JP2004155071A

JP2004155071A - Injection molding machine, injection molding method and controlling device for injection molding machine

Info

Publication number: JP2004155071A
Application number: JP2002323355A
Authority: JP
Inventors: Koji Kubota; 浩司久保田; Hakuotsu Matsushita; 博乙松下; Hidenori Asano; 英紀浅野
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2004-06-03
Anticipated expiration: 2022-11-07
Also published as: JP3795005B2

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a molded article being stable in respect to the weight, dimensions and shape, in an injection molding method wherein a mold having a plurality of cavities different in shape and size is used and the cavities are selected for molding. <P>SOLUTION: In this injection molding method, the mold having the cavities in a plurality different in shape and size is used. Molding ranging from injection filling to dwelling in each cavity is performed at the speed of an injection screw and with an injection pressure which are set beforehand, and when the injection filling/dwelling in one cavity is completed and the injection filling in the next cavity is started, correction of a screw position on the occasion of starting the injection is conducted. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、形状やサイズの異なった複数のキャビティを有する金型を用い、キャビティを選択して成形する射出成形方法及び射出と保圧の制御表示に関する。また、その射出成形をキャビティ毎に個別に行う射出成形方法と、個別及びキャビティ全部を同時に表示できるようにした射出成形機の制御装置に関する。
【０００２】
【従来の技術】
射出成形機の金型に、形状やサイズの異なった複数のキャビティを有するときに、溶融樹脂圧による型開力を低減し、射出成形による製品取数を増やす方法として例えば特許文献１（特開平５−３０９７０４号公報）に開示された射出成形方法がある。この射出成形方法は、複数のキャビティを有し、各キャビティ毎に樹脂通路を開閉できるゲートが設けられている金型に１つの射出シリンダから射出成形するとき、第１のキャビティに樹脂を射出し、適当な時間保圧した後、第１のキャビティのゲートを閉じると同時に、第２のキャビティのゲートを開いて樹脂を射出し同様に適当な時間保圧、ゲート閉の後、さらに次のキャビティへの射出工程へ移行するようにした射出成形方法である。
【０００３】
また、特許文献２（特開平７−４０３９３号公報）で開示された射出成形方法は、１回の成形中に射出、保圧を複数回行い、成形金型に設けたランナ開閉装置により、キャビティ別に樹脂を充填するタイミングを制御し、異なる形状のキャビティには同時に充填せず、時間をずらして充填することにより、各キャビティに充填する樹脂量を安定させる方法で、充填する順番を必要冷却時間によって決定することにより、効率的な成形効果を狙いとしている。
【０００４】
通常、射出成形機は射出成形サイクルにおける設定値と実測値を表示パネルに表示し、成形状態を確認できるようになっている。この確認項目は、例えば、特許文献３（特許第３２４８６２０号公報）に開示されているように、スクリュ位置、射出成形サイクル時間、クッション位置、樹脂充填時間、樹脂圧、保圧時間等である。表示は数値表示、グラフィック表示、あるいは表形式表示等でなされ、これらの表示は一括、又は、表示パネルの大きさに応じて、分割し画面を変換して表示されている。
【０００５】
【特許文献１】
特開平５−３０９７０４号公報
【特許文献２】
特開平７−４０３９３号公報
【特許文献３】
特許第３２４８６２０号公報
【０００６】
【発明が解決しようとする課題】
形状やサイズの異なった複数のキャビティ内に溶融樹脂を満遍なく充填するための従来の射出成形方法において、特開平５−３０９７０４号に開示された射出成形方法も、また、特開平７−４０３９３号で開示された方法も、各キャビティに個別に順番に射出充填して保圧し、各キャビティの個別の工程に従い射出スクリュを前進停止の位置と速度の制御を行ない、キャビティ毎の充填完了位置から保圧時間制御するようにしているが、そのとき、充填完了位置において射出スクリュは殆ど動かず一定位置であることを前提にしている。しかし、保圧完了時のスクリュ位置は、金型温度の変化、樹脂温度の変動、溶融樹脂の密度変化や、チェックリングの閉鎖時間のバラツキ等による溶融樹脂の洩れによって変動するので、次の射出のスタートまでにスクリュの位置が変わり、次の第２、第３の充填完了位置がずれ、充填樹脂量が変わってしまって、成形品の重量バラツキ、形状不良の原因となる。
【０００７】
マルチキャビティの成形品の不良率がキャビティによって異なると、成形品のセットの完成個数が合わなくなる。このようなときは、足りない部分のみ成形したいが、従来行われているように、全射出成形サイクルにより全部分を成形すると、余分なものも同時に成形され、余った成形品は、粉砕してリサイクルへ回す等の手間が掛かった。マルチキャビティの成形品の１部が補用品として要求される場合にも同様の問題が生じる。
【０００８】
射出成形サイクルにおける設定値と実測値の表示について、従来は表示パネルに一括、又は、表示パネルの大きさに応じて、分割し画面を換えて表示しているが、マルチキャビティの場合は、成形を順次組み合わせた状態での成形条件の設定値を数値表示し、実測値をグラフィック表示することができるが、最初のキャビティ成形から次のキャビティに切り替わるスクリュ位置が毎ショット変わるため、設定値と実測値の関連を監視できない問題があった。またキャビティ毎に設定値と実測値を比較するにしても、キャビティ毎に画面を切り換える必要があり、キャビティ間の制御を関連させたいときは、総合的な一括画面も必要になる。
【０００９】
本発明は、形状サイズの異なった複数のキャビティを有する金型を用いた射出成形方法において、各キャビテイにおける充填から保圧までを予め設定した射出スクリュの速度と射出圧力で成形を行うとき、射出開始時のスクリュ位置補正を行うことにより、重量、寸法、形状が安定した成形品を得られると同時に、複数のキャビティの中から任意のキャビティを選択して、任意の成形品だけを得るようにする射出成形方法と、このキャビティ選択が容易に実施できるように監視する制御表示パネルを提供することを課題としている。
【００１０】
【課題を解決するための手段】
以上の問題点に対して本発明は、以下の各項を特徴とする手段により課題の解決を図る。
（１）複数のキャビティと該キャビティへ通じる各々の溶融樹脂通路を開閉する開閉手段を有する金型と、射出スクリュと射出シリンダを有し溶融樹脂を前記金型へ射出充填・保圧する射出装置と、前記開閉手段の開閉と前記射出装置による前記金型への射出充填・保圧作動を制御する制御装置を備える射出成形機において、前記制御装置は、一つのキャビティへの射出充填・保圧後に該キャビティに通じる溶融樹脂通路を閉じ、前記射出シリンダと該射出シリンダに通じる前記樹脂通路の樹脂圧を抜き、その樹脂圧を抜いた後の射出スクリュ停止位置を射出工程開始起点として次のキャビティへの射出充填・保圧を行うように制御することを特徴とする射出成形機。
（２）前記複数のキャビティの内、溶融樹脂が射出充填されるキャビテイを選択する選択手段を備えた上記（１）に記載の射出成形機。
（３）操作表示パネルを備え、該操作表示パネルには、射出充填・保圧の条件設定画面が、選択手段で選択されたキャビティ毎に切り換え表示される上記（１）に記載の射出成形機。
（４）前記条件設定画面には、射出充填する工程においては、分割された射出スクリュ位置に対する射出スクリュの速度設定値及び射出圧力設定値が、また保圧する工程においては、分割された時間に対する射出圧力設定値が、数値表示及び／又はグラフ表示される上記（３）に記載の射出成形機。
（５）前記操作表示パネルには、同一の画面に、前記複数のキャビティの全てについて、射出充填する工程の射出速度と射出圧力の各々の設定値と実測値を重ねたグラフ及び保圧する工程の射出圧力と射出速度の各々の設定値と実測値を重ねたグラフが、各キャビティ毎に独立して表示される上記（３）に記載の射出成形機。
（６）形状やサイズの異なった複数のキャビティを有し、射出シリンダの射出ノズルに通じる樹脂通路から各キャビティへ通じる分岐樹脂通路をそれぞれ個別に開閉する樹脂ゲート手段を有する金型を用い、一つのキャビティの樹脂ゲート手段を開いて前記樹脂通路から溶融樹脂を予め設定された成形条件で射出充填し、設定時間保圧した後に当該樹脂ゲートを閉じ、次のキャビティの樹脂ゲート手段を開いて樹脂を射出充填、保圧、樹脂ゲートを閉じ、それ以降のキャビティに対しても同様の工程を繰り返して複数の成形品を成形する射出成形方法において、複数のキャビティの中から樹脂を充填して成形するキャビティを選択し、選択された各キャビティの充填量に相当する射出スクリュのストロークを算出し、その各キャビティの算出ストロークを加算し、計量スクリュストロークを前記加算値以上に設定してそのストロークまで可塑化し、選択した最初のキャビティの樹脂ゲートを開き、該キャビティの個別の設定条件に基づいて射出速度と射出圧力を制御し、射出充填保圧が完了した後、当該樹脂ゲート手段を閉じ、射出シリンダ先端とこれに通じる樹脂通路の樹脂圧を抜いた後の射出スクリュ停止位置を次のキャビティの射出工程開始起点として、次のキャビティの設定条件に基づく射出充填、保圧、ゲート閉、樹脂圧抜き動作を行い、それ以降のキャビティも同様に、樹脂圧抜、射出スクリュ停止位置を射出工程開始起点として、射出充填、保圧、ゲート閉、樹脂圧抜きを繰り返して、段階的に全キャビティ、又は、選択したキャビティに射出成形を行うようにした射出成形方法。
【００１１】
（７）上記（６）の射出成形方法において、前記複数のキャビティの内、樹脂を充填後の保圧冷却時間が長いキャビティから順に射出成形を行う射出成形方法。
（８）形状やサイズの異なった複数のキャビティを有し、射出シリンダの射出ノズルに通じる樹脂通路から各キャビティへ通じる分岐樹脂通路をそれぞれ個別に開閉する樹脂ゲート手段を有する金型を備え、一つのキャビティの樹脂ゲート手段を開いて前記樹脂通路から溶融樹脂を予め設定された条件で射出充填し、設定時間保圧した後に当該樹脂ゲートを閉じ、次のキャビティの樹脂ゲート手段を開いて樹脂を射出充填、保圧、樹脂ゲートを閉じ、それ以降のキャビティに対しても同様の工程を繰り返して複数の成形品を成形するように制御する射出成形機の制御装置において、
複数のキャビティの中から成形を実施するキャビティを選択する選択スイッチと、該スイッチにより選択されたキャビティ毎に切り換えられる画面に該キャビティに対する射出速度と射出圧力の設定値を数値表示する操作表示パネルと、選択された各キャビティの充填量に相当する射出スクリュのストロークを加算し、該加算値以上になるように可塑化ストロークを算出する可塑化計量ストローク算出回路と、前記キャビティ選択スイッチで選択したキャビティの樹脂ゲートに開を指令し、該キャビティへの個別の射出速度と射出圧力の設定値になるように射出速度と射出圧力を制御し、一つのキャビティへの射出充填保圧後、当該樹脂ゲート手段の閉を指令し、射出スクリュ駆動手段に樹脂通路の樹脂圧の圧抜き動作を指令し、そのときの射出スクリュ停止位置を次のキャビティの射出工程開始起点として、次のキャビティの射出を指令し、該キャビティの個別の設定条件に基づく射出充填、保圧、ゲート閉、樹脂圧抜き動作を指示し、それ以降のキャビティに対しても同様の樹脂圧抜後の射出スクリュ停止位置を射出工程開始起点として、射出充填、保圧、ゲート閉、樹脂圧抜きの指示を繰り返して、段階的に全キャビティ、又は、選択したキャビティに射出成形を行う、上記（６）の射出成形方法により射出成形制御する制御回路とにより構成された射出成形機の制御装置。
【００１２】
（９）上記（８）の射出成形機の制御装置において、
表示パネルに表示される射出充填、保圧工程の設定画面は、選択されたキャビティ毎に切り換えられ、射出工程は、分割された射出スクリュ位置に対する射出スクリュの速度と射出圧力の設定値を、保圧工程は、分割された時間に対する射出圧力の設定値を右側面に数値表示し、左側面には射出工程はスクリュ位置を横軸に速度と射出圧力の設定値をグラフィック表示、保圧工程は時間を横軸にして射出圧力の設定値をグラフィック表示し、スクリュ射出開始位置は当該キャビティの樹脂容量に見合うスクリュ移動距離を数値表示し、０点において当該キャビティに対する射出保圧工程が終了するように位置表示するものとし、一つのキャビティから次のキャビティへ画面が替わるとき、前回の射出と保圧が終わって樹脂を脱圧した時点のスクリュ停止位置を射出工程開始起点として横軸のスクリュ位置が設定されるようにして、選択されたキャビティへの射出開始時の射出スクリュ位置の数値を変えないようにした射出成形機の制御表示パネル。
【００１３】
（１０）上記（９）の射出成形機の制御装置において、同一画面に全キャビティに対する条件の設定数値表示、或いは、全キャビティに対する射出時の射出速度、射出速度の設定値に重ねて実測値を、保圧時の射出圧力、射出速度の設定値に重ねて実測値をグラフ表示することができるようにして、全部のキャビティの射出充填、保圧工程の射出スクリュ速度と射出圧力の条件設定値に対する実測値を同時に監視できる射出成形機の制御装置。
【００１４】
【発明の実施の形態】
本発明の実施の形態を、射出スクリュの前後進の直線駆動に電動式ボールねじ装置を使用した射出ユニットと、マルチキャビティを有し各キャビティへ通じる樹脂通路に樹脂ゲートが設置された金型を組み込んだ型締装置を有する射出成形機を用いて説明する。
図１は実施の形態に係わる射出成形方法が利用可能な複数のキャビティを有する金型と射出ユニットの制御系統を示す模式図、図２は図１の金型と射出ユニットの制御系統によって射出成形するときの工程順ブロック図、図３は図１の金型と射出ユニットの制御系統によって射出成形するときの、各キャビティへの充填保圧時のそれぞれのストロークを示すブロック図、図４は図１の制御装置の構成を示すブロック図、図５は図４に示す表示パネルの表示例（成形条件設定）、図６は図４に示す表示パネルの他の表示例（１次〜４次成形条件設定値と実測値を重ねたグラフィック表示例）である。
【００１５】
図１の射出成形機１の構成において、
射出ユニットは射出シリンダ３と、射出シリンダ３に内嵌する射出スクリュ２と、射出スクリュ２を回転するモータ４と、射出シリンダ３と一体に構成された固定フレーム１２と、図示略の基台の上を、射出シリンダ３の軸方向に移動可能な移動フレーム１４とで構成される。固定フレーム１２の両側にボールねじナット１６、１６が固設され、移動フレーム１４には、射出スクリュ２を回転駆動するモータ４と、射出スクリュ２の軸に対して対称にボールねじ軸１５、１５が回転可能に軸方向を拘束して取り付けられ、また、このボールねじ軸１５を回転駆動するサーボモータ１７、１７が備えられている。移動フレーム１４とサーボモータ１７に挟まれてボールねじ軸１５の負荷力を検出するロードセンサ４７が設置されている。モータ４及びサーボモータ１７、１７は制御装置３５により制御される。
【００１６】
固定金型７は射出成形機１に図示略の固定型盤と支持盤９を介して固定されている。図示略の型締機構により、固定金型７が可動金型８と結合したとき、溶融樹脂を受け入れる複数の金型キャビティ１１Ａ、１１Ｂ、１１Ｃを形成する（図１では、キャビティ３個を示しているが、例えばキャビティＤ、キャビティＥ…等が同時に設けられてもよい）。可動金型８は成形品取り出しのとき固定金型７から離れる方向に大きく移動可能である。固定金型７にはホットランナ１０が取り付けられ、ホットランナ１０には各キャビティ１１Ａ、１１Ｂ、１１Ｃへ溶融樹脂を供給する樹脂通路が設けられ、樹脂を溶融状態に保持するために常時加温されている。ホットランナ１０の各キャビティ１１Ａ、１１Ｂ、１１Ｃへの入り口１０ａ、１０ｂ、１０ｃは円錐形状に絞られて、プランジャー形状の樹脂ゲートバルブ１３Ａ、１３Ｂ、１３Ｃのバルブ受け座となっている。
【００１７】
樹脂ゲートバルブ１３Ａ、１３Ｂ、１３Ｃは、ホットランナ１０を突き通して支持盤９に設けられた３組の油圧シリンダ９ａ、９ａ、９ａに結合されている。
制御装置３５は、内蔵する制御回路３４によって、射出工程の各キャビティ１１Ａ，１１Ｂ，１１Ｃのタイミング順に従って３組の図示せぬ油圧切換バルブを設置する油圧圧切換弁２６に開閉作動の信号を送り、樹脂ゲートバルブ１３Ａ、１３Ｂ、１３Ｃを開閉する油圧シリンダ９ａに個別に圧油を送る。
【００１８】
制御装置の構成と制御機能について説明する。図４において、操作表示パネル３３には、複数のキャビティ１１の中から成形を実施するキャビティを選択するキャビティ選択スイッチ４２が設けられる。同スイッチ４２は図５に示す画面の上部に設けられ、パネルの記述枠をタッチすることにより、１次射出、２次射出、３次射出…ｎ次射出が選択できるもので、タッチされた次元の射出に対応するキャビテイが選択され、選択されたキャビテイへの射出速度と射出圧力の設定値が画面に数値表示される。例えば、１次射出４２Ａが選択されたとき（対応するキャビテイはキャビテイ１１Ａである）、１次射出４２Ａのタッチボタンは明色に変わり、キャビテイ１１Ａに射出充填するときの射出速度と射出圧力の設定値が画面に数値表示される。２次射出４２Ｂがタッチされると、１次射出４２Ａのタッチボタンは暗色になり、２次射出４２Ｂのタッチボタンが明色に変わり、設定画面にキャビテイ１１Ｂに射出充填するときの射出速度と射出圧力の設定値に変更して数値表示される。
【００１９】
また、１〜ｎ次射出のタッチボタンの隣の有効、無効のタッチボタンは押す度に有効、無効が交番に現れ、実成形工程において、有効と表示されたキャビテイのみが選択され実行される。
制御回路３４から射出の指令が出されたとき、１次射出から射出工程が始まり、数字の順に成形が行われる。
【００２０】
画面に表示される射出速度Ｖ１は、射出スクリュが移動するときの距離を適当に分割し、その分割位置Ｌ１毎に射出速度Ｖ１の設定と射出制限圧力ＰＨの圧設定をしている。保圧工程の射出圧力は保圧時間ＴＢを適当に分割しその分割時間毎に圧力ＰＬを設定している。
図５の例で説明すると、この画面の射出において、射出スクリュの移動距離は１２０ｍｍ、これを６分割しそれぞれのスクリュ位置の射出速度を枠内に数値表示をしてあり、この枠内の数値は枠をタッチすることにより、変更可能に明色になり、テンキー４１より新しい設定値を数値入力し、テンキー４１のエントリーキーを押すことにより決定され、設定値が表示され、暗色に変更する。スクリュの移動位置に対する射出制限圧力ＰＨを設定したいときは同様の手順で射出制限圧力ＰＨの枠内の数値の設定変更を行うことができる。図５の保圧工程の圧力ＰＬは保圧時間ＴＢを３分割し、圧力ＰＬと保圧継続時間ＴＢを枠内に数値表示し、この枠をタッチして数値変更可能にし、テンキー４１より新しい設定値を数値入力し、テンキー４１のエントリーキーにより、決定される。上記の射出スクリュ位置の区分番号は、作業側から見たときの射出スクリュの進行方向に合わせて右から左に数字が付けられ、スクリュの移動起点はスクリュ移動距離１２０ｍｍ、終点は０ｍｍとなっている。保圧工程の保圧時間ＴＢの進行方向も射出速度に合わせて右から左に時間が進められている。
【００２１】
図５の左側の画面には、射出速度設定値と射出制限圧力設定値及び保圧設定値をグラフィック表示し、射出速度設定値と射出制限圧力設定値にサーボモータ１７の回転速度から算出したスクリュ位置に対する射出速度と射出圧力の実測値を、保圧設定値に時間経過に対する射出圧力実測値を設定値グラフと違う色で重ねて表示してある。このグラフィック図においてもスクリュ位置、時間は右から左方向に進むように表示してある。
図６は操作表示パネル３３の画面において、複数のキャビテイに対する射出速度設定値と射出制限圧力設定値及び射出圧力設定値のグラフィック表示を同一面に表示したものであり、この画像においては、キャビテイ選択時に４次射出を無効としたため、このキャビテイに対して射出充填が行われず、実測値が記入されていない例を示してある。
【００２２】
図４において、３６は選択された各キャビティの充填量に相当する射出スクリュ２のストロークを加算し、該加算値以上になるように可塑化ストロークを算出する可塑化計量ストローク算出回路である。制御回路３４は、キャビティ選択スイッチ４２で選択した最初のキャビティ１１Ａの樹脂ゲート１３Ａに開を指令し、キャビティ１１Ａへの１次射出の画面に表示された射出速度になるようにサーボモータ１７の回転数をフィードバック制御し、ロードセンサ４７の圧力信号が射出圧力設定値になるようにサーボモータ１７のトルク（電流）を制御する。キャビティ１１Ａへの射出充填保圧後、制御回路３４は、樹脂ゲート１３Ａの閉を指令し、射出スクリュ駆動サーボモータ１７に樹脂通路の樹脂圧の圧抜きを指令し、そのときの射出スクリュ停止位置を次のキャビティ１１Ｂの射出工程開始起点として、キャビティ１１Ｂの射出を指令し、キャビティ１１Ｂの設定条件に基づく射出充填、保圧制御をし、ゲート閉、樹脂圧抜き動作を指示し、それ以降のキャビティに対しても同様の樹脂圧抜後の射出スクリュ停止位置を射出工程開始起点として、射出充填、保圧制御、ゲート閉、樹脂圧抜き動作の指令を繰り返して、段階的に全キャビティ、又は、選択したキャビティに射出成形制御を行う。
【００２３】
射出成形機１によって射出成形するときの工程を、図２の工程ブロック図によって説明する。
図２の横軸は時間軸である。最上段は射出ユニットの射出シリンダ３、射出スクリュ２による溶融樹脂の射出工程を示し、その下段にはキャビティ１１Ａの射出充填と樹脂圧力の保持、冷却をブロックで示し、その下にキャビティ１１Ａのゲートバルブ１３Ａ開閉のタイミングを示している。キャビティ１１Ａの作動形態の下側に、キャビティ１１Ｂの射出充填と樹脂圧力の保持、冷却をブロック図で示し、これに並行してキャビティ１１Ｂのゲートバルブ１３Ｂ開閉のタイミングを示す。キャビティ１１Ｂの作動形態の下側に、キャビティ１１Ｃの射出充填と樹脂圧力の保持、冷却をブロック図で示し、これに並行してキャビティ１１Ｃのゲートバルブ１３Ｃ開閉のタイミングを示す。又、その下には前記の各工程に合わせた射出スクリュのストローク位置を示している。Ｓは全ストロークを示す。射出工程は、射出ユニットのボールねじ軸１５、１５の回転速度と回転トルクによる各キャビテイへの個別の溶融樹脂の射出充填と樹脂圧保持の後、ボールねじ軸１５、１５の回転を戻して樹脂圧を降圧し、射出スクリュ２を回転しながら後退させて樹脂の溶融可塑化を行い、その間に型締装置は、圧力保持冷却の工程中は型締めを継続し、全てのキャビティ内樹脂の降圧の工程が終了し、成形品の冷却固化後に降圧、型開、成形品取出が行われ、射出工程の１サイクルが完了する。その後再び、型締が行われた後に次の射出充填が始まる。
【００２４】
射出成形するときの、各キャビティへの充填保圧時のそれぞれのストロークを示す図３のブロック図において、ＰＡの位置からサーボモータ１７の回転が始まって射出スクリュ２は設定された速度で制御され、キャビテイ１１Ａの射出保圧が開始し、保圧がタイムアップしたときに停止したときのストロークをｌＡとし、ゲートバルブ１３Ａを閉じ、サーボモータ１７、１７の電流を切ってトルクをゼロに脱力して射出シリンダ３先端の樹脂圧を圧抜きし、射出スクリュ２がｍＡ戻った位置で、サーボモータ１７、１７を保持制御してスクリュ２を停止させ、この射出スクリュ２の停止位置ＰＢをキャビティ１１Ｂへの射出開始位置にリセットし、このリセットした位置をキャビティ１１Ｂに対する射出スクリュ２の射出開始位置とする。その後、キャビティ１１Ｂへの設定条件に基づく射出充填、保圧、ゲート閉動作を行う。それ以降の他のキャビティ１１も同様に、射出開始位置リセット、射出充填、保圧、ゲート閉を繰り返して全キャビティでの段階的な射出充填、保圧を行った後、冷却をする。このように、キャビティが代わる度に射出スクリュ２の射出開始位置をリセットするようにしているので、成形品の重量バラツキ、形状不良等を生じることが無くなる。また、ボールねじ装置を電動駆動する機構は、油圧作動に見られる移動速度が早いときに予定停止位置をオーバーするような事が無く、より正確で精密な位置と速度制御が可能である。
【００２５】
各キャビテイに充填される樹脂量、形状はそれぞれ違っており、従って、各キャビテイに対する射出保圧の条件も異なってくるので、スクリュ２の設定速度、設定射出圧力も別個のものとなる場合がある。また、樹脂圧抜き時のスクリュ２の後退距離は、射出シリンダ３に溜まっている樹脂量、その時の金型（ホットランナ１０）の温度により変わるので一定になることはない。
【００２６】
従来の複数のキャビティを設けた金型へ多段射出する射出成形機の場合は、各キャビティに順番に射出充填して保圧し、各キャビティの個別の工程に従って、射出スクリュを前進停止の位置と速度が決められ、その位置と速度をキープする制御を行ない、キャビティ毎の充填完了位置から保圧時間制御するようにしているが、保圧完了時のスクリュ位置は、金型温度の変化、樹脂温度の変動、溶融樹脂の密度変化や、チェックリングの閉鎖時間のバラツキ等による溶融樹脂の洩れによって変動するので、次の射出のスタートまでにスクリュの位置が変わり、次の第２の充填完了位置までの樹脂量が変わってしまって、成形品の重量バラツキ、形状不良の原因となる。
【００２７】
キャビティの射出順を変えるとき、又は、任意のキャビティに射出しない場合でも、樹脂ゲート開閉の順を変更、又は、開閉を止めて、２番目以降の射出開始位置をリセットすることにより、容易に多段の射出保圧が可能であり、且つ、品質の良い成形品が得られる。
また、キャビティ１１Ａがキャビティ１１Ｂより大型で、キャビティ１１Ｃはキャビティ１１Ｂよりも小型であるとき、溶融樹脂の射出充填、保圧、冷却の時間は、キャビティ１１Ｃが最も短く、キャビティ１１Ｂはその次ぎに短く、キャビティ１１Ａが最も長くなり、各キャビティ内の樹脂の冷却工程は、次のキャビティの射出充填、保圧工程中に行われるので、図２のように、最も冷却の時間が短いキャビティＣを最後の工程とすれば、全体の射出工程１サイクルの時間を最短とすることができる。
【００２８】
【発明の効果】
本発明の射出成形方法によれば、形状やサイズの異なった複数のキャビティを有する金型を用いて複数の成形品を成形するときに、複数のキャビティの中から樹脂を充填して成形するキャビティを選択し、金型の各キャビティ毎に設けられている樹脂ゲートを用い、まず第１のキャビティの樹脂ゲートを開き、キャビティの個別の設定値に基づいて射出速度と射出圧力を制御し、射出充填保圧が完了した後、当該樹脂ゲート手段を閉じ、射出シリンダ先端とこれに通じる樹脂通路の樹脂圧を抜いた後の射出スクリュ停止位置を次のキャビティの射出工程開始起点として、第２のキャビティの設定値に基づいた射出速度と保圧を制御し、ゲート閉を行い、それ以降の他のキャビティも同様に、樹脂圧を抜いた後の射出スクリュ停止位置を次のキャビティの射出開始位置として、射出充填、保圧、ゲート閉を繰り返して全キャビティでの段階的な設定値に基づく射出充填、保圧制御を行うようにしたので、各キャビティ毎の充填量が安定し、成形品の重量寸法形状が安定する。また、キャビティの射出順を変えるとき、又は、任意のキャビティに射出しない場合でも、樹脂ゲート開閉の順を変更、又は開閉を止め、射出スクリュ停止位置を２番目以降の射出開始位置とすることにより、容易に多段の射出保圧が可能であり、且つ、品質の良い成形品が得られる。
【００２９】
操作表示パネルの射出選択スイッチにより、必要なキャビティを選択し、そのキャビテイへ射出保圧成形のみを有効とすれば、選択したキャビテイの条件を組み合わせて成形するので、条件を標準化でき、また、各キャビティ成形において、設定値と実測値とを併記することにより、キャビテイ毎の違いを見ながら成形条件を最適化することができる。
マルチキャビティの成形品の不良率がキャビティによって異なると、成形品のセットの完成個数が合わなくなるが、従来行われているように、全射出成形サイクルにより全部分を成形すると、余分なものも同時に成形され、余った成形品は、粉砕してリサイクルへ回す等の手間がかかる。また、マルチキャビティの成形品の１部が補用品として要求される場合にも同様の問題が生じるが、本発明のように、射出選択スイッチにより、必要なキャビティを選択して射出充填すれば、この問題は簡単に解決できる。
また、上記の射出成形方法において、複数のキャビティの内、樹脂を充填後、保圧冷却時間が長いキャビティから順に射出成形を行うので、全体の射出工程１サイクルの時間を最短とすることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係わる射出成形方法が利用可能な複数のキャビティを有する金型と射出ユニットの制御系統を示す模式図である。
【図２】図１の金型と射出ユニットの制御系統によって射出成形するときの工程順ブロック図である。
【図３】図１の金型と射出ユニットの制御系統によって射出成形するときの、各キャビティへの充填保圧時のそれぞれのストロークを示すブロック図である。
【図４】図１の制御装置の構成を示すブロック図である。
【図５】図４に示す表示パネルの表示例（成形条件設定）である。
【図６】図４に示す表示パネルの他の表示例（１次〜４次成形条件設定値と実測値を重ねたグラフィック表示例）である。
【符号の説明】
１…射出成形機
２…射出スクリュ
３…射出シリンダ
７…固定金型
８…可動金型
９…支持盤
９ａ…油圧シリンダ
１０…ホットランナ
１１Ａ…キャビティＡ
１１Ｂ…キャビティＢ
１１Ｃ…キャビティＣ
１２…固定フレーム
１３Ａ、１３Ｂ、１３Ｃ…樹脂ゲートバルブ
１４…移動フレーム
１５…ボールねじ軸
１６…ボールねじナット
１７…サーボモータ
２６…切換バルブ
３３…操作表示パネル
３４…制御回路
３５…制御装置
４２…キャビティ選択スイッチ
４７…射出スクリュロードセンサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding method for selecting and molding cavities using a mold having a plurality of cavities having different shapes and sizes, and to a control display of injection and holding pressure. Further, the present invention relates to an injection molding method for performing the injection molding individually for each cavity, and a control device for an injection molding machine capable of simultaneously displaying individual and all cavities.
[0002]
[Prior art]
When a mold of an injection molding machine has a plurality of cavities having different shapes and sizes, a method of reducing the mold opening force due to the molten resin pressure and increasing the number of products obtained by injection molding is disclosed in, for example, Japanese Patent Application Laid-Open No. H10-163,089. No. 5-309704). According to this injection molding method, when performing injection molding from one injection cylinder into a mold having a plurality of cavities and provided with a gate capable of opening and closing a resin passage for each cavity, the resin is injected into the first cavity. After holding the gate for an appropriate time, the gate of the first cavity is closed, and at the same time, the gate of the second cavity is opened and the resin is injected. This is an injection molding method in which the process shifts to an injection step.
[0003]
In addition, in the injection molding method disclosed in Patent Document 2 (Japanese Patent Application Laid-Open No. 7-40393), injection and holding pressure are performed a plurality of times during one molding, and a cavity is opened and closed by a runner opening / closing device provided in a molding die. Separately controls the timing of filling the resin, does not fill the cavities of different shapes at the same time, but staggers the time to fill the cavities. The aim is to achieve an efficient molding effect.
[0004]
Normally, an injection molding machine displays a set value and an actually measured value in an injection molding cycle on a display panel so that a molding state can be confirmed. This confirmation item is, for example, a screw position, an injection molding cycle time, a cushion position, a resin filling time, a resin pressure, a pressure holding time, etc., as disclosed in Patent Document 3 (Japanese Patent No. 3248620). The display is performed by numerical display, graphic display, tabular display, or the like. These displays are collectively or divided according to the size of the display panel, and the screen is converted and displayed.
[0005]
[Patent Document 1]
JP-A-5-309704
[Patent Document 2]
JP-A-7-40393
[Patent Document 3]
Japanese Patent No. 3248620
[0006]
[Problems to be solved by the invention]
In a conventional injection molding method for uniformly filling a plurality of cavities having different shapes and sizes with a molten resin, the injection molding method disclosed in Japanese Patent Application Laid-Open No. 5-309704 is also disclosed in Japanese Patent Application Laid-Open No. 7-409393. The disclosed method also injects and fills each cavity individually in order to hold the pressure, controls the position and speed of the advancement stop of the injection screw according to the individual process of each cavity, and maintains the pressure from the filling completion position for each cavity. Time control is performed, but at this time, it is assumed that the injection screw hardly moves at the filling completion position and remains at a constant position. However, the screw position at the time of completion of pressure holding varies due to changes in the mold temperature, fluctuations in the resin temperature, changes in the density of the molten resin, and leakage of the molten resin due to variations in the closing time of the check ring. The position of the screw is changed by the start of the process, the next second and third filling completion positions are shifted, and the amount of the filled resin is changed, which causes a variation in weight of the molded product and a defective shape.
[0007]
If the defective rate of the multi-cavity molded product differs depending on the cavity, the number of completed molded product sets does not match. In such a case, we would like to mold only the missing parts, but as in the past, if all the parts were molded by the entire injection molding cycle, the excess was molded at the same time, and the excess molded product was crushed. It took time to recycle. A similar problem occurs when a part of a multi-cavity molded article is required as a supplement.
[0008]
Conventionally, the display of the set value and the measured value in the injection molding cycle is displayed on the display panel all at once, or according to the size of the display panel, divided and the screen is changed. Can be displayed numerically and the measured values can be displayed graphically, but the screw position that switches from the first cavity molding to the next cavity changes every shot. There was a problem that the relationship between values could not be monitored. Further, even if the set value and the measured value are compared for each cavity, it is necessary to switch the screen for each cavity, and when it is desired to associate control between cavities, a comprehensive batch screen is also required.
[0009]
The present invention relates to an injection molding method using a mold having a plurality of cavities having different shapes and sizes, wherein when performing molding at a predetermined injection screw speed and injection pressure from filling to holding pressure in each cavity, injection is performed. By correcting the screw position at the start, a molded product with stable weight, dimensions and shape can be obtained, and at the same time, an arbitrary cavity can be selected from multiple cavities to obtain only an arbitrary molded product. It is an object of the present invention to provide an injection molding method and a control display panel for monitoring such that the cavity selection can be easily performed.
[0010]
[Means for Solving the Problems]
The present invention solves the above problems by means characterized by the following items.
(1) A mold having a plurality of cavities and an opening / closing means for opening and closing each molten resin passage communicating with the cavities, an injection device having an injection screw and an injection cylinder, and injecting and filling the molten resin into the mold with molten resin. An injection molding machine having a control device for controlling the opening / closing of the opening / closing means and the injection filling / holding operation to the mold by the injection device, wherein the control device is configured to perform injection filling / holding pressure on one cavity. The molten resin passage leading to the cavity is closed, the resin pressure in the injection cylinder and the resin passage leading to the injection cylinder is released, and the injection screw stop position after releasing the resin pressure is used as the starting point of the injection step to the next cavity. An injection molding machine characterized by controlling so as to perform injection filling and holding pressure.
(2) The injection molding machine according to (1), further including a selection unit that selects a cavity into which the molten resin is injected and filled, from among the plurality of cavities.
(3) The injection molding machine according to (1), further including an operation display panel, wherein an injection filling / holding pressure condition setting screen is switched and displayed for each cavity selected by the selection means. .
(4) In the condition setting screen, the injection screw speed setting value and the injection pressure setting value with respect to the divided injection screw position in the injection filling step, and the injection time with respect to the divided time in the step of maintaining the pressure. The injection molding machine according to the above (3), wherein the pressure set value is displayed numerically and / or graphically.
(5) In the operation display panel, a graph in which the set values and the measured values of the injection speed and the injection pressure of the injection filling step are superimposed on all of the plurality of cavities on the same screen and the pressure holding step The injection molding machine according to (3), wherein a graph in which the set value and the measured value of the injection pressure and the injection speed are superimposed is displayed independently for each cavity.
(6) A mold having a plurality of cavities having different shapes and sizes, and having a resin gate means for individually opening and closing a branch resin passage leading to each cavity from a resin passage leading to the injection nozzle of the injection cylinder. The resin gate means of one cavity is opened, the molten resin is injected and filled from the resin passage under a predetermined molding condition, the resin gate is closed after keeping the pressure for a set time, and the resin gate means of the next cavity is opened to open the resin gate means. Injection filling, holding pressure, closing the resin gate, and repeating the same process for the subsequent cavities to mold multiple molded products, filling the resin from multiple cavities and molding Select the cavities to be filled, calculate the stroke of the injection screw corresponding to the filling amount of each selected cavity, and calculate each cavity The stroke is added, the metering screw stroke is set to be equal to or more than the added value, the plasticization is performed until the stroke, the resin gate of the selected first cavity is opened, and the injection speed and the injection pressure are set based on the individual setting conditions of the cavity. Control, after the injection filling and holding pressure is completed, the resin gate means is closed, and the injection screw stop position after releasing the resin pressure of the injection cylinder tip and the resin passage communicating therewith is set as the starting point of the injection process of the next cavity. Performs injection filling, pressure holding, gate closing, and resin depressurizing operations based on the setting conditions of the next cavity. Similarly, in the subsequent cavities, resin injection and filling are performed with the injection screw stop position as the starting point of the injection process. , Holding pressure, gate closing and resin pressure relief are repeated, and injection molding is performed stepwise in all cavities or selected cavities. Molding method out.
[0011]
(7) The injection molding method according to the above (6), wherein the injection molding is performed in order from a cavity having a longer holding pressure and cooling time after filling the resin among the plurality of cavities.
(8) A mold having a plurality of cavities having different shapes and sizes, and a resin mold having resin gate means for individually opening and closing a branch resin passage leading to each cavity from a resin passage leading to the injection nozzle of the injection cylinder. Opening the resin gate means of one cavity, injecting and filling the molten resin from the resin passage under predetermined conditions, keeping the pressure for a set time, closing the resin gate, opening the resin gate means of the next cavity, and discharging the resin. Injection filling, holding pressure, closing the resin gate, in the control device of the injection molding machine to control to mold a plurality of molded products by repeating the same process for the subsequent cavity,
A selection switch for selecting a cavity for performing molding from a plurality of cavities, and an operation display panel for numerically displaying a set value of an injection speed and an injection pressure for the cavity on a screen switched for each cavity selected by the switch. A plasticizing weighing stroke calculating circuit for adding a stroke of the injection screw corresponding to a filling amount of each selected cavity and calculating a plasticizing stroke so as to be equal to or more than the added value; and a cavity selected by the cavity selecting switch. Command the resin gate to open, control the injection speed and injection pressure so that the individual injection speed and injection pressure set values for the cavity become the set values, and after the injection filling pressure holding for one cavity, the resin gate Commanding the closing of the means, and instructing the injection screw driving means to release the resin pressure in the resin passage. Using the exit screw stop position as the starting point of the next cavity injection process, instruct the next cavity to be injected, instruct injection filling, pressure holding, gate closing, and resin pressure relief operation based on individual setting conditions for the cavity, For the subsequent cavities, the same injection screw stop position after resin depressurization is used as the starting point of the injection process, and the injection filling, holding pressure, gate closing, and resin depressurization instructions are repeated, and all cavities are stepped. Alternatively, a control device for an injection molding machine, comprising: a control circuit for performing injection molding in the selected cavity by performing injection molding by the injection molding method of (6).
[0012]
(9) In the control device of the injection molding machine of (8),
The setting screen of the injection filling and pressure holding process displayed on the display panel is switched for each selected cavity. In the injection process, the set values of the injection screw speed and the injection pressure with respect to the divided injection screw positions are stored. In the pressure step, the set value of the injection pressure for the divided time is numerically displayed on the right side, and in the left side, the screw position is graphically displayed with the screw position on the horizontal axis, and the set value of the speed and injection pressure is graphically displayed. The injection pressure set value is graphically displayed with time as the horizontal axis, the screw injection start position is numerically displayed with the screw movement distance corresponding to the resin capacity of the cavity, and the injection pressure holding process for the cavity is completed at point 0. When the screen changes from one cavity to the next, the position at the time when the resin was released from the pressure after the previous injection and dwelling was completed The control display panel of the injection molding machine in which the screw position on the horizontal axis is set with the screw stop position as the starting point of the injection process, and the numerical value of the injection screw position at the start of injection into the selected cavity is not changed. .
[0013]
(10) In the control device of the injection molding machine of the above (9), numerical values of conditions for all cavities are displayed on the same screen, or an injection speed at the time of injection for all cavities, and an actually measured value are superimposed on the set value of the injection speed. The actual measured value can be displayed as a graph superimposed on the set values of injection pressure and injection speed during holding pressure, and the injection screw speed and injection pressure condition set value of all cavity injection filling and holding pressure processes A control device for an injection molding machine that can simultaneously monitor the measured values for
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention is directed to an injection unit using an electric ball screw device for linearly driving an injection screw back and forth, and a mold having a multi-cavity and having a resin gate installed in a resin passage leading to each cavity. Description will be made using an injection molding machine having a mold clamping device incorporated therein.
FIG. 1 is a schematic diagram showing a control system of a mold and an injection unit having a plurality of cavities in which the injection molding method according to the embodiment can be used, and FIG. 2 is injection molding by a control system of the mold and the injection unit of FIG. FIG. 3 is a block diagram showing respective strokes at the time of filling and holding each cavity when performing injection molding by the control system of the mold and the injection unit in FIG. 1, and FIG. 5 is a block diagram showing the configuration of the control device of FIG. 1, FIG. 5 is a display example of the display panel shown in FIG. 4 (setting of molding conditions), and FIG. 6 is another display example of the display panel shown in FIG. 5 is a graphic display example in which a condition setting value and an actual measurement value are superimposed.
[0015]
In the configuration of the injection molding machine 1 of FIG.
The injection unit includes an injection cylinder 3, an injection screw 2 fitted inside the injection cylinder 3, a motor 4 for rotating the injection screw 2, a fixed frame 12 integrated with the injection cylinder 3, and a base (not shown). The upper part comprises a movable frame 14 movable in the axial direction of the injection cylinder 3. Ball screw nuts 16, 16 are fixed on both sides of the fixed frame 12, and a motor 4 for rotating and driving the injection screw 2 and ball screw shafts 15, 15 symmetrically with respect to the axis of the injection screw 2 are provided on the moving frame 14. Are mounted so as to be rotatable in the axial direction, and servo motors 17 and 17 for rotating the ball screw shaft 15 are provided. A load sensor 47 is provided between the moving frame 14 and the servomotor 17 to detect a load on the ball screw shaft 15. The motor 4 and the servomotors 17 are controlled by a control device 35.
[0016]
The fixed mold 7 is fixed to the injection molding machine 1 via a fixed mold plate (not shown) and a support plate 9. A plurality of mold cavities 11A, 11B and 11C for receiving the molten resin are formed when the fixed mold 7 and the movable mold 8 are joined by a mold clamping mechanism (not shown) (FIG. 1 shows three cavities). However, for example, the cavity D, the cavity E, etc. may be provided at the same time). The movable mold 8 can largely move in a direction away from the fixed mold 7 when removing the molded product. A hot runner 10 is attached to the fixed mold 7, and a resin passage for supplying a molten resin to each of the cavities 11A, 11B, and 11C is provided in the hot runner 10, and the hot runner 10 is constantly heated to keep the resin in a molten state. ing. The entrances 10a, 10b, and 10c of the hot runner 10 to the cavities 11A, 11B, and 11C are conically narrowed to serve as valve seats for plunger-shaped resin gate valves 13A, 13B, and 13C.
[0017]
The resin gate valves 13A, 13B, 13C penetrate the hot runner 10 and are connected to three sets of hydraulic cylinders 9a, 9a, 9a provided on the support board 9.
The control device 35 sends an open / close operation signal to the hydraulic pressure switching valve 26 in which three sets of hydraulic switching valves (not shown) are installed in accordance with the timing order of the cavities 11A, 11B, and 11C in the injection process by the built-in control circuit 34. The pressure oil is individually sent to the hydraulic cylinder 9a that opens and closes the resin gate valves 13A, 13B, 13C.
[0018]
The configuration and control functions of the control device will be described. In FIG. 4, the operation display panel 33 is provided with a cavity selection switch 42 for selecting a cavity for performing molding from the plurality of cavities 11. The switch 42 is provided at the upper part of the screen shown in FIG. 5, and allows the user to select a primary injection, a secondary injection, a third injection,..., An n-th injection by touching a description frame of the panel. Is selected, and the set values of the injection speed and the injection pressure for the selected cavity are numerically displayed on the screen. For example, when the primary injection 42A is selected (the corresponding cavity is the cavity 11A), the touch button of the primary injection 42A changes to a light color, and the injection speed and the injection pressure when the cavity 11A is injected and filled are set. The value is displayed numerically on the screen. When the secondary injection 42B is touched, the touch button of the primary injection 42A turns dark, the touch button of the secondary injection 42B turns light, and the injection speed and the injection when the cavity 11B is injected and filled are displayed on the setting screen. The pressure is changed to the set value and displayed numerically.
[0019]
In addition, each time the pressed touch button of the 1st to n-th injections is pressed, the validity or invalidity appears alternately, and only the cavities indicated as valid are selected and executed in the actual molding process.
When an injection command is issued from the control circuit 34, the injection process starts from the primary injection and molding is performed in numerical order.
[0020]
The injection speed V1 displayed on the screen appropriately divides the distance at which the injection screw moves, and sets the injection speed V1 and the injection limit pressure PH for each of the division positions L1. For the injection pressure in the pressure holding step, the pressure holding time TB is appropriately divided, and the pressure PL is set for each divided time.
To explain with reference to the example of FIG. 5, in the injection of this screen, the moving distance of the injection screw is 120 mm, which is divided into six, and the injection speed at each screw position is numerically displayed in a frame. Is lightened so that it can be changed by touching the frame, and a new setting value is input numerically from the numeric keypad 41 and determined by pressing the entry key of the numeric keypad 41, and the setting value is displayed and changed to dark. When it is desired to set the injection limit pressure PH for the screw movement position, the setting of the numerical value within the frame of the injection limit pressure PH can be changed in the same procedure. The pressure PL in the pressure-holding step in FIG. 5 divides the pressure-holding time TB into three parts, displays the pressure PL and the pressure-holding duration TB in numerical values in a frame, and touches this frame to enable the numerical value to be changed. A set value is input as a numerical value, and is determined by an entry key of the ten keys 41. The above-mentioned section number of the injection screw position is numbered from right to left in accordance with the traveling direction of the injection screw when viewed from the working side, the screw movement starting point is the screw movement distance 120 mm, and the end point is 0 mm. I have. The advancing direction of the dwelling time TB in the dwelling step also advances from right to left in accordance with the injection speed.
[0021]
On the screen on the left side of FIG. 5, the injection speed set value, the injection limit pressure set value, and the holding pressure set value are graphically displayed, and the injection speed set value and the injection limit pressure set value are calculated from the rotation speed of the servo motor 17. The actual measured values of the injection speed and the injection pressure with respect to the position are displayed by superimposing the measured values of the injection pressure with respect to the elapse of time on the holding pressure set value in a different color from the set value graph. Also in this graphic diagram, the screw position and time are displayed so as to proceed from right to left.
FIG. 6 shows a graphic display of the injection speed set value, the injection limit pressure set value, and the injection pressure set value for a plurality of cavities on the same screen on the screen of the operation display panel 33. Since the fourth injection is sometimes invalidated, the injection filling is not performed for this cavity, and an example in which no actually measured value is entered is shown.
[0022]
In FIG. 4, reference numeral 36 denotes a plasticizing weighing stroke calculating circuit for adding the stroke of the injection screw 2 corresponding to the selected filling amount of each cavity and calculating the plasticizing stroke so as to be equal to or greater than the added value. The control circuit 34 instructs the resin gate 13A of the first cavity 11A selected by the cavity selection switch 42 to open, and rotates the servo motor 17 so that the injection speed displayed on the screen of the primary injection into the cavity 11A is achieved. The torque (current) of the servomotor 17 is controlled so that the pressure signal of the load sensor 47 becomes the injection pressure set value by feedback control of the number. After the injection filling and holding of the cavity 11A, the control circuit 34 instructs the closing of the resin gate 13A, and instructs the injection screw drive servomotor 17 to release the resin pressure in the resin passage, and the injection screw stop position at that time. Is set as the starting point of the injection process of the next cavity 11B, the injection of the cavity 11B is instructed, the injection filling and the pressure holding control are performed based on the setting conditions of the cavity 11B, the gate closing and the resin pressure release operation are instructed. With the same injection screw stop position after resin depressurization for the cavities, the injection process start point is used as the starting point, and injection filling, pressure holding control, gate closing, and resin depressurization operation commands are repeated, and all cavities or Then, injection molding control is performed on the selected cavity.
[0023]
A process for performing injection molding by the injection molding machine 1 will be described with reference to a process block diagram of FIG.
The horizontal axis in FIG. 2 is a time axis. The top row shows the injection process of the molten resin by the injection cylinder 3 and the injection screw 2 of the injection unit, and the bottom row shows the injection filling of the cavity 11A and the holding and cooling of the resin pressure by blocks, and the gate of the cavity 11A below. The timing of opening and closing the valve 13A is shown. Below the operation mode of the cavity 11A, the injection filling of the cavity 11B and the holding and cooling of the resin pressure are shown in a block diagram, and the timing of opening and closing the gate valve 13B of the cavity 11B is shown in parallel. Below the operation mode of the cavity 11B, the injection filling of the cavity 11C and the holding and cooling of the resin pressure are shown in a block diagram, and in parallel with this, the timing of opening and closing the gate valve 13C of the cavity 11C is shown. The stroke position of the injection screw corresponding to each of the above steps is shown below the stroke. S indicates the entire stroke. In the injection step, after the individual molten resin is injected and filled into each cavity by the rotation speed and the rotation torque of the ball screw shafts 15 and 15 of the injection unit, and the resin pressure is maintained, the rotation of the ball screw shafts 15 and 15 is returned to the resin. The pressure is reduced and the injection screw 2 is rotated and retracted while rotating to carry out melt plasticization of the resin. During that time, the mold clamping device continues the mold clamping during the pressure holding and cooling process, and reduces the pressure of all the resin in the cavity. Is completed, and after cooling and solidification of the molded product, the pressure is reduced, the mold is opened, and the molded product is removed, thereby completing one cycle of the injection process. After that, the next injection filling starts after the mold is clamped again.
[0024]
In the block diagram of FIG. 3 showing the respective strokes at the time of filling and holding the respective cavities during the injection molding, the rotation of the servomotor 17 starts from the position PA and the injection screw 2 is controlled at a set speed. The stroke when the injection pressure holding of the cavity 11A starts and stops when the pressure holding time is up is set to 1A, the gate valve 13A is closed, the current of the servomotors 17 and 17 is turned off, and the torque is reduced to zero. The resin pressure at the tip of the injection cylinder 3 is depressurized, and at the position where the injection screw 2 returns to mA, the servo motors 17 and 17 are held and controlled to stop the screw 2, and the stop position PB of the injection screw 2 is set to the cavity 11B. The injection position of the injection screw 2 is reset to the injection start position of the injection screw 2 with respect to the cavity 11B. Thereafter, injection filling, pressure holding, and gate closing operations are performed based on the set conditions for the cavity 11B. Similarly, the other cavities 11 thereafter are similarly cooled after the injection start position reset, the injection filling, the pressure holding, and the gate closing are repeated to perform the stepwise injection filling and the pressure holding in all the cavities. As described above, since the injection start position of the injection screw 2 is reset every time the cavity is changed, there is no occurrence of a variation in the weight of the molded product, a defective shape or the like. Further, the mechanism for electrically driving the ball screw device does not exceed the scheduled stop position when the moving speed seen in the hydraulic operation is high, and can perform more accurate and precise position and speed control.
[0025]
Since the amount and shape of the resin filled in each cavity are different from each other, and the conditions for the injection holding pressure for each cavity are also different, the set speed and the set injection pressure of the screw 2 may be different. . Further, the retreat distance of the screw 2 at the time of releasing the pressure of the resin varies depending on the amount of the resin accumulated in the injection cylinder 3 and the temperature of the mold (hot runner 10) at that time, and thus does not become constant.
[0026]
In the case of a conventional injection molding machine that performs multi-stage injection into a mold with multiple cavities, each cavity is sequentially filled with injection, the pressure is maintained, and the position and speed of the injection screw are stopped according to the individual process of each cavity. Is controlled to keep the position and speed, and the dwell time is controlled from the filling completion position for each cavity. Of the screw, changes in the density of the molten resin, and leakage of the molten resin due to variations in the closing time of the check ring, etc., so that the position of the screw changes by the start of the next injection and until the next second filling completion position. The amount of resin changes, which causes weight variation and shape defects of the molded product.
[0027]
Even when changing the injection order of the cavities, or even when not injecting into any cavity, changing the order of opening and closing the resin gate, or stopping the opening and closing, and resetting the second and subsequent injection start positions can be easily performed in multiple stages. And a high-quality molded product can be obtained.
Further, when the cavity 11A is larger than the cavity 11B and the cavity 11C is smaller than the cavity 11B, the time for injection filling, holding pressure and cooling of the molten resin is the shortest for the cavity 11C, and the next for the cavity 11B. Since the cavity 11A becomes the longest and the resin cooling process in each cavity is performed during the injection filling and pressure-holding process of the next cavity, as shown in FIG. In this case, the time for one cycle of the entire injection process can be minimized.
[0028]
【The invention's effect】
According to the injection molding method of the present invention, when molding a plurality of molded products using a mold having a plurality of cavities having different shapes and sizes, a cavity filled with a resin from among the plurality of cavities and molded. Using a resin gate provided for each cavity of the mold, first open the resin gate of the first cavity, control the injection speed and injection pressure based on the individual set values of the cavities, After the filling and holding pressure is completed, the resin gate means is closed, and the injection screw stop position after releasing the resin pressure of the tip of the injection cylinder and the resin passage communicating therewith is used as the starting point of the injection process of the next cavity, and the second The injection speed and holding pressure are controlled based on the set values of the cavities, the gate is closed, and the rest of the other cavities after that are released. Injection filling, holding pressure, and gate closing are repeated as the injection start position of the cavity to perform injection filling and holding pressure control based on stepwise set values in all cavities, so the filling amount for each cavity is stable As a result, the weight and shape of the molded product are stabilized. Also, when changing the injection order of the cavities, or even when not injecting into any cavity, by changing the order of opening and closing the resin gate or stopping the opening and closing, the injection screw stop position is set to the second or later injection start position. A multi-stage injection holding pressure can be easily obtained, and a high quality molded product can be obtained.
[0029]
If the required cavity is selected by the injection selection switch on the operation display panel and only the injection holding pressure molding is enabled for that cavity, molding is performed by combining the conditions of the selected cavity, so that the conditions can be standardized. In the cavity molding, the setting values and the measured values are described together, so that the molding conditions can be optimized while observing the difference for each cavity.
If the defect rate of the multi-cavity molded product differs from cavity to cavity, the number of completed molded product sets will not match, but if all parts are molded by full injection molding cycle as usual, extra It takes time and effort to crush and recycle the molded product and the surplus molded product. A similar problem also occurs when a part of a multi-cavity molded product is required as a supplement. However, as in the present invention, if a necessary cavity is selected and injected and filled by an injection selection switch, This problem is easy to solve.
In addition, in the above-described injection molding method, after filling the resin out of the plurality of cavities, injection molding is performed in order from the cavity having the longer holding pressure and cooling time, so that the time of one cycle of the entire injection process can be minimized. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a mold having a plurality of cavities and a control system of an injection unit which can be used in an injection molding method according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a process sequence when performing injection molding by a control system of a mold and an injection unit in FIG. 1;
FIG. 3 is a block diagram showing respective strokes at the time of filling and holding pressure in each cavity when performing injection molding by a control system of a mold and an injection unit in FIG. 1;
FIG. 4 is a block diagram illustrating a configuration of a control device in FIG. 1;
FIG. 5 is a display example (setting of molding conditions) on the display panel shown in FIG. 4;
6 is another display example of the display panel shown in FIG. 4 (a graphic display example in which primary to quaternary molding condition set values and actual measured values are superimposed).
[Explanation of symbols]
1. Injection molding machine
2. Injection screw
3. Injection cylinder
7 ... fixed mold
8 movable mold
9 ... Support board
9a ... Hydraulic cylinder
10 hot runner
11A ... cavity A
11B ... Cavity B
11C: Cavity C
12 ... fixed frame
13A, 13B, 13C ... resin gate valve
14. Moving frame
15 ... Ball screw shaft
16 ... Ball screw nut
17 ... Servo motor
26 ... Switching valve
33 ... Operation display panel
34 ... Control circuit
35 ... Control device
42 ... Cavity selection switch
47… Injection screw load sensor

Claims

A mold having a plurality of cavities and an opening and closing means for opening and closing each molten resin passage communicating with the cavities; an injection device having an injection screw and an injection cylinder for injecting and filling molten resin into the mold with the molten resin; In an injection molding machine having a control device for controlling opening and closing of means and an injection filling / holding operation to the mold by the injection device, the control device is configured to perform injection filling / holding pressure on one cavity, Close the molten resin passage leading to the injection cylinder and release the resin pressure of the resin passage leading to the injection cylinder, and use the injection screw stop position after releasing the resin pressure as the starting point of the injection process to perform injection filling to the next cavity. -An injection molding machine characterized by performing control so as to perform pressure holding.

The injection molding machine according to claim 1, further comprising a selection unit that selects a cavity into which the molten resin is injected and filled, from among the plurality of cavities.

2. The injection molding apparatus according to claim 1, further comprising an operation display panel, wherein the operation display panel displays an injection filling / holding pressure condition setting screen for each cavity selected by the selection means. Machine.

In the condition setting screen, in the injection filling step, the injection screw speed set value and the injection pressure set value for the divided injection screw position, and in the pressure holding step, the injection pressure set value for the divided time. 4. The injection molding machine according to claim 3, wherein is displayed numerically and / or graphically.

In the operation display panel, on the same screen, for all of the plurality of cavities, a graph in which each set value and measured value of the injection speed and injection pressure in the injection filling step and the measured value are superimposed, and the injection pressure in the pressure holding step. The injection molding machine according to claim 3, wherein a graph in which the set value of the injection speed and the measured value are superimposed is displayed independently for each cavity.

Using a mold having a plurality of cavities of different shapes and sizes, and having a resin gate means for individually opening and closing the branch resin passage from the resin passage leading to the injection nozzle of the injection cylinder to each cavity, and using one mold for one cavity Opening the resin gate means, injecting and filling the molten resin from the resin passage under a predetermined molding condition, keeping the pressure for a set time, closing the resin gate, opening the resin gate means of the next cavity, and injecting and filling the resin. , Holding pressure, resin gate closed, in the injection molding method of molding a plurality of molded products by repeating the same process for the subsequent cavity,
A cavity to be filled with resin is selected from a plurality of cavities, a stroke of an injection screw corresponding to a filling amount of each selected cavity is calculated, and a calculated stroke of each cavity is added, and a measuring screw stroke is calculated. Is set to a value equal to or greater than the above-mentioned added value, and plasticization is performed up to the stroke, the resin gate of the selected first cavity is opened, and the injection speed and the holding pressure of the resin are controlled based on the individual setting conditions of the cavity. After the pressure is completed, the resin gate means is closed, and the injection screw stop position after releasing the resin pressure of the injection cylinder tip and the resin passage leading thereto is set as the starting point of the next cavity injection process, and the next cavity is set. Performs injection filling, pressure holding, gate closing, and resin depressurizing operations based on the conditions. With the screw stop position as the starting point of the injection process, injection filling, pressure holding, gate closing, and resin pressure release are repeated, and injection molding is performed stepwise in all cavities or selected cavities. Injection molding method.

7. The injection molding method according to claim 6, wherein, among the plurality of cavities, injection molding is performed in order from a cavity having a longer holding pressure and cooling time after filling with resin.

A mold having a plurality of cavities having different shapes and sizes, and a resin mold having resin gate means for individually opening and closing a branch resin passage from the resin passage leading to the injection nozzle of the injection cylinder to each cavity is provided. Opening the resin gate means, injecting and filling the molten resin from the resin passage under predetermined conditions, closing the resin gate after keeping the pressure for a set time, opening the resin gate means of the next cavity, and injecting and filling the resin. In the control device of the injection molding machine, which controls to hold the pressure, close the resin gate, and repeat the same process for the subsequent cavities to form a plurality of molded products,
A selection switch for selecting a cavity for performing molding from a plurality of cavities, and an operation display panel for numerically displaying a set value of an injection speed and an injection pressure for the cavity on a screen switched for each cavity selected by the switch. A plasticizing weighing stroke calculating circuit for adding a stroke of the injection screw corresponding to a filling amount of each selected cavity and calculating a plasticizing stroke so as to be equal to or more than the added value; and a cavity selected by the cavity selecting switch. Command the resin gate to open, control the injection speed and injection pressure so that the individual injection speed and injection pressure set values for the cavity become the set values, and after the injection filling pressure holding for one cavity, the resin gate Commanding the closing of the means, and instructing the injection screw driving means to release the resin pressure in the resin passage. Using the exit screw stop position as the starting point of the next cavity injection process, instruct the next cavity to be injected, instruct injection filling, pressure holding, gate closing, and resin pressure relief operation based on individual setting conditions for the cavity, For the subsequent cavities, the same injection screw stop position after resin depressurization is used as the starting point of the injection process, and the injection filling, holding pressure, gate closing, and resin depressurization instructions are repeated, and all cavities are stepped. 7. A control device for an injection molding machine, comprising: a control circuit for performing injection molding by the injection molding method according to claim 6 for performing injection molding on a selected cavity.

9. The control apparatus for an injection molding machine according to claim 8, wherein the setting screen of the injection filling and pressure-holding steps displayed on the operation display panel is switched for each selected cavity, and the injection step is divided into the divided injection screws. Injection screw speed and injection pressure set value with respect to position, injection pressure set value with respect to divided time is displayed numerically on the right side in the pressure holding process, and the screw position is shown in the left side with the screw position in the injection process on the horizontal axis. Graphical display of set values of speed and injection pressure, graphic display of set values of injection pressure with time as the horizontal axis, and screw injection start position numerically display the screw travel distance corresponding to the resin capacity of the cavity. , At the zero point, the position is displayed so that the injection pressure-holding process for the cavity is completed, and when the screen changes from one cavity to the next cavity, The screw position on the horizontal axis is set with the screw stop position at the time when the resin pressure was released after the previous injection and holding pressure was completed, so that the screw position on the horizontal axis was set. A control device for an injection molding machine, wherein a numerical value of an injection screw position is not changed.

10. The control device for an injection molding machine according to claim 9, wherein the set values of the conditions for all cavities are displayed on the same screen, or the measured values are superimposed on the set values of the injection speed and the resin pressure at the time of injection for all cavities. The actual measured value can be displayed as a graph superimposed on the set value of the injection pressure and injection speed at the time of pressurization, and the actual measured value for the injection screw speed and resin pressure condition set value of the injection filling and holding pressure process of all cavities A control device for an injection molding machine characterized in that values can be monitored simultaneously.