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Precision Motors for Medical Infusion Systems

March 2, 2021

Precision Motors for Medical Infusion Systems


Portescap offers a range of motor technologies and accessories that enable innovation for Medical Infusion Systems. Whether it is a DC Coreless solution that utilizes its high efficiency to extend battery life or a stepper linear actuator that applies its mechanical precision for accurate dosing, Portescap marries the desired patient benefits to the infusion system requirements to create the optimum design. The addition of gearboxes and encoders provide flexibility in size, weight, and feedback for the motion solution.

Infusion system requirements differ based on the device being developed, so choosing the right motor technology and accessories can be challenging in the early stages of development. This blog series will cover the range of applications in Infusion systems, reviewing the needs of the patient translated into the requirements of the device, and how the motor technologies align to those needs and the benefits each brings forward.

Hospital Infusion Pumps

Infusion pumps in hospitals are designed to provide the patient with the proper dosing of drug, whether for resolving a current malady or sustaining life. The drug delivery is provided by a drive mechanism which includes a motion composite, typically a motor with encoder and gearbox. There are various requirements of the pump that reflect to the drive mechanism. This post will cover some of the main requirements and how an example motion solution, a 16 mm DC motor /gearbox/encoder, impacts the performance.

The key for an infusion pump is precise and accurate delivery. As drugs have different delivery profiles to the patient, the drive mechanism must handle a range of flow rates with high accuracy. The selection of the gear ratio is critical to enable the motion solution to cover from low to high flow rates. Choosing a high gear ratio may seem best but that requires a high motor speed when delivering the drug at the highest flow rates. A high motor speed impacts the noise and life of the motor, so an optimum gear ratio keeps the speed of the motor within the spec range while keeping the current draw of the motor at a minimum. The accuracy of the delivery can be monitored using an encoder, to ensure that the commanded delivery amount is achieved. With resolutions up to 1,204 the proper CPR can be calculated based on the selected gear ratio.

With the infusion pump being bedside in a quiet ambient environment, noise is a critical parameter to not disturb the patient. A DC coreless motor, based on the ironless rotor design, provides minimal noise during operation. The operational speed of the motor will have an impact on the noise produced, lower speeds producing less audible noise. For the gearbox, selecting a spur arrangement will provide lower noise than a planetary, based on fewer points of contact during rotation. The material selection of the gears will also help with the noise, plastic providing a lower noise profile than metal.

The infusion pump is designed to provide years of drug delivery in the hospital room, requiring the motion solution to maintain performance over the course of the pump life. For the DC motor, a high-quality precious metal commutation system delivers low brush wear to maintain operation. Within the gearbox, the material selection for the gears will influence their life. Plastic gears will be more subject to wear based on the material strength, so metal gears are typical to meet the lifetime.

The selection of the motion solution for a Hospital Infusion Pump is significant to meet the performance and life requirements. Contact a Portescap Engineer to review your requirements and let us guide you to the optimum solution.