Higher Speed and Extended life 2Lower torque, noise and vibration

Higher Speed and Extended life
- DN factor evolution
- Test cycle
- Results comparison
DN factor evolution
New hibrid design with optimal recirculation system
and NTG treatment improves results achieving up
to DN 160.000.
internal (dn=100000)
external (dn=120000)
high speed (dn=160000)
Rotational speed (RPM)
5800
5200
4600
4000
3400
2800
2200
1600
1000
30 40 50 60 70 80
Shaft diameter (mm)
Wear influence in the torque
This chart shows the relation between wear
of the different components of a ballscrew
and its torque variation:
- After 100 hours travel the conventional
ballscrew lose 30% of its torque while with
High Speed design only a 6%.
Conventional torque
Conventional wear
High speed torque
High speed wear
Torque (Nm)
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0.55
0.5
0 20 40 60 80 100
Time (h)
6
5
4
3
2
1
0
-1
Wear (µm)
Speed (m/sec)
0.75
0.25
1
0.5
0
0 1 2 3 4
Time (sec)
Results comparison
Diam=40
Lead=12
4000 RPM
a=1G
DN=160000
Test cicle
High Speed life test cycle used to compare
conventional with KORTA High Speed ballscrews.
Noise level dB (A)
90
85
80
75
70
65
60
55
50
45
600 1350 2100 2850 3600
Rotational speed (RPM)
High speed
Conventional
Measured noise level
Noise level comparison between a conventional
and a High Speed design ballscrew:
- A microphone placed at 500 mm distance
records a gap of 10 dB(A) between both types
of ballscrews.
Slight marks appear after 180 km travel in conventional Normal
ballscrews, in High Speed design marks do not appear Flaking 33%
until 2.180 km.
Critical
Flaking occur arround 33% of the screw shaft in
conventional ballscrews after 1,000 km travel, in High
Speed design after 4.000 km travel.
Nut deterioration occur after 1.500 km travel in
0 600 1200 1800 2400 3000 3600 4200
conventional, in High Speed after 4.200 km.
Distance (Km)
High Speed ballsrews follow up beyond 4.200 km travel.
2Lower torque, noise and vibration
- Torque chart
- Wear influence in the torque - Vibration chart
- Measured noise level
- Frecuency chart
Vibration chart
- High Speed ballscrews show 8 times less amplitude
than conventional ballscrews.
- The contact among the balls and the groove is reduced
using ceramic balls, specific design of the recirculating
system and high quality finishing of rolling surface.
- In order to measure the vibration an accelerometer
is installed radially in the nut.
High speed
Conventional
Torque chart
Torque chart
Dynamic friction torque comparison between a High Speed
design and a conventional ballscrew at 10 RPM, grease
lubrication and 100 hours travel:
- Conventional ballscrews lose torque.
- High Speed ballscrews run without any spike generation or
jamming. Torque fluctuation is low.
Frecuency chart
- The accelerometer signal is continuously monitorized.
- Frecuency analizer software performs a complex data
analysis.
- Different modules provide main features for vibration
and frecuency analysis.

3- Treatments comparison
- Mean wear of the components
Lower heat generation and less lube needed
- Heat generation
- Required lubrication comparison
High Speed Ballscrews
Treatments comparison
- Korta NTG surface treatment applied to High Speed design
ballscrews increases hardness and wear resistence reducing
frictional coefficient.
- Korta NTG treatment results 2 times better than nitriding
and 10 times better than conventional surface treatment.
Korta NTG
Nitriding
Conventional
Wear average
100%
80%
60%
40%
20%
0%
Pitting (p/1000)
7
6
5
4
3
2
1
0
0 1000 2000 3000
Distance (Km)
High speed
Conventional
Mean wear of the components
In order to measure the mean wear of the components
in a ballscrew, stress corrosion and cracking induced from
the combined influence of tensile stress and corrosive
enviroment are taken into consideration.
Several wear parameters are recorded at different travel
distances.
Ballscrew groove wear after 1.500 km. travel
Balls wear after 1.500 kn. travel
Conventional Ballscrew
High Speed Ballscrew
Steel Balls
Ceramic Balls
Heat generation
Conventional High Speed
Temperature generated 82 ºC 47 ºC
Temperature increase 62 ºC 27 ºC
High speed
Conventional
Temperature (ºC)
100
80
60
40
20
0
0 100 200 300 400
Cicles
500
100%
80%
60%
40%
20%
0%
Conventional Ballscrew
High Speed Ballscrew
Initial lubrication
Travel lubrication
Required lubrication comparison
The necessary rate of lubricant is in close relation with
working temperatures.
A raise in temperature increases need of lubricant supply:
- At the initial 100 cycles the estimated lubricant supply
for a conventional ballscrew is 4 times higher than for a
High Speed ballscrew.
- At the end of the test the amount of lubricant used for
a High Speed ballscrew is 5 times less than for a
conventional ballscrew.
DN=160.000
New Korta "NTG" Treatment
Hybrid Design
KORTA S.A. Joxe Mari Korta Industrigunea, 2, - Apdo. 6 - 20750 ZUMAIA (Gipuzkoa) Spain
Tel.: (34) 943 86 03 62 / 66 - Fax: (34) 943 86 01 42 - e-mail: info@korta.com
www.korta.com