Medical Design Briefs - July 2023 - 18

TECHNOLOGY LEADERS Motors/Motion Control/Robotics
Topic
Service Life and Reliability
Identifying the actuator's duty cycle is
a key component of sizing and selection.
Duty cycle is defined as the ratio of
operating time to resting time of an
electric actuator, expressed as a percentage.
For example, an actuator that
is moving for two seconds and stopped
for two seconds has a duty cycle of 50
percent. Underestimating the impact of
duty cycle on an actuator can lead to
overheating, faster wear, and premature
component failure.
Overestimating the impact of duty
cycle can lead to higher initial costs
due to oversizing. Overly conservative
duty cycle estimates often stem from
an incomplete understanding of the
application. This is another advantage
of using sizing software programs as
they can factor in duty cycles, move
times, and velocities.
Operation and Usage
Medical environments require lownoise
operation to ensure patient comfort
and minimize interference with sensitive
equipment. Noise and vibrations
can also affect the accuracy and precision
of the linear actuator technology.
Actuators should be designed to operate
quietly and produce minimal vibrations,
particularly in devices used during patient
examinations or procedures.
Prior to prototype, intangible aspects
like noise, vibration, or other aspects including
visual appearance can at times
be the most challenging and hardest to
quantify and manage throughout a design
exercise.
Size and Weight
The size and weight of the linear motion
and actuator technologies are also
vital design considerations. In many
cases, medical devices are designed
to be compact and lightweight
for portability, function,
operational environments, and
ease of use, while other applications
may be fixed installations,
quite large, heavy, and
demand utmost levels of stability
for accuracy and movement
precision. Even in the largest,
heavy-duty applications, there
are often underlying objectives
to produce desired performance
outcomes while minimizing
the physical footprint
and weight to deliver a more
practical and functional execution.
Operator
and Patient Safety
In medical devices and
In a controlled injection device, this rod-style electric actuator is
used to administer a slow, regulated injection of a treatment
contrast in a clinic, rather than a hospital setting.
equipment, the importance of
human factors cannot be overstated.
From functional considerations
for operators to essential
safety aspects for the
patient, consistency and failsafe
performance are of the utmost
importance. Linear actuators
and motion systems may be
required to incorporate safety
features such as position feedback
sensors, limit switches,
and emergency stop mechanisms
to prevent accidents or
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injuries during operation. These safety
features can help ensure proper device
functionality while protecting patients
and healthcare professionals.
Device Serviceability
Ease of maintenance and serviceability
is crucial for medical devices, as
they often require periodic inspections,
repairs or component replacements.
Electric linear actuators should
be designed with accessibility in mind,
allowing for straightforward maintenance
procedures and minimizing device
downtime. Specification
of IPrated
actuators (such as IP55, IP67, or
IP69K) not only protects the performance
and life cycle of the component
but helps ensure that the device itself
is tolerant of real-world cleaning and
maintenance practices in medical and
healthcare environments.
Manufacturability
Once the proper performance specifications
have been calculated, and operation,
safety, service, and life cycle characteristics
have been identified, the
design process then turns to evaluate
the viability of a solution. When considering
a component provider, it's best to
identify a vendor with the expertise,
agility, and willingness to make modifications.
It's important to remember that
" build to order " does not immediately
involve a complex and costly custom development
cycle.
In cases where custom innovation is
required, the development partner you
select should be not only qualified but
collaborative, with demonstrated capabilities,
engineering capacity, and willingness
to engage in a robust customization
dialog and process. The right
partner can also help identify the critical
design requirements and work with
you to evaluate iterations of the finished
product with
consideration
given
budget impacts and lead times.
Conclusion
The continued development of
emerging technologies ranging from
surgical, procedural, and diagnostic devices
to more advanced iterations of patient
positioning, ergonomics, and mobility
assistance, will propel the use of an
Medical Design Briefs, July 2023
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Medical Design Briefs - July 2023

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