Method for polishing silicone products

A method for polishing articles manufactured from silicone rubber or silicone elastomers is disclosed. This method includes tumble-polishing in a receptacle charged with polishing objects, an alcohol solvent, and silicone articles for a period of time and at a rotation speed sufficient to remove surface irregularities and produce the desired finish and/or improve the optical transparency of the silicone articles. This method is particularly useful in the polishing of biomedical articles such as intraocular or soft contact lenses, tips of cannulae, and articles such as O-rings for precision mechanical devices.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to methods of manufacturing products from 
silicone elastomers. More particularly, the present invention relates to 
an improved method of polishing silicone products in an alcohol or solvent 
solution and in the absence of any polishing abrasives to remove flashing 
or other sharp edges from the molded or stamped silicone or elastomer 
products. 
2. General Background 
Silicone materials such as silicone rubbers and silicone elastomers are 
used in the manufacture of a wide variety of products. These materials are 
particularly useful in biomedical applications because they are compatible 
with biological tissues and fluids, and are permeable to gases such as 
oxygen and carbon dioxide. Other desirable characteristics of silicone 
elastomer products include their flexibility, ease of molding, and 
relatively low cost. 
Examples of such silicone elastomer products include soft contact lenses, 
intraocular lenses, medical catheters and cannulae, prosthetic implants, 
contraceptive devices, O-rings and other products in the automotive and 
other industries which require articles having a rounded, smooth, highly 
polished finish. 
A highly polished finish, free of any sharp edges or surface 
irregularities, is required in biomedical applications. The silicone 
product is in direct contact with body tissues and the tearing or abrading 
of tissue by rough or non-smoothed surfaces could result in rupture of 
blood vessels, irritation or other trauma to the tissue. 
It has been found that even minute irregularities can cause irritation of 
body tissues. This is a particularly serious problem with contact lenses 
and portions of intraocular lenses that contact the eye, where the tissue 
is extremely sensitive. The use of silicone materials for intraocular 
lenses is a relatively new development. Intraocular lenses formed of 
silicone are advantageous in that they can be folded and inserted through 
smaller incisions in the cornea than previously possible, resulting in 
fewer post-operative complications. Rough edges due to cutting of the lens 
blanks or flashing as the result of molding can cause intraocular 
irritation. 
A satisfactory method of removing flashing from the edges of such lenses, 
and otherwise polishing them to obtain a smooth surface and enhanced 
optical clarity, was heretofore unknown. Such lenses are too small to trim 
by hand and polishing processes used for other types of lens materials 
such as polymethylmethacrylate are unsatisfactory. 
In addition, soft contact lenses require a highly polished finish to 
prevent irritation of the interior of the eyelid and corneal epithelium. 
The eye is extremely sensitive to imperfections in contact lenses, and 
even slight ridges resulting from the molding process can produce 
irritation and discomfort. To this date, only expensive molding procedures 
or individual hand-grinding techniques have been available to produce the 
desired finish for these lenses. 
Aside from intraocular lenses and contact lenses, other medical products 
manufactured from silicone elastomers and which require a highly polished 
finish include irrigation/aspiration cannula tip sleeves for use in 
phacoemulsification procedures. In this surgical procedure, ultrasonic 
energy is applied to break-up the natural lens of the eye. The cannula is 
inserted through a corneal incision to the vicinity of the lens and is 
used to aspirate or remove the lens fragments. During this procedure, the 
tip of the cannula often comes into contact with the sensitive eye tissue 
and therefore it must be devoid of sharp, rough, or irregular edges. 
Mechanical devices utilizing smooth, frictionless movement also require 
highly polished, smooth surfaces of their silicone products. Obtaining 
such a highly polished, smoothly-finished silicone article is often 
difficult as these products are manufactured by curing molten silicone 
material in molds, wherein even the most precise dies result in some 
flashing and/or irregular edges. The products may be trimmed and polished, 
but these finishing procedures are generally done by hand, and are both 
time consuming and expensive, as well as imprecise, so that they do not 
result in the totally smooth or regular surface required. Further, many of 
these articles, particularly those for biomedical applications, are 
relatively small, and/or irregularly shaped, causing difficulties in 
obtaining the desired finish, and/or clarity. 
The removal of imperfections from small and irregularly shaped silicone 
products is an unsolved problem in the art. It would be of great utility 
to provide a simple, economic, and effective method for polishing and/or 
clarifying silicone products for industrial, medical, and mechanical 
purposes. 
SUMMARY OF THE PRESENT INVENTION 
The present invention solves these prior art problems and shortcomings in a 
simple, straightforward, yet efficient manner by providing a method of 
polishing shaped, silicone articles. A receptacle is charged with the 
articles to be polished, a mixture of a polishing medium in the form of 
non-abrasive polishing beads, and a solvent which permits polishing action 
without abrading the surface of the silicone articles. The receptacle is, 
agitated for a time sufficient for the non-abrasive polishing beads and 
solvent to remove surface irregularities from the articles. The present 
invention also provides a method of polishing silicone articles which 
improves the optical clarity of the product. No abrasive material which 
may scratch, become imbedded within, or otherwise damage the soft silicone 
articles is in the polishing medium. 
In the preferred method, the solvent is an alcohol and the receptacle is a 
3ar having an irregular sidewall suitable for the tumble polishing of the 
contents. The tumbling jar is rotated at a speed and for a time sufficient 
to allow the contents of the jar to actively remove surface irregularities 
and flashing, and to smooth and round edges and/or holes of the silicone 
articles. The rotation rate will also vary with the size of the tumbling 
jar. 
An especially preferred embodiment uses absolute ethyl alcohol mixed with 
water as the solvent and glass polishing beads to polish and shape the 
edges of the silicone articles. In this method, the polishing beads are 
provided in a range of sizes, including beads preferably between 0.5 and 
3.0 mm. The receptacle is tumbled for a time period of 1-14 days with a 
preferable tumbling rate of 50-100 rpm or that rate sufficient to produce 
the desired polishing action. Most preferred is 1-6 days and 75-90 rpm in 
a 1000 ml tumbling jar with a generally square cross section. 
The polishing medium can be made up of non-abrasive beads which may be 
formed of glass, steel, or zirconia, and the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the subject invention silicone articles are placed in a receptacle along 
with a solvent and a polishing medium and tumble polished at a speed and 
for a duration which permits the silicone articles to attain the desired 
finish. The precise combination of factors used, for example, the 
particular solvent, the type and size of polishing medium, the size of the 
receptacle, the number of articles tumbled, the speed of rotation, and the 
time of tumbling will vary with the size, shape, and characteristics of 
the silicone product to be polished. 
The solvent may be an alcohol, such as ethyl, methyl, propyl, isopropyl 
alcohol, and the like. The alcohol may be mixed with deionized or 
distilled water, with preferred percentages of alcohol in the mixture 
ranging from 85 to 100%. 
The preferred solvent is ethyl alcohol mixed with water. Although different 
ratios of alcohol to water may be optimal for different silicone products, 
the recommended solvent for the silicone products discussed below is a 
mixture of 95% absolute ethyl alcohol and 5% water. Distilled or deionized 
water may be used. 
The polishing process may be performed in a variety of receptacles, and 
agitated in such a manner as to provide sufficient polishing action of the 
contained polishing objects upon the contained silicone articles. The 
receptacles may be various sizes and shapes, and may be formed of glass, 
polycarbonate, polysulphone, stainless steel, or other suitable material. 
A preferred receptacle, for example, is a 1000 ml square-shaped tumbling 
jar. This tumbling jar is charged with, for example, approximately 200 ml 
of the alcohol-water solvent and approximately 600 ml of polishing beads 
as the ,polishing, medium. The polishing medium may contain solid or 
filled beads which may be formed of glass, steel shot, zirconia, or other 
suitable material. Bead diameters may vary from about 0.5 to about 3.0 mm, 
and preferably from about 0.5 to about 1.5 mm, depending on the 
characteristics of the articles to be polished. The number of articles to 
be polished may vary depending upon the size, shape and other 
characteristics of the articles, and the size of the polishing jar and the 
volume of its contents, but in general the number of articles will vary 
from about 1 to about 500 articles. 
In one embodiment of this invention, intraocular lenses of the type shown 
in FIG. 1, which are 10.5 mm.times.6.0 mm and have manipulation holes of 
0.75 mm diameter are polished using a mixture of 300 ml of 0.6 mm glass 
beads and 300 ml of 1.4 mm glass beads. The selection of beads of 
different sizes is advantageous in polishing articles, for example, where 
in addition to an outer, more exposed surface, the inner surface of a 
smaller opening must be polished. For intraocular lenses, such smaller 
openings can be manipulation holes into which instruments are inserted to 
position the lens. From 1 to 150 lenses may be added to the 1000 ml jar, 
but to optimize the process, it is preferred to use between 10 and 60 
lenses. 
The receptacle is then capped and agitated in a manner sufficient to 
provide the desired polished finish. Agitation may be accomplished by 
attaching the receptacle to a rotational apparatus such as a tumbling 
machine, for example, Model 3BAR, (Topline Mfg. Co., Fullerton, CA). The 
jar and its contents are tumbled at room temperature at speeds of about 50 
to about 100 rpm, for 1 to 14 days, depending upon the characteristics of 
the articles to be polished, the number of articles to be polished, and 
the size of the tumbling receptacle. For example, in a 1000 ml tumbling 
jar, 50 irrigation/aspiration tips may require only 24 hours of tumbling 
whereas 15 intraocular lenses may require 3 days. If the tumbling speed is 
too fast, the contents of the jar will simply adhere to the sides of the 
jar and will not tumble. If the tumbling speed is too low, no polishing 
will occur. It is therefore important to optimize the speed and time of 
tumbling for the particular silicone articles to be polished. The optimal 
speed of rotation may be arrived at readily and with minimal 
experimentation. For typical intraocular lenses in a 1000 ml tumbling jar, 
for example, the speed of rotation may vary from about 75 to about 90 rpm, 
preferably about 80 rpm. 
The tumbled silicone articles are then removed from the receptacle and 
subjected to cleaning procedures. In the preferred method of cleaning, the 
articles are first rinsed with water or a suitable solvent, and then 
subjected to ultrasonic cleaning, or other suitable methods for removing 
residual pieces of waste silicone, tumbling beads, and tumbling solvent. 
For instance, a convenient method of rinsing polished articles such as 
intraocular lenses, which have a length of 10.5 mm and width of 6.0 mm, to 
separate them from the other contents of the tumbling jar, is to use a No. 
6 sieve arranged above a No. 45 sieve in a convenient drainage area, such 
as a sink. The contents of the jar are emptied into the No. 6 sieve, and 
deionized water or other suitable rinsing solvent is then sprayed or 
poured over the material, rinsing the beads and waste silicone particles 
through the No. 6 sieve and leaving the silicone articles. The beads will 
be retained by the No. 45 sieve for reuse, while the tumbling solvent and 
the waste silicone particles will pass through for disposal. 
The tumbled, rinsed silicone articles may then be removed from the No. 6 
sieve and immersed in 100% ethyl alcohol or other suitable cleaning 
solvent, and placed, for example, in a Pyrex dish and in a cleaning 
apparatus, for example, an ultrasonic bath such as Model T28, sold by L&R 
Co., Kearny, New Jersey, for about 5-10 minutes. After cleaning, the 
tumbled silicone articles can be swabbed with deionized water, ethyl 
alcohol, or other suitable solvent, and inspected for polishing 
effectiveness, flaws, and/or clarity. 
One method of inspection is the examination of the surfaces and edges of 
the polished silicone articles by microscopy. Scanning Electron Microscopy 
(SEM) clearly indicates the success or failure of the polishing process as 
photomicrographs depict high resolution images of the surface and/or edges 
of the articles. Less elaborate procedures for inspection of the polished 
silicone articles include the visual examination and rating of 
characteristics, for example, "roundness" of the edges, and the ease with 
which the articles are cleaned. 
The polishing method of this invention may also impart additional 
characteristics to articles processed. These include increased optical 
clarity, or transparency, an important characteristic of optical lenses 
manufactured from silicone, and polished by the process of this invention. 
The polishing method extracts low molecular weight fractiles or non-cured 
residues of silicone. The articles may be reduced 2-3% by weight after 
polishing, and visually appear to be more transparent. Thus inspection of 
the polished products may also include examination of their optical 
clarity, either visually or by measurement of light refraction and/or 
absorbance. 
The silicone articles to be polished by this method may include soft 
contact and intraocular lenses, biomedical products such as cannulae and 
catheters, prosthetic devices, various implants, and devices which contact 
biological tissues. Industrial applications may also include O-rings, 
bearings, and other articles which require a smooth, polished finish. In 
particular, this method is useful in the polishing of intraocular lenses 
and tips of cannulae used for phaco-emulsification procedures. 
The silicone articles to be polished by the method of this invention are 
manufactured from silicone rubber or silicone elastomeric materials. These 
include compounds such as polydimethylsiloxanes, polydiphenylsiloxanes, 
and polymethylphenylsiloxanes. The articles may be unfilled or filled to 
various degrees with a range of materials from small quantities of silica 
resins to highly-filled fumed silica. The material may be pigmented or 
non-pigmented, and comprises those silicone elastomers which vulcanize at 
room temperature or with heat. 
Silicone articles to be polished by the method of this invention may be 
manufactured materials such as RMX-3 (Starr Surgical, Corp. Monrovia, CA), 
Q9-5724 (Dow Corning Corp., Midland, MI), Silastic #598 (Dow Corning 
Corp., Midland, MI), and the like. 
EXAMPLES 
Example 1 
Polishing of Silicone Intraocular Lenses With Various Solvents 
To a 1000 ml square tumbling jar was added 200 ml of a solution consisting 
of 100% alcohol, about 600 ml of a mixture of 0.6 mm and 1.4 mm glass 
polishing beads in equal volume proportions, and 50 silicone intraocular 
lenses of mixed style types. 
Lenses used in this example were manufactured from silicone elastomer 
material obtained from Starr Surgical Corp., Monrovia, Calif. by its 
designation RMX-3. The lens styles used were mixtures of various 
combination of those described in the CooperVision-CILCO catalog as 
product number NR960B, NR961B, NR962S, NR963B, and NR964B. All lenses were 
similar but not identical to the one shown in FIG. 1, and varied in width 
and the presence of manipulation holes. The lenses were 10.5 or 11.0 mm in 
length and 6.0 mm in width. The type of alcohol used as the tumbling 
solvent was varied. Tests were run with 95% ethyl alcohol, (95 parts 100% 
ethyl alcohol and 5 parts deionized water), 70% isopropyl alcohol, and 
"Everclear" (190 proof grain alcohol, Worldwide Distilled Products Co., 
St. Louis, Mo.). The tumbling jar was sealed, and tumbled in a 3BAR, 
Topline Mfg. Co., tumbling machine for 6 days at 82 rpm. After tumbling, 
the contents of the jar were poured onto a No. 6 sieve, and the retained 
lenses were rinsed with deionized water and removed to a Pyrex dish. The 
lenses in the Pyrex dish were immersed in 100% ethyl alcohol and placed in 
an ultrasonic bath, Model T28, L&R Co., Kearney, New Jersey, for 10 
minutes. The lenses were then removed from the Pyrex dish, swabbed with 
deionized water, and were examined for roundness, a measure of the degree 
of edge polishing, and the ease of cleaning, a measure of the removal of 
surface irregularities. The analysis was a subjective one, wherein each 
tumbled lens was rated on a scale of 0 to 10, with 10 indicating both the 
most rounded and also the easiest to clean. Each lens within a test jar 
was independently rated by these scales, and a mean value was calculated 
for each test group. The results of these experiments indicated successful 
polishing in all solvents (mean scores greater than 4). The 95% ethyl 
alcohol solution was rated as the best solvent for this application by 
efficiency of polishing and ease of cleaning. 
Example 2 
Polishing of Silicone Intraocular Lenses With Varied Mixtures of Ethyl 
Alcohol and Water 
The polishing method of Example 1 was repeated comparing the use of ethyl 
alcohol and deionized water mixtures of 100%, 95%, and 90% ethyl alcohol, 
and using a tumbling duration of 3 days with 15 lenses per tumbling jar. 
The polished lenses were then examined and rated for roundness and ease of 
cleaning as described in Example 1. Review of the data from three 
individual experiments showed 95% ethyl alcohol to be the best solvent, 
and 90% ethyl alcohol to be better than 100% ethyl alcohol. Polished lots 
using 100% ethyl alcohol showed near-zero roundness, while the 95% alcohol 
group rated near the top of the scale (9-10), and the 90% ethyl alcohol 
group clustered around a lower, yet acceptable rating for intraocular 
lenses (4-6). 
Example 3 
Polishing of Silicone Intraocular Lenses With Varied Mixtures of Polishing 
Bead Sizes 
The polishing method of Example 2 was repeated using 95% ethyl alcohol as 
the polishing solvent, and comparing the use of either 400 ml of 0.6 mm 
beads and 200 ml of 1.0 mm beads, or 200 ml of 0.6 mm beads and 400 ml of 
1.0 mm beads. The smaller beads were needed to polish the interior edges 
and surfaces of the 0.75 mm diameter manipulation holes of the lenses. The 
polished lenses were then examined and rated for roundness and ease of 
cleaning as described in Example 1. Results indicated that the higher 
proportion of 1 mm beads (2-1 mm beads: 1-0.6 mm beads) gave more 
satisfactory overall polishing results for these intraocular lenses with 
manipulation holes than did the higher proportion of smaller beads (1-1 mm 
beads: 2-0.6 mm beads). 
Example 4 
Polishing of Silicone Intraocular Lenses With Varied Time of Tumbling 
The polishing method as described in Example 1 was followed using 95% ethyl 
alcohol. The duration of tumbling necessary to produce the desired finish 
was tested by removing tumbling jars from the tumbling machine at varied 
time periods between 0 and 14 days. All jars were placed onto the tumbling 
machine and the tumbling duration begun at the same time. Test groups of 
tumbling jars were removed for analysis at 8, 16, 24, 32, 40, and 48 hours 
and each 24 hours thereafter up to 14 days. The polished silicone lenses 
were then examined and rated for roundness and ease of cleaning as 
described in Example.1. While results indicated that the acceptable 
standard for polished lenses was achieved after 3 days of tumbling, the 
best polishing results were obtained after 7-8 days of tumbling. 
Continuing the tumbling process up to 14 days did not improve the quality 
of the product. 
Example 5 
Polishing of Silicone Intraocular Lenses With Varied Conditions of the 
Lenses: Water Saturated, Normal, and Overdried 
Three experimental groups of lenses were polished by the method described 
in Example 2: lenses which had been soaked in deionized water 24 hours 
prior to tumbling, normal lenses, and lenses which had been dried in an 
oven at 100.degree. C. for 4 hours prior to tumbling. The tumbling solvent 
was 95% ethyl alcohol, and the duration of the tumbling was 3 days. The 
lenses were then examined and rated for roundness and ease of cleaning as 
described in Example 1. No significant differences in polishing quality 
were seen between any of the three groups of lenses. 
Example 6 
Polishing of Silicone Intraocular Lenses With Varied Conditions of the 
Lenses: Ethyl Alcohol Saturated, Normal, and Overdried 
The polishing method of Example 5 was repeated comparing lenses of three 
groups: all lenses were soaked in 100% ethyl alcohol for 24 hours and then 
either placed directly into the tumbling jar, permitted to dry at room 
temperature for 4 hours, or dried in an oven at 100.degree. C. for 4 hours 
prior to tumble polishing. The lenses were then examined and rated for 
roundness and ease of cleaning as described in Example 1. No significant 
differences were noted between any of the groups of lenses. 
Example 7 
Polishing of Silicone Intraocular Lenses and Inspection by Scanning 
Electron Microscopy 
The method of polishing lenses was followed as described in Example 1, 
using 95% ethyl alcohol as the tumbling solvent. The resultant polished 
lenses and non-polished, control lenses were sputter-coated to provide a 
layer of gold approximately 100 Angstroms on the lenses. The coated lenses 
were then photographed in a Cambridge S120 Scanning Electron Microscope. 
FIG. 2 is a Scanning Electron Micrograph (SEM) (original magnification, 
38X) showing the edge of an intraocular lens prior to polishing. FIG. 3 is 
an SEM of a lens similar to the one shown in FIG. 2, taken after the lens 
had been tumble polished by the method of this Example 7 (original 
magnification, 38x). Note that the edges were smoothed and rounded by the 
polishing procedure. In a similar manner, FIG. 4 is an SEM of the 
manipulation holes of an intraocular lens prior to tumble polishing, and 
FIG. 5 is an SEM taken after a lens similar to the one shown in FIG. 4 had 
been tumble polished by the method of this Example 7. Note the contour of 
the rim of the manipulation holes after polishing was smoothed. (See FIG. 
1 for orientation of edges and manipulation holes of the intraocular 
lens.) 
Example 8 
Inspection of Clarity of Polished Lenses 
Intraocular lenses polished by the method described in Example 7 and 
non-polished lenses operating as a . control were steam sterilized in an 
autoclave apparatus at 121.degree. C. for 25 minutes. These lenses were 
then inspected for optical clarity by examination through a light 
microscope at 75X magnification. FIG. 6 is a transmission light 
microscopic photograph of the central portion of an intraocular lens which 
had been autoclaved, but not polished (original magnification 75X). FIG. 7 
is that of a similar lens which had been polished and then autoclaved 
(original magnification 75X). The mottled appearance of the non-polished 
lens in FIG. 6 is thought to be caused by the action of water and heat on 
non-cured silicone oligomers present in the non-polished lens. As shown in 
FIG. 7, a significant improvement in the optical clarity of the lens is 
apparent after polishing and autoclaving. This improvement is believed to 
be the result of the extraction of the low molecular weight silicone 
oligomers during the polishing process and prior to autoclaving the lens. 
Example 9 
Extraction of Uncured Silicon Oligomer From Non-Polished vs. Polished 
Lenses 
Intraocular lenses polished by the method of example 7 and non-polished 
lenses operating as a control were subjected to organic extraction 
procedures using hexane. The weights of the pre-extraction and 
post-extraction lenses were used to calculate the percentage of organic 
residue extracted. 
About one gram of cured silicone elastomer or intraocular lenses was 
accurately weighed and placed in a Soxhlet extractor with 200 ml of 
hexane. The extractor was permitted to reflux 4-6 times per hour, and the 
extraction time was four hours. The extracted silicone elastomer material 
was then transferred to a tared test tube, and the hexane evaporated to 
dryness on a water bath. The test tube containing the material was then 
heated in an oven at 100.degree. C. for one hour. The test tube was then 
cooled in a desicator and reweighed. 
The difference in weight prior to and after extraction was used to 
calculate the percentage of hexane-extractable material. The 
hexane-extract isolated from the silicone elastomer or intraocular lenses 
was evaporated to dryness to remove hexane. A small amount of the extract 
residue was smeared onto a NaCl plate and scanned in a Perkin-Elmer Model 
1320 Infrared spectrophotometer from 4000 CM.sup.-1 to 700 CM.sup.-1. 
The non-polished, control lenses yielded 4.0% hexane-extractable material, 
whereas only 0.47% was extracted from the polished lenses. The infrared 
absorption curve of the residue isolated from the non-polished lenses 
(FIG. 8) differed slightly from that of the polished lenses (FIG. 9) as 
indicated by the arrowheads, however both scans were identified as that of 
low molecular weight silicone oligomers. Three percent organic 
extractables were removed in the polishing process, which results in less 
than one percent organic extractables present in the polished lenses 
compared with approximately four percent organic extractables in the 
unpolished controls. 
Example 10 
Polishing of Irrigation/Aspiration Tips 
Irrigation/aspiration tips manufactured for use as disposable tip cap 
sleeves for use in phacoemulsification procedures were polished by the 
method of Example 8. The tip sleeves were manufactured from silicone 
rubber elastomer material obtained from Dow Corning Co. (Midland, MI) as 
product Silastic #598. The cannula tip dimensions were as follows: overall 
length, 1 inch; wall thickness, 0.004 inch; overall outer thickness, 0.07 
inch; diameter tip bore, 0.044 inch; diameter side aspiration bore, 0.040 
inch; maximal inside diameter, 0.062 inch. 
The tumbling solvent was 95% ethyl alcohol. The tumbling medium was made up 
of glass beads, 300 ml at 1.4 mm in diameter and 300 ml at 0.3 mm in 
diameter. Each tumbling jar contained 50 tips, and the tumbling duration 
was 24 hours. After tumbling, the tips were rinsed with deionized water, 
cleaned by hand-rubbing in 100% ethyl alcohol and blown dry with air. The 
resulting polished tips and control, non-polished tips were examined by 
Scanning Electron Microscopy as described in Example 8. 
FIG. 10 is a Scanning Electron Micrograph (SEM) of an unpolished tip, and 
FIG. 11 is an SEM of a similar tip after it had been polished by the 
method of this example (original magnification 50X). 
FIGS. 12 and 13 are scanning electron micrographs of the bore of tips 
similar but not identical to those as described in FIGS. 10 and 11 prior 
to and after polishing, respectively (original magnification 59X). 
Example 11 
Polishing of O-rings 
O-rings, manufactured for many applications in precision assembly were 
polished by the method of Example 2. Standard, commercially available 
silicone O-rings were obtained from McMaster-Carr, Los Angeles, Calif., by 
their part numbers 9396K15, 9396K17, and 9396K19. These O-rings were of 
the following dimensions: 9396K15, inside diameter, 1/4 inch, outside 
diameter 3/8 inch; 9396K17, inside diameter, 3/8 inch, outside diameter 
1/4 inch; and 9396K19, inside diameter 1/4 inch, outside diameter 5/8 
inch. The silicone material from which the O-rings were manufactured was 
resistant to brake fluid and high analine point oil, and had a temperature 
range of -80.degree. F. to +450.degree. F. 
The tumbling solvent used was 95% ethyl alcohol, and the tumbling beads 
used were 300 ml 1.4 mm and 300 ml 0.6 mm. Each 1000 ml tumbling jar 
contained 50 O-rings. The resulting polished O-rings and control 
non-polished O-rings were inspected visually. The polishing procedure 
produced smooth surfaces and polished flashing both on the outer and inner 
surfaces of the O-rings. 
The embodiments as described are intended to be exemplary and not limiting. 
Other embodiments and variations are contemplated as falling within the 
scope of the appended claims.