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Using
Circaflex™ Development Suite for Rapid Medical Device Testing
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Industry |
Medical Device Test |
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Application Area |
Embedded Control, Automated Testing |
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Date |
July 2011 |
Challenge
Developing an immediate and rapid deployable test system to perform a
series of leak and flow measurements on millions of plastic medical
devices, requiring high precision measurements, fast test time,
portability, and specific measurement capabilities called out by ISO and
FDA standards.
Solution
Implementing the Circaflex Developer Suite to
achieve accurate and repeatable measurements within three weeks and
validation of the final test solution within three months and to provide
a surprisingly small test system not thought of before. |
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Medical personnel use a variety of plastic tubing, valves, and fittings
to transfer fluid directly to patients for surgery, diagnostics,
research, and treatment. Regardless of the particular use of the
product, even the simplest plastic parts require extensive testing to
ensure that the medical personnel always have an effective component.
Leaks, cracks, or occlusions can be detrimental to the effectiveness of
the procedure and have caused injury to patients and staff. In fact,
with production volumes greater than 100 million per year, Six-Sigma
processes or yields as high as 99.999% also cause roughly 100 injuries
per year! When the health and lives of people are at risk, manufacturers
have a zero defect tolerance in the medical products they ship.
Some of the most common problems with plastic parts associated with
fluidics are leaks, improper path isolation, and occlusions in the fluid
path. A test system can detect defects in plastic parts by applying
pressurized air into one part of the system and look for unexpected
pressure changes, indicating leaks or blockages. A medical device
manufacturer needed a test system from Cyth that had a test time of
several seconds and a high resolution in pressure. The manufacturer also
needed an immediate solution to the test system to catch any potentially
defective components leaving the factory.
The client had
researched the use of an off-the-shelf leak tester, but for the required
volume of tests per day, the number of machines came with size and cost
issues that made the project unachievable. Rather than incurring costs
of buying complete ready-made test systems, purchasing an off-the-shelf
control system not only reduces cost, but also adds the flexibility
needed to customize and fulfill the requirements set out by the
customer. Our solution was to implement the Circaflex Developer Suite, a
commercial off-the-shelf control system based on the National
Instruments Single-Board RIO, to control the custom tester made
specifically for the manufacturer’s products. The FPGA component of
Circaflex handles all the input and output interaction, while the test
sequence for each test head was run in its own thread on the real-time
operating system. Utilizing the Microsoft Windows® interface of
Circaflex, we were able to monitor results and show a statistical
dashboard view of the throughput of the cell.
Testing for Leaks
To begin the leak test, the testing fixture seals the plastic
part and then opens it to a regulated air pressure. Once the pressure
stabilizes, the air input valve closes, forming a sealed section of the
plastic part at a known pressure. Over the next few seconds, the
controller monitors the pressure inside the plastic part to watch for a
drop in air pressure. The pressure sensor in each test fixture is
accurate to hundredths of a psi and the software graphs the output data
and compares it to limits prescribed by ISO standards for various
medical parts. If the pressure decreases past the acceptable limits, the
plastic parts fail the leak test.
Testing for Occlusions
The occlusion test measures the backpressure upon an object
that is restricting flow from the compressed air supply to the
atmosphere. The test measures the backpressure at the inlet of the
plastic part. If there is an occlusion, it will cause the inlet pressure
to increase and the backpressure will be higher than normal. This means
there is an obstruction in the part and the system acknowledges it as
defective.
Test
Time
Of all the requirements, the strictest was the test
time. The test for each part included filling, settling, and testing for
leaks and occlusions, as well as all part interaction and connections.
Yet any of those operations performed too quickly came with a trade-off
in accuracy. Therefore, the system had to be more flexible than any
off-the-shelf leak tester – welcome Circaflex. Leveraging the
flexibility and innovation of the Circaflex control system, engineers
were able to operate position sensors, grippers, and other electrical
components in concert, maximizing the speed while achieving accuracy.
As engineers certified the prototype for production standards and
the client reviewed the workflow and needs of the assembly-line workers,
a number of opportunities arose for new ideas and improvements that
Circaflex easily addressed. One of the new ideas was to test a variety
of plastic medical products in their production line, as opposed to just
one product. Rather than having to design a new test system for each
different product, Circaflex allowed us to add more valves and pressure
and flow sensors to the existing test system. Engineers made some
sections of the test system interchangeable for different products
instead of permanent for one product. The specialized solution involved
using interchangeable product holders and a pressure transducer using
the Circaflex control system to develop a prototype that could control
all of the air valves, apply the pressure as needed, and accurately
measure both flow and pressure changes. Cyth Systems engineers modified
and completed the new prototype with proven and accurate measurements
within one week.
Conclusion
The client wanted to work with an engineering company that
can immediately provide superior and reliable automated tests for their
ongoing production line. The client chose Cyth Systems for this project
based on our expertise in life science applications and our ability to
understand and cater to customer needs, including the quality of design,
time constraints, design limitations, and affordability.
Cyth
not only performed the electrical and software components of this test
system, but also designed and fabricated the control system and the
mechanical fixtures. Not only did the final test system perform all of
the required measurements and part handling, but also our test system
solution was compact in an enclosure the size of a shoebox. The test
system may be considered for used in hospitals because it is small and
unobtrusive. Our small test system was rapidly available, portable, and
eliminated the high cost for a large test system, while still
maintaining the precision and volume requirements.
The Circaflex
Developer Suite provided a rapid, portable and cost efficient solution.
With Circaflex, our engineers were able to perform all the input, output
and calculations required to not only perform tests for leaks and
blockages, but we were also able to handle mechanical interaction with
the part. Most importantly, we were able to do all of this within the
acceptable test time required by the client. The final test system saved
our client $7 million in potential costs that they would have
encountered with an off-the-shelf leak tester. By using our
off-the-shelf control system to build a custom tester, we exceeded the
customer’s requirements in several different aspects.
Next Steps
Contact Cyth Systems to learn how Circaflex can speed up your product development
See More
Circaflex Case Study - PBS Biotech Uses Circaflex Development Suite to
Cultivate Live Cells
Circaflex Case Study - Ready to Use Embedded Control System for DNA
Sequencing
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