Types of 3D Printing : Variation of FFF Printing: Pellet 3D printing

FDM 3D printing filament is made possible by processing the pellets from thermoplastic resin.
If the pellets could be used directly for printing instead of the filament, the cost will decrease, and additional types of materials can be used. When is it a good decision to choose a pellet 3D printer?

fabWeaver_Main logo

In a previous blog post, we discussed the various types of FFF (Fused Filament Fabrication) printers based on the movement of the print head. One variant of the FFF technology printer uses pellets instead of filaments. Today, let's take a look at this pellet 3D printing process.

Due to the reduced costs and the increased selection of materials, we have seen an increase in pellet 3D printers coming into the market in recent years.

This method is called Pellet Additive Manufacturing (PAM) or Fused Granule Manufacturing (FGF).


Pellet Extrusion Process

To use pellets as a raw material, a different type of extruder is required from the extruder used in FFF printers. As shown in <Fig.1>, the pellets injected through the inlet of the pellet extruder fall from the extruder screw vane along a spiral path by the rotating screw and gravity. The pellets are heated progressively until they reach their melting point (softening zone for amorphous polymers). A screw mechanism rotates to push the softened material out of the nozzle.

Filament Extruder and Pellet Extruder

<Fig 1. Filament Extruder and Pellet Extruder> 

Compared to filament 3D printing, the advantages and disadvantages of pellet 3D printing are:

Advantages of using pellets 

Low cost of materials

Since there is no process to produce filaments from pellets, material costs can be reduced up to 10 times.

Various materials 

Although the selection of filaments is constantly diversifying, there is a greater selection of pellets that are widely used in injection molding. Some of the pellets are difficult to process into filaments. For example, plastics with a high carbon fiber content are brittle and difficult to spool successfully.

 Fast print speed 

The flow rate of a pellet extruder is limited only by the size and speed of the screw. Pellet extruders typically have larger nozzle sizes, so more material can be extruded in less time and at higher flow rates.

Large build size 

Pellets can be continuously fed into the hopper automatically without an interruption in printing, which is useful when printing large objects.

Disadvantages of using pellets 

Resolution and Complexity 

Pellet 3D printing has a lower resolution compared to FFF printing due to the large nozzle size. Also, due to the large tolerances, detailed prints of complex geometries cannot be produced.

Flow control 

Most pellet printers do not process the plastic flowing out of the nozzle while the extruder moves to a new location. To prevent this, the pellet extruder needs to change the direction of the screw at the end of the path, which can damage the extruder.

Thermal management 

When printing with large pellet nozzles, one layer may not cool and solidify enough to support the next layer because the extruded beads may hold too much heat. On the other hand, if the layer time is too long, the previous layer will be too cold to adhere well, resulting in poor layer adhesion.

Huge and Heavy machine

Pellet extrusion systems are relatively heavy and take up a lot of space.

When to choose a pellet printer? 

When high-quality 3D printing is required, such as a high level of resolution and complex geometries, filament printers are still the best choice, even if they are more expensive. However, if you require high speeds, a large build size, are limited to material budget, and can sacrifice resolution and precision, then a pellet 3D printer may be a better choice.


Don't forget to share this post!