MEDICAL PORTESCAP
could be limited to ensuring that the torque and speed requirements can be achieved. This depends on the load, such as the viscosity of the drug, and the force with which the motion system must drive it. Even for applications when dosing precision required to balance cost, as well as size, which is important for ergonomic suitability. For reusable devices to withstand the rigors of
day-to-day use, they must also be durable, which also includes sterilisability. Reusable medical devices that come into close patient contact or provide invasive treatment must undergo an autoclave process, but this capability is dependent on the setting of use. will likely have autoclave facilities on-site, devices for community clinics or home use may instead need to be disposable to ensure hygiene and safety.
Reusable devices are inherently more sustainable from an environmental perspective. This means less waste, while for disposable devices, considerations over recyclability must also be made. However, design choice also needs to be based on economic sustainability. Reusable devices must be more durable, meaning they’re typically more expensive, yet value can be achieved through long-term use.
MOTOR TECHNOLOGY OPTIONS For disposable devices, a miniature brushed DC motor is the typical choice, although this motor type can also be applied to reusable applications. It’s a cost-effective
22 December/January 2025 Irish Manufacturing
design, combined with the capability to achieve the appropriate torque density suitable for a range of applications. Alternatively, stepper motors achieve precise steps. Important for drug delivery systems, stepper motors also retain their accuracy over with each current pulse, they don’t require a feedback device as their position is always achieved if sized properly. Stepper motors achieve higher torque at lower
speed, while if greater speed is required, brushless DC (BLDC) motors are the optimum choice. Removing the physical means of commutation, the BLDC motor instead relies on electronics, which optimises control precision as well as achieve a smaller footprint, ideal for ergonomic optimise battery use.
Gearheads are often required for applications demanding higher torque and lower speeds. Standard gearboxes might be appropriate for
disposable devices, given their typical rating that covers typical application requirements. However, for reusable designs, customisation enables form based on the anticipated number of operating hours and sterilisation cycles.
CUSTOMISATION FOR DISPOSABLE AND REUSABLE DESIGNS Even for disposable designs, motion system customisation can be preferable. Dependent on the materials and design, customised solutions can reach an improved scale of economy when a certain production volume is reached. However, when designing a medical device to or form factor, as is often required for reusable devices, customisation is typically recommended. This approach ensures a motion system with the
can involve customisable off-the-shelf (COTS) products, through to bespoke motion system development.
While the latter is more extensive, it can ultimately achieve the most cost- effective, well-performing system. demand close support from a motion specialist, and evaluating the design from the concept phase is essential to streamline development. Yet, even when less extensive customisation is required, establishing a
partnership with a motion specialist at an early stage is the most effective way of developing design.
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