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Advanced Engineering 2020

NEC, Birmingham(B40 1NT)

04/11/2020 - 05/11/2020

The UK's largest annual advanced manufacturing trade show, Advanced Engineering is your opportunity to (more)

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Bridging the gap when faced with obsolescence

Bridging the gap when faced with obsolescence

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.

Immunoassay analysers can be used in hospital and clinical laboratories to detect the presence and concentration of substances within samples. There are 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 become increasingly important.

Both of these types of equipment require a plethora of optical sensors to operate effectively. These include:

  • Reflective sensors – these non-contact sensors are used to detect the presence or absence of objects or measure the distance to those objects.
  • Slotted optical switches – also called opto switches, these are devices that are often used as home position sensors, encoders and safety switches such as monitoring if covers/doors are open or closed.
  • Fibre optic sensors – use optical fibre either as a sensing element, or as a means of relaying signals from a remote sensor to the electronics that process the signals.
  • LEDs and photodetectors – these discrete devices can be used for everything from position sensing to actual diagnostics.

Composed of many sequential processes to produce complete electrical or photonic circuits on semiconductor wafers, wafer fabrication plants are very expensive to maintain, and in a bid to reduce costs, some companies have, in recent years, taken the decision to shelve complete production lines. When one of its suppliers announced the decision to discontinue its entire production line of optoelectronic sensors, one medical device manufacturer faced a supplier gap that needed to be bridged.

However, this would prove to be extremely challenging.  The company needed to source replacement sensors that were ‘like for like’ both mechanically and electronically. If it didn’t, it would most likely have to conduct lengthy and costly re-verification and re-validation processes due to the stringent industry requirements and regulations that exist. This challenge was exacerbated due to the limitations of the company’s own internal engineering and R&D teams. Focused predominantly on developing new product designs, the team lacked the bandwidth to deal with obsolescence issues.

Although the company was able to buy remaining stock from the supplier to bridge the gap in the short term, it was keen to find replacement sensors through a new partner, rather than tying up thousands of dollars of stock that, if not used, could degrade and become unusable, creating unnecessary financial liabilities. And so it turned to Pacer International.

“Taking on a project like this, we firstly needed to understand the obsolete products and how those products were used within the context of the medical applications,” says Pacer’s James Woodhead. “Although we couldn’t source any technical data directly from the supplier, the customer was able to share its own technical specifications it had created, allowing us to understand the top-level performance characteristics we needed to align with.

“We then needed to consider and review particular aspects of the application that could not change, as well aspects that could be tweaked before making a decision as to whether or not we could design a like for like replacement that would align with the customer’s requirements and be commercially viable. With no specific technical detail on the individual components, we had to source suitable alternatives that would provide a similar function and output under the same operating conditions. 

“From the design perspective, there was no 3D model to work from, therefore we had to look at all parts of the mechanical and electronic design in order to design our own housings. This included all parts of the process, the equipment, as well as specific areas such as injection mould tooling. This was an opportunity to deep dive into the internal structure and look at how we might design a more effective solution and improve the reliability and robustness.”

In one example, the switch was originally manufactured by soldering wires directly onto the leads of the optical devices. In a very tight space, this can lead to short circuits and other long-term reliability complications. “We changed the internal design to a solution based on a very small PCB and standard production practices,” says Woodhead. “This led to a more robust and reliable product which was much easier to build. It is far more effective to solder multiple discrete optical components into a panel of PCBs using a flow solder process, than to rely on manually soldering wires to each leg of the discretes.

A plastic housing for a transmissive IR switch also had to be developed. “When we tested the switch separately, it functioned as we would expect, but when the switch was inserted into the application, we noticed that there was a light source in the equipment that is used for a diagnostic test that was flooding the switch and causing it to change state,” says Woodhead. “We had to alter the design and use an opaque-to-IR plastic to ensure it functioned correctly.”

Summing up the results of the project, Woodhead says: “Improved reliability has led to yield improvements not only for the customer but within our own internal production process, at a realistic level that allows us to continue to produce the parts. Ultimately, this project was focused on providing a 100% drop-in replacement that meant the customer didn’t have to change anything within the machines to allow it to work. As well as delivering this objective, a number of ‘bonus’ design improvements were identified, developed and implemented along the way, resulting in an even better product.”

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