In this blog, we’re diving deep into tuning 3D printed geometries, specifically focusing on a wheel designed for the Mars Rover SLH helicopter drone. This project, developed in collaboration with Caltech, involved extensive testing with different materials, including carbon fiber nylon, to ensure optimal performance in harsh environments.
Understanding the Geometry
The Mars Rover wheel’s design is intricate, with several complex geometrical features. A key element is the wheel hub, which connects the motor to the wheel. During printing, the hub’s mounting holes were intentionally covered with 200 microns of material to ensure a clean and precise print, avoiding support interference. Once printed, the extra layer of material can be easily removed to expose the mounting holes, ensuring the final part remains strong and well-defined.
Using Partial Prints to Fine-Tune Parameters
Before printing full parts, testing partial prints can save time and resources. By slicing sections of the design, we were able to analyze specific areas and fine-tune critical factors such as the extrusion multiplier. For example, increasing the extrusion multiplier to 115% resulted in better layer adhesion, creating a solid and robust final part.
Challenges Mars Rover wheel with Complex Wheel Geometry
Printing complex geometries like the Mars Rover wheel presented several challenges, particularly with overhangs and ensuring tight dimensional accuracy. Certain overhangs led to rough surface finishes due to moisture absorption in the filament. This was resolved by drying the filament properly to eliminate steam bubbles, which cause rough, matte surfaces and stringing.
Proper Filament Drying Techniques
Filament drying is crucial to achieving high-quality prints. Hygroscopic filaments like nylon can absorb moisture quickly, leading to printing defects. While some filaments can be dried by leaving them in the chamber overnight, for high-performance materials like carbon fiber nylon, a vacuum chamber or vacuum oven is recommended. This process ensures the filament is bone-dry before printing, preventing moisture-related issues like steam bubbles and poor layer adhesion.
Thermal Mass and Layer Adhesion
Maintaining proper thermal mass is vital when printing materials like polycarbonate and nylon. The heated chamber keeps the part warm, allowing layers to adhere more effectively as the print progresses. In testing, we identified that smaller parts appeared “melty” due to excessive heat, but this issue was less critical when printing larger sections of the part. By fine-tuning the heated chamber and cooling cycle, we achieved strong, consistent results with excellent layer adhesion.
Optimizing Support Structures
Support structures can significantly impact print quality and time. While dual extrusion with soluble supports offers a near-perfect surface finish, it also increases complexity and print duration. Instead, designing parts to minimize or eliminate supports, or carefully tuning the support interface layer, can save time and material while still achieving a high-quality result.
Iterative Testing for Mechanical Strength
Iterative testing is essential to ensure mechanical strength in 3D printed parts. By breaking test prints and analyzing failure points, we confirmed that strong layer adhesion was achieved, leading to parts that perform well under stress without breaking along the layer lines. This is particularly important for components like the Mars Rover wheel, where structural integrity is critical.
Final Thoughts on 3D Printing Complex Geometries
3D printing high-performance materials like carbon fiber nylon requires careful tuning of parameters, from filament drying to extrusion settings, to achieve both strong and visually appealing parts. The ability to iterate quickly and adjust for both aesthetic and mechanical needs makes additive manufacturing a powerful tool in modern engineering.
Interested in learning more about 3D printing for complex geometries or engineering materials? Contact us today to explore how advanced 3D printers can revolutionize your manufacturing process.