How to select the best fluids for 3D printing
Venesia Hurtubise, technical chemist for manufacturer MicroCare Medical, talks about how to select the best fluids for 3D printing operations.
As the pressure to produce more complex biomedical parts increases, medical device manufacturing using 3D printing, a subset of additive manufacturing, is gaining widespread acceptance. Initially 3D printing was considered by some manufacturers to be too slow and too expensive to be used on a large scale. However, recent advancements in both software and hardware technologies have lowered the costs and sped up the building process, making 3D printing a viable method for complex medical device manufacturing.
Historically, plastics were used to make the majority of 3D printed medical devices, and that trend continues. Today over 80% of 3D printed parts are made using thermoplastic or thermoset polymers. Metals, ceramics and other composite materials comprise the other 20%. 3D printed polymer parts are manufactured using any variety of 3D printing methods including fused filament fabrication, selective laser sintering, stereolithography, digital light projector or material jetting processes. What all these methods have in common is that the parts are constructed in progressive layers by depositing or extruding polymers, one level at a time, until the parts reach their final shape.
Building the parts is just the beginning of the 3D printing process. Choosing the correct smoothing and cleaning fluid also plays a key role in the successful construction of 3D printed components. Since 3D parts are built progressively, layer-by-layer, the process sometimes leaves the parts with a stepped or terraced surface that requires smoothing to get a finished part.
In order for the smoothing to work without damaging the parts, it is necessary to understand the composition of the polymer parts. Finding the best smoothing fluid can often be a delicate balance between selecting one with a high enough solvency to effectively level out the parts, but not so strong that it damages them or compromises their structural integrity.
In addition to smoothing the parts, the fluid must also be effective at removing soils or particulate left behind from any additional processes. Any stray particulate like dust or shavings are typically non-soluble and will not dissolve in the cleaning fluid. Therefore, the particulate must be removed using displacement cleaning where the cleaning fluid gets under the particulate, dissipates any static charge and lifts it off the surface. The key to effective displacement cleaning is to use a dense, heavy fluid that floats the particles of dust and dirt off the substrate surfaces. Today’s modern fluids are typically 20% heavier than water and 50% heavier than alcohol, making them an ideal choice for displacement cleaning of 3D printed polymer devices.
An added advantage of using a chemical-based fluid for smoothing and cleaning 3D printed medical devices is that it creates a nonpyrogenic environment and can significantly reduce the risk of bioburden. Modern day cleaning fluids dry very quickly and completely therefore leaving no residues on parts after they exit the vapor degreaser. This process offers an easy way for engineers to validate bioburden issues out of the 3D printing process. The modern-day 3D printing post-processing fluids are also nonflammable and safe for use in heated machines, cold operations or in ambient temperatures.
Today, the medical device manufacturing industry is in a constant state of flux with new designs being developed daily. Post-processing using specialty fluids can help to make plastic 3D printing a viable option within the medical device industry. It is essential to work with a partner that has particular experience and expertise in specialty cleaning fluids for 3D printed polymers and vapor degreasing technologies. They can guide part designers through the post-processing steps and recommend the fluids and methods that will work best.