JP4082897B2

JP4082897B2 - Grinding wheel

Info

Publication number: JP4082897B2
Application number: JP2001379000A
Authority: JP
Inventors: 直樹峠; 哲也野々下; 靖章井上
Original assignee: Noritake Co Ltd; Noritake Super Abrasive Co Ltd
Current assignee: Noritake Co Ltd; Noritake Super Abrasive Co Ltd
Priority date: 2001-12-12
Filing date: 2001-12-12
Publication date: 2008-04-30
Anticipated expiration: 2021-12-12
Also published as: JP2003175464A

Description

【０００１】
【発明の属する技術分野】
本発明はプラスチック、プラスチック複合材料、カーボン型材、非鉄金属材料などの目詰まりしやすい材料の研削加工に用いる研削砥石に関する。
【０００２】
【従来の技術】
ダイヤモンド砥粒やｃＢＮ砥粒などの砥粒をろう付け法により一層に固着した研削砥石がプラスチック、プラスチック複合材料、カーボン型材、非鉄金属材料などの研削加工に使用されている。このような研削砥石には、切れ味に優れ、しかもその切れ味が長期にわたって安定的に持続することが要求される。ところが、ダイヤモンド砥粒にしろ、ｃＢＮ砥粒にしろ、研削作業の進行に伴い切れ味と寿命が低下する。
【０００３】
その主な原因として、台金への砥粒の固着状態が不安定で砥粒が脱落しやすいこと、チップポケットが小さいこと、砥粒間隔のコントロールが不十分なために研削作業中に切粉によって目詰まりが生じることが挙げられる。とくにプラスチック類は研削によって発生する切粉の体積が大きくなることから目詰まりが生じやすい。このような目詰まりの生じやすい材料に使用する研削砥石として、特開平１１−９０８３４号公報に記載の研削砥石がある。
【０００４】
この公報に記載の研削砥石は、台金の外周面に砥粒をろう材により一層だけ固着させた砥石であって、砥粒を均一に規則配列した砥石である。規則配列パターンとして、たとえば砥粒を結ぶ線が四角形あるいは平行四辺形をなすように、各砥粒を均一に規則配列することにより、部分的な目詰まりが生じず、仮に目詰まりが生じても砥粒面全域に亘って均一となり、目詰まりを抑えた効率的な研削を行うことができる、とされている。
【０００５】
また本出願人も、砥粒を台金に一層配列してろう付けした研削砥石において、砥粒粒径の１／３〜１／２倍のろう材厚さで砥粒を保持するとともに、隣り合う砥粒との間に砥粒粒径の２／３〜２．５倍の幅で台金素地を露出させた部分を含むチップポケットを規則的に形成した砥石を開発し、特開２０００−３４３４３６号公報に開示した。
【０００６】
この研削砥石によれば、砥粒の保持力を確保したうえで、良好な切れ味を発揮するのに必要な砥粒の突出高さを確保することができる。とくに、砥粒粒径の２／３〜２．５倍の幅で台金素地を露出させた部分を含むチップポケットを規則的に形成することにより、砥粒層の全面にわたって砥粒の分布を均一にするとともに、研削液の供給と切粉の排出を良好にして目詰まりをなくし、切れ味を向上させることができる。
【０００７】
【発明が解決しようとする課題】
上記公報に記載の砥石によれば、砥粒が所定の間隔をもって一様に分布していることから、部分的な目詰まりが生じず、良好な切れ味を維持することができる。しかし、これらの砥石は、砥粒間隔の設定を広くすると、切粉の排出は良くなるが削り残しが発生し、加工面粗さが悪くなる。また、一つの砥粒に加わる力が大きくなって砥粒が脱落しやすくなり、砥石の耐用が短くなる。砥粒間隔を小さくした場合は、砥粒個数が多くなりすぎて研削加工時に目詰まりを生じ、充分な切れ味と切粉の排出が得られない。
【０００８】
本発明が解決すべき課題は、砥粒を台金に一層配列してろう付けにより固着した研削砥石において、砥粒の分布のあり方について検討を加え、より良好な加工精度と切れ味および切粉の排出を得ることにある。
【０００９】
【課題を解決するための手段】
本発明者らは、ダイヤモンド砥粒やｃＢＮ砥粒などの砥粒をろう付けによって一層配列した砥粒層中の砥粒の密集の態様および砥粒層の個々の分散と研削加工中の研削液の供給性、切粉の排出性との関係について鋭意研究を重ね、台金の砥粒層形成面の全面に一様に砥粒を分布させて砥粒層を形成するよりも、複数個の砥粒を一群とした島状の砥粒層を規則的に配列することにより、目詰まりを防止して、より良好な加工精度と切れ味および切粉の排出を得ることができることを見出した。
【００１０】
すなわち本発明は、ダイヤモンド砥粒、ｃＢＮ砥粒などの砥粒を台金に一層配列してろう付けにより固着した研削砥石であって、砥粒の平均粒径が７５〜３００μｍであり、砥粒平均粒径の２．２〜３．５倍の直径の円形の島状領域が規則的に配列され、各島状領域内に複数個の砥粒がろう材により固着され、かつ砥粒を固着したろう材の厚さが島状領域の外周側では砥粒平均粒径の０．１〜０．７倍の厚さであり、内部は外周側のろう材厚さの１．１〜１．２倍の厚さとした研削砥石である。
【００１１】
本発明の研削砥石では、砥粒の大きさを平均粒径７５〜３００μｍに限定する。砥粒の平均粒径が７５μｍより小さいと砥粒突き出し高さが小さくなり、加工面粗さは良くなるが研削能率が低下する。砥粒の平均粒径が３００μｍより大きくなると研削能率は向上するが、被加工材への食い込みが大きくなり、とくにプラスチックレンズなどの一定荷重下での研削加工では、そのときに発生する研削音、振動が大きくなる。
【００１２】
また本発明の研削砥石では、台金の砥粒層形成面の全面に一様に砥粒を分布させて砥粒層を形成するのではなく、複数個の砥粒を一群とした島状の砥粒層を規則的に配列する。島状領域の配列は、砥石の回転方向に対して傾斜した斜め格子状あるいは千鳥状などに配列するのが好ましい。
【００１３】
ここで、島状領域の形状を円形とし、その円形の直径を砥粒の平均粒径の２．２〜３．５倍の大きさとする。円形の島状領域の直径が砥粒の平均粒径の２．２倍より小さいと、島状領域内に砥粒を２個配列したときの砥粒間隔が小さくなって切粉が排出されにくく目詰まりが生じやすくなり、１個だけの配列とすると研削加工時における砥粒への負担が大きくなって砥粒が脱落しやすくなり、砥石の耐用が低下する。円形の島状領域の直径が砥粒の平均粒径の３．５倍より大きくなると、好ましい大きさの砥粒間隔をもって砥粒を配列しようとすると島状領域内の砥粒の数が多くなりすぎ、研削抵抗が高くなる。この島状領域内に好ましい大きさの砥粒間隔を確保したうえで２〜５個程度の砥粒を分散配置することにより、研削液の供給と切粉の排出が良好になり、目詰まりや焼付きが発生せず、かつ、研削加工時における砥粒への負担が小さく、砥粒の破砕や脱落が生じることなく、長期にわたって安定した加工精度と切れ味が得られ、砥石の寿命も延長する。
【００１４】
島状領域内の砥粒はろう材により固着されるが、本発明においては島状領域内の外周側と内部とでろう材厚さを変えて砥粒を固着する。島状領域の外周側（図２（ａ）において一点鎖線で示す境界Ｓの外側）ではろう材厚さ（図２（ｂ）に符号Ｔで示す）を砥粒平均粒径の０．１〜０．７倍とする。ろう材厚さが砥粒平均粒径の０．１倍未満であると砥粒保持力が不足し、０．７倍より厚いと砥粒の被加工材への食い込みが悪く切れ味が低下する。島状領域の内部では外周側のろう材厚さの１．１〜１．２倍とする。内部のろう材厚さが外周側のろう材厚さと同程度以下であれば切粉が内部に堆積しやすくなり、ろう材厚さが厚すぎると切粉の排出が悪くなるので、上記の範囲内とする。
【００１５】
また、前記島状領域の配列は、隣接する島状領域どうしの間に、隣接する両島状領域の中心を通る線上において島状領域の直径に対し０．７〜４倍の長さの間隔で配置する。ここで隣接する島状領域とは、最も近いところの隣接島状領域を指す。島状領域の配置間隔がこの範囲より小さいと、砥石全体としての切粉の排出経路が細かくなりすぎて研削加工時に目詰まりが生じやすくなり、島状領域の配置間隔がこの範囲より大きくなると、削り残しが発生して加工面粗さが悪くなり、また、被加工材が台金に当たって研削抵抗となり、被加工材および台金を損傷させてしまう。
【００１６】
島状領域内に配置する砥粒は、島状領域内の中心を通る線上において、砥粒平均粒径の０．２〜１倍の長さのチップポケットが一箇所以上形成されるように配置する。島状領域内でチップポケットの最小幅が砥粒平均粒径の０．２倍より小さいと、研削加工時に目詰まりが生じやすくなり、１倍より大きくなると、研削加工時における砥粒の負担が大きくなり、砥粒の脱落、破損が生じるので、砥粒数とその配置間隔を上記チップポケットが形成されるように調整する。島状領域内の砥粒の個数は、各島状領域とも同じ個数に揃えるほうが、島状領域内にある砥粒に局部的な負荷が生じることなく安定した研削能率が得られるという点からは望ましいが、島状領域によって砥粒の個数を変えて配置することもできる。
【００１７】
ここで、島状領域内にろう付けにより固着される砥粒は、ろう材面からの突出高さが砥粒平均粒径の５０〜７５％となるようにろう付けする。砥粒の突出高さが砥粒平均粒径の５０％より低いと、砥粒の研削に寄与する部分が小さいため研削量が少なく、切れ味が悪くなり、また、切粉が排出されにくく、ろう材が磨耗しやすくなる。砥粒の突出高さが砥粒平均粒径の７５％より高いと、ろう材による砥粒の保持力が低下し、砥粒が脱落しやすくなる。砥粒の突出高さをこの範囲内とし、砥粒間隔、島状領域の大きさ、間隔を前記の範囲内とすることによって、切粉を排出するのに十分な大きさのチップポケットが形成される。
【００１８】
さらに、研削加工後の面粗さを向上させるためには、ろう付けにより固着した後の砥粒の先端を、砥粒平均粒径の１〜１０％に相当する分だけ研削除去して砥粒先端高さを揃えることが望ましい。この先端除去量が砥粒平均粒径の１％より少ないと、先端高さのばらつきが生じて加工面の面粗さの向上に効果がなく、１０％より多いと砥粒の突き出し量が小さくなり、また島状領域内でのチップポケット領域も小さくなるため、研削抵抗が上昇し、研削能率が低下する。
【００１９】
【発明の実施の形態】
図１は本発明の実施形態における研削砥石を示す斜視図である。図２は図１の研削砥石の砥粒の配設を拡大して示す模式図であり、（ａ）は島状領域内の砥粒の配設を示す図、（ｂ）は（ａ）のＡ−Ａ線断面図である。
【００２０】
本実施形態は、プラスチックレンズの研削用の砥石に本発明を適用した例である。図１は砥石の全体形状と砥粒層形成部分の一部を拡大して示す図であり、１は台金、２は砥粒層を形成した島状領域である。図２において、３は砥粒、４はろう材である。この砥石の製造手順はつぎの通りである。
・台金１として外径１００ｍｍ、厚さ１７ｍｍの鉄製台金を準備する。
・砥粒３として＃１４０／１７０（平均粒径約１００μｍ）のダイヤモンド砥粒を準備する。
・台金１の砥粒層形成面に配列する直径３００μｍの円形の島状領域２を設定する。
・直径３００μｍの孔を孔の中心間距離７５０μｍ間隔で千鳥状に配列したスクリーンを用いて、台金１上で有機接着剤を塗布する。
・この有機接着剤の上に砥粒を配置する。この状態で砥粒は各島状領域２内に４個配置され、また隣接する島状領域どうしの間に４５０μｍの長さのチップポケットが存在し、各島状領域が中心間隔７５０μｍで千鳥状に配列されたかたちとなる。
・これを乾燥炉中で１２０℃、１時間乾燥させ、砥粒を仮固定する。
・三次元移動が可能なアプリケータ（吐出機）を用いて、接着部にろう材（Ｔｉ−Ａｇ−Ｃｕ−Ｉｎ）とバインダーの混合物を砥粒粒径の１／２の高さに塗布する。
・これを非酸化性雰囲気中で１０００℃、１時間加熱し、砥粒を台金に本固定する。
・砥粒３の先端部分を約５μｍ研削除去（図３（ｃ）の符号ｈ参照）して砥粒先端高さを揃える。
【００２１】
このようにして、砥粒平均粒径の約３倍の直径の円形の島状領域２内に４個のダイヤモンド砥粒３が、砥粒平均粒径の約６０％の突出高さＨで、かつ砥粒平均粒径の約０．４倍のチップポケット幅Ｗを有するように配置された研削砥石を製造した。この砥石（発明品）と、同じ砥粒と台金を用いて前述した特開平１１−９０８３４号公報記載の方法によって製造した砥石（比較品１）および特開２０００−３４３４３６号公報記載の方法によって製造した砥石（比較品２）について研削試験を行った。両砥石の仕様のうち数値の異なる項目を表１に示す。
【００２２】
【表１】

【００２３】
〔試験条件〕
砥石周速度：１２５０ｍ／ｍｉｎ
被研削材：プラスチックレンズ（ガラス繊維含有）
研削方式：湿式
【００２４】
表２に試験結果を示す。
【表２】

表２からわかるように、砥粒層を形成した島状領域を規則配列し、かつ適正なチップポケットを形成した発明品は、比較品１，２の砥石に比べて面粗度は向上し、切れ味を示す消費電力の指数は約３０％向上している。
【００２５】
さらに上記研削を続行して所定の仕上がり条件通りに研削できた加工枚数は、発明品の砥石では１００００枚以上であったが、比較品１の砥石では１０１１枚、比較品２の砥石では１２１枚であった。発明品１の砥石は、１００００枚研削後においても砥粒層面に切粉の溶着、砥粒の脱落はみられなかった。比較品１の砥石は１０１１枚研削後、砥粒の脱落が多くみられ、継続使用が不可能となった。また、比較品２の砥石は１２１枚研削後、切粉が溶着し加工が不安定となって継続使用が不可能となった。
【００２６】
【発明の効果】
本発明によって以下の効果を奏する。
【００２７】
（１）砥粒平均粒径の２．２〜３．５倍の直径の円形の島状領域に複数個の砥粒をろう材により単層に固着し、かつ島状領域を規則配列することによって、研削液の供給と切粉の排出を良好にして目詰まりや焼付きが発生せず、長期にわたって安定した加工精度と切れ味が得られ、砥石の寿命も延長する。
【００２８】
（２）隣接する島状領域どうしの間に最適な大きさのチップポケットが形成されるように島状領域を規則配列すること、および、隣接する砥粒どうしの間に最適な大きさのチップポケットが形成されるように島状領域内に砥粒を配置することにより、研削液の供給と切粉の排出がより良好となり、切れ味がより向上する。
【図面の簡単な説明】
【図１】本発明の実施形態における研削砥石を示す斜視図である。
【図２】図１の研削砥石の砥粒の配設を拡大して示す模式図であり、（ａ）は島状領域内の砥粒の配設を示す図、（ｂ）は（ａ）のＡ−Ａ線断面図である。
【符号の説明】
１台金
２島状領域
３砥粒
４ろう材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grinding wheel used for grinding clogging materials such as plastic, plastic composite material, carbon mold material, non-ferrous metal material and the like.
[0002]
[Prior art]
A grinding wheel in which abrasive grains such as diamond abrasive grains and cBN abrasive grains are further fixed by a brazing method is used for grinding plastics, plastic composite materials, carbon mold materials, non-ferrous metal materials and the like. Such a grinding wheel is required to have excellent sharpness and to maintain the sharpness stably over a long period of time. However, whether it is diamond abrasive grains or cBN abrasive grains, sharpness and service life are reduced as the grinding operation proceeds.
[0003]
The main causes are that the abrasive grains are unstablely fixed to the base metal and the grains are easy to fall off, the chip pockets are small, and the control of the grain spacing is insufficient, so that the chips during grinding work. Can cause clogging. In particular, plastics tend to clog because the volume of chips generated by grinding increases. As a grinding wheel used for such a material that is easily clogged, there is a grinding wheel described in JP-A-11-90834.
[0004]
The grinding wheel described in this publication is a grindstone in which abrasive grains are fixed to the outer peripheral surface of a base metal only by a brazing material, and the abrasive grains are uniformly and regularly arranged. As a regular arrangement pattern, for example, even if clogging occurs even if partial clogging does not occur by arranging each abrasive grain regularly so that the lines connecting the abrasive grains form a square or parallelogram It is said that it is uniform over the entire surface of the abrasive grain, and that efficient grinding with reduced clogging can be performed.
[0005]
The present applicant also holds the abrasive grains with a brazing material thickness that is 1/3 to 1/2 times the abrasive grain diameter in the grinding wheel in which the abrasive grains are further arranged on the base metal and brazed. Developed a grindstone in which chip pockets including a portion where the base metal substrate is exposed with a width of 2/3 to 2.5 times the grain size of the abrasive grains are regularly formed between the mating abrasive grains. No. 343436.
[0006]
According to this grinding wheel, it is possible to ensure the protrusion height of the abrasive grains necessary for exhibiting good sharpness after securing the holding power of the abrasive grains. In particular, by regularly forming chip pockets including portions where the base metal substrate is exposed with a width 2/3 to 2.5 times the grain size of the abrasive grains, the distribution of the abrasive grains over the entire surface of the abrasive layer is achieved. In addition to being uniform, it is possible to improve the sharpness by improving the supply of grinding fluid and discharging chips and eliminating clogging.
[0007]
[Problems to be solved by the invention]
According to the grindstone described in the above publication, since the abrasive grains are uniformly distributed with a predetermined interval, partial clogging does not occur and good sharpness can be maintained. However, in these grindstones, when the setting of the abrasive grain interval is widened, chip discharge is improved, but uncut parts are generated, and the processed surface roughness is deteriorated. In addition, the force applied to one abrasive grain becomes large and the abrasive grains easily fall off, and the durability of the grindstone is shortened. When the interval between the abrasive grains is reduced, the number of abrasive grains increases so that clogging occurs during the grinding process, and sufficient sharpness and chip discharge cannot be obtained.
[0008]
The problem to be solved by the present invention is to examine the distribution of abrasive grains in a grinding wheel in which abrasive grains are further arranged on a base metal and fixed by brazing. It is in getting emissions.
[0009]
[Means for Solving the Problems]
The inventors of the present invention have a mode of dense abrasive grains in an abrasive layer in which abrasive grains such as diamond abrasive grains and cBN abrasive grains are arranged in a single layer by brazing, and an individual dispersion of the abrasive grain layer and a grinding liquid during grinding. Rather than intensively researching the relationship between the supplyability of the steel and the dischargeability of the chips, the abrasive grains are uniformly distributed over the entire surface of the abrasive grain formation surface of the base metal. It has been found that by regularly arranging island-like abrasive grain layers with a group of abrasive grains, clogging can be prevented and better processing accuracy, sharpness and chip discharge can be obtained.
[0010]
That is, the present invention is a grinding wheel in which abrasive grains such as diamond abrasive grains and cBN abrasive grains are arranged on a base metal and fixed by brazing, and the average grain diameter of the abrasive grains is 75 to 300 μm. Circular island regions having a diameter 2.2 to 3.5 times the average particle size are regularly arranged, and a plurality of abrasive grains are fixed to each island region by brazing material, and the abrasive particles are fixed. The thickness of the brazing material is 0.1 to 0.7 times the average grain size of the abrasive grains on the outer peripheral side of the island-like region, and the inside is 1.1 to 1. It is a grinding wheel that is twice as thick.
[0011]
In the grinding wheel of the present invention, the size of the abrasive grains is limited to an average particle size of 75 to 300 μm. When the average grain size of the abrasive grains is smaller than 75 μm, the abrasive grain protruding height is reduced, and the surface roughness is improved, but the grinding efficiency is lowered. When the average grain size of the abrasive grains is larger than 300 μm, the grinding efficiency is improved, but the biting into the workpiece is increased. Especially in the grinding process under a constant load such as a plastic lens, the grinding sound generated at that time, Vibration increases.
[0012]
Further, in the grinding wheel of the present invention, an abrasive grain layer is not formed by uniformly distributing abrasive grains over the entire surface of the base metal abrasive grain layer forming surface, but an island-shaped group of a plurality of abrasive grains. The abrasive layer is regularly arranged. The island regions are preferably arranged in an oblique lattice shape or a staggered shape inclined with respect to the rotation direction of the grindstone.
[0013]
Here, the shape of the island-shaped region is a circle, and the diameter of the circle is 2.2 to 3.5 times the average grain size of the abrasive grains. When the diameter of the circular island-shaped region is smaller than 2.2 times the average particle size of the abrasive grains, the distance between the abrasive grains becomes small when two abrasive grains are arranged in the island-shaped region, and chips are not easily discharged. Clogging is likely to occur, and if only one array is used, the burden on the abrasive grains during grinding is increased, and the abrasive grains are likely to fall off, reducing the durability of the grindstone. When the diameter of the circular island region is larger than 3.5 times the average particle size of the abrasive grains, the number of abrasive grains in the island region increases when trying to arrange the abrasive grains with a preferable size of the abrasive grain spacing. Too much, grinding resistance increases. Distributing and arranging about 2 to 5 abrasive grains after securing a preferable size of abrasive grains in this island-shaped region improves the supply of grinding fluid and the discharge of chips, resulting in clogging and There is no seizure, the burden on the abrasive grains during grinding is small, the abrasive grains are not crushed or dropped off, stable machining accuracy and sharpness are obtained over a long period of time, and the life of the grinding wheel is extended. .
[0014]
The abrasive grains in the island-shaped region are fixed by the brazing material. In the present invention, the abrasive particles are fixed by changing the thickness of the brazing material between the outer peripheral side and the inside of the island-shaped region. On the outer peripheral side of the island-like region (outside the boundary S indicated by the alternate long and short dash line in FIG. 2A), the brazing material thickness (indicated by the symbol T in FIG. 2B) is 0.1 to the average grain size of the abrasive grains. 0.7 times. When the brazing material thickness is less than 0.1 times the average grain size of the abrasive grains, the abrasive grain retention is insufficient, and when the brazing material thickness is more than 0.7 times, the abrasive grains bite into the workpiece and the sharpness decreases. Within the island region, the thickness of the brazing material on the outer peripheral side is 1.1 to 1.2 times. If the internal brazing material thickness is less than or equal to the brazing material thickness on the outer peripheral side, chips will easily accumulate inside, and if the brazing material thickness is too thick, chip discharge will deteriorate, so the above range. Within.
[0015]
Further, the arrangement of the island regions is an interval between 0.7 to 4 times the diameter of the island regions on a line passing between the centers of the adjacent island regions between the adjacent island regions. Place with. Here, the adjacent island region refers to the nearest adjacent island region. If the island-shaped region arrangement interval is smaller than this range, the chip discharge path as a whole grindstone becomes too fine and clogging tends to occur during grinding, and the island-like region arrangement interval is larger than this range, An uncut portion is generated, resulting in poor surface roughness. Further, the workpiece hits the base metal and becomes a grinding resistance, which damages the workpiece and the base metal.
[0016]
The abrasive grains arranged in the island region are arranged so that one or more chip pockets having a length 0.2 to 1 times the average grain size of the abrasive grains are formed on a line passing through the center in the island region. To do. If the minimum width of the chip pocket is smaller than 0.2 times the average grain size of the abrasive grains in the island-like region, clogging is likely to occur during grinding, and if it is greater than 1 time, the burden of the abrasive grains during grinding is increased. Since it becomes larger and the abrasive grains fall off and break, the number of abrasive grains and the arrangement interval are adjusted so that the chip pocket is formed. The number of abrasive grains in the island region is the same as that in each island region, so that stable grinding efficiency can be obtained without causing local load on the abrasive grains in the island region. Although desirable, the number of abrasive grains may be changed depending on the island-shaped region.
[0017]
Here, the abrasive grains fixed by brazing in the island regions are brazed so that the protruding height from the brazing material surface is 50 to 75% of the average grain diameter of the abrasive grains. If the protruding height of the abrasive grains is lower than 50% of the average grain diameter of the abrasive grains, the portion that contributes to the grinding of the abrasive grains is small, so the amount of grinding is small, the sharpness is poor, and the chips are not easily discharged. The material tends to wear out. When the protruding height of the abrasive grains is higher than 75% of the average grain diameter of the abrasive grains, the holding power of the abrasive grains by the brazing material is reduced, and the abrasive grains are likely to fall off. By setting the protruding height of the abrasive grains within this range and the abrasive grain interval, the size of the island-like regions, and the interval within the above ranges, a chip pocket large enough to discharge chips is formed. Is done.
[0018]
Furthermore, in order to improve the surface roughness after grinding, the tip of the abrasive grains fixed by brazing is removed by grinding corresponding to 1 to 10% of the average grain diameter of the abrasive grains. It is desirable to align the tip height. If the removal amount of the tip is less than 1% of the average grain size of the abrasive grains, the height of the tip is varied, and the surface roughness of the processed surface is not improved. If the removal amount is more than 10%, the projection amount of the abrasive grain is small. In addition, since the chip pocket region in the island region is also reduced, the grinding resistance is increased and the grinding efficiency is lowered.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing a grinding wheel in an embodiment of the present invention. FIG. 2 is an enlarged schematic view showing the arrangement of the abrasive grains of the grinding wheel of FIG. 1, (a) is a diagram showing the arrangement of abrasive grains in the island region, and (b) is a diagram of (a). It is AA sectional view.
[0020]
The present embodiment is an example in which the present invention is applied to a grindstone for grinding a plastic lens. FIG. 1 is an enlarged view showing the entire shape of a grindstone and a part of an abrasive grain layer forming portion, where 1 is a base metal and 2 is an island-like region where an abrasive grain layer is formed. In FIG. 2, 3 is abrasive grains and 4 is a brazing material. The manufacturing procedure of this grindstone is as follows.
-An iron base metal having an outer diameter of 100 mm and a thickness of 17 mm is prepared as the base metal 1.
Prepare diamond abrasive grains of # 140/170 (average particle diameter of about 100 μm) as abrasive grains 3.
A circular island region 2 having a diameter of 300 μm arranged on the abrasive layer forming surface of the base metal 1 is set.
The organic adhesive is applied on the base metal 1 using a screen in which holes having a diameter of 300 μm are arranged in a staggered manner with a distance between the centers of the holes of 750 μm.
-An abrasive grain is arrange | positioned on this organic adhesive agent. In this state, four abrasive grains are arranged in each island-like region 2 and there are 450 μm long chip pockets between adjacent island-like regions, and each island-like region is staggered with a center interval of 750 μm. It becomes the form arranged in.
-This is dried at 120 degreeC for 1 hour in a drying furnace, and an abrasive grain is temporarily fixed.
・ Apply a mixture of brazing filler metal (Ti-Ag-Cu-In) and binder to the bonding part at a height of 1/2 of the grain size using an applicator capable of three-dimensional movement. .
-This is heated at 1000 ° C for 1 hour in a non-oxidizing atmosphere, and the abrasive grains are permanently fixed to the base metal.
-Grind and remove the tip part of the abrasive grain 3 by about 5 μm (see symbol h in FIG. 3C) to make the abrasive grain tip height uniform.
[0021]
In this way, four diamond abrasive grains 3 in the circular island-shaped region 2 having a diameter about three times the average grain diameter of the abrasive grains have a protruding height H of about 60% of the average grain diameter of the abrasive grains. And the grinding wheel arrange | positioned so that it might have the chip pocket width W of about 0.4 time of an abrasive grain average particle diameter was manufactured. By this whetstone (invention product), the whetstone (comparative product 1) manufactured by the method described in JP-A-11-90834 and the method described in JP-A-2000-343436 using the same abrasive grains and base metal. A grinding test was performed on the manufactured grinding wheel (Comparative product 2). Table 1 shows the items with different numerical values in the specifications of both grinding wheels.
[0022]
[Table 1]

[0023]
〔Test conditions〕
Wheel peripheral speed: 1250 m / min
Material to be ground: Plastic lens (containing glass fiber)
Grinding method: wet type [0024]
Table 2 shows the test results.
[Table 2]

As can be seen from Table 2, the invention in which the island-shaped regions in which the abrasive layer is formed is regularly arranged and the appropriate chip pocket is formed has improved surface roughness compared to the grinding stones of

comparative products

1 and 2, The power consumption index indicating sharpness is improved by about 30%.
[0025]
Further, the number of workpieces that were able to be ground according to predetermined finishing conditions by continuing the above grinding was 10000 or more for the grinding wheel of the invention, but 1011 for the grinding wheel of the comparative product 1 and 121 sheets for the grinding wheel of the comparative product 2 Met. The grindstone of Invention 1 showed no chip welding or abrasive drop-off on the abrasive layer surface even after grinding 10,000 sheets. After grinding 1011 pieces of the comparative product 1, a large number of abrasive grains dropped out, making continuous use impossible. Further, after grinding the 121 grinding wheels, chips were deposited and the processing became unstable, making it impossible to continue using.
[0026]
【The invention's effect】
The present invention has the following effects.
[0027]
(1) A plurality of abrasive grains are fixed to a single layer with a brazing material in a circular island-like region having a diameter 2.2 to 3.5 times the average grain size of the abrasive grains, and the island-like regions are regularly arranged. Thus, the supply of the grinding fluid and the discharge of the chips are improved, clogging and seizure do not occur, stable machining accuracy and sharpness are obtained over a long period of time, and the life of the grindstone is extended.
[0028]
(2) The island-shaped regions are regularly arranged so that chip pockets of an optimal size are formed between adjacent island-shaped regions, and the optimal size of chips between adjacent abrasive grains By disposing the abrasive grains in the island region so that the pocket is formed, the supply of the grinding fluid and the discharge of the chips become better, and the sharpness is further improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a grinding wheel in an embodiment of the present invention.
2 is an enlarged schematic diagram showing the arrangement of abrasive grains of the grinding wheel of FIG. 1, (a) is a diagram showing the arrangement of abrasive grains in an island-like region, and (b) is (a). It is an AA sectional view taken on the line.
[Explanation of symbols]
1 Base metal 2 Island area 3 Abrasive grain 4 Brazing material

Claims

A grinding wheel in which abrasive grains such as diamond abrasive grains and cBN abrasive grains are further arranged on a base metal and fixed by brazing, and the average grain diameter of the abrasive grains is 75 to 300 μm. The thickness of the brazing material in which circular island regions having a diameter of 2 to 3.5 times are regularly arranged, a plurality of abrasive grains are fixed in each island region by the brazing material, and the abrasive particles are fixed. When the thickness is the thickness of the brazing material in contact with the abrasive grains, the thickness of the brazing material is 0.1 to 0.7 times the average grain size of the abrasive grains on the outer peripheral side of the island-shaped region, interior Ri 1.1 to 1.2 times the thickness der brazing material thickness of the outer peripheral side, between the island regions each other adjacent island-like regions in the line passing through the centers of the adjacent two islands-like regions A chip pocket having a length 0.7 to 4 times as large as the diameter of the abrasive grains is formed. Grinding wheel for plastic lens grinding abrasive grains are arranged such to 1 times the length of the chip pockets are formed over one place.