JP4610102B2

JP4610102B2 - Ball end mill

Info

Publication number: JP4610102B2
Application number: JP2001047571A
Authority: JP
Inventors: 猛史赤松
Original assignee: Hitachi Tool Engineering Ltd
Current assignee: Moldino Tool Engineering Ltd
Priority date: 2001-02-23
Filing date: 2001-02-23
Publication date: 2011-01-12
Anticipated expiration: 2021-02-23
Also published as: JP2002254234A

Description

【０００１】
【産業上の利用分野】
本願発明は、マシニングセンタ等の工作機械を使用して用いる仕上げ加工用のボールエンドミルの改良に関し、更に詳しくは、ボ−ルエンドミルのボ−ル中心部の形状に関する。
【０００２】
【従来の技術】
ボールエンドミルの場合、ボール中心部付近は、工具回転軸近傍となり、切削速度が十分に得られず、特に平面に近い底面の切削では、ボール刃の逃げ面同士で形成されたチゼルエッジを有する部位（以下、チゼル部と称する。）において、該チゼルエッジにより生成された切り屑の逃げ場がなく、該切り屑はチゼル部と加工面の間で押し潰され、加工面に凝着したり、チゼルエッジに溶着し、構成刃先を形成することにより削り過ぎや、溶着、脱落を繰り返すことにより脱落時に工具の母材ごと欠落し、切れ味劣化によるムシレ加工面を形成する等、平面に近い底面の加工面粗さが得られない状態であった。
【０００３】
そこで、平面に近い底面の加工面粗さを良好にする目的で改善されたものとして、特開２０００−２３３３１１号公報に開示される仕上げ用ボールエンドミルがあり、ボールエンドミルのボール中心部分の強度を高め、かつ切り屑排出性を向上することによってチッピングを防止し、工具寿命を延長するとともに仕上げ面粗さを向上するというものである。
【０００４】
【発明が解決しようとする課題】
通常、ボール刃で切削された切り屑は、該ボール刃のアール部ギャッシュを介して排出されるが、工具正面視でボール刃を形成させる互いのアール部ギャッシュの間隔（以下、チゼル幅と称する。）を直径とする円（以下、チゼル内接円と称する。）の内側は、該アール部ギャッシュと交わりがなく、切り屑の逃げ場がなく、切り屑排出性を考慮するにおいて、チゼル幅の設定が重要となる。
【０００５】
しかしながら、前述の通りチゼル幅を大きくするとチゼル内接円も大きくなり、切り屑の排出性において課題があり、小さくするとチゼル部の強度が弱く、特に、マルテンサイト系ステンレス鋼に代表される硬さＨＲＣ４５を超えるような硬くて溶着及び凝着し易い被削材では、その硬さとともに、切削加工中に切れ刃に溶着、脱落を繰り返すこととなり、脱落時に工具の母材ごと欠落し、工具寿命や加工面粗さに課題があった。
【０００６】
また、特開２０００−２３３３１１号公報に開示されている仕上げ用ボールエンドミルでは、２枚のボール刃１のすくい面を含む平面の間隔が該ボール刃の半径の３％以下、即ちボール刃直径の１．５％以下に設定してあるが、重要点であるチゼル幅５の記載が無く、ボール中心付近の切り屑排出性の面から、その効果は極めて少ないものと考えられる。
【０００７】
ボール刃や外周刃のように、切れ刃設計に自由度があり、切れ刃強度を持たしながら十分なチップポケットが確保できる部位は問題ないが、大きな負のすくい角を有し、且つ切れ刃設計上自由度が少ないチゼルエッジが切れ刃となるボール中心部の形状において課題があった。
【０００８】
【本発明の目的】
本発明は、以上のような背景をもとになされたものであり、切り屑の排出性が良好で、加工面に切り屑が凝着し易い被削材やＨＲＣ４５以上の高硬度な被削材においても良好な仕上げ加工面が得ることができるボールエンドミルを提供することを目的とする。
【０００９】
【課題を解決するための手段】
そのため、第１の本発明は、工具軸心に対し略対称に２枚のボール刃を有するボールエンドミルにおいて、該ボール先端部のボール刃の逃げ面同士で形成されたチゼルエッジを有し、工具正面視でボール刃を形成させる互いのアール部ギャッシュの間隔をボール中心部でボール刃の半径の３〜１５％とし、該チゼルエッジの工具回転方向側に、該逃げ面の曲面に対し凹状の凹んだ部位となる凹状部をチゼルエッジ近傍の該逃げ面に設け、前記凹状部を少なくとも該アール部ギャッシュの間隔を直径とする円の内側に有し、該凹状部とチゼルエッジとの最短距離を０．０３〜０．１２ｍｍとしたことを特徴とするボールエンドミルである。
第２の本発明は、第１の本発明において、凹状部の深さを０．０５ｍｍ〜１ｍｍ設けたことを特徴とするボールエンドミルである。
第３の本発明は、第１または第２の本発明において、チゼルエッジ直角方向の凹状部幅を０．３〜１．５ｍｍとしたことを特徴とするボールエンドミルである。
第４の本発明は、第１乃至第３の何れかの本発明において、凹状部形状をチゼルエッジに対して垂直且つ工具軸に平行な断面視で、該チゼルエッジ側の側面を工具軸に対し４０〜８０°傾斜させたことを特徴とするボールエンドミルである。
第５の本発明は、第１乃至第４の何れかの本発明において、凹状部をギャッシュに開口させずにチゼル内接円の内側の範囲内でチゼルエッジの工具回転方向側に工具正面視で略楕円形状の凹状部を有したことを特徴とするボールエンドミルである。
【００１０】
加工面に切り屑が凝着し易い被削材を切削加工する場合、切削加工中に切れ刃に溶着、脱落を繰り返しによる溶着脱落時の工具の母材の欠落に耐えることのできる強度と、形状的に相反する切り屑排出性を含む切れ味とを両方兼ね備える形状が必要である。そこで本願発明では、先ず強度面を考慮し、チゼル幅をボール刃の半径の３〜１５％としたものである。チゼル幅がボール刃の半径の３％未満であると、強度が不十分であり、１５％を超えるとすくい角が負角であるチゼルエッジの長さ（以下、チゼル長さと称する。）が長くなり過ぎる又はボール刃とチゼルエッジがなす角（以下、チゼル角と称する。）が小さくなり、前者は切れ味が更に劣り、後者はボール刃とチゼルエッジの繋ぎ目の強度が劣るため、チゼル幅をボール刃の半径の３〜１５％とした。ここで、本願発明者等の研究により、チゼル長さは０．３〜０．６ｍｍ、チゼル角は、１６５〜１８０°が望ましい。
【００１１】
また、チゼル幅がボール刃の半径の３％以上にすることによって、ボール中心部の強度は得られるが、前述の通り、切り屑排出性に問題が生じる為、その対策として切り屑排出性の面から、少なくともチゼル内接円の内側において、逃げ面の曲面に対し凹状の凹んだ部位（以下、凹状部と称する。）を有し、該凹状部とチゼルエッジとの最短距離（以下、凹状部距離と称する。）が０．０３〜０．１２ｍｍとしたものである。
【００１２】
本発明を適用することにより、チゼルエッジで生成された切り屑はチゼル部と被削材との間に挟まれ、押し潰されること無く、チゼル内接円の内側に設けられた凹状部を介して排出される。ここで、一般にエンドミルによる加工は断続切削であり、例えば縦方向のみに切削を行うドリルのように連続切削のものより切れ刃の強度が必要となる。凹状部距離が０．０３ｍｍより小さいと、断続切削に耐えられず、ボール先端部が早く摩滅し易くなり、特に加工面に切り屑が凝着し易い被削材を切削加工する場合、切削加工中に切れ刃に溶着、脱落を繰り返しによる溶着脱落時の工具の母材の欠落に耐えることのできる強度が保てなくなる場合もあり、また０．１２ｍｍより大きいと、凹状部の効果が発揮できなくなってしまう為、凹状部距離を０．０３〜０．１２ｍｍとした。
【００１３】
【発明の実施の形態】
本発明を適用することにより、互いに相反する強度と切り屑排出性を兼ね備えることが可能になったので、加工面に切り屑が凝着し易い被削材においても良好な仕上げ加工面が得ることができ、且つ工具寿命が向上することができた。ここで、凹状部にあえて切り屑を止める必要はなく、凹状部を介して排出できれば良く、特にボ−ルエンドミルのボール中心部付近では、被削材とボール刃１との隙間が実切削部から外周側へ漸次広くなる為、凹状部は切り屑の排出を妨げない程度に必要に応じて浅くすることができ、また、切り屑の流れを考慮すると、該凹状部形状は工具正面視におけるチゼルエッジに対して垂直且つ工具軸に平行な断面視で滑らかな曲線状が好ましい。
【００１４】
また、前述の通り、凹状部は、切り屑の排出を妨げない程度に浅くするのがボール中心部の強度面に有利であり、被削材とボール刃との隙間が工具軸線部から外周側へ漸次広くなる為、切り屑の大きさを考慮し、逃げ面の曲面に対し凹状部の深さ（以下、凹状部深さと称する。）は０．０５ｍｍあれば十分であり、最大でもボール刃の半径の１０％程度が望ましい。
【００１５】
更に、凹状部における切り屑の流れを良好にする為、凹状部をギャッシュに開口しても良く、工具正面視において、工具中心を通る直線上で且つチゼルエッジ直角方向の凹状部の最大幅（以下、凹状部幅と称する。）を０．３〜１．５ｍｍとしても良く、該凹状部形状をチゼルエッジに対して垂直且つ工具軸に平行な断面視で、該チゼルエッジ側の側面が工具軸に対し４０〜８０°傾斜（以下、凹状部側面傾斜角と称する。）させても良い。
【００１６】
なお更に、工具中心に近づくに従って、排出される切り屑も小さくなるため、チゼル部の強度の面から、凹状部幅及び／または凹状部深さを工具軸からボール刃１の方向に漸次小さくしても良く、一度排出された切り屑がチゼル部と被削材の隙間に挟まれることによる凝着を抑制するために、工具中心を超えて対抗するチゼルエッジの逃げ面に当たる部位まで凹状部を連続しても良い。ここで、軸断面における凹状部の形状は矩形、Ｖ字、Ｕ字、楕円弧、円弧等があり、同様の作用効果がある。以下、実施例に基づき本発明を具体的に説明する。
【００１７】
（実施例１）
図１、２、３は本発明の一実施例であり、チゼル内接円６の内側でチゼルエッジ２の工具回転方向側にギャッシュに開口させた工具正面視で略半楕円形状の凹状部４を有したものである。また、図４は本発明の他の実施例であり、凹状部４をギャッシュに開口させずにチゼル内接円６の内側の範囲内でチゼルエッジ２の工具回転方向側に工具正面視で略楕円形状の凹状部４を有したものである。上記本発明例の２形状をチゼル幅５をボール刃の半径の５％、凹状部距離７を０．０５ｍｍに設定し、工具母材が超硬合金製の工具径１０ｍｍ（ボ−ル半径５ｍｍ）、刃数２枚刃、外周ねじれ角が３０°、ア−ル逃げ角が１３°、ア−ルすくい角が−５°のソリッドボールエンドミルに適用し、ＴｉＡｌＮコ−ティングを３μｍ被覆したものを製作し、同時に図５に示す凹状部４が無くチゼル幅５がボール刃の半径の１、３、５％の３種類の従来例を同様に製作、コ−ティングし、切削テストを行った。
【００１８】
切削条件は、被削材にマルテンサイト系ステンレス鋼であるＪＩＳ規格のＳＵＳ４２０Ｊ２相当の焼入れ材（５２ＨＲＣ）を用い、回転数１２５００ｍｉｎ^−１、送り速度２．５ｍ／ｍｉｎ、切り込み量は軸方向に０．２ｍｍ、ピック方向に０．２ｍｍとし、エアブロ−を用いて乾式による底面仕上げ切削を行い、切削長１００ｍ時の工具摩耗状態と加工面の状態を観察した。
【００１９】
その結果を図６、７、８に示し、図６は本発明例、図７、８は従来例の加工面の状態である。２種類の本発明例は、凹状部４がギャッシュ部に開口するしないの差異はほとんど見られず、ともに工具摩耗状態が正常摩耗で摩耗幅も小さく、図６に示す通り切り屑の凝着が非常に少ない光沢面が得られ、加工面粗さが良好であったのに対し、従来例である凹状部４が無く、チゼル幅５がボール刃の半径の１％、即ち０．０５ｍｍのものは、チゼル部の強度不足によりカケが発生し、図７に示す通り仕上げ面粗さも粗い結果となり、チゼル幅５がボール刃の半径の３％、即ち０．１５ｍｍ及び５％、即ち０．２５ｍｍのものは、強度的には十分であったが、切削加工中に生じる切り屑がチゼル部で押し潰され、図８に示す通り加工面に切り屑の凝着を生じ、ムシレた様な加工面状態であった。
【００２０】
（実施例２）
次に、前記製作品と同様にチゼル幅５をボール刃の半径の２、３、５、１０、１５、２０％、チゼルエッジ２の工具回転方向側にギャッシュに開口する略半楕円形状の凹状部４を有し、凹状部距離７を０．０５ｍｍに設定した５種類のボールエンドミルを製作し、前記同様の切削テストを行い、切削長１００ｍ時の加工面の状態を観察した。
【００２１】
本発明例である３〜１５％、即ち０．１５〜０．７５ｍｍのものは、チゼル幅５が大きくなるに従って、チゼル長さ８が長くなり、徐々に切削抵抗が大きくなったが、加工面に影響はなく、切り屑の凝着が非常に少ない光沢面が得られ、加工面粗さも良好であった。また、比較例である２０％、即ち１ｍｍのものは、本発明例である１５％、即ち０．７５ｍｍのものより急激に切削抵抗が増加し、ビビリ振動を生じ、ムシレた加工面状態となった。また、比較例であるチゼル幅５をボール刃の半径の２％、即ち０．１ｍｍのものは、チゼル部の強度不足により、カケが発生し仕上げ面粗さも粗い結果となった。
【００２２】
（実施例３）
次に、前記製作品と同様にチゼル幅５をボール刃の半径の５％、即ち０．２５ｍｍ、チゼルエッジ２の工具回転方向側にギャッシュ部に開口する工具正面視で略半楕円形状凹状部４を有し、凹状部距離７を０．０１、０．０３、０．０５、０．０８、０．１、０．１２、０．１５ｍｍに設定した７種類のボールエンドミルを製作し、前記同様の切削テストを行い、切削長１００ｍ時の工具摩耗状態と加工面の状態を観察した。
【００２３】
本発明例である０．０３〜０．１２ｍｍについては、０．１２ｍｍのもののチゼルエッジ２に僅かに溶着が認められたが、加工面に影響はなく、切り屑の凝着が非常に少ない光沢面が得られ、加工面粗さも良好であった。また、比較例である０．１５ｍｍのものになると、凹状部４の効果がほとんどなく、切削加工中に生じる切り屑がチゼル部で押し潰され、加工面に切り屑の凝着を生じ、ムシレた様な加工面状態であった。比較例である凹状部距離７が０．０１ｍｍのものは、チゼルエッジ２の一部にチッピングが認められ、工具回転中心付近が摩滅によりチゼルエッジ２自体がなくなり、平らな面状態となり、ムシレた加工面状態となった。
【００２４】
（実施例４）
次に、前記製作品と同様にチゼル幅５をボール刃の半径の５％即ち０．２５ｍｍ、チゼル内接円６の内側でチゼルエッジ２の工具回転方向側にギャッシュに開口する工具正面視で略半楕円形状の凹状部４を有し、凹状部距離７を０．０５ｍｍに設定し、更に凹状部深さ１１、凹状部幅１０、凹状部側面傾斜角１２を変化させたものを製作し、前記同様の切削テストを行い、切削長２００ｍ時の工具摩耗状態と加工面の状態を観察した。その結果を表１に示す。
【００２５】
【表１】

【００２６】
表１には、本発明例１である凹状部深さ１１を０．３ｍｍ、凹状部幅１０を０．５ｍｍ、凹状部側面傾斜角１２を６０°としたものを基準形状とし、本発明例２〜５は凹状部深さ１１を０．０５〜１ｍｍ、本発明例６〜１０は凹状部幅１０を０．１〜２ｍｍ、本発明例１１〜１４は凹状部側面傾斜角１２を２０〜９０°に変化させたものである。
【００２７】
表１より、本発明例１〜４に記したように凹状部深さを０．０５ｍｍから１ｍｍまでの範囲で切削長３００ｍ迄、光沢面が得られ、本発明例５〜９に記したように、凹状部幅は０．３ｍｍ以上の範囲で切削長３００ｍ迄、光沢面が得られ、本発明例１０〜１４に記したように、凹状部側面角は４０〜８０°の範囲において、加工面の粗さ、工具寿命ともに向上することが解った。更に、凹状部幅は最大でも１．５ｍｍあれば十分であり、凹状部幅を１．５ｍｍより大きくしても、切り屑排出性に関して、更なる効果向上は認められなかった。
【００２８】
【発明の効果】
上記説明したように、本願発明を適用することにより、加工面に切り屑が凝着し易い被削材においても良好な仕上げ加工面が得ることができ、且つ工具寿命が向上することができた。
【図面の簡単な説明】
【図１】図１は、本発明の一実施例であり、その正面図である。
【図２】図２は、図１のチゼル部の拡大図である。
【図３】図３は、図２のＡ−Ａ’軸平行断面図である。
【図４】図４は、本発明の他の実施例であり、そのチゼル部の正面拡大図である。
【図５】図５は、従来の一例であり、そのチゼル部の正面拡大図である。
【図６】図６は、本発明の一実施例のテスト結果を示す説明図である。
【図７】図７は、従来の一例のテスト結果を示す説明図である。
【図８】図８は、他の従来例のテスト結果を示す説明図である。
【符号の説明】
１ボ−ル刃
２チゼルエッジ
３アール部ギャッシュ
４凹状部
５チゼル幅
６チゼル内接円
７凹状部距離
８チゼル長さ
９チゼル角
１０凹状部幅
１１凹状部深さ
１２凹状部側面傾斜角[0001]
[Industrial application fields]
The present invention relates to an improvement of a ball end mill for finishing using a machine tool such as a machining center, and more particularly to a shape of a ball center portion of a ball end mill.
[0002]
[Prior art]
In the case of a ball end mill, the vicinity of the center of the ball is in the vicinity of the tool rotation axis, and the cutting speed is not sufficiently obtained. Particularly in the cutting of the bottom surface close to a flat surface, a portion having a chisel edge formed by the flank surfaces of the ball blades ( In the following, it is referred to as a chisel portion.) In this case, there is no escape space for chips generated by the chisel edge, and the chips are crushed between the chisel portion and the work surface and adhered to the work surface or welded to the chisel edge. However, the surface roughness of the bottom surface close to a flat surface, such as overcutting by forming the constituent cutting edge, missing the base material of the tool at the time of dropping by repeatedly welding and dropping, and forming a gusseted machining surface due to sharpness deterioration. Could not be obtained.
[0003]
Therefore, as an improvement for the purpose of improving the processed surface roughness of the bottom surface close to a flat surface, there is a finishing ball end mill disclosed in Japanese Patent Application Laid-Open No. 2000-233411, and the strength of the ball center portion of the ball end mill is increased. By increasing and improving chip discharge, chipping is prevented, the tool life is extended, and the finished surface roughness is improved.
[0004]
[Problems to be solved by the invention]
Usually, the chips cut by the ball blade are discharged through the rounded portion gasche of the ball blade, but the distance between the rounded portion gashes forming the ball blade in a front view of the tool (hereinafter referred to as chisel width). )) Inside the circle (hereinafter referred to as the chisel inscribed circle) does not intersect with the rounded portion gasche, there is no chip escape, and in consideration of chip discharge, the chisel width Setting is important.
[0005]
However, as described above, if the chisel width is increased, the inscribed circle of the chisel also increases, and there is a problem in chip dischargeability. If the chisel is decreased, the strength of the chisel portion is weak, and in particular, hardness represented by martensitic stainless steel. With a hard work material that exceeds HRC45 and easily welds and adheres, along with its hardness, it repeatedly welds and falls off on the cutting edge during cutting, and the tool base material is missing at the time of dropout. There was also a problem with the surface roughness.
[0006]
Further, in the finishing ball end mill disclosed in Japanese Patent Laid-Open No. 2000-233111, the interval between the planes including the rake face of the two ball blades 1 is 3% or less of the radius of the ball blade, that is, the ball blade diameter. Although it is set to 1.5% or less, the chisel width 5 which is an important point is not described, and the effect is considered to be extremely small from the viewpoint of chip dischargeability near the center of the ball.
[0007]
Like the ball blade and outer peripheral blade, there is a degree of freedom in the design of the cutting edge, and there is no problem with a part that can secure a sufficient chip pocket while having the cutting edge strength, but it has a large negative rake angle and the cutting edge There was a problem in the shape of the center of the ball where the chisel edge, which has little design freedom, becomes the cutting edge.
[0008]
[Object of the present invention]
The present invention has been made based on the background as described above, and has a good chip discharge property and a work material on which a chip easily adheres to a work surface or a hard work with HRC 45 or higher. An object of the present invention is to provide a ball end mill capable of obtaining a good finished surface even in a material.
[0009]
[Means for Solving the Problems]
Therefore, the first aspect of the present invention is a ball end mill having two ball blades substantially symmetrically with respect to the tool axis, and has a chisel edge formed between the flank faces of the ball blades at the tip of the ball. and 3 to 15% of the radius of the ball cutting edge a distance therebetween in the rounded portion gash to form a ball cutting edge of the ball center by vision, the tool rotational direction of the chisel edge, recessed concave relative to the curved surface of該逃up surface It provided a concave portion serving as a site該逃up surface of the chisel edge near said has a concave portion at least the spacing of the rounded portion gash inside the circle to the diameter, the shortest distance between the concave portion and the chisel edge 0.03 It is a ball end mill characterized by a thickness of ˜0.12 mm.
According to a second aspect of the present invention, there is provided a ball end mill according to the first aspect of the present invention, wherein the depth of the concave portion is set to 0.05 mm to 1 mm.
A third aspect of the present invention is the ball end mill according to the first or second aspect of the present invention, wherein the width of the concave portion in the direction perpendicular to the chisel edge is 0.3 to 1.5 mm.
According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the shape of the concave portion is a cross-sectional view perpendicular to the chisel edge and parallel to the tool axis, and the side surface on the chisel edge side is 40 It is a ball end mill characterized by being inclined by -80 °.
In a fifth aspect of the present invention according to any one of the first to fourth aspects of the present invention, the tool is viewed from the front of the tool in the tool rotation direction side of the chisel edge within the range of the inscribed circle of the chisel without opening the concave portion to the gasche. A ball end mill having a substantially elliptical concave portion.
[0010]
When cutting a work material where chips are likely to adhere to the work surface, the strength that can withstand the loss of the base material of the tool at the time of welding and dropping due to repeated welding and dropping on the cutting edge during cutting, The shape which has both sharpness including the chip discharge | emission property which is in conflict with shape is required. Therefore, in the present invention, first, considering the strength, the chisel width is set to 3 to 15% of the radius of the ball blade. When the chisel width is less than 3% of the radius of the ball blade, the strength is insufficient, and when it exceeds 15%, the length of the chisel edge having a negative rake angle (hereinafter referred to as chisel length) becomes long. Or the angle formed by the ball blade and the chisel edge (hereinafter referred to as the chisel angle) becomes smaller, the former is more inferior in sharpness, and the latter is inferior in the strength of the joint between the ball blade and the chisel edge. It was set to 3 to 15% of the radius. Here, it is desirable that the chisel length is 0.3 to 0.6 mm and the chisel angle is 165 to 180 ° based on research by the inventors of the present application.
[0011]
In addition, by setting the chisel width to 3% or more of the radius of the ball blade, the strength of the center of the ball can be obtained. However, as described above, there is a problem with the chip discharging property. A concave portion (hereinafter referred to as a concave portion) with respect to the curved surface of the flank, at least inside the chisel inscribed circle from the surface, and the shortest distance between the concave portion and the chisel edge (hereinafter referred to as the concave portion) The distance is referred to as 0.03 to 0.12 mm.
[0012]
By applying the present invention, the chips generated at the chisel edge are sandwiched between the chisel portion and the work material, and are not crushed, but through the concave portion provided inside the chisel inscribed circle. Discharged. Here, the machining by the end mill is generally intermittent cutting, and the strength of the cutting edge is required more than that of continuous cutting, for example, a drill that performs cutting only in the longitudinal direction. When the concave portion distance is less than 0.03 mm, the cutting of the workpiece, which cannot withstand intermittent cutting, easily wears off the tip of the ball quickly and is likely to have chips adhering to the machining surface, is performed. In some cases, it may not be possible to maintain the strength to withstand the loss of the tool base material when it is welded and removed by repeated welding and dropping to the cutting edge. If it is larger than 0.12 mm, the effect of the concave part can be exhibited. In order to eliminate this, the concave portion distance was set to 0.03 to 0.12 mm.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
By applying the present invention, it has become possible to have both strength and chip discharge properties that are opposite to each other, so that a good finished surface can be obtained even in a work material on which the chip tends to adhere to the processing surface. And the tool life could be improved. Here, it is not necessary to stop the chips on the concave portion, and it is sufficient that the chips can be discharged through the concave portion. Especially, in the vicinity of the ball center portion of the ball end mill, the gap between the work material and the ball blade 1 is the actual cutting portion. Therefore, the concave portion can be made shallower as necessary so as not to hinder the discharge of the chips. A smooth curved shape in a cross-sectional view perpendicular to the chisel edge and parallel to the tool axis is preferable.
[0014]
In addition, as described above, it is advantageous for the strength of the ball center to make the concave portion shallow enough not to disturb chip discharge, and the gap between the work material and the ball blade is on the outer peripheral side from the tool axis portion. In consideration of the size of the chips, it is sufficient that the depth of the concave portion (hereinafter referred to as the concave portion depth) is 0.05 mm with respect to the curved surface of the flank. About 10% of the radius is desirable.
[0015]
Furthermore, in order to improve the flow of chips in the concave portion, the concave portion may be opened in a gash, and in the front view of the tool, the maximum width of the concave portion on the straight line passing through the center of the tool and in the direction perpendicular to the chisel edge (below) The width of the concave portion may be 0.3 to 1.5 mm, and the shape of the concave portion is perpendicular to the chisel edge and parallel to the tool axis. You may make it incline 40-80 degrees (henceforth a concave part side surface inclination angle).
[0016]
Furthermore, since the chip to be discharged becomes smaller as it approaches the center of the tool, the width of the concave portion and / or the depth of the concave portion is gradually reduced from the tool axis toward the ball blade 1 in terms of the strength of the chisel portion. In order to suppress adhesion caused by the chip that has been discharged once being caught in the gap between the chisel part and the work material, the concave part is continuously connected to the part that hits the flank of the chisel edge that opposes the tool center. You may do it. Here, the shape of the concave portion in the axial section includes a rectangle, a V-shape, a U-shape, an elliptical arc, an arc, and the like, and has the same effect. Hereinafter, the present invention will be specifically described based on examples.
[0017]
Example 1
1, 2 and 3 show an embodiment of the present invention. A concave part 4 having a substantially semi-elliptical shape in a front view of a tool opened in a gash manner on the tool rotation direction side of the chisel edge 2 inside the chisel inscribed circle 6 is shown. I have it. FIG. 4 shows another embodiment of the present invention. The concave portion 4 is not elliptically opened in the tool rotation direction side of the chisel edge 2 within the chisel inscribed circle 6 without opening the concave portion 4 in a gash. It has a concave portion 4 having a shape. The two shapes of the present invention were set such that the chisel width 5 was set to 5% of the radius of the ball blade, the concave portion distance 7 was set to 0.05 mm, and the tool base material was made of cemented carbide with a tool diameter of 10 mm (ball radius 5 mm). ), Applied to a solid ball end mill with 2 blades, outer helix angle of 30 °, arm relief angle of 13 °, and rake angle of -5 °, and coated with 3μm of TiAlN coating At the same time, three types of conventional examples having no concave portion 4 shown in FIG. 5 and having a chisel width 5 of 1, 3, 5% of the radius of the ball blade were similarly manufactured, coated, and subjected to a cutting test. .
[0018]
The cutting conditions were a martensitic stainless steel SUS420J2 quenching material equivalent to SUS420J2 (52HRC), the rotational speed was 12500 min ⁻¹ , the feed rate was 2.5 m / min, and the cutting amount was 0 in the axial direction. 0.2 mm in the pick direction, 0.2 mm in the pick direction, and bottom finish cutting was performed by dry using an air blower, and the state of tool wear and the state of the machined surface at a cutting length of 100 m were observed.
[0019]
The results are shown in FIGS. 6, 7, and 8, where FIG. 6 shows the state of the processed surface of the example of the present invention, and FIGS. In the two examples of the present invention, the difference that the concave portion 4 does not open to the gash portion is hardly observed, both the tool wear state is normal wear and the wear width is small, and chip adhesion is observed as shown in FIG. While a very small glossy surface was obtained and the machined surface was good, the conventional concave portion 4 was not present, and the chisel width 5 was 1% of the radius of the ball blade, that is, 0.05 mm. As shown in FIG. 7, chipping occurs due to insufficient strength of the chisel part, resulting in a rough finish surface. The chisel width 5 is 3% of the radius of the ball blade, that is, 0.15 mm and 5%, that is, 0.25 mm. However, the chip generated during the cutting process was crushed by the chisel, causing chip adhesion on the processed surface as shown in FIG. The surface condition.
[0020]
(Example 2)
Next, in the same manner as in the above-mentioned product, the chisel width 5 is set to 2, 3, 5, 10, 15, 20% of the radius of the ball blade, and the substantially semi-elliptical concave portion that opens to the tool rotation direction side of the chisel edge 2 in a gash. 5 and 5 types of ball end mills having a concave portion distance 7 set to 0.05 mm were manufactured, and the same cutting test as described above was performed to observe the state of the processed surface when the cutting length was 100 m.
[0021]
In the example of the present invention having 3 to 15%, that is, 0.15 to 0.75 mm, as the chisel width 5 is increased, the chisel length 8 is increased and the cutting resistance is gradually increased. The glossy surface with very little chip adhesion was obtained, and the surface roughness was good. Further, the comparative example of 20%, i.e. 1 mm, has a sharper increase in cutting resistance than the 15% example of the present invention, i.e., 0.75 mm. It was. Further, when the chisel width 5 as a comparative example was 2% of the radius of the ball blade, that is, 0.1 mm, chipping occurred due to insufficient strength of the chisel portion and the finished surface was rough.
[0022]
(Example 3)
Next, the chisel width 5 is set to 5% of the radius of the ball blade, that is, 0.25 mm, and the chisel edge 2 has a substantially semi-elliptical concave portion 4 as viewed from the front of the tool that opens to the gash portion on the tool rotation direction side in the same manner as in the manufactured product. 7 types of ball end mills having a concave portion distance 7 set to 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, and 0.15 mm are manufactured as described above. A cutting test was performed, and the state of tool wear and the state of the machined surface at a cutting length of 100 m were observed.
[0023]
In the case of 0.03-0.12 mm, which is an example of the present invention, slight welding was observed on the chisel edge 2 of 0.12 mm, but there was no effect on the processed surface, and the glossy surface with very little chip adhesion Was obtained, and the roughness of the processed surface was also good. Further, in the case of 0.15 mm which is a comparative example, there is almost no effect of the concave portion 4, and chips generated during the cutting process are crushed by the chisel part, causing chip adhesion on the processed surface, and mus The machined surface state was In the comparative example having a concave portion distance 7 of 0.01 mm, chipping is recognized at a part of the chisel edge 2, and the chisel edge 2 itself disappears due to wear near the tool rotation center, resulting in a flat surface state. It became a state.
[0024]
Example 4
Next, the chisel width 5 is set to 5% of the radius of the ball blade, that is, 0.25 mm, as in the above-described product, and the tool is opened from the chisel inscribed circle 6 to the tool rotation direction side of the chisel edge 2 in a gash direction when viewed from the front of the tool. Produced with a semi-elliptical concave portion 4, with the concave portion distance 7 set to 0.05 mm, and the concave portion depth 11, the concave portion width 10, and the concave portion side surface inclination angle 12 changed, The same cutting test was performed, and the state of tool wear and the state of the machined surface when the cutting length was 200 m were observed. The results are shown in Table 1.
[0025]
[Table 1]

[0026]
Table 1 shows an example of the present invention in which the concave portion depth 11 of the present invention example 1 is 0.3 mm, the concave portion width 10 is 0.5 mm, and the concave portion side surface inclination angle 12 is 60 °. 2 to 5 has a recessed portion depth 11 of 0.05 to 1 mm, Invention Examples 6 to 10 have a recessed portion width 10 of 0.1 to 2 mm, and Invention Examples 11 to 14 have a recessed portion side surface tilt angle 12 of 20 to 20 mm. It was changed to 90 °.
[0027]
From Table 1, as described in Invention Examples 1 to 4, a glossy surface was obtained with a concave portion depth ranging from 0.05 mm to 1 mm up to a cutting length of 300 m. As described in Invention Examples 5 to 9 In addition, a glossy surface is obtained with a concave portion width of 0.3 mm or more and a cutting length of 300 m, and as described in Examples 10 to 14 of the present invention, the side surface angle of the concave portion is 40 to 80 °. It was found that both surface roughness and tool life were improved. Furthermore, it is sufficient that the width of the concave portion is 1.5 mm at the maximum, and even if the width of the concave portion is larger than 1.5 mm, no further improvement in the effect on the chip discharging property is recognized.
[0028]
【The invention's effect】
As described above, by applying the present invention, it was possible to obtain a good finished surface even in a work material in which chips are likely to adhere to the processed surface, and to improve the tool life. .
[Brief description of the drawings]
FIG. 1 is a front view of an embodiment of the present invention.
FIG. 2 is an enlarged view of the chisel portion of FIG. 1;
FIG. 3 is a cross-sectional view taken along the line AA ′ in FIG. 2;
FIG. 4 is a front enlarged view of a chisel portion according to another embodiment of the present invention.
FIG. 5 is an enlarged front view of the chisel portion as an example of the prior art.
FIG. 6 is an explanatory diagram showing test results of an example of the present invention.
FIG. 7 is an explanatory diagram showing a conventional test result.
FIG. 8 is an explanatory diagram showing test results of another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ball blade 2 Chisel edge 3 Earl part gasche 4 Concave part 5 Chisel width 6 Chisel inscribed circle 7 Concave part distance 8 Chisel length 9 Chisel angle 10 Concave part width 11 Concave part depth 12 Concave part side surface inclination angle

Claims

In a ball end mill having two ball blades substantially symmetrically with respect to the tool axis, each of the ball end mills has a chisel edge formed by the flank faces of the ball blades at the tip of the ball, and forms the ball blades in front view of the tool. The distance between the rounded portion gashes is 3 to 15% of the radius of the ball blade at the center of the ball, and a concave portion that is a concave portion with respect to the curved surface of the flank is located near the chisel edge on the tool rotation direction side of the chisel edge. It is provided on the flank, and has the concave portion at least inside a circle whose diameter is the distance between the round portion gashes, and the shortest distance between the concave portion and the chisel edge is 0.03 to 0.12 mm. And ball end mill.

The ball end mill according to claim 1, wherein the depth of the concave portion is 0.05 mm to 1 mm.

The ball end mill according to claim 1 or 2, wherein the width of the concave portion in the direction perpendicular to the chisel edge is 0.3 to 1.5 mm.

4. The ball end mill according to claim 1, wherein the shape of the concave portion is inclined with respect to the tool axis by 40 to 80 [deg.] With respect to the tool axis in a cross-sectional view perpendicular to the chisel edge and parallel to the tool axis. Ball end mill characterized by that.

5. The ball end mill according to claim 1, wherein the concave portion has a substantially elliptical shape when viewed from the front of the tool on the tool rotation direction side of the chisel edge within a range inside the inscribed circle of the chisel without opening the concave portion to the gasche. A ball end mill characterized by having a portion .