Improving Surgical Robot Performance Through Seal Design.pdf
- 1. Improving Surgical Robot Performance Through Seal Design Karina Chavez Global Market Manager 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 SURGICAL ROBOTS B A L S E A L . C O M 2 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 ADVANCES IN ROBOTIC SURGERY Image property of NISI Image property of Landmark Medical B A L S E A L . C O M 3
- 4. Goals Challenges Better control & dexterity Equipment with greater degrees of freedom Improve haptic sensing & feedback Reduce system static & dynamic friction in kinematic chain Smaller access sites Reduce instrument footprint Greater functionality Increase instrument capabilities SOME SURGICAL ROBOT CHALLENGES B A L S E A L . C O M 4
- 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 CRITICAL COMPONENTS: SEALS 5 B A L S E A L . C O M
- 6. SEALING APPLICATION EXAMPLES End Effectors Arms/Joints Actuators Motors B A L S E A L . C O M 6
- 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 FACTORS THAT IMPACT SEAL DESIGN B A L S E A L . C O M 7
- 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 8 B A L S E A L . C O M A CLOSER LOOK: SEAL MATERIALS 0 0.1 0.2 0.3 0.4 0.5 0.6 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 CLOSER LOOK: CUSTOM GEOMETRY 9 B A L S E A L . C O M 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 CLOSER LOOK: CANTED COIL ENERGIZER B A L S E A L . C O M 10
- 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 11 B A L S E A L . C O M HARDWARE INSIGHTS: SURFACE FINISH (1.8) (3.6) (7.2) (14.4) (28.8) Surface finish microinches RMS (microinches Ra) 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 HARDWARE INSIGHTS: DYNAMIC SURFACE HARDNESS 12 B A L S E A L . C O M
- 13. CASE STUDY: SURGICAL ROBOTIC ARM Features Requirements Size Ø7mm shaft Speed 500 to 1K RPM Service type Rotary & oscillating Media Air & oil (dry/wet) Forces Breakout: 4mN-m Running: 2mN-m Lifecycles 9 million revolutions Size constraints 2.5mm x 2.5mm B A L S E A L . C O M 13
- 14. • Polymer-filled PTFE seal ▪ Low CoF ▪ Low stiction ▪ Low wear rate CASE STUDY: SURGICAL ROBOTIC ARM 14 B A L S E A L . C O M 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. BETTER ACCESS & ACCURACY: TAKEAWAYS Challenge Requirement The right seal can provide … Better control & dexterity Equipment with greater degrees of freedom • Multiple degrees 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 limiting features 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 B A L S E A L . C O M 15
- 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 16 B A L S E A L . C O M
- 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 BAL SEAL ENGINEERING 17 B A L S E A L . C O M
- 18. RESOURCES & CONTACT INFORMATION Start the conversation with a robotics sealing expert: Karina Chavez Global Market Manager Bal Seal Engineering P: 949.460.2118 kchavez@balseal.com B A L S E A L . C O M 18 solutions@balseal.com www.balseal.com +1 949.460.2100 Design Request Form
- 19. August 22 © Copyright, Bal Seal Engineering, LLC. This document contains and/or refers to information that is PROPRIETARY to Bal Seal Engineering, LLC, and may not be reproduced, copied, published, or distributed in any form or disclosed to a third party, in whole or in part, without the written authorization of an officer of Bal Seal Engineering, LLC. Products are the subject of issued or pending United States and foreign patents. Products of Bal Seal Engineering, LLC and this document are PROPRIETARY and products may not be manufactured, or caused to be manufactured, by any other party. Rev. 02.28.22 Thank you.