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In order to provide a better adhesion in polymeric 3D prints together with Zbigniew Skok we created a custom designs and some concepts for nozzle shapes and possible filament additives that potentially can improve layer-to-layer adhesion strenght.
3D printing today is a developing technology that faces many major challenges. One of the most important is the interlayer adhesion. In the process called FDM printing (Fused Deposition Modeling) the extruder pumps out molten polymer and puts one thin layer of it over another. Making the extruded material to stack up and produce a three dimensional plastic part.
It is this stacking up that may lead to issues if one layer does not stick to the previous one strong enough. These adhesion forces in between the layers determine the overall part quality and durability. Printer settings are not the only factor responsible for this quality. It can be further adjusted by selecting a specific nozzle diameter (ranging from 0.25 to 1 mm typically), which can help in optimizing time (larger nozzle prints faster) and detail of the print (smaller nozzle will be able to print better small details).
Overall a print procedure can be summarized in following points:
Creating a 3D model in CAD program
Slicing the model in a slicer program. Slicer splits the model into smaller, printable sections and creates a g-code, which is a direction of nozzle path for the printer
In slicer speed, precision, print temperature, material declaration, infill and layer height is declared
G-code is transferred to the printer
Printer heats up the filament in the extruder and pushes it out through the nozzle, which usually has a round hole to push through
In this research a design of custom 0.6 diameter nozzle was tested against its classic, round counterparts.
The custom nozzle was designed to extrude a filament with a different cross-section shape than circle in order to increase the contact surface area in between the layers. This approach is similar to many biomimetic solutions such as the way beeswax is made and how geckos’ feet work, which is with maximizing surface contact.
Standard PRUSA nozzle
Broken sample after tensile test
The initial results for this solution proved that our custom nozzle produces mechanically better prints at steep printing angles (3 point bending test) and has increased tensile strength of printed single layers. The printing was carried on several different speed levels and g-code settings.
Most importantly the design did not clog nor presented any significant difficulty during the printing process at PRUSA i3MKS printer. The classic nozzle had larger issues and spilled filamet while printing the steep and difficult shapes.
The full analysis of the nozzles performence should be conducted in the future, as current amount of testing for this solution was limited and on budget.
In conclusion this project has the potential to improve printing process and demonstrably does not harm nor impare it.
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