Drilling with high rpm compared to drilling with conventional speed

IACDS Bauma 2013 seminar 2013-04-19
Background - High speed Machining
Drilling with high rpm compared to
drilling with conventional speed
The engineers behind Tractive
were pioneers in Scandinavia in
using high speed machining in the
production of
high strength
high quality and
high integrity
Structurally loaded aluminium
components.
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
Background - High speed Machining
Background - High rpm drilling in the 80’s
No castings
- More expensive
+ Higher strength
Save cost
Machining with higher
speed
Already in the early 1980’s we experimented
with drilling steel tubes with concrete lining
inside the tubes.
Several types of machines were built and
tested, using peripheral speeds up to 40
meters per second on specially designed
core bits.
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
1

IACDS Bauma 2013 seminar 2013-04-19
High rpm drilling today
Why is 40 - 50 m/sec peripheral speed normal for a wall saw but not for a core drill?
4.5 m/ second peripheral speed is
often standard in Sweden,
whereas some would consider this
high speed drilling.
Different manufacturers have
different recommendations.
Bohrmotor Pentruder MDU mit Untersetzungsspindel SH
Umfangsgeschwindigkeit m/s
Stufe 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Drehzahl 320 400 480 560 640 720 800 880 960 1040 1120 1200 1280 1360 1440
Ø 52 0,87 1,09 1,31 1,52 1,74 1,96 2,18 2,39 2,61 2,83 3,05 3,27 3,48 3,70 3,92
Ø 62 1,04 1,30 1,56 1,82 2,08 2,34 2,60 2,86 3,11 3,37 3,63 3,89 4,15 4,41 4,67
Ø 72 1,21 1,51 1,81 2,11 2,41 2,71 3,01 3,32 3,62 3,92 4,22 4,52 4,82 5,12 5,43
Ø 82 1,37 1,72 2,06 2,40 2,75 3,09 3,43 3,78 4,12 4,46 4,81 5,15 5,49 5,84 6,18
Ø 92 1,54 1,93 2,31 2,70 3,08 3,47 3,85 4,24 4,62 5,01 5,39 5,78 6,16 6,55 6,93
Ø 102 1,71 2,14 2,56 2,99 3,42 3,84 4,27 4,70 5,12 5,55 5,98 6,41 6,83 7,26 7,69
Ø 107 1,79 2,24 2,69 3,14 3,58 4,03 4,48 4,93 5,38 5,82 6,27 6,72 7,17 7,62 8,06
Ø 112 1,88 2,34 2,81 3,28 3,75 4,22 4,69 5,16 5,63 6,10 6,56 7,03 7,50 7,97 8,44
Ø 122 2,04 2,55 3,06 3,58 4,09 4,60 5,11 5,62 6,13 6,64 7,15 7,66 8,17 8,68 9,19
Ø 132 2,21 2,76 3,32 3,87 4,42 4,97 5,53 6,08 6,63 7,18 7,74 8,29 8,84 9,39 9,95
Ø 142 2,38 2,97 3,57 4,16 4,76 5,35 5,95 6,54 7,13 7,73 8,32 8,92 9,51 10,11 10,70
Ø 152 2,55 3,18 3,82 4,45 5,09 5,73 6,36 7,00 7,64 8,27 8,91 9,55 10,18 10,82 11,45
Ø 162 2,71 3,39 4,07 4,75 5,43 6,10 6,78 7,46 8,14 8,82 9,50 10,17 10,85 11,53 12,21
Ø 172 2,88 3,60 4,32 5,04 5,76 6,48 7,20 7,92 8,64 9,36 10,08 10,80 11,52 12,24 12,96
Ø 182 3,05 3,81 4,57 5,33 6,10 6,86 7,62 8,38 9,14 9,91 10,67 11,43 12,19 12,95 13,72
Ø 192 3,22 4,02 4,82 5,63 6,43 7,23 8,04 8,84 9,65 10,45 11,25 12,06 12,86 13,67 14,47
Ø 200 3,35 4,19 5,02 5,86 6,70 7,54 8,37 9,21 10,05 10,89 11,72 12,56 13,40 14,23 15,07
Ø 225 3,77 4,71 5,65 6,59 7,54 8,48 9,42 10,36 11,30 12,25 13,19 14,13 15,07 16,01 16,96
Ø 250 4,19 5,23 6,28 7,33 8,37 9,42 10,47 11,51 12,56 13,61 14,65 15,70 16,75 17,79 18,84
Ø 300 5,02 6,28 7,54 8,79 10,05 11,30 12,56 13,82 15,07 16,33 17,58 18,84 20,10 21,35 22,61
Ø 350 5,86 7,33 8,79 10,26 11,72 13,19 14,65 16,12 17,58 19,05 20,51 21,98 23,45 24,91 26,38
Ø 400 6,70 8,37 10,05 11,72 13,40 15,07 16,75 18,42 20,10 21,77 23,45 25,12 26,79 28,47 30,14
Ø 450 7,54 9,42 11,30 13,19 15,07 16,96 18,84 20,72 22,61 24,49 26,38 28,26 30,14 32,03 33,91
Ø 500 8,37 10,47 12,56 14,65 16,75 18,84 20,93 23,03 25,12 27,21 29,31 31,40 33,49 35,59 37,68
Ø 550 9,21 11,51 13,82 16,12 18,42 20,72 23,03 25,33 27,63 29,93 32,24 34,54 36,84 39,15 41,45
Ø 600 10,05 12,56 15,07 17,58 20,10 22,61 25,12 27,63 30,14 32,66 35,17 37,68 40,19 42,70 45,22
Ø 650 10,89 13,61 16,33 19,05 21,77 24,49 27,21 29,93 32,66 35,38 38,10 40,82 43,54 46,26 48,98
Ø 700 11,72 14,65 17,58 20,51 23,45 26,38 29,31 32,24 35,17 38,10 41,03 43,96 46,89 49,82 52,75
Ø 750 12,56 15,70 18,84 21,98 25,12 28,26 31,40 34,54 37,68 40,82 43,96 47,10 50,24 53,38 56,52
Standard-Bohrkronen mit optimaler Umfangsgeschwindigkeit 2-4 m/s
High-Speed Bohrkronen mit erhöhter Umfangsgeschwindigkeit 4-6 m/s
• More difficult to cool drill bit.
• More difficult to remove slurry.
• Lower price Lower quality of Core
drill, Drill rig and Core bit
• Price pressure Difficult for tool
manufacturers to produce the optimal
drill bit.
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
Our thesis – Higher speeds Faster drilling
High speed drilling – Important criteria for success
Power = Constant
Peripheral speed x 2 Concrete removal rate x 2
rpm
Powerful core drill
Adjustment of rpm
Rigidity of drill
system
Drill bit
Sufficient cooling
Concrete
removal
rate
Skilled operator
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
2

IACDS Bauma 2013 seminar 2013-04-19
Powerful core drill
High power can be achieved in different ways
High power is important to maintain a good level of
torque and high speed, at the same time.
Many manufacturers of core drills focus on high torque,
not high spindle speed.
But isn’t power on the drill bit most important?
Power = Torque x rpm
Power in kW = Torque x rpm
9550
40 Nm x 570 rpm = 2.4 kW
175 Nm x 260 rpm = 4.8 kW
482 Nm x 115 rpm = 5.8 kW
154 Nm x 360 rpm = 5.8 kW
216 Nm x 425 rpm = 9.6 kW
108 Nm x 850 rpm = 9.6 kW
67 Nm x 1360 rpm = 9.6 kW
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
Test result
High power as a result of high torque vs.
high power as a result of high rpm
Thickness:
Concrete:
Re-bar:
Power output:
Core bit:
Bauma 2013
Munich seminar
47 cm
Hard aggregate with very tough stones
1 x 30 mm
9 kW
200 mm high speed core bit from Adamas
11 m/second: 3 minutes, 36 seconds
6,6 m/ second: 5 minutes
3,4 m/ second: 6 minutes, 50 seconds
High torque / Low rpm
Bauma 2013
Munich seminar
More vibrations
Higher risk of tearing out anchor
Higher force / stress on drill rig
Requires higher feeding pressure
Need of well adapted segments of drill bit
High wear of segments.
Higher load on core drill transmission
Medium torque / High rpm Less vibrations
Less risk of tearing out anchor
Less force / stress on drill rig
Requires lower feeding pressure
Need of well adapted segments of drill bit
Less load on core drill transmission
3

IACDS Bauma 2013 seminar 2013-04-19
Possibility to adjust spindle speed in many steps to
avoid vibration.
Rigidity of complete drill system
Chatter and vibrations Biggest problem when:
• Drilling initial few centimeters into the concrete.
• Cutting through re-bars.
Wide speed range and many steps to choose from
a spindle speed can be chosen where vibration
is lower.
• Stiff and rigid drill rig.
Drill rig may not sway in any direction.
• Very important that base is properly secured.
• Bearing arrangement of the core drill
is critical. Very rigid, preferably
pre-loaded taper
roller bearings to eliminate vibrations.
• Carriage with low friction.
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
The drill bit is crucial for high rpm drilling
Sufficient cooling of drill bit
• There is no single ”universal” segment specification
that suits all machines and aggregates.
• Use of right drill bit specially developed for this
high speed drilling.
• Too soft bonds Diamonds are pushed in to
segment or fall out.
• Too hard bond Not enough diamonds will cut.
• Tool geometries must be suitable for high speed
drilling to minimize friction between barrel and
cored hole.
• As the concrete reduction rate
increases, the water flow must
be allowed to increase as well.
• Use of more water but during a
shorter time
No more cooling water totally.
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
4

IACDS Bauma 2013 seminar 2013-04-19
Skilled operator
Pros and cons – High speed drilling vs. Conventional speed drilling
• Set up.
• Feeding the drill bit.
• Adjusting rpm for optimal performance.
• Not too high feeding pressure in re-bar.
• Using enough cooling water.
High speed drilling
Conventional speed drilling
- More to ”think about” for operator + Common practice. Easier for operator
- Important to have right drill bit. - Important to have the right drill bit.
+ Faster drilling +/- Normal cutting rates
+ Lower feed pressure - Higher feed pressure
+ Less vibrations - More vibrations
Bauma 2013
Munich seminar
Bauma 2013
Munich seminar
5