Micro-drilling Using Step-forward Method Micro-drilling Using Step-forward Method

1. 한국기계연구
원
Korea Institute of Machinery &
Micro-drilling Using Step-forward MethodMicro-drilling Using Step-forward Method
Waqas CH
.

2. 한국기계연구
원
Korea Institute of Machinery &
Medical devices
IntroductionIntroduction
Spinneret & dies
Micro-drilling is regarded as useful process technology to make tiny holes
and widely used at electronic, semiconductor, medical, fuel injection, watch,
spinneret, dies related industry fields
Micro-drill
Human hair
(D)80 µm
Micro-drill
(D) 30 µm
Watch component
Electronics & semiconductor
Fuel injection nozzle
Military & aerospace components

3. 한국기계연구
원
Korea Institute of Machinery &
MotivationMotivation
Recently, creative precision has complete micro hole drilling capabilities for holes
down to 30 µm in diameter
But conventional micro-drilling has also several problems such as excessive forces,
tool breakage, chatter, burr formation in metals
It became a common understanding that it is necessary for machining tiny holes
smaller than 100 µm in diameter to apply the laser systems
However, it is also true that laser systems have several disadvantages compared to
conventional mechanical drilling
And the mechanical system could be competitive against the laser system, if they can
have micro drilling capabilities
Thus, many manufacturers have been making efforts to retry the traditional
mechanical precision drilling machine for machining tiny holes with high
productivity

4. 한국기계연구
원
Korea Institute of Machinery &
ObjectivesObjectives
Trouble-shooting to occurred tool breakage mode frequently during previous
precedent conventional micro-drilling experiment
Examination to application capability of presented proper method to control tool damage
Accomplishment of direct practice to obtain preliminary knowledge for ascertain
mechanical micro-drilling behavior through the experimental study
Presumption as the trouble is resulted in the poor chip cutting & evacuation
Application of step-forward feeding method during micro-drilling process
*
*
*

5. 한국기계연구
원
Korea Institute of Machinery &
Drilling ability 0.05 ~ 2.0(Φ) mm
Tool speed
(Revolution)
50,000(Max.) rpm
Torque 500 gr-cm
Air pressure (Bearing) 5 ~ 6 kgf/cm2
Step feed rate 0.01 ~ 99.99 mm
Total stroke 75 mm
Height to collets
From table surface
30 ~ 200 mm
Size of machine body 300 × 350 × 680 mm
Weight 35 kg
Specifications of the micro drilling apparatus
Experimental apparatus for micro drilling experiment
Air bearing spindle
Controller
Stepping motor
Tool dynamometer
Pressure gauge box
Experimental System for Micro-drillingExperimental System for Micro-drilling
Micro-drill
Work-piece

6. 한국기계연구
원
Korea Institute of Machinery &
Work-piece
SM45C (35 × 35 × 2.3 mm)
C : 0.12 ~ 0.20%
Tensile strength : 38~44kgf/mm2
Dynamometer Kistler Co Type 9257A
Amplifier Kistler Co Type 5011B
A/D converter DAQ Card-Al_16XE-50
Microscope with
built-in monitor
FORTEC CORPORATION
(sometech)
Measuring instruments for cutting force
Microscope with built-in monitoring system
Data acquisition system
A/D converter
DAQ
Amplifier
Vision system
Micro drill
Measuring InstrumentMeasuring Instrument
Work-piece

7. 한국기계연구
원
Korea Institute of Machinery &
Tool
Material
Undercut Diameter
Φd (mm)
Body Length
L1 (mm)
Tip angle
Θ ( 0
)
Vanadium
Carbide Tool
0.2 2.8 120
0.3 5.5 120
0.4 7.0 120
0.5 7.0 120
Micro-drill ToolMicro-drill Tool
Geometric feature of micro-drill
Dimensions of micro-drill
Straight-fluted Micro-drill
0.2(d)mm
0.3(d)mm
0.5(d)mm

8. 한국기계연구
원
Korea Institute of Machinery &
Amplifier
YY ZZ
A/D Board
Computer
Data acquisition system
Work-piece
Work-piece
(dummy style)
B. F
U. F
Tool Dynamometer
Micro drill
Work-piece Mounting DeviceWork-piece Mounting Device
Work-piece
Mounting device
Tool dynamometer
Experimental setup components for secure clamping of work-piece

9. 한국기계연구
원
Korea Institute of Machinery &
S t a r t p o s i t i o n
U p p e r l i m i t s t o p
i n o n e c y c l e
Totalstroke
O r i g i n p o s i t i o n
o f c u t t i n g
C u t t i n g o r i g i n s t o p
i n o n e c y c l e
Platethickness
Tool diameter
(mm)
Step number
of times
Cutting depth
(mm/step)
Feed-rate
(mm/sec)
Tool speed
(RPM)
0.2 4 0.3 0.5 25,000
0.3 5 0.5 0.5 25,000
0.4 5 0.5 0.5 25,000
0.5 5 0.5 0.5 25,000
Machining Conditions of Micro-drilling
Experimental ConditionsExperimental Conditions
Diagram of Step-forward Feeding Type
Trouble-shooting to Bird Nesting Problem
- proper chip cutting
- efficient chip evacuation
Non Step Micro-drilling

10. 한국기계연구
원
Korea Institute of Machinery &
Cutting oil supplied drilling Dry drilling
Comparison of Cutting ForceComparison of Cutting Force
Micro-drill diameter : 0.2mm, Step number of times : 4
Micro-drill diameter : 0.3mm, Step number of times : 5
Cutting oil supplied drilling Dry drilling

11. 한국기계연구
원
Korea Institute of Machinery &
Comparison of Cutting ForceComparison of Cutting Force
Micro-drill diameter : 0.4mm, Step number of times : 5
Micro-drill diameter : 0.5mm, Step number of times : 5
Cutting oil supplied drilling Dry drilling
Cutting oil supplied drilling Dry drilling

12. 한국기계연구
원
Korea Institute of Machinery &
Comparison of Cutting ForceComparison of Cutting Force
Variation of cutting force according to tool diameter
For cutting oil supplied drilling, the cutting force is lower than dry drilling distinctly
But, there is a little difference in cutting force between cutting oil supplied drilling and
dry drilling as the hole diameter is smaller
--- Caused by insufficient supply condition of cutting oil

13. 한국기계연구
원
Korea Institute of Machinery &
Cutting oil supplied drilling Dry drilling
drill diameter 0.2mm0.2mm
BurrBurr
Comparison of Burr FormedComparison of Burr Formed
Cutting oil supplied drilling Dry drilling
drill diameter 0.3mm0.3mm
Cutting oil supplied drilling Dry drilling
drill diameter 0.4mm0.4mm
Cutting oil supplied drilling Dry drilling
drill diameter 0.5mm0.5mm
For cutting oil supplied drilling, the burr formed extent is diminished than dry drilling
in a greater or less degree

14. 한국기계연구
원
Korea Institute of Machinery &
Morphology Comparison of Chip FormedMorphology Comparison of Chip Formed
Cutting oil supplied drilling Dry drilling
drill diameter 0.2mm0.2mm
Cutting oil supplied drilling Dry drilling
drill diameter 0.3mm0.3mm
Cutting oil supplied drilling Dry drilling
drill diameter 0.4mm0.4mm
Cutting oil supplied drilling Dry drilling
drill diameter 0.5mm0.5mm
For cutting oil supplied drilling, the continuous flow type chip can be obtained distinctly
relatively to dry drilling

15. 한국기계연구
원
Korea Institute of Machinery &
Comparison of Tool MorphologyComparison of Tool Morphology
Initial tool morphology Tool breakage mode Closed-up broken region
For step-forward drilling, the tool damage can be restrained efficiently
relatively to conventional drilling
Conventional micro-drillingConventional micro-drilling
( Example 1 : Trouble mode occurred at 5th
hole machining process )
( Example 2 : Trouble mode
occurred at a moment tool
contacted to work-piece ) The other tool breakage mode
Step-forward type micro-drillingStep-forward type micro-drilling
( Example 1 : Normal mode maintained after 3rd
hole machining completed )

16. 한국기계연구
원
Korea Institute of Machinery &
Summary & ConclusionSummary & Conclusion
Preliminary experiment were performed to obtain basic knowledge for ascertain process
behavior of micro-drilling
Step-forward type feeding method was applied for micro-drilling process to cope with troubles
occurred precedent case study
Cutting force was decreased in micro-drilling using tool diameter of 0.3mm or under
For cutting oil supplied drilling, the burr formed extent is diminished than dry drilling
in a greater or less degree
For cutting oil supplied drilling, the continuous flow type chip can be obtained distinctly
relatively to dry drilling
For step-forward drilling, the tool damage can be restrained efficiently relatively to
conventional drilling
For cutting oil supplied drilling, the cutting force is lower degree of 5~15% than dry
drilling distinctly
There is a little difference in cutting force between cutting oil supplied drilling and
dry drilling as the hole diameter is smaller

17. 한국기계연구
원
Korea Institute of Machinery &
… for your attention