JP4219550B2

JP4219550B2 - Polishing method and polishing apparatus

Info

Publication number: JP4219550B2
Application number: JP2000394464A
Authority: JP
Inventors: 明弘渕上
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2000-12-26
Filing date: 2000-12-26
Publication date: 2009-02-04
Anticipated expiration: 2020-12-26
Also published as: JP2002192462A

Description

【０００１】
【発明の属する技術分野】
この発明は、例えば自由曲面を有する光学素子などの複雑な曲面を有する各種部品やプラスチック成形金型等を高精度に、かつ均一に研磨するの研磨方法及び研磨装置に関するものである。
【０００２】
【従来の技術】
例えば自由曲面を有する光学素子などを作製するプラスチック成形金型等の自由曲面を形成するために、自由曲面を研磨工具により倣わせながら研磨している。この研磨装置は、図１０に示すように、Ｘ−Ｙテーブル２にセットされた被加工物１の加工面に研磨工具３を定圧機構部５により一定の押付け圧力で押し付け、Ｘ−Ｙテーブル２のＸ軸駆動モータ１０とＹ軸駆動モータ１２を駆動して被加工物１をＸ軸方向とＹ軸方向に移動しながら加工面を一定の研磨除去量で研磨する。この研磨工具３を加工面に押し付ける定圧機構部５はエアシリンダ１６とレギュレータ２８により一定の圧力を発生し続ける方式が多く利用されている。
【０００３】
このような研磨加工において、研磨除去量はプレストンの経験則といわれる下記（１）式により得られることが知られている。
【０００４】
【数１】

【０００５】
（１）式において、Ｈ（ｘ）はｘ座標における研磨除去量、ｋは被加工物や研磨工具などによる係数、ｖ（ｘ，ｔ）は加工面と研磨工具の相対速度、ｐ（ｘ，ｔ）は研磨圧力、ｔ１は工具滞留時間を示す。研磨工具回転速度をＶ、被加工物の送り速度をｆｖとすると、加工面と研磨工具の相対速度ｖ＝（Ｖ＋ｆｖ）で表すことができる。
【０００６】
上記プレストンの経験則により研磨除去量を制御するためには、送り速度による滞留時間の制御、もしくは研磨圧力と研磨工具回転数のいずれか、又は全てを制御する必要がある。従来の研磨加工法では研磨圧力と研磨工具回転数を一定に保ち、送り速度を変化させることにより目的の研磨除去量を得る方法が採用されて実用化されている。また、特開平９−３２３２５２号公報に示された曲面研磨方法は、目的の研磨除去量に対して研磨圧力又は研磨工具回転数に重み付けを行い、研磨面の任意の位置で研磨除去量を制御するようにしている。また、研磨加工点の姿勢を制御し、法線方向を常に一定に保つことにより高精度の加工を実現する用にしている。特開平７−６８４５６号公報に示された研磨方法は、同一個所を研磨する研磨回数により研磨除去量を制御するようにしている。
【０００７】
倣い研磨方法では、定圧機構が特定の周波数以上の変動には追従しない特性を利用することにより、細かい誤差成分であるところの面荒さを除去するようにしている。一方、前記従来の倣い研磨方法は、図１１の制御回路図に示すように、研磨除去量指令値に定圧機構部５による研磨圧力をフィードバックして制御出力を得るようにしており、定圧機構部５中のエアシリンダ１６が研磨工具３と共に摺動するため、定圧機構部５の応答特性が研磨結果に影響することが知られている。この従来の研磨方法で使用しているエアシリンダ１６とレギュレータ２８を用いて構成した定圧機構部５に接続された研磨工具３は、図１２に示すように、１Ｈｚ以下の周波数の変動に追従する。例えば送り速度１ｍｍ／ｓｅｃで、図１３（ａ），（ｂ）に示すように、理想面２９に対してうねり３０を持つ被加工物１の加工面を研磨した場合、（ｃ）に示すように、研磨工具３は１ｍｍ以上の波長のうねり３０に追従してしまう。より高精度の加工を行うためには、より長い波長を持つうねり成分を除去する必要がある。しかしながら従来の定圧機構部による研磨圧力がうねり成分に追従してしまい、倣い研磨によりうねり成分を除去することは困難であるという短所があった。
【０００８】
この発明はかかる短所を改善し、平均的な研磨除去量を一定に保ちつつ、特定の周波数帯域のうねり成分を除去し、理想面への追従などを精度良く行い、精密な研磨を実現することができる研磨方法及び研磨装置を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
この発明に係る研磨方法は、研磨工具を回転させて加工面に押し当て、被加工物を研磨方向に送ることによって研磨を行う研磨方法において、測定した研磨圧力と被加工物の送り速度とにより研磨除去量を算出し、算出した研磨除去量により研磨除去量指令値を補正し、補正した研磨除去量指令値をフィードバックして研磨圧力目標値を補正し、補正した研磨圧力目標値に測定した研磨圧力をフィードバックして送り速度の変化に対して研磨量が一定になるように制御することを特徴とする。
【００１１】
また、被加工物の送り速度を、理想面に対する加工面のうねりの波長に応じて変化させ、送り速度の変化に対して研磨量が一定になるように研磨圧力と研磨工具回転数のいづれか又は両方を制御することが望ましい。
【００１２】
さらに、被加工物の加工面の状態を測定し、加工面の状態に対応して送り速度を変化させると良い。
【００１４】
この発明に係る研磨装置は、被加工物をセットして被加工物の送り速度を可変するＸ−Ｙテーブルを駆動するテーブル駆動部と、研磨工具を装着して回転する研磨工具駆動部と、研磨工具駆動部に装着した研磨工具を被加工物に一定の研磨圧力で押し付ける定圧機構部及び制御部とを有する研磨装置において、上記制御部は、上記定圧機構部で測定した研磨圧力と上記テーブル駆動部から出力する被加工物の送り速度とにより研磨除去量を算出し、算出した研磨除去量により研磨除去量指令値を補正し、補正した研磨除去量指令値をフィードバックして研磨圧力目標値を補正し、補正した研磨圧力目標値に上記定圧機構部で測定した研磨圧力をフィードバックして送り速度の変化に対して研磨量が一定になるように制御することを特徴とする。
【００１６】
【発明の実施の形態】
この発明の研磨装置は、被加工物をセットして被加工物の送り速度を可変するＸ−Ｙテーブルと、研磨工具を装着して回転する研磨工具駆動部と、研磨工具駆動部に装着した研磨工具を被加工物に一定の研磨圧力で押し付ける定圧機構部とを有する。Ｘ−Ｙテーブルはテーブル制御装置により制御され、研磨工具駆動部は研磨工具回転制御計算機により制御されて研磨工具の回転数を可変し、定圧機構部は研磨圧力制御計算機により制御されて研磨工具に加える研磨圧力を可変する。このテーブル制御装置と研磨工具回転数制御計算機及び研磨圧力制御計算機は研磨手順を記憶した制御用計算機に接続されている。
【００１７】
この研磨装置で精密な研磨をするときに問題となる定圧機構部と研磨工具の応答性は、研磨工具が接触する研磨加工点の変動に影響される。また、研磨加工点の変動の周波数は、変動量と送り速度によって制御することができる。そこで制御用計算機は、被加工物の送り速度を研磨面の任意の研磨加工点で変化させ、かつ研磨圧力を、送り速度の変動に対して研磨量を一定に保つ条件になるよう制御する。
【００１８】
【実施例】
図１はこの発明の一実施例の研磨装置の構成図である。図に示すように、研磨装置は、被加工物１をセットするＸ−Ｙテーブル２と、研磨工具３を装着する研磨工具駆動部４と、研磨工具駆動部４に装着した研磨工具３を被加工物１に一定の押付け圧力で押し付ける定圧機構部５と、Ｘ−Ｙテーブル２の駆動を制御するテーブル制御装置６と、研磨工具３の回転数を制御する研磨工具回転制御計算機７及び定圧機構部５の駆動を制御する研磨圧力制御計算機８を有する。Ｘ−ＹテーブルのＸ軸テーブル９にはエンコーダーを有するＸ軸駆動モータ１０を有し、Ｙ軸テーブル１１にはエンコーダーを有するＹ軸駆動モータ１２を有する。研磨工具駆動部４は、図２のブロック図に示すように、研磨工具回転制御計算機７に接続されたモータアンプ１３と駆動モータ１４を有する。定圧機構部５は電圧レギュレータ１５に接続されたエアシリンダ１６と、エアシリンダ１６のピストンロッドに取り付けられ研磨工具駆動部４に連結された力センサ１７を有する。テーブル制御装置６と研磨工具回転数制御計算機７及び研磨圧力制御計算機８は、図２のブロック図に示すように、研磨手順を記憶した制御用計算機１８に接続されている。
【００１９】
この研磨装置でＸ−Ｙテーブル２にセットされた被加工物１の加工面を研磨するとき、定圧機構部５の電圧レギュレータ１５によって発生するエア圧をエアシリンダ１６に加え、エアシリンダ１６により研磨工具３を被加工物の加工面に押し付けながら、研磨工具駆動部４のモーターアンプ１３とモーター１４によって研磨工具３を回転させて研磨する。この研磨工具３を加工面に押し付ける研磨圧力を発生する電圧レギュレータ１５は研磨工具駆動部４に連結された力センサ１７の読取値を指令値に追従させるようフィードバック制御されている。研磨工具３を回転させる研磨工具駆動部４は研磨工具回転数制御計算機７によって制御され、モーターアンプ１８への電圧入力によって研磨工具３の回転数がオープンループ制御される。また、被加工物１の送り速度、すなわちＸ−Ｙテーブル２の移動量は、研磨手順を記憶した制御計算機１８からの出力によりテーブル制御装置６で制御される。
【００２０】
上記のように構成した研磨装置で被加工物１の加工面を精密に研磨する場合、定圧機構部５と研磨工具３の応答性は、研磨工具３が接触する研磨加工点の変動に影響される。また、研磨加工点の変動の周波数は、研磨加工点の変動量と送り速度によって制御することができる。そこで研磨装置で被加工物１を研磨するときに、被加工物１の送り速度を加工面の任意の研磨加工点で変化させる。この被加工物１の送り速度のみを変動させた場合、研磨除去量にむらが生じる。この送り速度の変動量をプレストンの経験則にしたがい補正し、研磨量を一定に保つように、研磨圧力と研磨工具回転数のいずれか又は全てを重み付けて制御する。
ることにより、目的の研磨除去量を得る。
【００２１】
例えば被加工物１の送り速度を加工面の任意の研磨加工点で変化させながら、図３の制御回路図に示すように、研磨圧力の指示出力は、力センサ１７の読取値に加えて送り速度の計測値をフィードバックし、プレストンの経験則に従って目標の研磨除去量を得るようダブルループ制御する。この送り速度の計測値と研磨圧力の径時変化を図４に示す。図４に示すように、被加工物１に加えられる研磨圧力の応答特性を大幅に改善することができる。
【００２２】
また、送り速度と研磨圧力及び研磨工具回転数をそれぞれ独立したテーブル制御装置６と研磨圧力制御計算機８及び研磨工具回転数制御計算機７で制御することにより、信頼性のある制御を高速に行うことができる。さらに、研磨手順を記憶した制御計算機１８から送り速度と研磨圧力及び研磨工具回転数の指令値を出力し、テーブル制御装置６と研磨圧力制御計算機８及び研磨工具回転数制御計算機７に指示することにより、制御出力の同期を確実にとることができる。
【００２３】
また、図５（ｂ）に示すように、理想面に対してうねり２０を持つ加工面を加工するときに、送り速度を、（ａ）に示すように、うねり２０の波長が長い部分では速くし、うねり２０の波長が短い部分では遅くなるように制御し、この送り速度に対して一定の条件を満たすように研磨圧力若しくは研磨工具回転数を制御する。このように理想面に対する加工面のうねり２０の波長に応じて送り速度を制御することにより、図５（ｃ）に示すように、研磨工具３と定圧機構部５が倣い加工において追従しないよう研磨工具３のうねり成分２１の周波数を制御することができ、被加工物１の加工面の傾きや曲率あるいはうねりの形状に適した送り速度で研磨加工を行えるとともに研磨除去量を任意に制御することができる。
【００２４】
このように理想面に対する加工面のうねり２０の波長に応じて送り速度を制御するときに、図６に示すように、非接触表面形状センサ２２で研磨加工前の被加工物１の加工面の状態をインプロセスで測定して制御計算機１８に入力する。制御計算機１８は測定された被加工物１の加工面と理想面との誤差を計算して除去すべきうねりの波長を推定し、各研磨加工点における送り速度を計画する。また、理想面よりの誤差から各研磨加工点における研磨除去量を計画する。この計画された送り速度にしたがってＸ−Ｙテーブル２の送り量を制御して被加工物１を送りながら、計画された研磨除去量を得るように研磨圧力を制御することにより、被加工物１の加工面のうねりの形状に適した送り速度で研磨加工を行うことができる。
【００２５】
また、被加工物１の加工面が、図７（ａ）に示すように凸面２３になっている場合、凸面２３の頂点では、研磨工具３の摺動方向が反転するため、従来の倣い研磨方法では凸面２３の頂点近傍で圧力特性が変化し、定圧で研磨できずに加工面を損ねてしまう。そこで図７（ｂ）に示すように、凸面２３の頂点近傍では送り速度を低速にし、（ｃ）に示すように、研磨圧力を送り速度に応じて高くして研磨することにより、理想面に対して研磨工具３を確実に追従させることができる。
【００２６】
このように研磨加工点の位置に対応して送り速度を変化させることにより、研磨工具３と定圧機構部５の応答特性に適した値に調整することができる。さらに、送り速度の変動に対して研磨圧力及び研磨工具回転数のいずれか又は全てをプレストンの経験則にしたがって重みづけすることにより、研磨除去量を一定に保つことができる。
【００２７】
上記実施例は、送り速度と研磨圧力及び研磨工具回転数をそれぞれ独立したテーブル制御装置６と研磨圧力制御計算機８及び研磨工具回転数制御計算機７で制御する場合について説明したが、図８の構成図に示すように、Ｘ−Ｙテーブル２のＸ軸モータ１０とＹ軸モータ１２と、定圧機構部５のモーターアンプ１３及び研磨工具駆動部４をアナログＩ／Ｏユニット２４を介して制御計算機１８に接続し、Ｘ−Ｙテーブル２と定圧機構部５及び研磨工具駆動部４を制御計算機１８に記憶されたソフトウェアによってフィードバック演算処理して、送り速度と研磨圧力及び研磨工具回転数を制御するようにしても良い。このように１台の制御計算機１８で送り速度と研磨圧力及び研磨工具回転数を制御することにより、容易に同期をとることができる。
【００２８】
上記実施例はＸ−Ｙテーブル２と定圧機構部５及び研磨工具駆動部４を制御計算機１８に接続するためにアナログＩ／Ｏユニット２４を設けた場合について説明したが、図９の構成図に示すように、制御計算機１８にモーションコントロールボード２５とアナログ入出力ボード２６及びデジタル信号処理ボード２７を組み込む。そしてモーションコントロールボード２５でＸ−Ｙテーブル２を駆動するＸ軸駆動モータ１０とＹ軸駆動モータ１２を制御し、デジタル信号処理ボード２７で定圧機構部５の電圧レギュレータ１５への出力と力センサ１７の入力値をフィードバック演算処理し、アナログ入出力ボード２６により研磨工具回転数の指示値を出力するようにしても良い。このようにして各入出力を制御計算機１８に記憶されたソフトウェアから指示若しくは参照することができ、同期をとった制御が容易に実現することができる。
【００２９】
上記各実施例は被加工物１の送り速度の変化に応じて研磨圧力を可変した場合について説明したが、被加工物１の送り速度の変化に応じて研磨圧力と研磨工具回転数のいづれか又は両方を可変するようにしても良い。
【００３０】
【発明の効果】
この発明は以上説明したように、測定した研磨圧力と被加工物の送り速度とにより研磨除去量を算出し、算出した研磨除去量により研磨除去量指令値を補正し、補正した研磨除去量指令値をフィードバックして研磨圧力目標値を補正し、補正した研磨圧力目標値に測定した研磨圧力をフィードバックして送り速度の変化に対して研磨量が一定になるように制御するから、被加工物に加えられる研磨圧力の応答特性を大幅に改善することができ、加工面の傾きや曲率やうねりの形状に適した送り速度で研磨加工を行えるとともに、研磨除去量を任意に制御することができる。
【００３２】
さらに、被加工物の送り速度を、理想面に対する加工面のうねりの波長に応じて変化させ、送り速度の変化に対して研磨量が一定になるように研磨圧力と研磨工具回転数のいづれか又は両方を制御することにより、研磨工具と定圧機構部が倣い加工において追従しないように、うねりの周波数を制御でき研磨精度を向上させることができる。
【００３３】
また、加工物の加工面の状態を測定し、加工面の状態に対応して送り速度を変化させることにより、事前のプログラミングの手間を軽減することができるとともに、研磨精度を向上させることができる。
【図面の簡単な説明】
【図１】この発明の実施例の構成図である。
【図２】上記実施例の制御部の構成を示すブロック図である。
【図３】上記実施例の制御回路図である。
【図４】上記実施例における送り速度と研磨圧力の変動特性図である。
【図５】うねり成分に対する送り速度の変化特性図である。
【図６】加工面のうねり成分の測定を示す配置図である。
【図７】凸面からなる加工面を研磨するときの送り速度と研磨圧力の変化特性図である。
【図８】第２の実施例の構成図である。
【図９】第３の実施例の構成図である。
【図１０】従来例の構成図である。
【図１１】従来例の制御回路図である。
【図１２】従来例の研磨工具の周波数応答特性図である。
【図１３】従来例でうねりを有する加工面を研磨するときの状態を示す説明図である。
【符号の説明】
１；被加工物、２；Ｘ−Ｙテーブル、３；研磨工具、４；研磨工具駆動部、
５；定圧機構部、６；テーブル制御装置、７；研磨工具回転制御計算機、
８；研磨圧力制御計算機、９；Ｘ軸テーブル、１０；Ｘ軸駆動モータ、
１１；Ｙ軸テーブル、１２；Ｙ軸駆動モータ、１３；モータアンプ、
１４；駆動モータ、１５；電圧レギュレータ、１６；エアシリンダ、
１７；力センサ、１８；制御用計算機。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing method and a polishing apparatus for polishing various parts having a complicated curved surface, such as an optical element having a free curved surface, a plastic mold, and the like with high accuracy and uniformity.
[0002]
[Prior art]
For example, in order to form a free-form surface such as a plastic mold for producing an optical element having a free-form surface, the free-form surface is polished while following the polishing tool. As shown in FIG. 10, the polishing apparatus presses the polishing tool 3 against the processing surface of the workpiece 1 set on the XY table 2 with a constant pressing pressure by the constant pressure mechanism unit 5. The X-axis drive motor 10 and the Y-axis drive motor 12 are driven to move the workpiece 1 in the X-axis direction and the Y-axis direction, and the processed surface is polished with a constant polishing removal amount. As the constant pressure mechanism 5 that presses the polishing tool 3 against the processing surface, a method of continuously generating a constant pressure by the air cylinder 16 and the regulator 28 is often used.
[0003]
In such a polishing process, it is known that the polishing removal amount can be obtained by the following equation (1), which is called Preston's rule of thumb.
[0004]
[Expression 1]

[0005]
In equation (1), H (x) is the amount of polishing removal at the x coordinate, k is a coefficient depending on the workpiece or polishing tool, v (x, t) is the relative speed between the processing surface and the polishing tool, and p (x, t) shows the polishing pressure, and t1 shows the tool residence time. When the polishing tool rotation speed is V and the workpiece feed speed is fv, it can be expressed as a relative speed v = (V + fv) between the processing surface and the polishing tool.
[0006]
In order to control the polishing removal amount based on the above-mentioned Preston rule of thumb, it is necessary to control the dwell time based on the feed rate, or either or all of the polishing pressure and the polishing tool rotation speed. In the conventional polishing method, a method of obtaining a target polishing removal amount by keeping the polishing pressure and the number of revolutions of the polishing tool constant and changing the feed rate is put into practical use. Also, the curved surface polishing method disclosed in Japanese Patent Application Laid-Open No. 9-323252 weights the polishing pressure or the number of revolutions of the polishing tool with respect to the target polishing removal amount, and controls the polishing removal amount at an arbitrary position on the polishing surface. Like to do. In addition, the position of the polishing point is controlled, and the normal direction is always kept constant to achieve high-precision machining. In the polishing method disclosed in Japanese Patent Application Laid-Open No. 7-68456, the removal amount of polishing is controlled by the number of polishings for polishing the same portion.
[0007]
In the profile polishing method, the surface roughness, which is a fine error component, is removed by utilizing the characteristic that the constant pressure mechanism does not follow fluctuations of a specific frequency or higher. On the other hand, in the conventional copying polishing method, as shown in the control circuit diagram of FIG. 11, the polishing pressure from the constant pressure mechanism unit 5 is fed back to the polishing removal amount command value to obtain a control output. It is known that the response characteristic of the constant pressure mechanism unit 5 affects the polishing result because the air cylinder 16 in FIG. As shown in FIG. 12, the polishing tool 3 connected to the constant pressure mechanism 5 configured by using the air cylinder 16 and the regulator 28 used in this conventional polishing method follows a frequency fluctuation of 1 Hz or less. . For example, when the processing surface of the workpiece 1 having the undulation 30 with respect to the ideal surface 29 is polished at a feed rate of 1 mm / sec as shown in FIGS. 13A and 13B, as shown in FIG. In addition, the polishing tool 3 follows the undulation 30 having a wavelength of 1 mm or more. In order to perform processing with higher accuracy, it is necessary to remove a swell component having a longer wavelength. However, there is a disadvantage that the polishing pressure by the conventional constant pressure mechanism portion follows the waviness component, and it is difficult to remove the waviness component by copying polishing.
[0008]
The present invention improves such disadvantages, removes waviness components in a specific frequency band while keeping the average polishing removal amount constant, and accurately follows the ideal surface to achieve precise polishing. It is an object of the present invention to provide a polishing method and a polishing apparatus capable of performing the above.
[0009]
[Means for Solving the Problems]
The polishing method according to the present invention is a polishing method in which polishing is performed by rotating a polishing tool and pressing it against a processing surface, and feeding the workpiece in the polishing direction. The polishing method is based on the measured polishing pressure and the workpiece feed rate. The polishing removal amount was calculated, the polishing removal amount command value was corrected by the calculated polishing removal amount, the corrected polishing removal amount command value was fed back to correct the polishing pressure target value, and the corrected polishing pressure target value was measured. The polishing pressure is fed back to control the polishing amount to be constant with respect to the change in feed rate.
[0011]
Further, the feed speed of the workpiece is changed according to the wavelength of the waviness of the processed surface with respect to the ideal surface, and either the polishing pressure or the polishing tool rotational speed is set so that the polishing amount becomes constant with respect to the change of the feed speed, or It is desirable to control both.
[0012]
Furthermore, it is preferable to measure the state of the processed surface of the workpiece and change the feed rate in accordance with the state of the processed surface.
[0014]
A polishing apparatus according to the present invention includes a table driving unit that drives an XY table that sets a workpiece and varies a feed speed of the workpiece, a polishing tool driving unit that rotates by mounting a polishing tool, In a polishing apparatus having a constant pressure mechanism unit and a control unit for pressing a polishing tool mounted on a polishing tool driving unit against a workpiece with a constant polishing pressure, the control unit includes the polishing pressure measured by the constant pressure mechanism unit and the table. The polishing removal amount is calculated based on the workpiece feed rate output from the drive unit, the polishing removal amount command value is corrected by the calculated polishing removal amount, and the corrected polishing removal amount command value is fed back to obtain the polishing pressure target value. The polishing pressure measured by the constant pressure mechanism unit is fed back to the corrected polishing pressure target value, and the polishing amount is controlled to be constant with respect to the change in the feed rate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The polishing apparatus according to the present invention is mounted on an XY table that sets a workpiece and varies the feed rate of the workpiece, an abrasive tool driving unit that rotates by mounting an abrasive tool, and an abrasive tool driving unit. A constant pressure mechanism that presses the polishing tool against the workpiece with a constant polishing pressure. The XY table is controlled by a table controller, the polishing tool drive unit is controlled by a polishing tool rotation control computer to vary the rotation speed of the polishing tool, and the constant pressure mechanism unit is controlled by the polishing pressure control computer to be used as a polishing tool. The polishing pressure to be applied is varied. The table control device, the polishing tool rotation speed control computer, and the polishing pressure control computer are connected to a control computer that stores a polishing procedure.
[0017]
The responsiveness between the constant pressure mechanism and the polishing tool, which is a problem when performing precise polishing with this polishing apparatus, is affected by fluctuations in the polishing processing point where the polishing tool comes into contact. Further, the frequency of fluctuation of the polishing processing point can be controlled by the fluctuation amount and the feed rate. Therefore, the control computer changes the feed speed of the workpiece at any polishing point on the polishing surface, and controls the polishing pressure so that the polishing amount is kept constant against fluctuations in the feed speed.
[0018]
【Example】
FIG. 1 is a block diagram of a polishing apparatus according to an embodiment of the present invention. As shown in the figure, the polishing apparatus receives an XY table 2 for setting a workpiece 1, a polishing tool driving unit 4 for mounting a polishing tool 3, and a polishing tool 3 mounted on the polishing tool driving unit 4. A constant pressure mechanism 5 that presses against the workpiece 1 with a constant pressing pressure, a table control device 6 that controls the drive of the XY table 2, a polishing tool rotation control computer 7 that controls the number of rotations of the polishing tool 3, and a constant pressure mechanism A polishing pressure control computer 8 that controls the driving of the unit 5 is included. The X-axis table 9 of the XY table has an X-axis drive motor 10 having an encoder, and the Y-axis table 11 has a Y-axis drive motor 12 having an encoder. As shown in the block diagram of FIG. 2, the polishing tool drive unit 4 includes a motor amplifier 13 and a drive motor 14 connected to the polishing tool rotation control computer 7. The constant pressure mechanism 5 includes an air cylinder 16 connected to the voltage regulator 15 and a force sensor 17 attached to the piston rod of the air cylinder 16 and connected to the polishing tool drive unit 4. As shown in the block diagram of FIG. 2, the table controller 6, the polishing tool rotation speed control computer 7, and the polishing pressure control computer 8 are connected to a control computer 18 that stores a polishing procedure.
[0019]
When the processed surface of the workpiece 1 set on the XY table 2 is polished by this polishing apparatus, the air pressure generated by the voltage regulator 15 of the constant pressure mechanism 5 is applied to the air cylinder 16 and is polished by the air cylinder 16. Polishing is performed by rotating the polishing tool 3 by the motor amplifier 13 and the motor 14 of the polishing tool driving unit 4 while pressing the tool 3 against the processing surface of the workpiece. The voltage regulator 15 that generates a polishing pressure that presses the polishing tool 3 against the processing surface is feedback-controlled so that the reading value of the force sensor 17 connected to the polishing tool driving unit 4 follows the command value. The polishing tool drive unit 4 that rotates the polishing tool 3 is controlled by a polishing tool rotation speed control computer 7, and the rotation speed of the polishing tool 3 is controlled in an open loop by voltage input to the motor amplifier 18. Further, the feed speed of the workpiece 1, that is, the movement amount of the XY table 2 is controlled by the table control device 6 by the output from the control computer 18 storing the polishing procedure.
[0020]
When the processing surface of the workpiece 1 is precisely polished with the polishing apparatus configured as described above, the responsiveness of the constant pressure mechanism unit 5 and the polishing tool 3 is affected by fluctuations in the polishing processing point where the polishing tool 3 contacts. The Further, the frequency of fluctuation of the polishing process point can be controlled by the fluctuation amount of the polishing process point and the feed rate. Therefore, when the workpiece 1 is polished by the polishing apparatus, the feed speed of the workpiece 1 is changed at any polishing point on the processing surface. When only the feed speed of the workpiece 1 is changed, unevenness in the amount of polishing removal occurs. The amount of fluctuation of the feed rate is corrected according to Preston's rule of thumb, and control is performed by weighting either or all of the polishing pressure and the polishing tool rotational speed so as to keep the polishing amount constant.
As a result, the desired polishing removal amount is obtained.
[0021]
For example, as shown in the control circuit diagram of FIG. 3, while the feed speed of the workpiece 1 is changed at an arbitrary polishing processing point on the processing surface, the polishing pressure instruction output is sent in addition to the reading value of the force sensor 17. The measured value of the speed is fed back, and the double loop control is performed so as to obtain the target polishing removal amount according to Preston's rule of thumb. FIG. 4 shows the measured value of the feed rate and the change in polishing pressure with time. As shown in FIG. 4, the response characteristic of the polishing pressure applied to the workpiece 1 can be greatly improved.
[0022]
Also, reliable control can be performed at high speed by controlling the feed speed, polishing pressure, and polishing tool rotation speed by the independent table controller 6, polishing pressure control computer 8, and polishing tool rotation speed control computer 7, respectively. Can do. Further, a command value of the feed speed, polishing pressure, and polishing tool rotation speed is output from the control computer 18 that stores the polishing procedure, and instructions are given to the table control device 6, the polishing pressure control calculator 8, and the polishing tool rotation speed control computer 7. Thus, the control output can be reliably synchronized.
[0023]
Further, as shown in FIG. 5 (b), when machining a machined surface having an undulation 20 with respect to the ideal surface, the feed rate is increased at a portion where the wavelength of the undulation 20 is long as shown in (a). Then, control is performed so that the undulation 20 has a shorter wavelength, and the polishing pressure or the number of rotations of the polishing tool is controlled so as to satisfy a certain condition with respect to the feed speed. By controlling the feed speed according to the wavelength of the waviness 20 of the processed surface with respect to the ideal surface in this way, as shown in FIG. 5C, the polishing tool 3 and the constant pressure mechanism 5 are polished so as not to follow in the copying process. The frequency of the undulation component 21 of the tool 3 can be controlled, the polishing process can be performed at a feed rate suitable for the inclination and curvature of the processed surface of the workpiece 1 or the shape of the undulation, and the polishing removal amount can be arbitrarily controlled. Can do.
[0024]
In this way, when the feed rate is controlled according to the wavelength of the undulation 20 of the processed surface with respect to the ideal surface, as shown in FIG. 6, the processed surface of the workpiece 1 before polishing is processed by the non-contact surface shape sensor 22. The state is measured in-process and input to the control computer 18. The control computer 18 calculates the error between the measured processed surface of the workpiece 1 and the ideal surface, estimates the wave length of the waviness to be removed, and plans the feed rate at each polishing processing point. Also, the amount of polishing removal at each polishing processing point is planned from the error from the ideal surface. The workpiece 1 is controlled by controlling the polishing pressure so as to obtain the planned polishing removal amount while feeding the workpiece 1 by controlling the feeding amount of the XY table 2 in accordance with the planned feeding speed. Polishing can be performed at a feed rate suitable for the shape of the waviness of the processed surface.
[0025]
Further, when the processed surface of the workpiece 1 is a convex surface 23 as shown in FIG. 7A, the sliding direction of the polishing tool 3 is reversed at the apex of the convex surface 23, so that the conventional profile polishing is performed. In the method, pressure characteristics change near the apex of the convex surface 23, and polishing cannot be performed at a constant pressure, and the processed surface is damaged. Therefore, as shown in FIG. 7B, the feed rate is reduced near the apex of the convex surface 23, and the polishing pressure is increased according to the feed rate as shown in FIG. On the other hand, the polishing tool 3 can be surely followed.
[0026]
In this way, by changing the feed rate corresponding to the position of the polishing processing point, it is possible to adjust to a value suitable for the response characteristics of the polishing tool 3 and the constant pressure mechanism unit 5. Further, the weight of polishing removal can be kept constant by weighting any or all of the polishing pressure and the number of rotations of the polishing tool according to Preston's rule of thumb with respect to fluctuations in the feed rate.
[0027]
In the above embodiment, the case where the feed speed, the polishing pressure, and the polishing tool rotation speed are controlled by the independent table control device 6, the polishing pressure control computer 8, and the polishing tool rotation speed control computer 7 has been described. As shown in the figure, the X-axis motor 10 and the Y-axis motor 12 of the XY table 2, the motor amplifier 13 of the constant pressure mechanism unit 5, and the polishing tool drive unit 4 are controlled via an analog I / O unit 24. The XY table 2, the constant pressure mechanism unit 5 and the polishing tool driving unit 4 are subjected to feedback calculation processing by software stored in the control computer 18 so as to control the feed speed, polishing pressure and polishing tool rotation speed. Anyway. Thus, by controlling the feed speed, the polishing pressure, and the number of rotations of the polishing tool with one control computer 18, synchronization can be easily achieved.
[0028]
In the above embodiment, the case where the analog I / O unit 24 is provided to connect the XY table 2, the constant pressure mechanism unit 5 and the polishing tool drive unit 4 to the control computer 18 has been described. As shown, a motion control board 25, an analog input / output board 26, and a digital signal processing board 27 are incorporated in the control computer 18. The motion control board 25 controls the X-axis drive motor 10 and the Y-axis drive motor 12 that drive the XY table 2, and the digital signal processing board 27 outputs to the voltage regulator 15 of the constant pressure mechanism 5 and the force sensor 17. May be subjected to feedback calculation processing, and the analog input / output board 26 may output an instruction value for the number of rotations of the polishing tool. In this way, each input / output can be instructed or referred to from the software stored in the control computer 18, and the synchronized control can be easily realized.
[0029]
In each of the above-described embodiments, the case where the polishing pressure is varied in accordance with the change in the feed speed of the workpiece 1 has been described. However, either the polishing pressure or the polishing tool rotational speed is determined in accordance with the change in the feed speed of the workpiece 1 or Both may be variable.
[0030]
【The invention's effect】
As described above, according to the present invention, the polishing removal amount is calculated based on the measured polishing pressure and the workpiece feed rate, the polishing removal amount command value is corrected based on the calculated polishing removal amount, and the corrected polishing removal amount command is corrected. The value is fed back to correct the polishing pressure target value, and the measured polishing pressure is fed back to the corrected polishing pressure target value to control the polishing amount to be constant with changes in the feed rate. The response characteristics of the polishing pressure applied to the material can be greatly improved , the polishing process can be performed at a feed rate suitable for the inclination, curvature and waviness of the processed surface, and the amount of polishing removal can be controlled arbitrarily. .
[0032]
Furthermore, the feed speed of the workpiece is changed according to the wavelength of the waviness of the processed surface with respect to the ideal surface, and either the polishing pressure or the polishing tool rotational speed is set so that the polishing amount becomes constant with respect to the change of the feed speed, or By controlling both, the waviness frequency can be controlled and the polishing accuracy can be improved so that the polishing tool and the constant pressure mechanism do not follow in the copying process.
[0033]
In addition, by measuring the state of the processed surface of the workpiece and changing the feed rate according to the state of the processed surface, it is possible to reduce the effort of prior programming and improve the polishing accuracy. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a control unit according to the embodiment.
FIG. 3 is a control circuit diagram of the embodiment.
FIG. 4 is a fluctuation characteristic diagram of a feed rate and a polishing pressure in the embodiment.
FIG. 5 is a change characteristic diagram of a feed rate with respect to a swell component.
FIG. 6 is a layout view showing measurement of a waviness component of a processed surface.
FIG. 7 is a change characteristic diagram of a feed rate and a polishing pressure when a processed surface including a convex surface is polished.
FIG. 8 is a configuration diagram of a second embodiment.
FIG. 9 is a configuration diagram of a third embodiment.
FIG. 10 is a configuration diagram of a conventional example.
FIG. 11 is a control circuit diagram of a conventional example.
FIG. 12 is a frequency response characteristic diagram of a conventional polishing tool.
FIG. 13 is an explanatory view showing a state when a processed surface having waviness is polished in a conventional example.
[Explanation of symbols]
1; work piece, 2; XY table, 3; polishing tool, 4; polishing tool drive unit,
5; constant pressure mechanism, 6; table control device, 7; polishing tool rotation control computer,
8; polishing pressure control computer, 9; X-axis table, 10; X-axis drive motor,
11: Y-axis table, 12: Y-axis drive motor, 13: Motor amplifier,
14; drive motor, 15; voltage regulator, 16; air cylinder,
17; Force sensor, 18; Control computer.

Claims

In a polishing method in which a polishing tool is rotated and pressed against a processing surface, and polishing is performed by sending a workpiece in a polishing direction.
The polishing removal amount is calculated based on the measured polishing pressure and the workpiece feed rate, the polishing removal amount command value is corrected by the calculated polishing removal amount, and the corrected polishing removal amount command value is fed back to obtain the polishing pressure target value. The polishing method is characterized in that the polishing pressure is fed back to the corrected polishing pressure target value and controlled so that the polishing amount becomes constant with respect to the change in feed rate.

The polishing method according to claim 1, wherein a feed speed of the workpiece is changed according to a wavelength of waviness of the processed surface with respect to an ideal surface.

The polishing method according to claim 1 or 2, wherein the state of the processed surface of the workpiece is measured, and the feed rate is changed in accordance with the state of the processed surface.

A table driving unit that drives an XY table that sets a workpiece and varies the feed speed of the workpiece, a polishing tool driving unit that rotates by attaching a polishing tool, and a polishing that is mounted on the polishing tool driving unit In a polishing apparatus having a constant pressure mechanism unit and a control unit for pressing a tool against a workpiece with a constant polishing pressure,
The control unit calculates the polishing removal amount based on the polishing pressure measured by the constant pressure mechanism unit and the workpiece feed rate output from the table driving unit, and corrects the polishing removal amount command value based on the calculated polishing removal amount. The corrected polishing removal amount command value is fed back to correct the polishing pressure target value, and the polishing pressure measured by the constant pressure mechanism is fed back to the corrected polishing pressure target value to correct the polishing amount against the change in feed rate. A polishing apparatus characterized by controlling so as to be constant.