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DESIGN ENGINEERING

When faced with obsolescence

MEDICAL INDUSTRY

ALTHOUGH OBSOLESCENCE HAS BECOME PART OF THE NORM WITHIN THE CONSUMER MARKET, IT
CAN CAUSE MAJOR CHALLENGES IN MEDICAL TECHNOLOGY – PARTICULARLY FOR HIGHLY COMPLEX AND
EXPENSIVE EQUIPMENT WHERE THE ENTIRE SYSTEM HAS TO BE TAKEN INTO CONSIDERATION WHEN
REPLACING A PART TO ENSURE STRINGENT REQUIREMENTS AND REGULATIONS CONTINUE TO BE MET

mmunoassay analysers can be used in hospital and
clinical laboratories to detect the presence and
concentration of substances within samples. There
Iare many types of tests that they can perform,
including testing for cancer markers, diagnosing infectious
diseases, cardiac analysis, therapeutic drug monitoring
and allergy testing. Given the necessity to carry out fast,
frequent and accurate blood gas screening and monitoring
for critical patients on ventilator support, including those
that are experiencing a variety of health complications as
a result of COVID-19, blood gas testing machines have medical device manufacturer faced a supplier gap that
become increasingly important. needed to be bridged.
Both of these types of equipment require a plethora of However, this would prove to be extremely challenging.
optical sensors to operate effectively. These include: The company needed to source replacement sensors that own housings. This included all parts of the process, the
l Reflective sensors – these non-contact sensors are were ‘like for like’ both mechanically and electronically. If equipment, as well as specific areas such as injection
used to detect the presence or absence of objects or it didn’t, it would most likely have to conduct lengthy and mould tooling. This was an opportunity to deep dive into
measure the distance to those objects. costly re-verification and re-validation processes due to the internal structure and look at how we might design a
l Slotted optical switches – also called opto switches, the stringent industry requirements and regulations that more effective solution and improve the reliability and
these are devices that are often used as home exist. This challenge was exacerbated due to the robustness.”
position sensors, encoders and safety switches such limitations of the company’s own internal engineering and In one example, the switch was originally
as monitoring if covers/doors are open or closed. R&D teams. Focused predominantly on developing new manufactured by soldering wires directly onto the leads of
l Fibre optic sensors – use optical fibre either as a product designs, the team lacked the bandwidth to deal the optical devices. In a very tight space, this can lead to
sensing element, or as a means of relaying signals with obsolescence issues. short circuits and other long-term reliability complications.
from a remote sensor to the electronics that process Although the company was able to buy remaining “We changed the internal design to a solution based on a
the signals. stock from the supplier to bridge the gap in the short term, very small PCB and standard production practices,” says
l LEDs and photodetectors – these discrete devices can it was keen to find replacement sensors through a new Woodhead. “This led to a more robust and reliable product
be used for everything from position sensing to actual partner, rather than tying up thousands of dollars of stock which was much easier to build. It is far more effective to
diagnostics. that, if not used, could degrade and become unusable, solder multiple discrete optical components into a panel of
Composed of many sequential processes to produce creating unnecessary financial liabilities. And so it turned PCBs using a flow solder process, than to rely on manually
complete electrical or photonic circuits on semiconductor to Pacer International. soldering wires to each leg of the discretes.
wafers, wafer fabrication plants are very expensive to “Taking on a project like this, we firstly needed to A plastic housing for a transmissive IR switch also had
maintain, and in a bid to reduce costs, some companies understand the obsolete products and how those products to be developed. “When we tested the switch separately,
have, in recent years, taken the decision to shelve were used within the context of the medical applications,” it functioned as we would expect, but when the switch
complete production lines. When one of its suppliers says Pacer’s James Woodhead. “Although we couldn’t was inserted into the application, we noticed that there
announced the decision to source any technical data directly from the supplier, the was a light source in the equipment that is used for a
discontinue its entire customer was able to share its own technical diagnostic test that was flooding the switch and causing it
production line of specifications it had created, allowing us to understand to change state,” says Woodhead. “We had to alter the
optoelectronic sensors, one the top-level performance characteristics we needed to design and use an opaque-to-IR plastic to ensure it
align with. functioned correctly.”
“We then needed to consider and review particular Summing up the results of the project, Woodhead
aspects of the application that could not change, as well says: “Improved reliability has led to yield improvements
aspects that could be tweaked before making a decision not only for the customer but within our own internal
as to whether or not we could design a like for like production process, at a realistic level that allows us to
replacement that would align with the customer’s continue to produce the parts. Ultimately, this project was
requirements and be commercially viable. With no specific focused on providing a 100% drop-in replacement that
technical detail on the individual components, we had to meant the customer didn’t have to change anything within
source suitable alternatives that would provide a similar the machines to allow it to work. As well as delivering this
function and output under the same operating conditions. objective, a number of ‘bonus’ design improvements were
“From the design perspective, there was no 3D model identified, developed and implemented along the way,
to work from, therefore we had to look at all parts of the resulting in an even better product.”
mechanical and electronic design in order to design our MORE INFORMATION: www.pacer.co.uk

April 2020 •INDUSTRIAL TECHNOLOGY 11