The Challenge Faced in a Medical Environment

The company produce immunoassay analysers, used in hospital and clinical laboratories to detect the presence and concentration of substances within samples, and also blood gas screening and monitoring machines. Both types of equipment require a plethora of optical sensors to operate effectively. These include:

  • Reflective sensors – non-contact sensors 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.

The discontinuation would prove to be extremely challenging. The company needed to source replacement sensors that were ‘like for like’ both mechanically and electronically, in order to avoid lengthy and costly re-verification and re-validation processes due to the stringent industry requirements and regulations that exist. The company’s own internal engineering and R&D teams were also focused predominantly on developing new product designs, and lacked the bandwidth to deal with obsolescence issues.

The company was keen to find replacement sensors through a new partner, rather than investing in a large last-time-buy of stock that could degrade and become unusable – and so they turned to Pacer.

“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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