Pellets
Pellets are loaded into the hopper and enter the extruder's feed zone. At this stage, the material consists of separate solid particles.
Material state: solid pellets.
FGF PRO / TECHNOLOGY
How 3D printingfrom pelletsworks
FGF is a technology for printing directly from polymer pellets. Inside the extruder, heat from the heaters melts the material, while a rotating screw feeds it toward the nozzle. The printer deposits the melt layer by layer to form a part from a digital model.
From pellets
to a finished part
What happens to the material inside the extruder and during printing — step by step.
Feeding
The rotating screw takes up the pellets and moves them toward the heated part of the extruder. Its job is to move the material further along the channel.
Material state: solid pellets moving through the channel.
Heating
In the transition region near the heat break, the pellets warm up. Their surfaces soften and begin to melt, so pellets in contact gradually stick together. Solid regions remain inside them.
Material state: softened surfaces with solid regions inside.
Melt
After the heat break, the material enters the compaction zone. The screw advances and compacts it, reducing the gaps between pellets. Heat gradually melts the remaining solid regions, turning separate pellets into a continuous mass of melt.
Material state: pellets gradually melting.
Nozzle
The material reaches the nozzle as a melt. The screw supplies it, and it flows through the nozzle opening onto the printing surface.
Material state: melt flowing through the nozzle.
Part
The printer deposits material along defined toolpaths. The melt bonds to the previous layer and solidifies as it cools. Successive layers turn the digital model into a finished part.
Material state: a printed layer that retains its shape.
Key advantages
of the technology
More affordable
feedstock
Printing directly from pellets eliminates the intermediate filament manufacturing step. This can reduce material costs, especially for bulky products. The savings depend on the specific polymer, supplier, and purchase volume.
A wide choice
of polymers
Material choice is not limited to the available range of filament. FGF provides access to thermoplastic pellets, including soft elastomers that are difficult to feed as a strand. Compatibility with a specific grade depends on the printer's capabilities.
Potential for high
throughput
A screw extruder can provide a high melt flow rate. Fast printing is possible even with a small nozzle. When the extruder has sufficient capacity, speed depends on the printer's motion system, part geometry, and selected settings.
Using
recycled feedstock
FGF can use suitable recycled feedstock without first making filament. This creates opportunities to return recycled thermoplastics to the production of new products. Suitability depends on the feedstock's composition, condition, and compatibility with the feeding system.
Limitations
of the technology
Flow control depends on the extruder design. The other points also apply to FDM/FFF.
| Characteristic | What it means for the part |
|---|---|
| Flow control and retraction |
Residual pressure after the screw stops can cause oozing and stringing between print sections. Rapidly relieving pressure and restoring stable flow is an engineering challenge in its own right. Retraction effectiveness depends on the extruder design and control system. |
| Balancing throughput and detail |
Increasing nozzle diameter and layer height for higher throughput affects fine features and makes layers more visible. Smooth surfaces and accurate mating features may require post-processing. |
| Strength of interlayer bonding |
Incomplete fusion between adjacent extruded strands and layers, as well as internal voids, can weaken a part. This must be considered when designing load-bearing products and selecting print conditions. |
| Shrinkage and deformation |
Uneven cooling of the polymer can cause warping and deviations from the intended shape. The extent depends on the material, product geometry, and temperature conditions. |
| Supports for overhanging features |
Some overhangs require supports, a different part orientation, or design changes. This affects material use and post-processing. |
Comparison with other
manufacturing technologies
| Criterion | FDM / FFFFilament printing | FGFPellet printing | Injection moldingMolding from pellets |
|---|---|---|---|
| Materials | Thermoplastics supplied as filament: rigid, flexible, and filled. Choice depends on suitable filament availability and the printer's capabilities. | Thermoplastic pellets, including soft elastomers and filled polymers. Choice is not limited to the filament range; the material must be compatible with the extruder and printing conditions. | Thermoplastic pellets, including elastomers and filled polymers. The grade is selected to suit product requirements, mold filling, and equipment capabilities. |
| Production preparation | Preparing the model in a slicer and setting up the print. No mold is required. A modified model can be prepared for the next run. | Preparing the model in a slicer and adjusting extrusion and print settings for the material and nozzle. No mold is required. Design changes are made through the digital model. | Designing and manufacturing a mold, then setting up the process. Changes to product geometry may require modifying or replacing the mold. |
| Geometry | Complex shapes and internal cavities are possible. Overhangs may need supports and access for their removal. Thin walls and fine features depend on the nozzle and print settings. | Complex shapes and internal cavities are possible. Overhangs may need supports and access for their removal. Thin walls and fine features require a suitable nozzle and stable melt flow. | The design must allow the mold to fill and the part to be ejected. Cavities and undercuts can complicate tooling. Thin walls and fine features depend on mold design and melt flowability. |
| Part quality | Accuracy and surface finish depend on the equipment, nozzle, layer height and shrinkage. Layers may be visible. Strength depends on bonding between extruded strands and on print orientation. | Accuracy and surface finish depend on the equipment, nozzle, layer height, shrinkage and extrusion stability. Strength depends on bonding between extruded strands and layers, as well as print orientation. | The surface reproduces the mold texture. Accuracy depends on tooling, shrinkage, and process stability. Weld lines and fiber orientation in filled materials may affect strength. |
| Time to a finished part | Includes preparation, printing, cooling, and any required finishing. Print time depends on the mechanics, toolpaths, and selected settings. Material flow is limited by filament feeding and hotend melting capacity. | Includes preparation, printing, cooling, and any required finishing. Fast printing is possible even with a small nozzle. With sufficient extruder capacity, print time depends on the motion system's speed and acceleration, part geometry, and selected settings. | The first production run includes mold manufacturing and process setup. Once running, products are made through repeated filling, cooling, and ejection cycles. Sprue and flash removal may also be needed. |
| Economics | Feedstock: filament usually costs more than comparable pellets. Setup: preparation and adjustment without mold costs. Product: cost depends on material use, machine time, and finishing. As batch size grows, preparation is spread across more products, but printing each part remains a cost. |
Feedstock: pellets can reduce the material component of production cost. Setup: preparation and adjustment without a mold. Product: the economic outcome depends on feedstock use, throughput, machine time, and finishing. With larger batches, preparation is spread across the whole run, while each part still incurs printing costs. |
Feedstock: pellets. Setup: costs for mold design, manufacture, and process setup. Product: as batch size increases, tooling costs are spread across more parts, while the short production cycle reduces the cost of series production. |
Specific lead times, quality, and production costs are assessed for the chosen material, equipment, product geometry, and batch size.