Extrusion AM Systems

Extrusion-based Additive Manufacturing (AM) systems are subject to several constraints that can affect their efficiency, resolution, and the range of applications they can tackle. Here are some constraints:

• Single-Bead Deposition Limitations: The nature of extrusion-based systems means they deposit material in single beads, which limits the resolution to the width of the extrusion nozzle. This can result in a trade-off between print speed and detail, as finer nozzles can produce higher detail but at a slower rate due to reduced flow rates.

• Flow Rates of Materials: The viscosity and thermal characteristics of the materials being extruded can impose limits on the speed and quality of the print. Materials that do not flow easily or that require very specific temperature control can slow down the printing process and lead to inconsistencies in the final product.

• System Movement Precision: The accuracy of the print is directly related to the precision of the system's mechanical movements. Any backlash, vibration, or imprecision in the stepper motors or rails can lead to defects in the layer alignment and overall print quality.

• Wire Filament vs. Pellet Systems:

  • Wire Filament Systems: These are typically limited to materials that can be formed into filaments, which excludes a wide range of potential printing materials. Filament-based systems can also suffer from issues such as filament tangling, snapping, or jamming.

  • Pellet Systems: While they can potentially use a wider range of materials and are often more cost-effective (as pellets are cheaper than filament), pellet systems can be less precise due to the challenge of consistently metering pellets into the extrusion mechanism. They can also require more force to extrude the material, which might lead to higher wear and tear on the machinery.

• Material Properties: Not all materials are suitable for extrusion-based AM due to their melting properties, strength, or reactivity. For example, high-temperature materials may require specialized extrusion heads that can withstand those temperatures without degrading.

• Support Structures: Overhangs and complex geometries require support structures that can sometimes be difficult to remove or may leave blemishes on the final product, especially if using the same material for supports and the object itself.

• Post-Processing: Many extrusion-based AM parts require significant post-processing, including support removal, surface finishing, and sometimes curing or annealing, which adds time and cost to the manufacturing process.

• Size Limitations: The build volume of the printer confines the size of parts that can be produced, and larger parts may require bonding of smaller sections post-printing, which can compromise structural integrity.

• Speed vs. Quality: There is often a trade-off between the speed of production and the quality of the final print. Higher speeds can lead to imperfections such as poor layer adhesion and lower resolution, while higher quality prints require slower speeds and more material, increasing print time and cost.

These constraints mean that while extrusion-based AM systems are versatile and increasingly popular, they are not universally suitable for all manufacturing applications. Careful consideration of the desired material properties, part geometry, and application requirements is necessary when selecting an AM process for a particular use case.

Multi-material systems in extrusion-based AM technologies are an attempt at overcome many of the constraints of extrusion-based AM systems.

• Multi-material systems offer significant advantages by allowing for the printing of multiple materials and colors within a single object, facilitating complex geometries through soluble supports, and increasing throughput with simultaneous multi-part printing.

• These systems enhance product functionality with the capability to create gradients and hybrid materials, improve productivity by minimizing material-change downtime, and reduce waste with precise support material application.

Although they present complexities and potential cost increases, the benefits they offer make them a powerful tool for innovation in manufacturing and prototyping.

Multi-Material Systems come in all shapes and sizes, many of which are visually demonstrated below:

Kinematic systems for extrusion-based additive manufacturing dictate how the printer moves and positions the extruder to lay down material, ranging from the straightforward linear motion of Cartesian systems, the efficient vertical dynamics of Delta printers, the compact and rapid movement of CoreXY arrangements, to the highly flexible and multi-directional capabilities of robotic arms.

• Each system offers a different balance of precision, speed, build volume, and complexity, significantly influencing the printer's application and performance: