JP4061247B2

JP4061247B2 - Drill and end mill

Info

Publication number: JP4061247B2
Application number: JP2003200196A
Authority: JP
Inventors: 大輔柴田
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-07-23
Filing date: 2003-07-23
Publication date: 2008-03-12
Anticipated expiration: 2023-07-23
Also published as: JP2005040869A

Description

【０００１】
【発明の属する技術分野】
本発明は鋼やプリント基板等の被削材に穴あけ加工するためのドリルや側面加工するためのエンドミル、およびその製造方法に関する。
【０００２】
【従来の技術】
従来より、配線回路基板の回路パターンの１つであるビアホールを形成する方法の１つとして基板の所定位置にドリルを用いて穴あけ加工する方法が用いられている。近年、回路基板の高集積化につれてドリル加工に対しても加工数の増加および高速化、加工径の小径化が要求されている。
【０００３】
しかしながら、従来のドリルで高速加工を行うとドリルの回転数が上がって外周刃の摩耗が顕著になり、また中心部では外周部に比べて速度が上がらずスラスト荷重によってドリルの中心部に圧壊や折損を生じるという問題があった。また、ドリル径が小径化すると耐折損性はますます低下することが知られている。
【０００４】
また、エンドミル加工においても切削効率の向上を目的として高切り込みや高送りの高能率切削が余儀なくされる傾向にあるが、先端切刃面に十分な強度・靭性を具備するもので無いために、高衝撃の加わる切削に用いると先端切刃にチッピングが発生しやすくなり、短寿命の原因となる。
【０００５】
そこで、特許文献１では、中心部を靭性の高い超硬合金とし、その外周に中心部とは異なる組成の高硬度超硬合金を配設したドリル構成とすることにより、耐摩耗性および耐折損性に優れたドリルとなることが記載されている。また、特許文献２では、ドリルをセラミックス成分と金属成分で構成するとともにドリル中の金属成分を傾斜させて、表面が耐摩耗性に優れ、かつ内部が耐欠損性に優れる構成としたドリルが記載されている。
【０００６】
【特許文献１】
特開昭５９−１７５９１２号公報
【０００７】
【特許文献２】
特開平１２−２９６４０５号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、特許文献１乃至２に記載された中心に高靭性材を配するとともにその周囲に高硬度材を配した単芯構造からなるドリルでは、特にドリル径が小径化した場合、ドリルのシャンク部分での剛性が不足して折損が発生しやすくなるという問題があった。また、上記特許文献１乃至２の単芯構造を耐折損性向上の目的で単純に多芯構造とすると、低硬度の芯材が切刃部として部分的に露出し、切刃部にチッピングや欠損が発生するという問題があった。また、エンドミル加工についても同様の問題が発生する可能性があった。
【０００９】
本発明は上記課題を解決するためになされたもので、その目的は、ドリルまたはエンドミル加工の高速化、小径化によっても高い耐摩耗性および耐折損性を兼ね備えた穴あけ工具を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者らは上記課題に対し、小径高速穴あけ加工に用いても優れた耐欠損性を発揮するとともに、長期にわたって使用が可能な穴あけ工具を開発すべく研究を行った結果、長尺状の靭性の高い材料からなる芯材の外周を前記芯材とは異なる高硬度組成からなる表皮材にて被覆してなる単芯繊維体を複数本集束した多芯繊維体にて穴あけ工具を構成し、かつ、前記穴あけ工具の切刃部に前記芯材が存在しない構成、つまり、切刃部を硬度の高い表皮材にて構成することによって、ドリルやエンドミルの耐摩耗性および耐折損性をともに高めることができることを知見した。また、本発明の第１の実施態様においては、前記単芯繊維体が長尺方向に複数本ねじれた状態で集束され多芯構造体をなしていることが、切刃部に芯材が露出せず確実に表皮材のみにて形成できる点で重要である。
【００１２】
また、本発明の第２の実施態様においては、前記切刃部の横断面における前記表皮材の占める面積が前記切刃部の断面積全体に対して７０〜９０％の割合で存在することが、耐摩耗性を向上させる点で重要である。
【００１６】
【発明の実施の形態】
本発明のドリルについてその好適例であるツイストドリルの一例についての概略側面図である図１を基に説明する。
【００１７】
図１によれば、ツイストドリル（以下、単にドリルと略す。）１は、全体が略円柱状をなし、その先端にチゼル形状の切刃部２を形成した形状からなる。また、ドリル１は図２（ｂ）に示すように芯材４の外周を表皮材５にて被覆した単芯繊維体６が複数本集束された多芯繊維体７からなる。
【００１８】
本発明によれば、ドリル１の耐折損性を主として担う芯材４に高靭性材料を用い、かつその周囲に高硬度の異種材料を組み合わせた単芯繊維体６を集束した多芯繊維体７にてドリル１を構成することによってドリル１の強度を高めることができ、かつクラックの進展を抑制してドリル１が根元から破壊することを防止して耐折損性を向上させることができるとともに、切刃部２においては刃立て性がよいことにより切れ味がよく、かつ摩耗しにくい特性を付与することができて、優れた耐摩耗性と耐折損性を併せ持つ工具寿命の長いドリルとなる。また、単芯繊維体６を複数本集束させることにより、ドリル１の強度の向上やクラックを偏向してクラックの進展を抑制する作用により、ドリル１全体としての耐折損性を飛躍的に高めることができる。さらに、本発明によれば、部分的な切削抵抗の偏りが生じることもないので安定した穴位置精度を達成することができる。
【００１９】
また、本発明のドリルによれば、図２（ｂ）に示すように、切刃部２が表皮材５にて形成され、芯材４が存在しないことが大きな特徴である。すなわち、図４（ａ）、（ｂ）に示すように、切刃部２に芯材４が存在すると、靭性は高いものの硬度が低いため耐摩耗性に劣り、切削の際に切刃部２中の芯材４からなる部分が高硬度の表皮材５よりも早期に摩耗し、その部分から異常摩耗が発生してしまいドリル１の工具寿命が極端に短くなってしまう。そこで、本発明のように切刃部２を表皮材５にて構成にすることで、上記のような異常摩耗の発生を防ぐことができ、かつ、複合構造体の優れた耐折損性をも有する工具寿命の優れたドリルを作製することができる。
【００２０】
なお、図１，２のドリル１において、本発明のドリルにおける切刃部２とは、ドリル１先端からドリル径が広角する部分（図２のＡ領域における交差稜部分）を指す。
【００２１】
また、本発明の第１の実施態様においては、切刃部２の軸方向に垂直な横断面、図１のドリル１の先端付近の断面（ａ−ａ面）における表皮材５の面積Ｓ_ｓが、多芯繊維体７断面の面積全体Ｓ_ｔに対して（Ｓ_ｓ／Ｓ_ｔで）７０〜９０％、好ましくは７５〜９０％であることが、耐折損性を損ねることなく異常摩耗の防止効果を持つことができる点で重要である。
【００２２】
ここで、本発明の第１の実施態様においては、単芯繊維体６が長尺方向に複数本ねじれた状態で集束され多芯繊維体７をなしていることが、切刃部２に芯材４が露出せず確実に高硬度な表皮材５のみにて形成できる点で重要である。
【００２３】
なお、図２（ａ）のドリル１のａ−ａ断面で見たときに、芯材４は円柱形あるいは多角柱であることが応力集中を防止する点で望ましいが、芯材４が星形や花びら形、波形等の突起を有する断面形状であってもよい。
【００２４】
また、ドリル１を構成する多芯繊維体７は、図１（ｂ）に示すように、長尺方向に複数本ねじれた状態で集束されていることが望ましい。また、この場合には、ドリル１の中心部は単芯繊維体６がほとんど位置を変えることなく単独でねじられており、外周部は近接する単芯繊維体６とともに大幅に位置を変えるようにねじられた構造となる。
【００２５】
なお、単芯繊維体６のねじり方向とドリル１のフルートのねじれ方向とを同じとすると、芯材４が切刃部２に対して垂直に近い角度で配列されるために、切刃部２における芯材４の露出面積が最も少なくなり耐摩耗性に優れる表皮材５の占める割合が多くなるので、ドリル１の耐摩耗性が向上する。
【００２６】
逆に、単芯繊維体６のねじり方向とドリル１の切刃部２のねじれ方向とが逆方向になるように配置すると、隣接する単芯繊維体６間に残留した応力が切削時のトルク抵抗に対して効果的に働き、ねじれによる折損に対する性能が向上する。ドリル１の穴あけ性能のバランスを考慮すると、単芯繊維体６のねじり方向とドリル１の切刃部２のねじれ方向とが逆方向になって直交するような配置とすることが望ましい。
【００２７】
他方、たとえば一般的なドリル径０．３〜１．０ｍｍ、溝長（切刃部＋フルート部）５〜１５ｍｍのプリント基板加工用小径ドリルにおいて多芯繊維体７は、ドリル１の横断面で見たときに単一繊維体平均直径１０〜１００μｍ、特に２０〜５０μｍからなることがドリル全体における強度と硬度を保持させる点で望ましい。
【００２８】
本発明におけるドリル１は、芯材４と表皮材５の材質の選択により熱膨張係数の差から芯材４と表皮材５間に残留応力を生じさせることが可能であり、その制御によってドリル１の耐折損性を向上させることができる。
【００２９】
芯材４−表皮材５の材質としては、ハイス鋼などの金属、超硬合金、サーメット、セラミック、ダイヤモンド、ｃＢＮ等が挙げられ、中でも、ドリル１の耐摩耗性および耐折損性、穴位置精度、焼成等の製造の容易性、コスト等を勘案すると、芯材４および表皮材５共にＷＣを主成分とする硬質相と、ＣｏやＮｉ等の鉄族金属を主成分とする結合相を有するＷＣ基超硬合金とすることが望ましい。また、ＷＣ基超硬合金を表皮材５に用いることにより加工時に発生した熱を効率的に逃がす効果もある。さらに、表皮材５を構成するＷＣ基超硬合金としては、硬度が高く、耐摩耗性の優れているＷＣ粒子の平均粒径が１μｍ未満と微細な超微粒超硬合金を用いることがより耐摩耗性の優れたドリルを作製できるため望ましい。
【００３０】
また、本発明によれば、切刃部２の耐摩耗性をさらに高めるために、単芯繊維体６を複数本集束した多芯繊維体７の外周の少なくとも一部に、周期律表４ａ，５ａ，６ａ族金属の炭化物、窒化物、炭窒化物、Ａｌ_２Ｏ_３、ＺｒＯ_２、ＢＮ、ＤＬＣ等の硬質被覆膜を少なくとも１層形成することもできる。
【００３１】
（製造方法）
次に、本発明のドリルを製造する方法について、図３の模式図をもとに説明する。
【００３２】
まず、芯材４用の原料として、例えば平均粒径０．０１〜１０μｍの芯材を形成する粉末に、パラフィンワックス、ポリスチレン、ポリエチレン、エチレン‐エチルアクリレート、エチレン‐ビニルアセテート、ポリブチルメタクリレート、ポリエチレングリコールおよびジブチルフタレート等の有機バインダ、可塑剤および溶剤を添加して混錬して芯材用混合物８ａ、またはこの芯材用混合物８ａをプレス成形または鋳込み成形等の成形法により円柱形状に成形した芯材用成形体８ｂを作製する。ここで、後述する共押出成形によって均質な多芯成形体１２を得るためには、前記有機バインダの添加量は芯材を形成する粉末に対して５０〜２００体積部、特に７０〜１５０体積部とすることが望ましい。
【００３３】
一方、上述した表皮材５をなす原料粉末を前述したバインダとともに混錬してプレス成形、押出成形または鋳込み成形等の成形方法により中空部を有する円筒形状の表皮材用成形体９を作製し、この表皮材用成形体９の中空部に芯材用混合物８ａを充填するか、もしくは芯材用成形体８ｂを挿入することで成形体１０を作製する（図３（ａ）参照）。なお、表皮材用成形体９の外径Ｒｓに対する芯材用混合物８ａの直径Ｒｃの比（Ｒｃ／Ｒｓ）は０．２〜０．８、特に０．２〜０．６であることがドリル１の切刃部２を確実に表皮材５にて構成する点で望ましい。
【００３４】
なお、成形体１０を作製する際、表皮材用成形体９は半割り形状の成形体２つ等の複数の成形体を芯材用成形体８ｂの外周に配置する方法であっても良いが、本発明によれば、成形や後述する共押出成形用に成形体をセットする際に容易な点、および芯材用成形体８ｂの直径が表皮材用成形体９の肉厚にて対して小さくなることから、芯材用成形体８ｂが折れたり曲がったりしやすく、上述した中空状の表皮材用成形体を作製する方法を用いて、この表皮材用成形体の中空部に芯材用混合物８ａを充填する方法を採用することが望ましい。また、芯材および表皮材の構成比、成形体の強度に合わせて作成法を選ぶことが可能である。
【００３５】
そして、上記成形体１０を押出成形して芯材用混合物８ａまたは芯材用成形体８ｂと表皮材用成形体９を共押出成形することにより芯材用混合物８ａの周囲に表皮材用成形体９が被覆され、細い径に伸延された単芯成形体１１を作製する（図３（ｂ）参照）。
【００３６】
次に、上記共押出しした長尺状の単芯成形体１１を複数本集束して再度共押出成形することにより、単芯成形体１１が複数本集束された多芯成形体１２を作製する（図３（ｃ）参照）。
【００３７】
さらに、本発明によれば、上記伸延された長尺状の多芯成形体１２を所望によりさらに繰り返して再度共押出成形して、多芯成形体１２をさらに細く束ねた多芯成形体を製作することも可能である。
【００３８】
ここで、切刃部２に芯材４が存在しないようにするために、多芯繊維体７の軸方向に垂直な横断面における表皮材５の占める面積Ｓ_ｓと芯材４の占める面積Ｓ_ｃとの比（Ｓ_ｓ／Ｓ_ｃ）が１〜１０となるように成形体を調整することが望ましく、切刃部２に芯材４が露出せず確実に高硬度な表皮材５のみの構成を容易に作製することができ、異常摩耗を防ぐことができる。
【００３９】
また、多芯成形体１２をねじれ構造にするには図３（ｃ）に用いる押出成形機の口金１３にねじり溝を設けることによるねじり押出しにより得ることが可能であるが、ストレートに押し出された多芯成形体１２に可塑性をもたせた状態で物理的に一端を固定して他端を回転させることによってねじれ構造を形成したり、両端を固定して互いに逆向きに回転させることによってねじれ構造を形成したりすることも可能である（図３（ｄ）参照）。
【００４０】
次に、上記多芯成形体１２を３００〜７００℃で１０〜２００時間昇温または保持する脱バインダ処理した後、さらに所定の条件にて焼成を行う。焼成については通常の無加圧焼成であってもよいが、ホットプレスやＨＩＰ焼成、超高圧焼成を用いてもよい。
【００４１】
そして、上記工程にて得られた焼結体に対し、所望により外周研磨を施した後、繊維体の配置を勘案しつつ、上記多芯成形体１２の先端に切刃を、および周面にフルートを研削によって形成して表皮材からなる切刃部を形成することにより本発明のドリル１を作製することができる（図３（ｅ）参照）。
【００４２】
なお、図１乃至３については、ドリルについて説明したが、本発明はこれに限定されるものではなく、エンドミルであってもよい。本発明によれば、エンドミル１５の場合には、ドリルのフルート部とランド部との交差稜線に相当する部分が横切刃をなし切削に関与することから、多芯繊維体は必然的に横切刃のねじれ方向と同じ方向にねじれた構成となる。（図１（ｃ）参照）
【００４３】
【実施例】
（実施例）
原料粉末として、ＷＣ粉末（平均粒径０．３μｍ）、Ｃｏ粉末（平均粒径０．６μｍ）、ＶＣ粉末（平均粒径１．０μｍ）、Ｃｒ_３Ｃ_２粉末（平均粒径１．２μｍ）を用意し、これら原料粉末を表１に示す配合組成に配合し、湿式ボールミルで７２時間混合した。さらに、所定量の有機バインダとして、ポリビニルアルコール、セルロース、ポリエチレングリコールを用い、潤滑剤、分散剤を上記混合粉末に対して１００体積部添加して混練機で混練して表１に示す２種の混練物を作製した。
【００４４】
【表１】

【００４５】
次に、図３に示した方法により外径２２ｍｍの中空の表皮材用成形体と直径１１ｍｍの芯材用成形体をそれぞれ成形した後、表皮材用成形体に芯材用成形体を挿入し、共押出成形して単芯成形体を作製し、さらにこの単芯成形体を２５０本束ねて再度共押出成形し、多芯成形体（サンプル１）を得た。
【００４６】
また、サンプル１の成形に際して、押し出された多芯成形体の一端を固定して回転させることによって、長尺方向に対してねじれた多芯成形体（サンプル２）も作製した。
【００４７】
上記多芯成形体を５００℃で５０時間脱バインダ処理を行った後、真空中、１４００℃で１時間焼成し、引き続いてＡｒ雰囲気中、温度：１３４０℃、圧力：１００ＭＰａ、保持時間：１時間の条件でＨＩＰ処理を施し、外周加工を施して直径が３．５ｍｍ、全長４０ｍｍの円柱形状の多芯繊維体を作製した。
【００４８】
さらに、上記複合構造体の外周に芯材の位置を確認しながら先端に切刃部を、側面にフルート（刃溝）を加工によって形成して溝長（切刃部＋フルート部）９．０ｍｍ（そのうち切刃部：０．１１６６ｍｍ）で外径φ０．５ｍｍのドリルを作製した。なお、切刃部の横断面（フルート部との境界面：図１のａ−ａ面）において、顕微鏡観察したところ、表皮材の占める面積は断面全体に対して７５％であった。
【００４９】
得られたドリルを用いて、厚さ０．２ｍｍのガラス基板と厚さ０．２ｍｍのエポキシ樹脂基板とを交互に４層ずつ積層した擬似プリント基板に対し、下記の条件で孔あけ加工を行い、ドリルが折損するまでに加工できた加工数および基板上面の穴位置に対する基板下面の穴位置のずれを穴位置精度として竹内製作所製ピクセルを用いて測定した。結果は表２に示した。
【００５０】
加工条件
主軸回転数：１２ｋｒｐｍ
送り：２．０ｍ／ｍｉｎ．
基板：エポキシ系０．８ｍｍ厚みの3枚重ね
（比較例１）
図３に示した方法により外径２０ｍｍの芯成形体の周囲に厚さ１ｍｍの半割り形状の表皮材用成形体をかぶせ、共押出成形し単芯成形体を作製した（比較例１）。これを実施例と同様に脱バインダ処理および焼成を行い、同様にドリルを作製した。実施例の押出成形において、長さ方向に均一な形状の単芯繊維体を作製し、実施例と同様に脱バインダ処理および焼成を行い、同様に加工して単芯構造のドリルを作製した。なお、ドリルのチゼル形状は実施例と同じとしたところ、ドリル断面は図４（ｂ）のような構成となっていた。実施例と同様に孔あけ加工を行ったところ、表２に示すように加工数５０００個を加工した時点でドリルのチャック部から折損が発生した。
【００５１】
（比較例２）
つぎに、表皮用材料を外径２０ｍｍの円柱状に成型し、その周囲に厚さ１ｍｍの半割り形状に成型した芯材成形体を被覆させ、図３（ｂ）以降の共押出成形し単芯成形体を作製し、さらにこの単芯成形体を２５０本束ねて再度共押出成形し、多芯成形体（比較例２）を得た。これを実施例と同様に脱バインダ処理および焼成を行い、同様にドリルを作製した。ドリル断面は図４（a）のような構成となっていた。実施例と同様に穴あけ加工を行ったところ、表２に示すように８０００個を加工が可能であったが、穴位置精度の測定結果からもばらつきが大きかった。これは、芯材材料部において局所的に摩耗が進行したことが原因であると考えられる。
【００５２】
（比較例３）
実施例の芯材の組成に有機バインダを加えた後、金型成形を行って均一な組成からなる成形体を作製する以外は実施例と全く同様にドリルを作製した。なお、ドリルの外観形状は実施例と同じとした。実施例と同様に穴あけ加工を行ったところ、表２に示すように加工数２０００個を加工した時点でドリルのチャック部から折損が発生した。
【００５３】
【表２】

【００５４】
表２の結果から明らかなように、芯材と表皮材とからなる単芯繊維体を複数本集束した多芯繊維体からなり、切刃部を表皮材にて形成したドリルでは、実使用上十分な加工数１００００個まで折損することなく良好な加工ができ、かつ穴位置精度も優れていた。また、長尺方向にねじれた構造をもつサンプル２については１２０００個以上の加工が可能であった。
【００５５】
【発明の効果】
以上詳述したとおり、本発明のドリルおよびエンドミルによれば、長尺状の硬度の高い材料からなる芯材の外周を前記芯材とは異なる組成で靭性の高い材料からなる表皮材にて被覆してなる単芯繊維体を複数本集束した多芯繊維体にて構成し、かつ、切刃部に前記芯材が存在しない構成、つまり、切刃部を芯材以外の表皮材にて構成するとともに、前記切刃部の横断面における前記表皮材の占める面積が前記切刃部の断面積全体に対して７０〜９０％の割合で存在する構成か、または前記単芯繊維体が長尺方向に複数本ねじれた状態で集束されて多芯構造体をなしている構成とすることによって、耐摩耗性および耐折損性をともに高めることができる。また、部分的な切削抵抗の偏りが生じることもないので安定した穴位置精度を達成することができる。
【図面の簡単な説明】
【図１】本発明のドリルおよびエンドミルの概略側面図であり、（ａ）多芯繊維体をねじらない構成のドリル、（ｂ）多芯繊維体をフルートに沿ってねじった構成のドリル、（ｃ）多芯繊維体をフルートに沿ってねじった構成のエンドミル、をそれぞれ示している。
【図２】（ａ）図１（ａ）のドリルの先端部拡大図、（ｂ）図２（ａ）のａ−ａ断面図（一部透視図）である。
【図３】（ａ）から（ｅ）は、本発明の穴あけ工具の製造方法を説明するための工程図である。
【図４】（ａ）と（ｂ）は複合構造体を用いた従来のドリルの断面図（一部透視図）である。
【符号の説明】
１ツイストドリル（ドリル）
２切刃部
３複合構造体
４芯材
５表皮材
６単芯繊維体
７多芯繊維体
８ａ芯材用混合物
８ｂ芯材用成形体
９表皮材用成形体
１０成形体
１１単芯成形体
１２多芯成形体
１３口金
１５エンドミル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill for drilling a work material such as steel or a printed circuit board, an end mill for side machining, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, as one method for forming a via hole, which is one of circuit patterns of a printed circuit board, a method of drilling a predetermined position on a substrate using a drill has been used. In recent years, as circuit boards are highly integrated, drilling has been required to increase the number of processing, increase the speed, and reduce the processing diameter.
[0003]
However, when high-speed machining is performed with a conventional drill, the number of rotations of the drill increases and wear of the outer peripheral blade becomes noticeable. Also, the central portion does not increase in speed compared to the outer peripheral portion, and the thrust load causes crushing to the central portion of the drill. There was a problem of causing breakage. Further, it is known that the breakage resistance is further lowered when the drill diameter is reduced.
[0004]
Also, in end mill processing, there is a tendency for high-cutting and high-efficiency cutting for the purpose of improving cutting efficiency, but because the tip cutting edge surface does not have sufficient strength and toughness, If it is used for cutting with high impact, chipping is likely to occur at the leading edge, causing a short life.
[0005]
Therefore, in Patent Document 1, the center portion is made of a cemented carbide having high toughness, and the outer periphery thereof has a drill configuration in which a high hardness cemented carbide having a composition different from that of the center portion is arranged, thereby providing wear resistance and fracture resistance. It is described that the drill is excellent in properties. Patent Document 2 describes a drill in which the drill is composed of a ceramic component and a metal component, and the metal component in the drill is inclined so that the surface has excellent wear resistance and the interior has excellent fracture resistance. Has been.
[0006]
[Patent Document 1]
JP 59-175912 A
[Patent Document 2]
Japanese Patent Laid-Open No. 12-296405
[Problems to be solved by the invention]
However, in a drill having a single core structure in which a high toughness material is arranged at the center described in

Patent Documents

1 and 2 and a high hardness material is arranged around the center, especially when the drill diameter is reduced, the shank portion of the drill There is a problem in that the rigidity at this point is insufficient and breakage tends to occur. Further, when the single-core structure of

Patent Documents

1 and 2 is simply made into a multi-core structure for the purpose of improving breakage resistance, a low-hardness core material is partially exposed as a cutting edge part, and chipping or There was a problem that defects occurred. In addition, similar problems may occur with end milling.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a drilling tool having high wear resistance and breakage resistance even when drilling or end milling is speeded up and reduced in diameter. .
[0010]
[Means for Solving the Problems]
In response to the above problems, the present inventors have conducted research to develop a drilling tool that can be used over a long period of time while exhibiting excellent fracture resistance even when used in small-diameter high-speed drilling. A drilling tool is composed of a multi-core fiber body in which a plurality of single-core fiber bodies are formed by coating the outer periphery of a core material made of a highly tough material with a skin material having a high hardness composition different from that of the core material. And, the structure in which the core material does not exist in the cutting edge part of the drilling tool, that is, the cutting edge part is made of a skin material having high hardness, so that both wear resistance and breakage resistance of the drill and end mill are achieved. It was found that it can be increased . Further, in the first embodiment of the present invention, the core material is exposed at the cutting edge part, wherein the single-core fiber body is converged in a state where a plurality of single-core fiber bodies are twisted in the longitudinal direction to form a multi-core structure. It is important in that it can be reliably formed only with the skin material.
[0012]
Moreover, in the 2nd embodiment of this invention, the area which the said skin material accounts in the cross section of the said cutting-blade part exists in the ratio of 70 to 90% with respect to the whole cross-sectional area of the said cutting-blade part. It is important in terms of improving wear resistance.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The drill of the present invention will be described with reference to FIG. 1 which is a schematic side view of an example of a twist drill which is a preferred example.
[0017]
According to FIG. 1, a twist drill (hereinafter simply referred to as a drill) 1 has a substantially cylindrical shape, and has a shape in which a chisel-shaped cutting edge portion 2 is formed at the tip thereof. As shown in FIG. 2B, the drill 1 includes a multi-core fiber body 7 in which a plurality of single-core fiber bodies 6 in which the outer periphery of the core material 4 is covered with a skin material 5 are converged.
[0018]
According to the present invention, a multi-core fiber body 7 in which a high-toughness material is used for the core material 4 mainly responsible for breakage resistance of the drill 1 and a single-core fiber body 6 in which different materials with high hardness are combined around the core material 4. By configuring the drill 1 with the above, the strength of the drill 1 can be increased, and the crack progress can be suppressed to prevent the drill 1 from being broken from the root, thereby improving the breakage resistance. The cutting edge 2 has a sharp edge and good wear resistance due to its good sharpness, so that the tool has a long tool life with excellent wear resistance and breakage resistance. Further, by concentrating a plurality of single-core fiber bodies 6, the fracture resistance of the drill 1 as a whole can be greatly improved by improving the strength of the drill 1 and deflecting cracks to suppress the progress of cracks. Can do. Furthermore, according to the present invention, since partial deviation of cutting resistance does not occur, stable hole position accuracy can be achieved.
[0019]
Moreover, according to the drill of this invention, as shown in FIG.2 (b), the cutting blade part 2 is formed with the skin material 5, and it is the big characteristics that the core material 4 does not exist. That is, as shown in FIGS. 4 (a) and 4 (b), when the core material 4 is present in the cutting edge part 2, the toughness is high but the hardness is low, so that the wear resistance is inferior. The portion made of the core material 4 is worn earlier than the high-hardness skin material 5, and abnormal wear occurs from that portion, so that the tool life of the drill 1 is extremely shortened. Therefore, by forming the cutting edge portion 2 with the skin material 5 as in the present invention, the occurrence of abnormal wear as described above can be prevented, and the excellent breakage resistance of the composite structure can also be achieved. A drill having excellent tool life can be produced.
[0020]
In the drill 1 of FIGS. 1 and 2, the cutting edge portion 2 in the drill of the present invention refers to a portion where the drill diameter is wide-angled from the tip of the drill 1 (intersecting ridge portion in the region A in FIG. 2).
[0021]
Further, in the first embodiment of the present invention, the area S _s of the skin material 5 in the cross section perpendicular to the axial direction of the cutting edge portion 2 and the cross section (a-a plane) near the tip of the drill 1 in FIG. but multi-core to the fiber body 7 entire area of the cross section _{S t} _(at _{S s / S t) 70~90%} , preferably be 75 to 90% of abnormal wear without compromising breakage resistance It is important in that it can have a preventive effect.
[0022]
Here, in the first embodiment of the present invention, the multi-core fiber body 7 is formed in a state where a plurality of single-core fiber bodies 6 are twisted in the longitudinal direction to form the multi-core fiber body 7. This is important in that the material 4 is not exposed and can be reliably formed only from the skin material 5 having a high hardness.
[0023]
In addition, when it sees in the aa cross section of the drill 1 of Fig.2 (a), it is desirable for the core material 4 to be a column shape or a polygonal column in terms of preventing stress concentration, but the core material 4 is a star shape. Alternatively, it may have a cross-sectional shape having protrusions such as a petal shape or a waveform.
[0024]
Moreover, as shown in FIG.1 (b), it is desirable for the multi-core fiber body 7 which comprises the drill 1 to be converged in the state twisted in the elongate direction. Further, in this case, the center portion of the drill 1 is twisted independently with almost no change in the position of the single-core fiber body 6, and the outer peripheral portion is greatly changed in position with the adjacent single-core fiber body 6. It becomes a twisted structure.
[0025]
If the twisting direction of the single-core fiber body 6 and the twisting direction of the flute of the drill 1 are the same, the core member 4 is arranged at an angle close to perpendicular to the cutting edge part 2, so that the cutting edge part 2 Since the exposed area of the core material 4 is the smallest and the proportion of the skin material 5 having excellent wear resistance is increased, the wear resistance of the drill 1 is improved.
[0026]
On the other hand, when the twisted direction of the single-core fiber body 6 and the twist direction of the cutting edge portion 2 of the drill 1 are opposite to each other, the stress remaining between the adjacent single-core fiber bodies 6 is the torque during cutting. Works effectively against resistance and improves performance against breakage due to torsion. Considering the balance of the drilling performance of the drill 1, it is desirable that the twisting direction of the single-core fiber body 6 and the twisting direction of the cutting edge portion 2 of the drill 1 be reversed and orthogonal to each other.
[0027]
On the other hand, for example, in a small-diameter drill for processing a printed circuit board having a general drill diameter of 0.3 to 1.0 mm and a groove length (cutting edge portion + flute portion) of 5 to 15 mm, the multi-core fiber body 7 is a cross section of the drill 1. When viewed, it is desirable that the single fiber body has an average diameter of 10 to 100 μm, particularly 20 to 50 μm, from the viewpoint of maintaining the strength and hardness of the entire drill.
[0028]
The drill 1 in the present invention can generate a residual stress between the core material 4 and the skin material 5 from the difference in thermal expansion coefficient by selecting the material of the core material 4 and the skin material 5, and the drill 1 can be controlled by the control. The breakage resistance can be improved.
[0029]
Examples of the material of the core material 4 -skin material 5 include metals such as high-speed steel, cemented carbide, cermet, ceramic, diamond, cBN, etc. Among them, wear resistance and breakage resistance of the drill 1, hole position accuracy Taking into account the ease of manufacturing such as firing, cost, etc., both the core material 4 and the skin material 5 have a hard phase mainly composed of WC and a binder phase mainly composed of an iron group metal such as Co or Ni. A WC-based cemented carbide is desirable. Further, the use of the WC-based cemented carbide for the skin material 5 also has an effect of efficiently releasing heat generated during processing. Furthermore, as the WC-based cemented carbide constituting the skin material 5, it is more preferable to use a fine ultrafine cemented carbide having a high hardness and excellent wear resistance and having an average particle size of less than 1 μm. This is desirable because a drill with excellent wear can be produced.
[0030]
Further, according to the present invention, in order to further improve the wear resistance of the cutting edge portion 2, the periodic table 4a, at least a part of the outer periphery of the multi-core fiber body 7 obtained by converging a plurality of single-core fiber bodies 6 is provided. 5a, carbides 6a group metal, nitrides, _{_{_{carbonitrides, a l 2 O 3, ZrO}}} 2, BN, a hard coating of DLC or the like can also be formed at least one layer.
[0031]
(Production method)
Next, a method for manufacturing the drill of the present invention will be described based on the schematic view of FIG.
[0032]
First, as a raw material for the core material 4, for example, paraffin wax, polystyrene, polyethylene, ethylene-ethyl acrylate, ethylene-vinyl acetate, polybutyl methacrylate, polyethylene are used to form a core material having an average particle diameter of 0.01 to 10 μm. An organic binder such as glycol and dibutyl phthalate, a plasticizer and a solvent were added and kneaded to form a core material mixture 8a, or the core material mixture 8a into a cylindrical shape by a molding method such as press molding or casting. A molded body 8b for core material is produced. Here, in order to obtain a homogeneous multi-core molded body 12 by coextrusion molding to be described later, the amount of the organic binder added is 50 to 200 parts by volume, particularly 70 to 150 parts by volume with respect to the powder forming the core. Is desirable.
[0033]
On the other hand, the raw material powder forming the skin material 5 described above is kneaded together with the binder described above to produce a cylindrical skin material molded body 9 having a hollow portion by a molding method such as press molding, extrusion molding or casting molding, The hollow body of the skin material molded body 9 is filled with the core material mixture 8a, or the core material molded body 8b is inserted to produce the molded body 10 (see FIG. 3A). The ratio (Rc / Rs) of the diameter Rc of the core material mixture 8a to the outer diameter Rs of the skin material molded body 9 is 0.2 to 0.8, particularly 0.2 to 0.6. It is desirable in that the one cutting edge portion 2 is reliably constituted by the skin material 5.
[0034]
When the molded body 10 is produced, the skin material molded body 9 may be a method in which a plurality of molded bodies such as two half-shaped molded bodies are arranged on the outer periphery of the core molded body 8b. According to the present invention, when the molded body is set for molding or coextrusion molding to be described later, the diameter of the core material molded body 8b is compared with the thickness of the skin material molded body 9. Since the core material molded body 8b is easily bent or bent, the core material is formed in the hollow portion of the skin material molded body using the above-described method for producing the hollow skin material molded body. It is desirable to employ a method of filling the mixture 8a. Moreover, it is possible to select a production method according to the composition ratio of the core material and the skin material and the strength of the molded body.
[0035]
Then, the molded body 10 is extruded and the core material mixture 8a or the core material molded body 8b and the skin material molded body 9 are coextruded to form a skin material molded body around the core material mixture 8a. A single-core molded body 11 covered with 9 and stretched to a thin diameter is produced (see FIG. 3B).
[0036]
Next, a plurality of the co-extruded long single-core molded bodies 11 are focused and co-extruded again to produce a multi-core molded body 12 in which a plurality of single-core molded bodies 11 are focused ( (Refer FIG.3 (c)).
[0037]
Further, according to the present invention, the elongated long multi-core molded body 12 is repeatedly coextruded again as desired to produce a multi-core molded body in which the multi-core molded body 12 is further bundled. It is also possible to do.
[0038]
Here, in order to prevent the core material 4 from being present in the cutting edge portion 2, the area S _s occupied by the skin material 5 and the area S occupied by the core material 4 in the cross section perpendicular to the axial direction of the multicore fiber body 7. it is desirable that the ratio of _c _(S s _/ S _{_c)} to adjust the shaped body so that 1 to 10, ensures high hardness skin material 5 only without exposed core 4 to the cutting edge 2 The configuration can be easily manufactured, and abnormal wear can be prevented.
[0039]
Moreover, in order to make the multi-core molded body 12 into a twisted structure, it can be obtained by twisting extrusion by providing a twisted groove in the die 13 of the extruder used in FIG. 3C, but it is extruded straight. In a state where the multi-core molded body 12 is plasticized, one end is physically fixed and the other end is rotated to form a twisted structure, or both ends are fixed and rotated opposite to each other to form a twisted structure. It can also be formed (see FIG. 3D).
[0040]
Next, the multi-core molded body 12 is subjected to a binder removal treatment in which the temperature is increased or maintained at 300 to 700 ° C. for 10 to 200 hours, and further fired under predetermined conditions. The firing may be ordinary pressureless firing, but hot pressing, HIP firing, or ultra-high pressure firing may be used.
[0041]
Then, after subjecting the sintered body obtained in the above step to peripheral polishing as desired, the cutting edge is provided at the tip of the multi-core molded body 12 and the peripheral surface while considering the arrangement of the fiber body. The drill 1 of the present invention can be manufactured by forming a flute by grinding to form a cutting edge portion made of a skin material (see FIG. 3 (e)).
[0042]
1 to 3, the drill has been described. However, the present invention is not limited to this, and an end mill may be used. According to the present invention, in the case of the end mill 15, since the portion corresponding to the intersecting ridge line between the flute portion and the land portion of the drill forms a side cutting edge and participates in the cutting, the multi-core fiber body is inevitably lateral. It becomes the structure twisted in the same direction as the twist direction of a cutting blade. (See Fig. 1 (c))
[0043]
【Example】
(Example)
As raw material powders, WC powder (average particle size 0.3 μm), Co powder (average particle size 0.6 μm), VC powder (average particle size 1.0 μm), Cr ₃ C ₂ powder (average particle size 1.2 μm) These raw material powders were blended in the blending composition shown in Table 1 and mixed for 72 hours by a wet ball mill. Furthermore, as a predetermined amount of organic binder, polyvinyl alcohol, cellulose, and polyethylene glycol were used, and 100 parts by volume of a lubricant and a dispersant were added to the above mixed powder, and kneaded with a kneader. A kneaded material was prepared.
[0044]
[Table 1]

[0045]
Next, after forming a hollow skin material molded body having an outer diameter of 22 mm and a core material molded body having a diameter of 11 mm by the method shown in FIG. 3, the core material molded body is inserted into the skin material molded body. Then, a single-core molded body was produced by co-extrusion molding, and 250 single-core molded bodies were bundled and co-extrusion molded again to obtain a multi-core molded body (Sample 1).
[0046]
Further, when the sample 1 was molded, one end of the extruded multi-core molded body was fixed and rotated to produce a multi-core molded body (sample 2) twisted in the longitudinal direction.
[0047]
The multi-core molded body was subjected to a binder removal treatment at 500 ° C. for 50 hours, and then fired in vacuum at 1400 ° C. for 1 hour. Subsequently, in an Ar atmosphere, temperature: 1340 ° C., pressure: 100 MPa, holding time: 1 hour A cylindrical multi-core fiber body having a diameter of 3.5 mm and a total length of 40 mm was manufactured by performing HIP treatment under the conditions described above, and performing peripheral processing.
[0048]
Further, while confirming the position of the core material on the outer periphery of the composite structure, a cutting edge part is formed at the tip and a flute (blade groove) is formed on the side surface by machining to form a groove length (cutting edge part + flute part) 9.0 mm. A drill with an outer diameter of φ0.5 mm was manufactured (of which the cutting edge was 0.1166 mm). In addition, when the cross section of the cutting edge portion (boundary surface with the flute portion: aa plane in FIG. 1) was observed with a microscope, the area occupied by the skin material was 75% of the entire cross section.
[0049]
Using the obtained drill, drilling was performed under the following conditions on a pseudo printed circuit board in which four layers of 0.2 mm thick glass substrates and 0.2 mm thick epoxy resin substrates were alternately laminated. Then, the number of processing that could be processed before the drill broke and the deviation of the hole position on the lower surface of the substrate from the hole position on the upper surface of the substrate were measured using a pixel made by Takeuchi Seisakusho as the hole position accuracy. The results are shown in Table 2.
[0050]
Machining conditions Spindle speed: 12krpm
Feeding: 2.0 m / min.
Substrate: 3 layers of epoxy-based 0.8mm thickness (Comparative Example 1)
A single core molded body was manufactured by covering the core molded body having an outer diameter of 20 mm with a half-shaped skin material molded body by the method shown in FIG. 3 and co-extrusion molding (Comparative Example 1). This was subjected to binder removal processing and firing in the same manner as in Example, and a drill was produced in the same manner. In the extrusion molding of the example, a single-core fiber body having a uniform shape in the length direction was prepared, subjected to binder removal treatment and firing in the same manner as in the example, and processed in the same manner to produce a single-core drill. In addition, when the chisel shape of the drill was the same as that of the example, the drill cross-section was configured as shown in FIG. When drilling was performed in the same manner as in the example, as shown in Table 2, breakage occurred from the chuck portion of the drill when the number of processing was 5,000.
[0051]
(Comparative Example 2)
Next, the skin material is molded into a cylindrical shape having an outer diameter of 20 mm, and the core material molded into a halved shape with a thickness of 1 mm is coated around the outer periphery, and coextrusion molding as shown in FIG. A core molded body was produced, and 250 single-core molded bodies were bundled and coextruded again to obtain a multi-core molded body (Comparative Example 2). This was subjected to binder removal processing and firing in the same manner as in Example, and a drill was produced in the same manner. The drill cross section was configured as shown in FIG. When drilling was performed in the same manner as in the example, 8000 pieces could be processed as shown in Table 2, but the variation was also great from the measurement results of hole position accuracy. This is considered to be caused by the local progress of wear in the core material part.
[0052]
(Comparative Example 3)
After adding an organic binder to the composition of the core material of the example, a drill was produced in exactly the same manner as in the example except that a molded body having a uniform composition was produced by molding. The external shape of the drill was the same as in the example. When drilling was performed in the same manner as in the example, as shown in Table 2, breakage occurred from the chuck portion of the drill when the number of machining was 2,000.
[0053]
[Table 2]

[0054]
As is apparent from the results in Table 2, in a practical use, a drill composed of a multi-core fiber body obtained by converging a plurality of single-core fiber bodies composed of a core material and a skin material, and having a cutting edge portion formed of the skin material. Good processing was possible without breaking up to a sufficient number of processing 10,000, and the hole position accuracy was excellent. Further, for sample 2 having a structure twisted in the longitudinal direction, 12,000 or more processings were possible.
[0055]
【The invention's effect】
As described above in detail, according to the drill and end mill of the present invention, the outer periphery of the core material made of a long, high-hardness material is covered with a skin material made of a material having a different composition from the core material and having a high toughness. The multi-core fiber body is formed by concentrating a plurality of single-core fiber bodies, and the core material does not exist in the cutting edge part, that is, the cutting edge part is constituted by a skin material other than the core material. In addition, the area occupied by the skin material in the cross section of the cutting edge portion is present in a ratio of 70 to 90% with respect to the entire cross-sectional area of the cutting edge portion, or the single-core fiber body is long. By adopting a configuration in which a multi-core structure is formed in a state where a plurality of wires are twisted in the direction, both wear resistance and breakage resistance can be improved. In addition, since the partial cutting resistance is not biased, stable hole position accuracy can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a drill and an end mill of the present invention, (a) a drill having a configuration in which a multicore fiber body is not twisted, (b) a drill having a configuration in which a multicore fiber body is twisted along a flute, (C) An end mill having a configuration in which a multicore fiber body is twisted along a flute is shown.
2A is an enlarged view of the tip of the drill shown in FIG. 1A, and FIG. 2B is a cross-sectional view taken along line aa in FIG.
FIGS. 3A to 3E are process diagrams for explaining a method for manufacturing a drilling tool according to the present invention. FIGS.
FIGS. 4A and 4B are cross-sectional views (partially perspective view) of a conventional drill using a composite structure. FIGS.
[Explanation of symbols]
1 Twist drill (drill)
2 Cutting edge portion 3 Composite structure 4 Core material 5 Skin material 6 Single-core fiber body 7 Multi-core fiber body 8a Core material mixture 8b Core material molded body 9 Skin material molded body 10 Molded body 11 Single-core molded body 12 Multi-core molded body 13 Base 15 End mill

Claims

In a drill comprising a multi-core fiber body in which a plurality of single-core fiber bodies composed of a long core material and a skin material having a composition different from that of the core material are formed, and a cutting edge portion is formed at the tip The skin material is made of a material whose hardness is higher than that of the core material, the cutting blade portion is constituted by the skin material, and an area occupied by the skin material in a cross section of the cutting blade portion is the cutting blade. drill you being present in a proportion of 70% to 90% relative to the total cross-sectional area of the part.

In a drill comprising a multi-core fiber body in which a plurality of single-core fiber bodies composed of a long core material and a skin material having a composition different from that of the core material are formed, and a cutting edge portion is formed at the tip The skin material is made of a material having a hardness higher than that of the core material, the cutting edge portion is formed of the skin material, and the single core fiber bodies are converged in a state of being twisted in the longitudinal direction. drill you, characterized in that it forms a multi-core structure Te.

It consists of a multi-core fiber body, which is a multi-core fiber body that consists of a long core material and a skin material having a composition different from that of the core material. In the end mill, the skin material is made of a material whose hardness is higher than that of the core material, and the cutting blade portion is constituted by the skin material, and an area occupied by the skin material in a cross section of the cutting blade portion is features and to Rue Ndomiru that present in a proportion of 70% to 90% relative to the total cross-sectional area of the cutting edge.