Effects of Bit Shape of Electroplated Diamond Tool Used for Drilling Small Diameter Holes in Glass Plate on Machining Fluid Flow and Chip Discharge

Our laboratory has been exploring the development of tools for drilling holes in glass plates, and the drilling techniques to be adopted for it. A devised tool shape that could prevent the occurrence of cracks at the exit holes achieved high quality through hole drilling of 100 holes or more using only the drilling cycle. However, crack-free drilling beyond this number of holes cannot be performed. This is due to the adhesion of the residual chip on the tool surface when the number of holes increases. Therefore, further improvement of chip discharge is needed to achieve crack-free drilling. In this report, we consider that chip discharge results from the flow of the machining fluid. To investigate the cause of chip discharge, we analyzed the flow of the machining fluid in the hole using computational fluid dynamics and the supposed chip discharge conditions. The results obtained in this study are summarized as follows. (1) In the case of a cylindrical tool, the Z-axis directional flow of the machining fluid did not occur in the hole. This is because the tool does not have bumps to agitate the fluid on the side, and the gap between the tool and the inner surface of the hole is narrow. (2) The plate side widened the gap between the tool and inner surface of the hole. Therefore, the fluid was likely to flow in the Z-axis direction in the hole. (3) For the tool with the plane side bit, the flow entered the hole from one plane side and exited the hole from the other plane side. (4) When the tool end is spherical, the Z-axis directional flow of the fluid occurs at the tool end. (5) The fluid flow of the devised tool weakened as the drilling depth increased. To improve the chip discharge performance of the designed tool, the Z-axis directional flow of the machining fluid must occur in an area deeper than 2 mm.

本研究室では，ガラス板に穴を開けるための工具の開発とその穴あけ技術の研究を行っている．抜け穴でのクラックの発生を防止できる工夫された工具形状により，穴あけサイクルのみで100穴以上の高品質な貫通穴加工を実現した．ただし，この穴数を超えるクラックフリー穴あけはできない．穴数が増えると工具表面に切りくず残りが付着するためである．したがって，クラックのない穴あけ加工を実現するには，切りくず排出のさらなる改善が必要である．本報告では，切りくず排出は加工液の流れによるものと考えている．切りくず排出の原因を究明するため，穴内の加工液の流れを解析した．この研究で得られた結果は以下のように要約される．(1)円筒工具の場合，加工液のZ軸方向の流れが穴内で発生しなかった．これは，ツールの側面に流体を攪拌するための凹凸がなく，ツールと穴の内面との隙間が狭いためである．(2)プレート側はツールと穴の内面とのギャップを広げる．このため，流体は穴内をZ軸方向に流れやすかった．(3)平面側ビット付きのツールでは，流れは一方の平面側から穴に入り，他方の平面側から穴を出た．(4)工具先端が球面の場合，流体のZ軸方向の流れは工具先端で発生した．(5)工夫されたツールの流体の流れは，掘削深さが増加するにつれて弱まった．設計された工具の切りくず排出性能を向上させるには，加工液のZ軸方向の流れが2mmよりも深い領域で発生する必要がある．

International Journal of Automation Technology (IJAT)


Polishing Performance of a Recycled Grinding Wheel Using Grinding Wheel Scraps for the Wet Polishing of Stainless-Steel Sheets

The surfaces of large austenitic stainless-steel sheets, which have side lengths of at least 1 m a sheet thickness of at least 6 mm, used for food tanks and sliding plates in seismic isolation devices, must be finished to a mirror surface. Polishing is performed to improve the surface quality of such sheets and dry machining is typically applied. The problems associated with dry machining are the exhaust heat of machining and treatment of chips. A transition to wet machining is required to solve these problems. In our laboratory, we have developed a wet polishing machine and researched the selection of grinding wheels to develop wet polishing technology for large stainless-steel sheets. In this study, to reduce tool cost and reuse resources, we attempted to manufacture a recycled grinding wheel using snippets of grinding wheel scraps. A polyvinyl alcohol (PVA) aqueous solution was used as the bonding agent for the recycled grinding wheel to reduce environmental load. To overcome the ease of dissolution of PVA in water, we attempted to improve the water resistance of the PVA aqueous solution by incorporating an organic titanium compound. This is one of our efforts to contribute to sustainable development goals. The results are summarized below. (1) A recycled grinding wheel was fabricated by kneading crushed pieces of grinding wheel scrap with a bonding agent. (2) The maintenance of the shape of the recycled grinding wheel was controlled by the concentration of the bonding agent. (3) The recycled grinding wheel with a PVA bonding agent was vulnerable to water. In contrast, the recycled grinding wheel to which the organic titanium compound was added exhibited improved water resistance. (4) The polishing of stainless-steel sheets using the plain PVA recycled wheel was relatively ineffective, but polishing using the recycled wheel with the titanium additive was comparable to polishing with a new grinding wheel.

食品タンクや免震装置のすべり板などに使用される一辺1m以上，板厚6mm以上の大型オーステナイト系ステンレス板は表面を鏡面に仕上げる必要がある．このようなシートの表面品質を改善するために研磨が行われ，通常は乾式機械加工が適用される．乾式加工の課題は加工時の排熱と切りくず処理である．これらの問題を解決するには，湿式加工への移行が必要である．本研究室では，大型ステンレス鋼板の湿式研磨技術を開発するため，湿式研磨機の開発と砥石の選定を検討した．本研究では，工具コストを削減し，資源を再利用するために砥石スクラップの断片を使用して再生砥石の製造を試みた．再生砥石の接着剤にはポリビニルアルコール(PVA)水溶液を使用し，環境負荷を低減した．PVAの水への溶けやすさを克服するため，有機チタン化合物を配合することでPVA水溶液の耐水性を向上させようとした．これは持続可能な開発目標に貢献するための私たちの取り組みの 1 つです．結果を以下に要約する．(1)砥石廃材の破砕片を接着剤で練り合わせて再生砥石を作製した．(2)再生砥石の形状維持は結合剤の濃度によって制御された．(3)PVA 結合剤を使用した再生砥石は水に弱かった．一方，有機チタン化合物を添加した再生砥石は耐水性が向上した．(4)PVA 再生砥石を使用したステンレス鋼の研磨は比較的効果がなかったが，有機チタンを添加した再生砥石を使用した研磨は通常の砥石での研磨に匹敵した．


Slag Suppression in Gas Cutting of Extreme-Thick Steel Plate by Compressed Air Blow Support

厚物鋼材ガス切断における圧縮空気ブロー支援によるスラグ抑制

Gas cutting is one of the main methods used for cutting steel plates. Gas cutting produces molten steel and it cools down and adheres strongly to the back of the steel. This adhesion is called slag, and it is difficult to remove. In this study, a method of blowing compressed air onto a steel plate in gas cutting to blow away the molten metal, that is, the "Compressed Air Blow Support Method" was conceived. A device for blowing compressed air onto a steel plate was fabricated, and the effects of the blowing direction and input compression pressure on the amount of slag adhering to the steel were investigated. When the compressed air was blown onto the steel plate in the direction perpendicular to the direction of gas cutting, the molten metal stuck to the bottom of the steel plate was blown away and almost no slag adhesion was observed. When the input pressure was changed from 0.1, 0.2 and 0.3 MPa, the amount of slag adhered was large at the highest blowing pressure of 0.3 MPa, and the amount of slag adhered was minimal at 0.2 MPa.

スラグが付着したままの鋼材は製品として寸法精度や意匠性に問題が生じるため，スラグは除去しなければならない．これまで，スラグの除去作業はグラインダーを使った手作業で行われており，労働環境におけ る多くの課題を内在し，また，製造リードタイム短縮を阻害する要因ともなっている．そこで，筆者らは，ガス切断実施時に発生するスラグを高圧力の圧縮空気で吹き飛ばすことを企図した．ガス切断機に圧縮空気導入用のノズルを併設し，切断部付近へ圧縮空気ブローを導入する圧縮空気ブロー支援型ガス切断装置を試作し，本手法を用いて鋼材切断実験を実施した．スラグの挙動とスラグ付着度合の関連性の検証を行い，本提案手法の有効性について検討した結果を報告する．

Journal of Japan Society for Design Engineering


Optimization of Wet Grinding Conditions of Sheets Made of Stainless Steel

This study addresses the wet grinding of large stainless steel sheets, because it is difficult to subject them to dry grinding. Because stainless steel has a low thermal conductivity and a high coefficient of thermal expansion, it easily causes grinding burn and thermal deformation while dry grinding on the wheel without applying a cooling effect. Therefore, wet grinding is a better alternative. In this study, we made several types of grinding wheels, performed the wet grinding of stainless steel sheets, and identified the wheels most suitable for the process. As such, this study developed a special accessory that could be attached to a wet grinding workpiece. The attachment can maintain constant pressure, rotational speed, and supply grinding fluid during work. A set of experiments was conducted to see how some grinding wheels subjected to some grinding conditions affected the surface roughness of a workpiece made of a stainless steel sheet (SUS 304, according to Japanese Industrial Standards: JIS). It was found that the roughness of the sheet could be minimized when a polyvinyl alcohol (PVA) grinding wheel was used as the grinding wheel and tap water was used as the grinding fluid at an attachment pressure of 0.2 MPa and a rotational speed of 150 rpm. It was shown that a surface roughness of up to 0.3 μm in terms of the arithmetic average height could be achieved if the above conditions were satisfied during wet grinding. The final surface roughness was 0.03 μm after finish polishing by buffing. Since the wet grinding of steel has yet to be studied in detail, this article will serve as a valuable reference.

Journal of Manufacturing and Materials Processing


炭素添加ペーストによる鋼板のガス溶断におけるスラグ固着抑制

炭素添加ペーストによる鋼板のガス溶断におけるスラグ固着抑制


Mechanics of Slag Control in Gas Cutting of Steel Plate by Slag Pasting

スラグペーストによる鋼板のガス切断におけるスラグ抑制メカニクス

The gas cutting process is one of the primary methods employed for cutting steel sheets. However, during gas cutting, the adhesion of slag to the back surface of the steel plate cannot be avoided. In this study, to prevent slag adhesion on the bottom plate, the bottom plate was coated with an iron oxide paste. Several aspects such as the effect of iron oxide paste on slag adhesion, discharge and separation of slag from the steel plates back surface, and the formation and growth of adhesive slag were experimentally investigated. Consequently, based on the concept that slag is separated from the steel plate with paste, it can be concluded that the proposed iron oxide pasting method aids in easy removal of adhered slag.


Helical Micro-Hole Drilling of Chemically Strengthened Glass Using Capsule-shaped Electroplated Diamond Tool

This study investigates the microhole drilling performance of chemically strengthened glass plate by using a capsuleshaped electroplated diamond tool and the helical drilling method. Three different helical pitch conditions were tested to drill holes with a diameter of 1 mm. The number of drilled holes, grinding force, and maximum crack size were measured along with the observation of the drilled holes to evaluate the performance of the microhole drilling. From the experimental results, it was found that as the size of helical pitch decreased, the number of drilled holes increases where the average grinding force generated becomes smaller. By using small helical pitch condition, 43 holes could be drilled but the maximum crack size generated at the outlet side of the drilled hole is not able to achieve the highgrade quality compared to the inlet side. The resultant grinding force generated when the tool tip nearing the outlet side of the glass plate has caused the large crack at a certain position on the outlet side.

Journal of Advanced Manufacturing Technology


Chip Discharge Performance of Micro-hole Drilling through a Glass Plate using an Electroplated Diamond Tool with Different Drill Bits

This research aims to identify a high-quality, efficient, and low-cost micro-hole drilling process through glass plates that employs an electroplated diamond tool with different drill bits. Three different drill bits were tested to determine how varying the chip discharge volume influences chip discharge performance, which is an important factor that affects the effectiveness of the drilling process. The chip discharge performance of each electroplated diamond tool was experimentally investigated by observing the drilling quality and the number of the drilled holes. From the experimental results, it was found that the drilled chips could not discharge smoothly when the drill bit possesses a small chip discharge volume, leading to the drill bit breaking, which thus limits the number of drilled holes. Furthermore, the changes in thrust force and the crack size were high, and there were also cracks on the drilled glass plate. However, drilling with a drill bit that possesses a larger chip discharge volume resulted in excellent chip discharge performance and increased the number of drilled holes. This type of drill bit is effective in drilling holes through glass plates, with minimum hole defects and no issues associated with chips clogging the hole during drilling.

International Journal of Precision Engineering and Manufacturing


Prevention of chip adhesion by acting non-ionic surfactant physical properties

非イオン系界面活性剤の物性による切りくず付着の抑制

穴加工において，切りくずは穴内に残留しやすく，工具に付着しやすい状況にある.本研究室では先端部を半球形状とした円筒形ダイヤモンド電着工具の側面の一部を削り取り，ここが切りくず排出の役割を担うストレート面付き工具を開発した.この工具は，加工中に生成される切りくずを効率的に排出し，工具への切りくず付着を抑えてい た.しかし，少量の切りくずが穴内に残留し，加工穴数の増加に伴い，切りくず排出領域に付着した.本研究は加工液に含有する界面活性剤の物性に着目し，この物性が切りくず付着に及ぼす影響について検討した.

Journal of the Japan Society for Abrasive Technology


Improved Chip Discharge in Drilling of Glass Plate Using Back Tapered Electroplated Diamond Tool

Previous studies of a through-hole drilling for hard and brittle materials using electroplated diamond tool devised by the authors have led to several challenges such as a restraint of crack size at the inlet and outside, a suppression of chip adhesion on the tool and an improvement of processing efficiency. In this paper, the devised tool was redesigned in order to restrain cracks of the inlet side as well as to improve the chip discharge. The new design of the tool featured a back taper which was expected to bring an effect of restraining crack size by preventing any interference between the tool cylindrical surface and the hole inner surface during drilling process. In addition, the chip can be discharged from the drilled hole through the back taper. Results of the experiment indicated that by providing the back tapered shape, the width of the inlet hole can be reduced slightly as the interference between the glass plate and the tool cylindrical surface was suppressed. Furthermore, the adhesion of chip on tool can be restrained by using the tool with large chip discharge space as the chip was easily discharged to the outside of the hole. Moreover, an abrupt change in thrust force was not detected, and the crack width was found in small size.


Investigation of Grinding Fluid for Prevention of Chip Adhesion in Miniature Drilling of Glass Plate Using Electroplated Diamond Tool


Mechanical Properties and Cutting Performance of Electroless Ternary Ni-W-P Coated Cutting Tools


Miniature Drilling of Chemically Strengthened Glass Plate Using Electroplated Diamond Tool

It is well known that chemically strengthened glass plate has excellent strength and hardness properties. These characteristic properties are advantageous for the touch screens used in mobile devices. However, they are detrimental to the process of machining the glass plate. For example, chipping and crack occur around the inlet and outlet of the drilled hole, and the rate of tool wear is significant. Therefore, the surface quality and machining efficiency are low. The drilling process is extremely difficult. In this study, we de- scribe the use of a miniature drilling method to achieve high-quality drilled holes in chemically strengthened glass plate using an electroplated diamond tool with a diameter of 1 mm or less. Using the developed tool with a diameter of 0.5 mm, it is demonstrated that the conventional drilling method can be used to drill a through-hole in the glass plate.

International Journal of Automation Technology (IJAT)


Fundamental Study on Hole Fabrication inside a Hole by Means of Electrical Discharge Machining


Development of electroplated diamond tool for fracture size minimization in miniature drilling of glass plate

ガラス板への高品位通り穴加工を目的とした小径ダイヤモンド電着工具の開発

To minimize fracture size in through-hole drilling of glass plate, this paper examines drilling behavior of commercial tool shape, as well as the availability of a tool shape designed by the authors. The chipping size occurring at the hole edge is related to the form of tool end and the chip elimination efficiency. The designed tool, which is an electroplated diamond tool with a diameter of 1 mm, has a unique shape. The tool shape has a hemispherical tool end and a few straight planes. During drilling, the hole enlarges gradually due to the hemispherical shape of the tool end. The occurrence of chipping at the edge of the exit hole is reduced because the hemispherical shape can reduce the abrupt decrease in drilling force. That is, large chipping and cracking corresponding to the hole diameter can be suppressed. In addition, the straight planes play a role in eliminating chipping, and the adhesion of chips is suppressed. The results of this investigate indicate that the designed tool allows drilling of drilling cycle.

本論文は，ガラス板への小径通り穴加工において，穴縁周りの欠けを小さく抑える工具形状についての検討を行うとともに工具の開発を行った．穴縁に生じる欠けの大きさは工具先端の形状と切りくずの排出性能に関係した．得られた知見から，著者らは工具穿孔部が他に類を見ない形状を持つ小径ダイヤモンド電着工具を開発し，この工具の有効性を調査した．本工具の特長的な点は，工具先端部が半球状であることと穿孔部がストレート面をもつことである．工具先端部を半球形状にすることで，穴は徐々に繰り広げられるような加工となる．この形状により，加工抵抗の急激な変化は抑えられるため，欠けは小さくなった．すなわち，穴径に相当するほどの大きな欠けや割れは抑制できた．そして，ストレート面は切りくずを排出する役目を担い，切りくずの付着を抑制した．本工具1本のみを使用した通常のドリリングサイクルでの穴加工を可能とした


Restraint of Thermal Crack on Rake Face of Cermet Tool in Intermittent Cutting


Relationship Between In-Plane Stress and Modal Shape of Disk

円板の面内応力と振動モード形状に関する研究

In this paper, we analytically considered the effects of the in-plane stress of the disk on the changes of modal shape. The purpose of this study is to confirm whether the modal shape changes according to the in-plane stress. The results make it clear that the in-plane stress changes the modal shape and its curvature. The curvature of the modal shape is proportional to the reciprocal number of the bending stiffness. Thus, it is confirmed that the in-plane stress serves to change the bending stiffness distributions on the disk. Moreover, the natural frequencies of the disk are evaluated by two energy methods in which the variations of modal shapes are considered or not. The difference in the natural frequencies from two energy methods shows the effect of the changes in the modal shape of the disk due to the small difference in the results of the energy methods (maximum difference of strain energy: 7.1%). Finally, the two energy methods are compared to investigate the effects on the natural frequencies with hammering test. The experimental results show the traditional energy method is allowed to evaluate the natural frequencies practically.

Transactions of The Japan Society of Mechanical Engineers, Series C

日本機械学会論文集(C編)


A Study on the Transverse Vibration of the High Speed Rotating Circular Saw and the Countermeasure

高速回転する丸鋸の振動とその対策に関する研究

In this paper, we considered a new tensioning method by the centrifugal stress on the base metal of rotating circular saw. First, the residual stress distribution on the base metal generated by roll tensioning and the centrifugal stress distribution was compared by calculation using a disk model (Φ305mm). As the results, it was confirmed that the tangential stress ςϑR by centrifugal force at outer of disk became larger than the residual stress ςϑP by roll tensioning when the rotational speed is higher than 7300 rpm. This rotational speed is larger than 1.4 times of the critical speed (resonance rotational speed) of disk. And it is concerned that the unstable vibration may be generated. Therefore, we investigated the behavior of the unstable vibration and established the countermeasure by the rotating experiment. As the results of the rotating experiment, we considered that the unstable vibration is the self-excited vibration as the negative damping caused by the effects of the high-speed airflow around the rotating disk. According to this consideration, we investigated the relationship of the damping coefficient of disk and the behavior of the unstable vibration. As the result, it is confirmed that the rotational speed of the unstable vibration occurred becomes higher with the increase of the damping coefficient of disk. It is confirmed that it is possible to suppress the unstable vibration of disk and provide the tensioning effect by centrifugal force of disk.

日本機械学会論文集(C編)


Relationship Between In-plate Stress and Modal Shape of Disk


Through-Hole Drilling of Glass Plate Using Electroplated Diamond Tool


Drilling conditions and crack restraint of step drilling method in through-hole drilling of glass plate

ガラス基板への通り穴加工におけるステップ加工時の加工条件と欠けの抑制

Hard and brittle materials such as ceramics and glass are not only difficult-to-machine but also occur easily cracks at the exit surface in through-hole drilling. This paper deals with through-hole drilling of soda-lime glass plate using an electroplated diamond tool in order to find out drilling conditions for smaller cracks, higher processing efficiency and longer tool life. The crack is smallest under a spindle revolution of 15000min-1, a feed speed of 1mm/min, a step feed of 0.1mm/step and a mesh size of #600. A large decrease of thrust force results from the penetration that the large cracks occur. The maximum diameter included the crack is smaller than that of the tool. The residual is removed as the tool feeds. The cracks at the exit increase with the drilling numbers. The drilling time is about 430s per a hole.

Journal of the Japan Society for Precision Engineering


Grinding force and crack size on through-hole drilling of glass plate used electroplated diamond tool in helical drilling

ダイヤモンド電着工具によるガラス基板へのヘリカル加工時の研削抵抗と欠け

Journal of the Japan Society for Abrasive Technology


ダイヤモンド電着工具によるガラス基板への通り穴加工時の加工精度と加工能率

ダイヤモンド電着工具によるガラス基板への通り穴加工時の加工精度と加工能率


Study on Applying Cavitation in Micro Drilling of Austenite Stainless Steel --- Control of Burr in Through Hole Drilling

International Journal of Automation Technology (IJAT)


Influence of Tapping Conditions and Tool Geometries on Tool Life in Tapping of Inconel 625®

Inconel 625® contained Ni 61%, Cr 21.5%, Mo 9% and so on is one of the nickel base super heat resistant alloys and is used for parts in food machine. The nickel base alloys are generally difficult-to-cut materials because of high thermal resistance, high work hardening, high chemical activity and low thermal conductivity. In tapping, furthermore, the tool failure such as chippings, cracks and tool fractures has been frequently observed owing to low rigidity of tool. This paper deals with the influence of surface treatment, tool geometry etc. on the cutting phenomena such as the tool failure, the cutting force and so on when tapping Inconel 625® using the high speed steel tool. The damage of oxidizing tool is slower than that of nitriding tool. The large thrust force in backward tapping causes rapid tool fractures. The smaller helix angle leads to the lower thrust force in backward tapping.


Effects of Cavitation on Burr and Tool Life in Micro Through Hole Drilling (3rd Report) --- Researches on Applying Ultrasonic Vibration on Machining Fluid

小径貫通穴あけ加工時のバリや工具寿命に及ぼすキャビテーションの効果(第3報) --- 工作液超音波振動法に関する研究

Micro drilling is required in order to produce nozzles for fiber, fuel and so on. This paper deals with cavitation effects when applying ultrasonic vibration on machining fluid in micro through-hole drilling. In addition, burr and tool life are investigated when micro-drilling on SUS304 under various feed speeds. The obtained results are as follows. Cavitation occurs in a blister generated by machining fluid at the exit hole in through-hole drilling. The burr height in cavitation assisted drilling is smaller than that in conventional one and increases with the drilling number. The tool life in through-hole drilling is same as in blind hole one under various feed speeds and is the longest at a feed speed of 200mm/min. The effect of cavitation on the burr removal was investigated using B_4C powder and was observed at the early drilling holes.

貫通穴あけ加工時のキャビテーション挙動を調べるために，アクリル樹脂の穴あけを高速ビデオカメラによって観察した．SUS304への直径0.1mmの貫通穴あけ加工を取り上げ，バリ抑制の観点から，本加工法における送り条件とスラスト力による穴出入口のバリの性状について検討した．また，本加工法を応用したバリ取りについても検討した．


Drilling machinability of resin-less "green" composites reinforced by bamboo fiber

この論文では，穴あけ加工時における竹繊維グリーンコンポジットの被削性について述べる．グリーンコンポジット，竹および杉を鉄工用ドリル，木工用ドリルを使って穴あけ加工し，スラスト力，比切削抵抗，加工穴の性状，切りくず形状および工具摩耗によって被削性を検討した．レジンレス竹繊維強化グリーンコンポジットのスラスト力は，他の被削材に比べて大きく，切りくずは非常に長かった．鉄工用ドリルを用いて，切削速度15m/min，送り0.03mm/revで穴あけ加工を行うとレジンレス竹繊維強化グリーンコンポジットの加工穴に発生するバリやコバ崩れは小さかった．穴周りの欠陥を少なくするためには，グリーンコンポジットの単繊維を鋭い切れ刃で切削しなければならず，工具としてダイヤモンド電着工具の使用が考えられる．

WIT Transactions on the Built Environment


Flexural properties of all bamboo "green'' composites

本論文は，竹の強度改善を目的としてマダケに対して種々の条件でホットプレス成形を行った結果をまとめたものである．評価すべき強度特性として，3点曲げ強度，曲げ弾性率，圧縮強度，アイゾット衝撃強度に注目した．その結果，曲げ強度，圧縮強度，衝撃強度はホットプレス成形温度の上昇につれて向上し，160℃でピーク値を示すことが分かった．さらに内部組織の調査から，維管束部と柔細胞部の圧縮変形により試料の高密度化が行われ，この密度向上に対応して各種強度特性が向上することが分かった．


Relation between Drilling Conditions and Tool Life in Micro Drilling(2nd Report) --- Researches on Applying Ultrasonic Vibration on Machining Fluid

小径穴あけ加工における加工条件と工具寿命(第2報) --- 工作液超音波振動法に関する研究

The most important problem in the micro drilling of ductile materials such as steels is a tool breakage due to poor tool rigidity and chip removal. The cavitation, which is generated by ultrasonic vibration applied on machining fluid, accelerates the chip removal. This paper deals with thrust force, tool life, chip geometry etc. for various drilling conditions in drilling SUS304 with (Ti,Al)N coated tool with a diameter of 0.1mm. In addition, the effects of pre-drilling using a center drill on tool life and of G73 cord on the machining efficiency are investigated. The obtained results are as follows. The thrust force hardly varies with feed speed and increases with step feed. The micro drilling assisted with cavitation achieves very longer tool life compared to the conventional drilling. Furthermore, the quick bite leads to longer tool life. The smaller feed speed and the larger step feed, respectively, bring out the shorter tool life.


Through Hole Drilling of Alumina Ceramic with Electroplated Diamond Tool (2nd Report) --- Effects of Oil Through and Mesh Size on Drilling Performance

小径ダイヤモンド電着工具によるアルミナセラミックへの通し穴加工(第2報) --- オイルスルー方式と粒度の効果

直径1mmの通し穴加工において工具先端領域に付着する切りくずの除去および電着工具の安定性を上げるために，オイルスルー方式や粒度の影響を検討している．低速域の切りくずの付着を少なくし，工具寿命を長くするとともに穴直径の寸法精度を良くする．粒度が大きいほどスラスト力と欠け幅は小さくなる．

Journal of the Japan Society for Precision Engineering, Contributed Papers


小径穴あけ加工における油剤のキャビテーション効果(第1報) --- 工作液超音波振動法に関する研究

小径ドリル加工において，工作液に超音波振動を付与することにより生じるキャビテーション現象を応用する手法を提案し，工具損傷，工具寿命，表面粗さなどを検討した．加工穴内部から生じるキャビテーションにより切りくず排出性が向上し，工具チゼル部や逃げ面での凝着の減少により，工具寿命が延び，加工面粗さの低下が確認できた．


磁性流体を利用したダイナミックダンパー内蔵ボーリングバーの開発(第1報) --- -ダイナミックダンパーの形状と振動剛性-

深穴の加工においてびびり振動対策は極めて重要である．磁性流体を減衰剤に使用して減衰能の大きい中ぐりバイトを開発するために，磁性流体の効果を実験的に評価したものである．市販バイトと同程度の減衰能が得られることがわかった．


Through Hole Drilling of Alumina Ceramic with Electroplated Diamond Tool (1st Report) : Investigation of Tool Geometry and Machining Conditions --- 工具形状と加工条件の検討

小径ダイヤモンド電着工具によるアルミナセラミックへの通し穴加工(第1報) --- 工具形状と加工条件の検討

In through hole drilling of hard and brittle materials such as ceramics, glass etc., cracks occur at the exit surface. This paper deals with a miniature drilling of Al_2O_3 (1600HV) using an electroplated diamond tool. The main purpose of this research is to find out tool geometries and drilling conditions in which the exit cracks are very small and the tool life is very long. A tool with rectangle section and bowl end is effective on the chip removal and the control of fracture size. A method assisted by step feed, in addition, produces a numerous drilling number of 100th or more at a workpiece with a thickness of 3.4mm. The desirable drilling speed should be 50-100m/min and the preferable feed rate arrangement should be 5mm/min at the entrance while 1.5mm/min at the exit. When the tool end reaches the position about 40m from the exit surface, a hole passes through and large cracks occur around the hole. At the same time, the thrust force falls rapidly. As the tool end moves further, the hole diameter increases and the fracture size decreases. However, large cracks may occur rarely in the progressive process.

硬脆材料であるセラミックに精度のよい直径1mmのノズル穴をあけることのできるダイヤモンド電着工具を開発するために，形状や加工条件について実験的に検討を行った．先端形状がボールであり，切りくずの収容できるスペースを構えることが必須であること，さらに20000rpm以上の回転数が必要であることがわかった．


The Behavior of Tool Life and Cutting Temperature on High Speed Milling of Hardened Alloy Tool Steels

焼入れ合金工具鋼の高速エンドミル加工時の工具寿命と切削温度

A high speed milling is being received with keen interest in the manufacturing shop where cut hardened alloy tool steels used for metal molds. However, there are some difficult problems, such as high cutting temperature, low stiffness of NC machine, low follow-up ability of NC servo motor etc. This paper deals with cutting phenomena such as cutting temperature, tool life etc. when milling the steels using cemented carbide with grade K1O under various cutting conditions. Furthermore, based on the cutting temperature measured using a work-tool thermocouple technique, the tool wear rate is discussed. The results obtained are as follows. The longest tool life is obtained at cutting speed of 110-130 m/min and feed of about O.05 mm/tooth. The relationship between work hardness and tool life is linear for each cutting speed on the semilogarithmic coordinate. When the cutting speed is 130 m/min or more, the tool life correlates very closely with the cutting temperature. (Ti, Al)N coated tool has longer tool life of about 2 times and higher thermal resistance of about 100 compared with carbide tool.

硬さの異なる合金工具鋼を主軸回転数7000~26000rpmで超硬合金製のエンドミルでミーリング加工したときの切削温度を工具·工作物熱電対法で測定するとともに，工具寿命試験を行い，切削温度と摩耗速度の関係を検討している．1000K付近(切削速度約130m/min)から熱による摩耗が顕著になり，(Ti,Al)Nコーティングの有効性を証明している．

Journal of the Japan Society for Precision Engineering


Slanting-hole drilling of glass plate using an electroplated diamond tool

小径ダイヤモンド電着工具によるガラス板への高品位斜め穴加工

The utility of slanting-hole drilling using an electroplated diamond tool of small-diameter devised by the authors was investigated. As with straight-hole drilling, a normal drilling cycle could be adopted with slanting-hole drilling because the unique shape of the tool increases chip discharge. In addition, the drilled hole showed a small degree of chipping without using an underlay board and/or ultrasonic wave instrument. The chipping width was influenced by the behavior of the axial component of the grinding force before completion of the drilling process.

著者らが考案した小径ダイヤモンド電着工具を用いて，ガラス板への斜め穴加工を行い，本工具の斜め穴加工への有用性を調査した．直穴加工時と同様に，本工具の特長的な形状により，切りくず排出のためのステップ送りを採用しなくとも切りくずの排出は良好であり，通常の一方向送りのドリリングサイクルでの穴加工は可能であった．また，座ぐりや捨て座，超音波援用装置などを用いなくとも，工具の食付き側および抜け側に生じる欠けは小さかった．工具抜け側の欠け幅は加工終了間際の軸方向成分の挙動に左右した．

Journal of the Japan Society for Abrasive Technology