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MICRO HOLE MACHINING WITH MINIMUM BURR FORMATION USING

MICRO COMPOUND TOOL

SUBMITTED BY TISS ISAC S7 MECH 52

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CONTENTS

• Introduction

• Literature Review

• Objectives

• Design of Micro Compound Tool

• Experimental Method

• Results and Discussions

• Conclusion

• References

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INTRODUCTION

• Conventional machining

• Micro manufacturing

• Burr formation is major problem in micro hole machining

• Stainless steel is used as industrial material for micro

machining

• Necessity of micro tool for machining stainless steel

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LITERATURE REVIEW

• Churn et.al (2007) has inferred that existence of burr on

manufactured products could decrease product quality.

• Imbibe et.al (2010) reported that stainless steel is the most

adopted industrial material in micro components.

• Lining et.al (1998) proposed that assistance of ultrasonic

vibration could increase rigidity of drill and reduce drill

skidding.

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OBJECTIVES

• Development of new micro tool with capability of drilling and

finishing in one step process.

• Effect of drill point angle.

• Influence of ultrasonic vibration on the burr formation.

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DESIGN OF MICRO COMPOUND TOOL

• Micro compound tool is a combination of micro flat drill as

drilling part and an electroplated part as grinding part

Fundamental design of developed micro compound tool

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DESIGN OF MICRO COMPOUND TOOL (contd…)

• Machining process using micro compound tool is divided into four steps: preparation, pilot hole machining by drilling part, grinding by tapered grinding part, hole finishing by grinding part

Machining steps by the developed micro compound tool.

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EXPERIMENTAL METHODS

• Two continuous process

-Fabrication of micro compound tool

-Hole machining with micro compound tool

• Fabrication of micro compound tool

-grinding of micro flat drill as drilling part

-substrate of grinding part

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EXPERIMENTAL METHODS (contd…) Machining of drilling part and substrate for grinding part

• Tool blank made of ultra-fine cemented carbide having an average particle diameter of 90 nm.

• Diamond grinding wheel clamped on main spindle.

• Rotary table mounted on XY table of machining center.

• Grinding is performed in the order of flank, cylindrical and flute surfaces.

Machining of micro flat drill and substrate for grinding part

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• In the flank surface grinding, the rotary table, as well as the tool

blank, was rotated and fixed by an angle corresponding to the

desired drill point angle.

• For the cylindrical surface grinding, the tool blank was ground

by feeding the grinding wheel linearly in the −Z direction.

• For the flute surface grinding, the fixed tool blank was rotated

and fixed according to the decided chisel edge and then it was

ground by feeding the grinding wheel linearly in the −Z

direction.

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EXPERIMENTAL METHODS (contd…)Grinding conditionGrinding Wheel Synthetic Diamond

Grit Number #3000Outer Diameter 12 mmBonding Material Bronze

Tool Blank Material ultra-fine cementedCarbide. WC particle size: 90 nmInitial Diameter 1.05 mm

Target Geometry Drilling PartDiameterFlute LengthPoint angleClearance angleChisel edge angleWeb thicknessBack taperGrinding part Substrate diameterSubstrate lengthGrinding part taper

90 m300 m100-1301611550 µm5/100

90 µ m300 µm10/100

Grinding conditionRotor speedFeed rate

4200 min-1

100 m min-1 for flank and periphery grinding50 m min-1 for flute surface grinding

Coolant Dresser type

Water based coolantGC type dresser. Grit size of #3000

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EXPERIMENTAL METHODS (contd…) Electroplating of grinding part

• Process- cleaning of substrate, masking, strike plating by

nickel for 2 min, electroplating of diamond grits and

embedding them into the electroplated layer.

Electroplating conditions.Electroplating of grinding part

Bath Ammonia citrate bathNi(so3)2H20(NH4 )10 W12 O41 ·5H2 O C6 H5 O7 (COOH)3

Strike plating liquid sulfuric acid andNickel sulfate

Strike plating period 2 min

Diamond grit diameter 2–4 µm

Stirring method Automatic intermittent stirring

Current density 2 A dm−2

Electroplating period 15 min

Deposition period 2 min

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EXPERIMENTAL METHODS (contd…)Through hole machining

• Metal shim tape which is made of SUS304 was selected as the

work piece.

• USV table providing the vibration to the work piece is installed on

the XY table.

• To provide a high rotational speed, a high speed motor driven

spindle was fixed on the Z axis of machining center.

• In hole machining without ultrasonic vibration, the work piece

was clamped on the jig having some pilot holes which was

installed on the XY table of machining center.

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EXPERIMENTAL METHODS (contd…)

• In hole machining with ultrasonic vibration, work piece was

clamped on jig which was vibrated with natural frequency and

double amplitude of about 63.5 kHz and 1.5 m.

Hole machining condition Hole machining with USV

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RESULTS & DISCUSSIONS

Fabricated micro compound tool

Comparison of the burr condition

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RESULTS & DISCUSSIONS (contd …)

• The developed micro compound tool decrease the burr size both

at the entrance and exit holes.

• Improved the hole wall surface significantly.

Surface roughness comparison of the hole inner wall

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RESULTS & DISCUSSIONS (contd …)

Effect of ultrasonic vibration

Burr formation at 100th hole in hole machining Burr comparison between drilling

with and without USV

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RESULTS & DISCUSSIONS (contd …)

• The hole entrance, burrs under both conditions seems equal in

size but it is significantly different at the hole exit.

• For both conditions, as the number of holes is increasing, burr

width and height are also gradually getting larger.

• In machining without ultrasonic vibration causes a very

progressive increase of burr width and height compared to

machining with ultrasonic vibration.

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RESULTS & DISCUSSIONS (contd …)

Effect of drill point angle

Fabricated micro compound tool with different point angle

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RESULTS & DISCUSSIONS (contd …)

• There is no significant

change in entrance burr for

both burr width and height

although the number of hole

is increasing.

• At the hole exit there is a

very significant difference

among them.

Burr formation

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RESULTS & DISCUSSIONS (contd…)

Burr for different drill point angle

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RESULTS & DISCUSSIONS (contd…)

• Drill point angle of 100◦ produced the largest burr width and

height compared with other two point angles.

• On the other hand, drill point angle of 118◦ formed almost a

stagnant growth of burr width and height even the number of

hole is progressing.

• Drill point angle of 130◦ resulted in significant changes of burr

width and height.

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RESULTS & DISCUSSIONS (contd…)

• It can be observed clearly that the tool wear is growing faster as the drill point angle is getting larger.

Tool wear comparison with different drill point angles after drilling

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CONCLUSIONS• Micro flat drill is developed by fabrication of micro flat drill

and electroplating.

• Micro compound tool decreases the size of burr

• Application of ultrasonic vibration reduces the plastic

deformation and enhances the performance of the tool.

• Burr formation is restrained and the tool life increases as

machining force decreases

• Tool with drill point angle of 118◦ is considered as the best

geometry because it forms burrs in smaller size stagnantly and

showed a moderate tool wear

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REFERENCE• Muhammad Aziz a,∗ , Osamu Ohnishi b, Hiromichi Onikura b

2011. Innovative micro hole machining with minimum burr formation by the use of newly developed micro compound tool

• Koi SL, Lee JK. Analysis on burr formation in drilling with new concept drill. J Mater Process Techno 2001;113:392–8.

• Chang SSF, Bone GM. Burr size reduction in drilling by ultrasonic assistance. Robot CIM-Into Manu 2005;21:442–50.

• Churn GL, Engine Wu YJ, Cheng JC, Yao JC. Study on burr formation in micro-machining using micro-tools fabricated by micro EDM. Precision Eng. 2007;31:122–9.

• Allen DM, Shore P, Evans RW, Fanfare C, O’Brien W, Mason S, et al. Ion beam focused ion beam and plasma discharge machining. CIRP Ann Manu Techno 2009;58:647–62