Blower for ventilators: Faster with 3D printing

Introduction

Despite years of experience in ventilation technology, IMT, like many others, encountered new problems during the COVID-19 pandemic. The increased demand for ventilators and accessories, along with political decisions and disrupted supply chains, made it difficult to provide equipment.

Confronted with this situation, IMT decided to develop a ventilator using available components. This was done with the aim of bringing the device to market with an exceptional license in case of a ventilator shortage in Switzerland. Fortunately, this scenario never occurred, but the device was still developed within a few months.

The high demands on ventilator components further limited the choice of available parts. The blower, as a fan wheel or turbine, is a central component, and its limited availability necessitated the development of a separate blower. The requirements for such a blower include speeds up to 60’000 rpm, service life of several 10’000 hours, temperature range from -20 °C to +60 °C, vibrations up to 15G rms, biocompatibility and, of course, manufacturability in relevant quantities and delivery times.

Sophisticated design reduces material and components

The high flexibility offered by additive manufacturing, combined with availability and the targeted quantities, led to the selection of this process. Within a very short time, a working prototype was developed according to the motto “Fail fast, fail early”. This short development time was supported by a combined approach of innovative engineering and design. The greatest risks were dealt with early and, where possible, in parallel to keep the development time to a minimum.

In addition to the actual function as a blower, the design focused on manufacturability and assembly. The slogan “think additive” was consistently implemented in detail to minimize material, number of components, and lead time. Design iterations within two days were only possible by choosing additive manufacturing and reliable suppliers. With a single post-processing for an interference fit, all additively manufactured parts could be joined without adhesives or welding.

According to data sheets, two materials and 3D printing technologies were considered that met all requirements on paper. Measurements of VVOC emissions (Volatile Organic Compounds) then narrowed them down to one process and material. This was examined for relevant properties such as tensile strength and creep behavior. Material samples were subjected to accelerated aging and periodically tested. Other important factors were the manufacturing tolerances and the dispersion of these within the design space of the 3D printer. For quality assurance, the nesting of the parts was defined along with a reference piece and tensile specimens. These are distributed in the build space according to a defined pattern and must be measured for each batch.

The printed parts were then measured by CT and compared with the manufacturer’s specifications regarding manufacturing tolerance. It was found that the dimensional accuracy was not homogeneous, but this could be taken into account in the design by widening the profile tolerances. Since the blower design was already designed for additive manufacturing, no changes had to be made to the design despite this.

Process validation and test stand for the blower

With the design complete, process validation of the additive manufacturing process began, analog to the injection molding process. Specifically, IQ, OQ, and PQ were performed and cmk values ≥=1.33 were achieved.

To guarantee the required service life, a test rig was developed on which 32 blowers were tested with different operating patterns. This was done under elevated temperature and electrical voltage to simulate the worst case. The specified cyclic life was exceeded by several times. Further, the blower specifications were achieved without reservation during a Highly accelerated life test (HALT) performed in an external laboratory.

This project demonstrated that additive manufacturing can be used for highly dynamically loaded parts in medical technology, provided there is a process-compliant design and full validation of both the design and manufacturing processes.

IMT successfully tackled the challenges of additive manufacturing in medical technology to develop a blower for patient ventilators. Despite high requirements, such as biocompatibility, we developed a functional prototype in a very short time. Combining classical engineering and design we reduced the use of materials and components as well as minimized the development time. Comprehensive validation processes and test rigs ensured quality assurance.

Are you interested in innovative solutions for your own medical technology challenges? Contact our experts at IMT to find out how our innovative approaches can help your company overcome similar problems.