-12 2013-03-13 Mitsubishi Denki Kabushiki Kaisha Method and apparatus for electrodischarge machining
JP4513772B2 (en) * 2006-03-09 2010-07-28 三菱電機株式会社 Wire electrical discharge machine

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