Traditionally , in medical instruments , bearings — that optimise the rotation of axes like robot arms by limiting or avoiding friction and jolts — have been made from high purity metals such as martensitic stainless steel . Examples include medical robots that help undertake keyhole surgery where the utmost precision is required . Surgical robot bearings must deliver the highest possible rotational accuracy , while also being small enough to fit into these often compact and portable hospital devices .
However , steel bearings have limitations including contamination . While steel bearings are tough and capable of withstanding highly-corrosive environments , they are susceptible to particulate contamination due to the very high contact pressures against the steel within the bearing while it moves . If left unchecked , this contamination can cause denting and wear .
Of course , contamination in general is unacceptable in health and safety environments . As robots become more prevalent in medical applications , regulations are getting stricter in order to prevent contamination .
Replacing steel
The need to avoid contamination accompanies other design requirements such as high speeds , low noise and non-magnetic properties . For instance , because Magnetic Resonance Imaging ( MRI ) scanners use a strong magnetic field to generate two- or threedimensional images of any living subject , steel bearings cannot be used due to their magnetic properties .
All of these factors influence the choice of material for bearings in medical environments — but what material can replace steel ? The medical equipment sector is increasingly choosing bearings made exclusively of zirconia ( ZrO2 ), or other exotic ceramic compounds . According to the Institute of
Ceramic bearings hold a number of advantages for medical environments .
Although surgical robots are becoming cheaper , modern medical applications are also demanding higher precision and speed capabilities from these robots .
Materials , Minerals and Mining , “ ceramic bearings made from ZrO 2 are tough with similar expansion properties to chrome steel and 440 stainless steel , although they are 30 per cent lighter .”
Indeed , full ceramic precision bearings are harder than steel , with superior corrosion and heat resistance , higher dimensional stability and lower density . However , ceramic bearings are expensive . This is a big issue for health institutes that operate within tight budgets , so the decision to invest in them must be well-considered . Fortunately , ceramic bearings hold a number of advantages for medical environments .
One is that the bearings don ’ t react to chemicals . That means they don ’ t corrode or weaken when subjected to harsh chemicals used for sterilisation in hospitals . Ceramics don ’ t require lubrication that would otherwise draw contaminants like dust , water or humidity and this also eliminates the need for maintenance processes like relubrication . They are also waterresistant , so can be washed-down regularly .
High-value applications
So , is investing in ceramic bearings for medical environments worth it ? There are still certain applications where the speed and precision of steel are crucial , like in surgical robots for example . However , there are other instances where using the wrong components in such medical or laboratory equipment can contaminate study conditions , or cause the study to cease altogether .
Instead , the extra investment in ceramic bearings can help ensure that medical robots run with effectiveness and longevity — especially as they are “ cast more as companions providing emotional support , rather than seen as tools .”
For more information on how specialist precision bearings can support longer service life in medical devices , visits SMB Bearings ’ website or email sales @ smbbearings . com .
For further information , please visit www . smbbearings . com
Issue 65 PECM 57