Improving Surgical Robot Performance Through Seal Design.pdf

Ever wonder how something as "simple" as a seal can impact surgical robot accuracy and reliability? Take quick a spin through this informative deck today, and use what you've learned to build a better robot tomorrow.

1. Improving Surgical Robot
Performance Through Seal Design
Adriana Borcea
Global Category Manager, Seals
Bal Seal Engineering

2. •Complex devices that assist
surgeons in procedures ranging
from hip arthroplasty and
coronary bypass to kidney
transplant
•Increase dexterity, compensate
for tremor, support hand- eye
coordination & improve
visualization
•Enable doctors to perform
surgeries from remote locations
SURGICALROBOTS
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Photo: United States Army

3. •Improved precision
Arms/instruments with multiple
degrees of freedom
•Enhanced functionality
Greater visualization
Motion scaling/filtering
•Smaller footprint
Instrument level
Platform level
ADVANCESIN ROBOTICSURGERY
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4. Goals Challenges
Better control& dexterity
Equipment with greaterdegrees
of freedom
Improve haptic sensing &
feedback
Reduce system static & dynamic
friction in kinematic chain
Smaller accesssites Reduce instrument footprint
Greater functionalityIncreaseinstrument capabilities
SOMESURGICALROBOTCHALLENGES
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5. •Functions
Protect equipment from
bodily fluids, dust, grease,
wipe downs/sterilization
Maintain media pressure
•Goals
Minimize static and dynamic
friction
Maintain consistent dynamic
friction
Protect equipment from
premature wear
CRITICALCOMPONENTS: SEALS
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6. SEALINGAPPLICATIONEXAMPLES
End Effectors Arms/Joints Actuators Motors
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7. •Performance conditions
RPM
Pressure
Media
Life expectancy
Torque capacity
Temperature limits
•Hardware conditions
Shaft diameter, material, surface finish, surface hardness,
tolerances
Shaft/bore misalignment
•Reprocessing conditions
Autoclave
Gamma sterilization
FACTORSTHATIMPACTSEALDESIGN
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8. •PTFE-based composition
materials provide the
lowest friction, stiction &
wear, and also:
Exhibit excellent chemical
compatibility, can run dry
as well/no lubrication
Withstand wide
temperature range of -
400°F up to 550°F+
FDA compatible & USP
class VI certified
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A CLOSERLOOK: SEALMATERIALS
0 0.10.20.30.40.50.6
PTFE
PFA
FEP
PEEK
UHMWPE
HDPE
Delrin
PVC
Nylon
Static Coefficient of Friction

9. Dynamic lip engineered to
minimize friction, optimize sealing
performance, prevent media
ingress.
•Engineered designs that …
Handle rotary, oscillating,
reciprocating + angular
motion
Balance sealing effectiveness
+ low friction & stiction
Promote continuous laminar
flow, preventing bioburden
buildup
Reach compact sizes -IDs to
5mm and below
A CLOSERLOOK: CUSTOMGEOMETRY
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Metal locking ring prevents seal rotation in hardware, promotes consistent sealing contact under thermal cycling conditions.

10. •Customized loads
•Preloads sealing lip to maintain
protective barrier during
thermal cycling
•Chemical compatibility
Implantable options
•Wide amount of sizes
Smallest ID = 0.5mm
•Accommodate large tolerances
A CLOSERLOOK: CANTEDCOILENERGIZER
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11. 391
765
1366
2488
4735
0
1000
2000
3000
4000
5000
2.0 4.0 8.0 16.0 32.0
Frictional Force vs. Surface Finish
•High/rough surface
finish can increase
friction and cause
material to wear
faster
•Minimal friction
enables smooth
system operation &
increased life
•Friction can
influence haptic
sensing, sensor
feedback, and
motor operation
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HARDWAREINSIGHTS: SURFACEFINISH
(1.8) (3.6) (7.2) (14.4) (28.8)
Surface finish microinches RMS (microinchesRa)
Frictional force (grams)

12. •Dependent on seal ring
material
•If low, can increase adhesion of
material and friction, causing
premature seal wear
•Some materials require
elevated hardness to ensure
longevity of the dynamic
surfaces
HARDWAREINSIGHTS: DYNAMICSURFACEHARDNESS
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13. CASESTUDY: SURGICALROBOTICARM
Features Requirements
Size Ø7mm shaft
Speed 500to 1KRPM
Service typeRotary & oscillating
Media Air& oil (dry/wet)
Forces Breakout:4mN-m
Running: 2mN- m
Lifecycles9 million revolutions
Size constraints2.5mm x 2.5mm
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14. •Polymer- filled PTFE
seal
Low CoF
Low stiction
Low wear rate
CASESTUDY: SURGICALROBOTICARM
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Dynamic lip
to minimize
friction
Canted coil spring
applying
consistent light
force
Locking ring to
easily press into
hardware and
enhance stability
FDA & RoHS
compliant
material
Thin, flexible
hinge point

15. BETTERACCESS& ACCURACY: TAKEAWAYS
Challenge Requirement The right seal can provide …
Better control&
dexterity
Equipment with greater
degrees of freedom
•Multipledegrees of freedom to enable rotation,
translation& articulation
•Greater tolerance absorption
Improve haptic
sensing & feedback
Reduce system static and
dynamic friction in
kinematic chain
•Low friction for improved kinematics &
responsiveness
•Flat force curve for controlled and predictable
friction
•Wear limitingfeatures to maintain consistency
Smaller access
sites
Reduced instrument
footprint
•Smaller, compact design (axial & radial)
Greater equipment
functionality
Increase instrument
capabilities
•Dry-running, low wear with locking mechanisms
enable additional capabilities in smaller spaces
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16. •To eliminate costly mistakes and delays, consider
sealing requirements as part of overall robot
design
•In early design stages, collaborate with Bal Seal
Engineering to:
Get consultative engineering advice
Review robot hardware design
Estimate frictional outcome
Engage in collaborative seal design discussion
Custom design a seal that meets all your
system/application requirements
▸Determine recommended test failure criteria
Produce high-quality seal prototypes
Scale up to full production
SUMMARY& RECOMMENDATIONS
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17. •“We make seals, springs and
contacts that make your designs
great”
•Established in 1958
•~650 employees
•Offices in US, EMEA, Asia
•Quality-driven and ISO certified
•Solutions tailored to your design
BALSEALENGINEERING
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18. RESOURCES& CONTACTINFORMATION
Start the conversation with a robotics sealing expert:
Adriana Borcea
Global Category Manager, Seals
Bal Seal Engineering
P: 949.460.2160
[email protected]
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[email protected] +1 949.460.2100 Design Request Form