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Transport and Engineering. Production Technologies
2013 / 35________________________________________________________________________________________________________
34
Ball Burnishing as Finish Method of Compressor
Shaft Wear Sleeve
Guntis Pikurs1, Guntis Bunga2, Viktors Gutakovskis3, Artis Kromanis4, 1-4 Riga Technical University,
Institute of Mechanical Engineering
Abstract – Nowadays more and more advanced technologies in
surface finish are developed. The ball burnishing technology of
wear sleeve gives smoothened surface characteristics, which im-
proves initial abrasive wear resistance, bearing rate, and residual
compressive stresses in the surface layer of the wear sleeve. These
parameters may significantly increase the life cycle of PTFE seal-
ing knot. This paper recognizes the technology advances in wear
sleeve manufacturing and gives directions for further research
and discussion.
Keywords – ball burnishing, wear sleeve, PTFE seal.
I. INTRODUCTION
Traditional technology of PTFE wear sleeve manufacturing
is plunge grinding. This is the way how to process hardened
shaft wear sleeve and obtain reasonable surface texture for seal-
ing surface [1.]. The wear sleeves of PTFE lip seals, which are
highly reliable in standard working conditions, are made from
100Cr6 (AISI52100) tempered steel. Most of the sealing knot
manufacturers use needle roller bearing inner race for shaft pro-
tection (Fig.1), because its surface texture and roughness sat-
isfy good sealing requirements (Table.1). These sleeves guar-
antee leakage free operating of a screw compressor at least for
10,000 hours. Sometimes during these periods of time, we find
out deep wear grooves on the wear sleeve sealing surface,
which may become a cause of oil leaks (Fig.2). Small abrasive
particles in size up to 5-10µm, which often are present in the
working environment, are the cause of excessive wear of the
shaft protective sleeve.
The one of ways how to improve wear endurance of the
sleeve against small abrasive particles is the usage of sleeve
material with higher surface wear resistance. Residual com-
pressive stress, which remains in the surface layer after plastic
deformation, is the factor which increases fatigue strength of
the processed material. Hence it increases wear resistance
against sliding wear. Thus, the problem solution is to make a
wear sleeve with higher initial surface hardness, lower friction
coefficient, and enough deep and large residual compressive
stresses in the surface layer. This may be successfully obtained
with the change the manufacturing technology of the wear
sleeve. The ball burnishing process can provide same surface
quality as grinding. Usage of tungsten carbide balls allows per-
forming plastic deformation even on hardened and tempered
steels with surface hardness up to 65HRC. The abrasive pro-
cessing technology nowadays is replaceable with surface plas-
tic deformation, thus giving opportunity to obtain 5-10% harder
upper layer of the surface with the same surface roughness pa-
rameters. The other advantage of this processing technology is
that this technology works without material cutting or remov-
ing. Hence at the same time burnishing process is much friend-
lier to the working environment, there are no small grinding
grains in the processing area, and there is no need for a large
amount of cooling liquid, because temperature increase in the
processing area is much lower than in abrasive cutting with un-
defined cutting angles. Extensive research on temperature
fields in burnishing process has been made by Russian scientist
D.Papshev [3.]. The plastically deformed materials have higher
density of crystal grid and are more resistant to any external
influences. One of the attractive aspects of burnishing technol-
ogy is relieving of residual tensile stresses, which are in the sur-
face layer after hard turning. After burnishing the surface often
has compressive stresses in the upper layer.
Burnishing technology is quite simple and available for any
machine shop, but still now potential users of this technology
do not have sufficient knowledge on the advantages of plastic
deformation technology. Thus, the burnishing technology still
is like a non-traditional or alternative processing technology.
The best samples of using of burnishing can be found in avia-
tion, marine and military industries.
Fig. 1.Sealing knot assembly of GHH OS 70 screw compressor air end.
Fig. 2.New and hardly worn out shaft protective sleeve.
Transport and Engineering. Production Technologies
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TABLE 1
SOME STANDARDS AND SEALING MANUFACTURER RECOMMENDATIONS FOR SHAFT SURFACE QUALITY
DIN 3760
DIN 3761
Elring
SKF
Garlock
IDG
Ra[µm]
0.2 – 0.8
0.2 – 0.8
0.2 – 0.8
0.2 – 0.8
0.2 – 0.3 – 0.5 – 0.6
0.05 – 0.5
Rz[µm]
1 – 5
1 – 4
1 – 4
1 – 4
Rmax[µm]
6.3
6.3
6.3
0.8 – 1 – 2 – 3
Spiralfree
Yes
Yes
Yes
Yes
Hardness
45HRC
600HV
>45HRC
55HRC/600HV
40–45HRC
>58HRC
Other
DIN 3761
Ra and Rmax depend on speed v>16m/s,
v=11–16m/s, v<16m/s
Tp>50%
Rt=0.05 - 2
II. TECHNOLOGY
The processing technology how to obtain a wear sleeve with
an attractive surface quality and spend less money in manufac-
turing includes initial hard turning of the hardened steel pipe
with the cubic boron nitride cutting tool (CBN) and sequential
low plasticity burnishing with the tungsten carbide ball. This
technology excludes abrasive processing. Thus, it eliminates
abrasive grain penetrating in sleeve material during processing,
which may heighten initial abrasive wear of protective sleeve
and sealing lips at the beginning of exploitation.
The technology of hard turning and sequential burnishing of
some hard materials was already developed many years ago by
Russian, German and other scientists. The most prominent of
them are D.Pashev, F.Klocke [4]. A couple of recent researches
in this area are done by L.Luca [8] and Yung – Chang Yen [6].
The hard turning processing for surface preparation for ball
burnishing is done by CBN cutting tool with 60̊ major and mi-
nor cutting edge angles and relative small tool nose radius
R=0.1mm (Fig.3). The theoretical peak to valley height can be
easily calculated by equation:
(1)
where rε – tool nose radius, mm ;
S- feed mm/rpm.
The selected geometry ensures that the hard turned surface
profile will be capable for surface plastic deformation with
enough high deformation and burnishing speed and feed.
Fig.3. CBN cutting tool base plane geometry
The surface contact between the burnishing tool and the work-
piece often is an ellipse, with the major axis oriented in parallel
to the longitudinal axis of the workpiece. Therefore, according
to
sphere-to-sphere elastic contact [5] contact length of minor axis
may be calculated.
(2)
where
(3)
(4)
rw,rt – workpiece and tool radius;
Ew,Et – Young’s modulus of the workpiece and tool;
- workpiece’s Poisson’s ratio, (0.3)
More easily contact surface can be calculated by Hertz
stress calculator like HertzWin 1.2.2.or mesys.chonline stress
calculator.
Fig.4. HertzWin1.2.2 calculation sample for 2500N normal force
Transport and Engineering. Production Technologies
2013 / 35________________________________________________________________________________________________________
36
Hertz Win stress application calculates and displays contact
stress values and surface radiuses. Contact radius in the longi-
tudinal direction of the workpiece is slightly larger (341.57µm)
than in cross direction (307.38µm); The depth of impression
draws up 37.89µm in case of 2500N normal force.
The surface contact area of ellipse:
(5)
F=0.33mm2
Further contact time of any surface point may be calculated:
(6)
tc=0.0004sec
III. MATHEMATICAL MODEL OF SLEEVE BURNISHING
PROCESS
Low plasticity ball burnishing was performed on conven-
tional lathe 16K20. The full three factor experiment was done
for characterization of the burnishing process. Burnishing
force, speed and feed rates are chosen as factors, which have
the most significant influence on the processed surface quality.
The initial surface roughness of sample pieces before burnish-
ing tests: Ra≈2µm, processed material: hardened steel 100Cr6,
with initial surface hardness 53HRC. The burnishing tool: 6mm
tungsten carbide ball (grade25), preloaded by a spring mecha-
nism. Spring tension force of burnishing tool was calibrated by
indicator gauge and 3000N force dynamometer.
The surface roughness profile of wear sleeve before and af-
ter burnishing is displayed in Fig.4a.
Fig.4a. General view of hard turned and ball burnished wear sleeve surface.
TABLE 2
VARYING FACTORS OF BURNISHING EXPERIMENT
Force, Fb(N)
1500 – 2500
Speed, vb(m/min)
88 – 135
Feed, Sb(mm/rpm)
0.05 – 0.15
TABLE 3
EXPERIMENTALLY OBTAINED RESULTS
N
Sb,
mm/rpm
Vb,
m/min
Fb, N
Y1
Y2
Y3
Ra
1.
0.05
88
1500
0.65
0.71
0.65
0.67
2.
0.15
88
1500
0.55
0.58
0.55
0.56
3.
0.05
137
1500
0.76
0.77
0.87
0.80
4.
0.15
137
1500
0.8
0.76
0.72
0.76
5.
0.05
88
2500
0.54
0.48
0.57
0.54
6.
0.15
88
2500
0.45
0.47
0.55
0.49
7.
0.05
137
2500
0.49
0.55
0.64
0.56
8.
0.15
137
2500
0.59
0.54
0.61
0.59
The obtained mathematical model for prediction of surface
roughness after ball burnishing is presented as follows:
The obtained surface roughness is acceptable for sealing ap-
plication paired with PTFE lip seal. Wear resistance and fric-
tion losses have higher characteristics for wear sleeve applica-
tion. In addition, surface layer has compressive stresses, which
significantly increases sliding wear resistance and strongly re-
duces spread and formation of corrosion seeds.
Analysis of the mathematical model displays that increasing
of burnishing speed generally has a tendency for producing a
rougher burnished surface, it could be explained by too short
contact force time for plastic deformation of sample material.
The experiment also displays that too small burnishing feed rate
did not yield the expected result, and better results were ob-
tained with 0.15mm/rpm feed rate.
Fig.5. Corrosion seeds on ball burnished – left, and grinded shaft wear sleeve
– right.
IV. CONCLUSION
1. The replacement of grinding technology allows exclud-
ing abrasive grain penetration in the surface of protective
sleeve, thus eliminating the initial wear of shaft protective
sleeve and PTFE lip seal.
2. The low plasticity ball burnishing of 100Cr6 wear sleeve
raises the hardness of the sleeve surface layer for about 3HRC
units. An experimental test gives results of hardness increasing
from 53 to 56HRC units.
Transport and Engineering. Production Technologies
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3. Hard cutting parameters for further low plastic burnish-
ing are as follows: cutting speed 100m/min., depth<0.15mm,
feed rate 0.05mm/rpm.
4. The parameters for ball burnishing technology of hard-
ened 100Cr6 steel pipe, which give the acceptable surface seal-
ing applications: burnishing force2000N on 6mm tungsten car-
bide ball, speed v=100m/min, feed S≤0.1mm/rpm.
V. REFERENCES
1. Heinz K.Muller, Bernard S.Nau, Fluid Sealing Technology principles
and applications. Marcell Dekker, New York 1998 p.504.
2. König W., Berktold A., KochK.F., Turning versus grinding – a compa-
rison of surface integrity aspects and attainable accuracies. Ann CIRP
1993, 42:39–43.
3. Папшев Д. Д. Упрочнение деталейобкаткой шариками. - М.:
Машиностроение, 1968. - 132 с.
4. F. Klocke, J. Liermann, Roller burnishing of hard turned surfaces, Inter-
national Journal of Machine Tools and Manufacture 38 (1996) 419–423.
5. B. Bhushan, Principles and Applications of Tribology, Wiley, New York
1999.
6. Yung-Chang Yen, Modelling of metal cutting and ball burnishing, pre-
diction of tool wear and surface properties, PhD Thesis, the Ohio State
University, 2004.
7. Loh NH, Tam SC. Effects of ball burnishing parameters on surface fi-
nish—a literature survey and discussion. PrecEng 1988;10(4):215–20.
8. L. Luca, Investigations into the use of ball-burnishing of hardened steels
components as a finishing process, PhD Thesis, University of Toledo,
2002.
9. Sui H., Pohl H., Schomburg U., Upper G., Heine S. Wear and friction
of PTFE seals Wear, Volume 224, Issue 2, February 1999, Pages 175-182.
Guntis Pikurs is a PhD student at the Faculty of Transport and Mechanical
Engineering and his dissertation includes a study of technological influence on
the performance of machine parts. He was awarded the degree of M.sc.ing. by
Riga Technical University in 1999. He is an assistant at the Department of Ma-
terial Processing responsible for laboratory works in manufacturing engineer-
ing.
His fields of scientific interest include: cutting theory; machining tools;
fluid mechanics; machine diagnostics and monitoring; and Computer Numeri-
cal Control machines.
Guntis Bunga is a graduate of the Faculty of Transport and Mechanical
Engineering and has been awarded the degree of Dr.sc.ing. by Riga Technical
University. He is an associate professor at the Department of Material Pro-
cessing. He has written many books and publications in the field of industrial
engineering, especially in the field of cutting theory.
His fields of scientific interest include: manufacturing technologies; ma-
chining tools; designing of machining tools; Computer Numerical Control ma-
chines. His main scientific interest is cutting theory, including research and de-
velopment of new cutting tools.
Viktors Gutakovskis is a PhD student at the Faculty of Transport and
Mechanical Engineering. His dissertation includes a study of cutting processes,
especially research and development of technological processes cutting stain-
less steel materials. He works as a lecturer at Riga Technical University since
2009. He lectures on manufacturing engineering, especially cutting theory.
His fields of scientific interest include: engineering technology, metal cut-
ting, material science, Finite Element Method analysis and military technolo-
gies.
Artis Kromanis is a graduate of the Faculty of Transport and Mechanical
Engineering and was awarded the degree of Dr.sc.ing. by Riga Technical Uni-
versity (2011). The author’s major field of study is mechanical engineering,
especially manufacturing engineering. He is also a Latvian Patent Attorney spe-
cializing in mechanical engineering and mechatronics.
He is an assistant professor at the Institute of Mechanical Engineering in
Riga Technical University. From 2013 he is the Head of the Department of
Material Processing. He is also a patent attorney in the field of mechanical en-
gineering and electronics. His fields of scientific interest include: manufactur-
ing technologies; CNC; cutting theory; CAD; CAM; Lean manufacturing and
3D printing.
Guntis Pikurs, Guntis Bunga, Viktors Gutakovskis, Artis Kromanis. Virskārtas plastiskā deformēšana ar lodīti kā nobeiguma apstrāde kompresora
vārpstas aizsargčaulai
Zinātniskā raksta tēma ir skrūves kompresora blīvslēga mezgla ekspluatācijas īpašību uzlabošana, paaugstinot blīvslēga mezgla vārpstas aizsargčaulas nodilu-
mizturību pret sīkajām abrazīvajām daļiņām. Vārpstas aizsargčaulas nodilumizturības paaugstināšanās tiek panākta, izmantojot šīs detaļas izgatavošanas tehno-
loģijas nomaiņu no bezcentra slīpēšanas tehnoloģijas uz virskārtas plastiskās deformēšanas tehnoloģiju. Lai noteiktu izgatavošanas tehnoloģijas parametrus, tika
veikti triju faktoru eksperimenti aizsargčaulas izgatavošanas tehnoloģiskajām operācijām.
Pēc triju faktoru eksperimenta veikšanas un datu apstrādes, tika iegūts matemātiskais modelis plastiskajā deformēšanā iegūstamā virsmas raupjuma vidējās arit-
mētiskās novirzes atkarībai no plastiskās deformēšanas apstrādes parametriem.
Vārpstas aizsargčaulas izgatavošana ar plastiskās deformēšanas metodi izslēdz abrazīvo daļiņu nonākšanu aizsargčaulas materiāla virskārtā, kas ir raksturīga
slīpēšanas operācijām, tādējādi izslēdzot abrazīva sākotnējo nonākšanu starp PTFE blīvslēga un 100Cr6 vārpstas aizsargčaulas virsmām un intensīvāku sākotnējo
dilšanu.
Гунтис Пикурс, Гунтис Бунга, Виктор Гутаковский, Артис Кроманис. Обкатка шариком как метод завершающей обработки для защитной
гильзы вала винтового компрессора.
Тема научной статьи - повышение качества эксплуатационных свойств винтового компрессора за счет улучшения качества работы уплотнительного
узла, защиты истирания гильзы валa от крошечных абразивных частиц. Увеличение износостойкости гильзы валa достигается за счет использования
технологий поверхностно-пластической деформации и замены технологии шлифовки. Исследование проводилось при производстве защитной пленки
с помощью пластического деформирования поверхности. Для определения параметров технологии обработки было проведено три опыта для изучения
защитных факторов технологических операций.
После трехфакторного эксперимента и обработки данных были получены математические модели пластической деформации для определения
зависимости шероховатости поверхности от среднего отклонения по пластическим параметрам обработки деформации.
Производство защитной гильзы вала методом пластического деформирования исключает попадание абразивных частиц в защитный поверхностный
материал, в отличие от шлифовальных операций, тем самым исключает попадание абразива в исходное PTFE-уплотнение и защитной гильзы 100Cr6
поверхностей, а также повышенный износ оригинала.
