Download - Report Quality
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A
REPORT
ON
QUALITY PARAMETERS AND METHDS AT SKF INDIA
1) Gaurav Mittal
2)
PREPARED IN PARTIAL FULFILMENT
OF QULITY CONTROL
AT
BITS PILANI
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Acknowledgements
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Table of Contents:
Acknowledgements
1. Introduction
1.1 SKF
1.1.1 SKF Quality Program
1.1.2 SKF Six Sigma
1.2 Bearing Basics
1.2.1 Tapered Roller Bearing
1.3 Shop Floor
1.3.1 The T8 Channel
2. Quality Measurement and Machines
2.1 Waviness and Roundness Analyser
2.2 Ring Dimension Measuring Machine
2.3 Ultrasonic Tester
2.4 Vibration tester (MVR)
2.5 Capability Test
3. Problem Statement and Losses
4. Methodology Followed (Rejection analysis)
4.1 Analysis
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4.2 Dominant Causes and Suggestions
5. Appendix
6. Conclusion
7. References
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1. Introduction
The purpose of this project is to apply our knowledge in an organization. Through this, we
will have better understanding of quality control methods..
SKF, Svenska Kullagerfabriken AB, later AB SKF, is a Swedish bearing company founded
in 1907 bySven Wingqvist as a multi-row self-aligning radial ball bearing production
company. By 1910, the company had 325 employees and a subsidiary in theUnited
Kingdom. By 1912, SKF was represented in 32 countries and by 1930, a staff of over
21,000 were employed in 12 manufacturingfacilities worldwide with the largest in
Philadelphia. In the 1970s SKF embarked on a massive production rationalization program
in Europe. Today SKF is the largest bearing manufacturer in the world and employs
approximately 40,000 people in approximately 100 manufacturing sites that span 70
countries. The SKF Group currently consists of approximately one hundred and fifty
companies all over the world. Presently supplying bearings, seals, lubrication and
lubrication systems, maintenance products, mechatronics products, power transmission
product and related services globally.
SKF India delivers high end technical knowledge starting with self-aligning ball bearing,
spherical roller bearing, the hub bearing units that are widely used in cars & truck wheelends in addition to the new and latest revolutionary CARB bearings that find specialized
application in steel plants & paper mills. In fact the company domestically manufactures
around 60 sizes of deep groove ball bearings, 70 sizes of taper roller bearings, textile
machinery component in addition to catering the needs of automobile, electrical & industrial
OEM and aftermarket customers.
SKF QUALITY PROGRAM
http://en.wikipedia.org/wiki/Swedenhttp://en.wikipedia.org/wiki/Rolling-element_bearinghttp://en.wikipedia.org/wiki/Companyhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/Companyhttp://en.wikipedia.org/wiki/Rolling-element_bearinghttp://en.wikipedia.org/wiki/Sweden -
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1.1 SKF SIX SIGMA
SKF employs a Six Sigma business approach. CEO Tom Johnstone was recognized as the
Premier Six Sigma Leader of the year (2006) in Europe. Six Sigma (also written as 6
Sigma, 6) is a systematic, measurement-based methodology that focuses on process
improvement and variation reduction through the identification and removal of the causes of
defects and errors. By eliminating variability and defects which undermine product and
service quality, Six Sigma can bring about vast improvements in performance, profits,
employee morale, quality of products and services and customer confidence. At the heart of
the Six Sigma methodology is the DMAIC (Define, Measure, Analyse, Improve, Control)
model.
1.1.1 Benefits of Six Sigma
Reduces variability
Improves quality reduces defects and errors
Improves reliability of products and processes
Reduces cost of operations
Improves capacity and output
Improve productivity
Improves customer satisfaction
Improves profits
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Bearing Basics
Bearings are designed to overcome friction to provide ease of rotation . Bearings are
designed to support shafts and allow free rotation on applied loads. There are three basic
types of load
Radialloads are applied perpendicular to the shaft (the bearings axis of rotation )
Axial(thrust) loads are applied parallel to the axis of rotation.
Combination load is encountered when the bearing simultaneously experiences a radial
and axial load
Bearing types-
1)-Plain 4)-Self aligning ball 7)-Needle
2)-Deep groove 5)-Cylindrical roller 8)-Spherical
3)-Angular contact 6)-Tapered roller 9)-Toroidal
Tapered Roller-
Tapered roller bearings are bearings that can take large axial forces (i.e., they are
good thrust bearings) as well as being able to sustain large radial forces. The inner and
outer ring raceways are segments of cones and the rollers are also made with a taper so
that the conical surfaces of the raceways and the roller axes if projected, would all meet at
a common point on the main axis of the bearing.
The basic components of a tapered roller bearing are:
Cage
Roller
Inner Ring
Outer Ring
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Figure 1: BT1-0222A type of TRB
The figure shows the CAD model of a bearing BT1-0222A made in Pro E Wildfire 4.0. The
outer ring is partially cut so as to show the arrangement of rollers in the assembled cone.
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1.3 Shop Floor
The shop floor has a large number of channels each devoted to different processes and
machining different kinds of bearings like T1,T2,T8 make tapered roller bearings and the
DGBB make deep grooved ball bearings. Our report is based on reducing the rejection of
the MVR machine which is situated near the end of the T8 channel. A brief description of
the T8 channel is given below.
1.3.1 The T8 channel
The T8 channel manufactures tapered roller bearings. It is subdivided into two channels for
the inner and the outer ring respectively. After heat treatment the IR & OR come to the T8
channel. Here they undergo the following processes sequentially:-
1.3.1.1 Inner ring channel
1 hardness checking
2 face grinding
3 width checking
4 land track grinding
5
bore grinding
6 flange grinding
7 track honing
8 marking
9 assembly.
10
cone height checking
11 oiling
12 MVR
13 missing roller checking
13 visual inspection
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1.3.1.2 Outer ring channel
The channel is dedicated to meet the demands of many companies like Volkswagen,
John Deere, Ford, Volvo, Maruti-Suzuki.
1 face grinding
2 OD grinding
3 track grinding
4 track honing
5 marking
6 oiling
7 cup height checking
8 visual inspection
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2. Quality Measurement and Machines-
As a major engineering company, SKF relies on making sure that the products and services
it provides live up to its own high expectations. Measurement and quality-assurance
systems provide the SKF Group with the means to do just that. The SKF Group has its own
dedicated Quality Technology Centre (QTC) that is now offering its expertise to other
companies worldwide
2.1 Quality Measuring Machines
A range of technologies and measurement approaches are available:
Waviness, roundness and form analysis
Low noise and vibration of bearings is becoming more and more important in mostapplications. One of the main reasons for high vibration levels is waviness on the bearingcomponents
Noise and vibration testing for bearings
low noise and vibration is becoming more and more important in most applications. Besideothers, a noisy application might be caused by wavy bearing components, by localdefects in the rings and balls, or by dirt particles in the bearing. All of these bearing qualityissues can be tested with QTCs bearing vibration equipment
Dimension testing
Stricter process requirements due to tighter tolerances and higher output results inhigher demands on the measuring machine capability and time pressure when resetting
measuring equipment.
Optical inspection
in optical systems the following basic physical principle is involved:
"The appearance of the product is different to what we have decided to be acceptable."
That appearance is dependent on three factors:
The condition of the object - colour, roughness, etc. The nature of the illumination - White light, coloured light, laser light etc.
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The properties of the sensors - Matrix Camera, Line Camera, Single Photo-detectoretc.
QTC is specialised in all three of these areas, as well as in signal processing and handlingof the products
Non-destructive testing
Is the inspection of components in a way that ensures that the components are defect freeor comply with certain quality requirements in such a way as to retain their usability. Thismeans that where necessary, 100% of production can be inspected in real time, removingoutliers from your production without adding to your production cycle time.
2.2. Capability test
After every finishing process for the accuracy up to micron level it is necessary to do
capability test.
The methodology follows is
1) Data collection
2) Analysis
3) Suggestions to improve performance
Data collection - can be done in to different ways:-
1) Short term data collection- We collect continuous data of 100-150 bearing.
2) Long term data collection- We collect samples of 5-10 bearings from different shifts at
Different times.
Analysis- Collected data is loaded into statistical software like MINITAB. Then upper
specified and lower specified limits are entered. After that mean and rang control chart are
prepared. Then the points which Lie outside the USL and LSL analysed by using remarks
which we have noted in data collection sheet. So the points which corresponds to the
special causes are eliminated and responsible main causes can be find out.
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Short term data :
Time Min Max Ovality Avg Min Max
-4 -1 -6 -2-6 -3 -7 -4
-5 -2 -5 -3
1 4 -1 1
-3 0 -4 0
-2 0 -3 -1
-2 0 -5 -1
Bore grinding m/c no : 1806 Inner Ring :BT1022A
Top Bottom
Mean and Rang chart for top
Mean and rang chart for bottom
343128252219161310741
2
0
-2
-4
-6
Sample
SampleMean
__X=-2.09
UC L=2.55
LCL=-6.72
343128252219161310741
8
6
4
2
0
Sample
SampleRange
_R=2.467
UC L=8.059
LCL=0
Xbar-R Chart of C1, ..., C2
343128252219161310741
0
-2
-4
-6
-8
Sample
Sample
Mean
__
X=-3.46
UC L=1.28
LCL=-8.19
343128252219161310741
8
6
4
2
0
Sample
SampleRange
_R=2.518
UC L=8.229
LCL=0
Xbar-R Chart of C1, ..., C2
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Long term data:
Time Min Max Ovality Avg Min Max
10:00 -9 -7 -8 -5
-11 -9 -13 -10
-10 -7 -9 -7
-4.5 -2 -7 -3.5
-9 -7 -8.5 -7
10:10 -7 -3 -5 -3
-8 -5 -8 -5
Bore grinding m/c no : 845 Inner Ring :6308
Top Bottom
Mean and rang chart for top
343128252219161310741
0.0
-2.5
-5.0
-7.5
-10.0
Sample
SampleMean
__X=-6.53
UC L=-2.60
LCL=-10.46
343128252219161310741
6.0
4.5
3.0
1.5
0.0
Sample
SampleRange
_R=2.090
UC L=6.830
LCL=0
1
1
11
11
Xbar-R Chart of C1, ..., C2
343128252219161310741
0.0
-2.5
-5.0
-7.5
-10.0
Sample
SampleMean
__X=-6.65
UC L=-2.36
LCL=-10.94
343128252219161310741
8
6
4
2
0
Sample
Sam
pleRange
_R=2.281
UC L=7.454
LCL=0
111
11
Xbar-R Chart of C1, ..., C2
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MVR (Vibration Tester):
The MVR is a vibration testing machine for bearings. It has an OR which fixes itself onto the
cone and accepts or rejects it by vibrational analysis on the basis of Fourier analysis in theform of 62 bands relating the IR, the tapered roller as well as the bearing as a whole. The
bands check for waviness and hit marks on the track and flange of the IR which constitute
its functional areas.
By doing Fourier analysis of the incoming bearing data, the MVR can detect from which
component noise (vibration) is coming and what kind of noise it is. The following
parameters are used in the MVR:-
1) Crest: for Inner Ring (IR)
for TR (Tapered Roller)
for Mix (complete signal)
Crest is a hint for hit marks on IR or roller.However, If Crest Mix is indicated, it is a hint for
dirt or for a defect in the OR.
2) Peak: it is analogous to Crest. It implies hit marks or dirt.
3) RMS: IR: IR part of RMS signal
TR: roller part of RMS signal
Mix: complete signal
RMS is the root mean square signal which detects honing error and Mix RMS is a hint for
defect in the OR.
4)Bands: the Fourier analysis does also detect waviness of the components.
The signal is split up into 10 bands (0...9) each into IR-signals(SK1) and Roller-
signals(SK2)
False rejections
While using the MVR, however, we have to be very careful while dealing with rejections
because there is also the possibility that the MVR would falsely reject bearings. This could
happen due to the following reasons:-
1) Belt from the motor to the spindle is defective.
2) The mandrel diameter too small (IR is sliding on the mandrel).
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3) Mandrel height is incorrect. This may cause the IR to slide on the plate and create noise.
4) Presence of dirt or hit mark in the mandrel holder in the spindle
5) Spindle misalignment.
6) Heating up of the bearing resulting in its expansion and hence causing 2)
In spite of all this, it is worth knowing that the MVR does not give false acceptance. If a
bearing has a fault it is sure to be rejected by the MVR
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3. Origin of the Problem Statement:
Recent observations showed that the T8 Taper Roller Bearing manufacturing channel was
not performing efficiently and the amount of rejection on the MVR vibration testing machine
was very high in addition to the process losses at various stages along the channel. It has
been observed that the daily efficiency of the channel is around 60% which is quite low and
the daily rejection on an average is around 10% which is also quite significant. Therefore
our project aims at reducing the rejection on this channel
Losses incurred due to rejection:
SKF follows 100% inspection methodology. T8 Taper Roller Bearing manufacturing
channel has very high rejection around 12%. The accepted bearings are sent to the large scale manufacturers,
The rejected bearing are tested on noise and vibration analyzer and are sold in the
retail markets with a loss of 30% in price.
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4. Methodology followed:
The Six Sigma methodology for problem solving includes the following stages:
Define
Measure Analyse
Improve
Control
Following the Six Sigma methodology we will be first collecting the data at various stages
along the channel focusing primarily on collecting the data for MVR rejection for different
shifts. The data collection will be followed by the analysis of the data using different
statistical tools and methods of analysis. The analysis aims to identify the major causes of
rejection. Based on the results of the analysis we will try to suggest suitable measures so
as to reduce the rejection.
MVR Rejection Parameters:
Waviness IR(Inner Ring)
Waviness TR(Taper Roller)
Waviness Bearing
Hitmark IR
Hitmark TR
Hitmark Bearing
IR Loud
Bearing Loud
Index Time Type Serial ClassificatBand_0: I Limit
0 ######## 30206_27 81015 i .O. 19.777 5000
1 ######## 30206_27 81015 i.O. 121.137 5000
2 ######## 30206_27 81015 n.i.O. 140.355 5000
3 ######## 30206_27 81015 i .O. 84.145 5000
4 ######## 30206_27 81015 i .O. 68.856 5000
5 ######## 30206_27 81015 i.O. 115.083 5000
6 ######## 30206_27 81015 i.O. 217.688 5000
7 ######## 30206_27 81015 i .O. 54.993 5000
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Data collection: Sample of 50 bearings is collected from rejected MVR lot. Then these 50
bearings are again tested on MVR and vibration data of these 50 bearings are collected
from MVR database. These rejected bearings are also tested manually by opening them,
because MVR can give false rejection. So after validation of data a Pareto chart of the data
is plotted and dominant band are find out.
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0
20
40
60
80
100
120
NOISEPEAK
NOISERMS
SK1MIX7
SK2MIX7
NOISE4
SK1MIX5
SK1MIX4
SK2MIX4
SK2MIX5
NOISE5
NOISE7
SK1MIX8
SK2MIX8
NOISE8
SK1MIX6
SK24
SK2MIX3
NOISE6
SK25
SK2MIX6
NOISE3
SK1MIX3
NOISEHIGH
SK15
IRFPEAK
SK28
SK17
SK1MIX9
SK23
SK26
SK27
SK2MIX9
NOISE9
NOISEMEDIUM
TRFPEAK
SK10
SK11
SK12
SK13
SK14
SK16
SK18
SK19
SK1MIX0
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0
5
10
15
20
25
30
35
40
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
SK1 MIX SK2 MIX NOIS
Frequency of Defect
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The frequency chart and the Pareto chart show that the Noise Peak and Noise Rms bands
have the highest frequency of crossing the limiting value followed by the band no. 4,5,7,8 inthe Mix region.
These 50 rings were visually inspected for surface defects and the rings were sorted
category wise according to the type of defect. The rings were sorted into those having
honing defects, those having dents. There were some severe unusual types of surface
defects observed. These defects were probably due to sudden stopping of the grinding
wheel. Out of 50, 26 rings were found to have honing defects, 34 rings were found to have
dents or scratches. Out of 50, 14 rings had severe surface defects. These defects can be
seen in the following photographs:
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Figure 2: Photographs of defective inner rings of 30206 type of TRB
7. Appendix
Tapered roller bearing (TRB):
Vibration Analysis-
Vibration analysis is used to detect the early precursors to machine failure, allowing
machinery to be repaired or replaced before an expensive failure occurs. All rotating
equipment vibrates to some degree, but as older bearings reach the end of their product life
they begin to vibrate more dramatically, and in distinct ways. So monitoring of equipment
allows these signs of wear and damage to be identified well before the damage becomes
an expensive problem.
Noise-
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Noise means any unwanted sound. In both analog and digital electronics,noiseis an
unwanted perturbation to a wanted signal; it is called noise as a generalisation of the
audible noise heard when listening to a weakradiotransmission.
Waviness-
Waviness is the measure of the more widely spaced component ofsurface texture. It is a
broader view ofroughnessbecause it is more strictly defined as "the irregularities whose
spacing is greater than the roughness sampling length". It can occur from machine or
workdeflections, chatter,residual stress,vibrations, orheat treatment
MVR-
MVR is a vibration testing machine used for bearing. When inner ring passes through MVR
then it shows band values for around 62 parameters. First we have to feed the limiting
value of each parameter then if the actual value crosses the limiting value then thecorresponding band is displayed as rejected band.
Mix-
Inner ring and tapered roller are two parts responsible for vibration in bearing. Mix is the
vibration generated by both inner ring and tapered roller.
Crest-
The crest factor or peak-to-average ratio (PAR) or peak-to-average power ratio (PAPR) is a
measurement of awaveform, calculated from thepeak amplitudeof the waveform divided
by theRMSvalue of the waveform.
Rms-
Root Mean Square The measure of energy displayed in a frequency spectrum. It is
derived by squaring each spectrum line, taking their average, then taking the square root of
average. It also equals to (Peak)*0.707.
Peak
The maximum positive amplitude shown on a sine curve. It is one of the 62 bands which
are checked by the MVR. It represents dirt or hit marks in the inner ring.
http://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Noise_(electronics)http://en.wikipedia.org/wiki/Noise_(electronics)http://en.wikipedia.org/wiki/Noise_(electronics)http://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Surface_roughnesshttp://en.wikipedia.org/wiki/Surface_roughnesshttp://en.wikipedia.org/wiki/Surface_roughnesshttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Residual_stresshttp://en.wikipedia.org/wiki/Residual_stresshttp://en.wikipedia.org/wiki/Residual_stresshttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Peak_amplitudehttp://en.wikipedia.org/wiki/Peak_amplitudehttp://en.wikipedia.org/wiki/Peak_amplitudehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Peak_amplitudehttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Residual_stresshttp://en.wikipedia.org/wiki/Deflectionhttp://en.wikipedia.org/wiki/Surface_roughnesshttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Noise_(electronics)http://en.wikipedia.org/wiki/Sound -
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Grinding-
Grinding is anabrasive machiningprocess that uses a grinding wheel as thecutting tool.
Grinding can produce very fine finishes and very accurate dimensions; yet in mass
production contexts it can also rough out large volumes of metal quite rapidly. Grinding is a
subset of cutting, as grinding is a true metal-cutting process.
Honing-
Honing is anabrasive machiningprocess that produces aprecision surfaceon ametalwork
piece by scrubbing anabrasivestone against it along a controlled path. Honing is primarily
used to improve the geometric form of a surface, but may also improve thesurface texture.
Different types of honing is-
Track/Raceway honing
Spherical honing
OD through-feed honing (taper and straight)
Flat honing
Bore honing
Dent-
Dent is a slight depression, or small notch or hollow, made by a blow or by pressure; anindentation. It may be generated during the manufacturing or finishing processes or at
points on the channel where there is a possibility of severe impact. It contributes
significantly to MVR rejection.
Dirt-
Dirt is unclean matter. Common types of dirt include:
dust a general powder of organic or mineral matter
filth foul matter such as excrement
grime a black, ingrained dust such assoot
soil the mix of clay, sand and humus which lies over the bedrock
Dirt is interpreted as peak noise and leads to false rejection in the MVR.
.
Conclusion:
http://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Surface_integrityhttp://en.wikipedia.org/wiki/Surface_integrityhttp://en.wikipedia.org/wiki/Surface_integrityhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Abrasivehttp://en.wikipedia.org/wiki/Abrasivehttp://en.wikipedia.org/wiki/Abrasivehttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Flat_honinghttp://en.wikipedia.org/wiki/Flat_honinghttp://en.wikipedia.org/wiki/Dusthttp://en.wikipedia.org/wiki/Dusthttp://en.wikipedia.org/wiki/Filthhttp://en.wikipedia.org/wiki/Filthhttp://en.wikipedia.org/wiki/Grimehttp://en.wikipedia.org/wiki/Grimehttp://en.wikipedia.org/wiki/Soothttp://en.wikipedia.org/wiki/Soothttp://en.wikipedia.org/wiki/Soothttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Soothttp://en.wikipedia.org/wiki/Grimehttp://en.wikipedia.org/wiki/Filthhttp://en.wikipedia.org/wiki/Dusthttp://en.wikipedia.org/wiki/Flat_honinghttp://en.wikipedia.org/wiki/Surface_texturehttp://en.wikipedia.org/wiki/Abrasivehttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Surface_integrityhttp://en.wikipedia.org/wiki/Abrasive_machininghttp://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Abrasive_machining -
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8. References
PS diary
http://www.skf.com/portal/skf_in/home/about?contentId=149396&la
ng=en http://www.skf.com/portal/skf_in/home/products?contentId=149391
&lang=en
http://en.wikipedia.org/wiki/SKF
http://www.google.com/search?q=skf&oe=utf-8&rls=org.mozilla:en-
US:official&client=firefox-a&um=1&ie=UTF-
8&tbm=isch&source=og&sa=N&hl=en&tab=wi&biw=1366&bih=672
http://www.google.com/search?um=1&hl=en&client=firefox-
a&rls=org.mozilla%3Aen-US%3Aofficial&biw=1366&bih=672&tbm=isch&sa=1&q=skf+six+sig
ma&oq=skf+six+sigma&aq=f&aqi=&aql=&gs_sm=e&gs_upl=3663l4
335l0l4l4l0l0l0l0l148l280l0.2l2
http://www.mydigitallife.info/combine-and-merge-multiple-
documents-in-microsoft-office-word-2007/
http://en.wikipedia.org/wiki/Waviness
http://en.wikipedia.org/wiki/Bearing_%28mechanical%29
http://en.wikipedia.org/wiki/Pareto_chart
http://en.wikipedia.org/wiki/Pareto_distribution
http://en.wikipedia.org/wiki/Pareto_principle
http://www.google.com/search?q=bearing+defects&oe=utf-
8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-
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