What Is Extrusion In 3D Printing?
While 3D printing is considered to be rather new technology, the process of extrusion was first developed in the 80s by S. Scott Crump. In 3D printing applications, the extrusion system can build objects by laying down the printing filament in layers.
“Extrusion” is a term that you may have heard of from folks who talk about 3D printers, but have you really thought about what the extruder in a 3D printer actually does? We thought so too, which is why you’re going to learn all about the extruder and its role in the 3D printer right here. But first, let’s try to understand what the process of extrusion means in the context of 3D printers.
Extrusion is considered to be an additive technology that is used in 3D printing to build models, prototypes, and for production applications. It is the simplest printing technique and is also the most common method used in 3D printing.
Under ASTM International standards organization, the name “extrusion” has been given to the process in which the filament in 3D printers is dispensed via the nozzle. It is also known as “Fused Deposition Modeling.”
The extruder is also called “the cold end” since the filament is cold when it’s passed through the extruder and makes its way to the hot end. There are two types of extrusion systems available in the market today. The lower cost extrusion systems are used along with drive belts and stepper motors to move the plotter system in the 3D printer. However, these low-cost extrusion systems come at the cost of speed as well as accuracy. On the other hand, more expensive 3D printers that use more extrusion systems use lead screws and servo drivers for enhanced precision.
Direct Extruders and Bowden Extruders
Extruders come in two variations - direct extruders and Bowden extruders. Let’s take a closer look at these two types of extruders commonly seen in 3D printers.
The Bowden extruder does not directly attach to the 3D printer’s hot end. Rather, it is a tube called the “Bowden Tube,” which extends from the body of the extruder to the hot end in the 3D printer. The Bowden tube is usually a section of the PTFE tubing. In 3D printers, the filament is restricted to this tube while it travels through to the hot end in the 3D printer.
This type of extruder is attached directly to the hot end of the 3D printer. One of the common mistakes made by first-time 3D printer users is mistaking the direct extruders for direct-drive extruders, which are not necessarily similar. Since the direct drive extruder means the filament drive mechanism has been mounted directly to the motor shaft, both the direct extruder and the Bowden extruder can be considered a direct drive.
Direct Extruder vs. Bowden Extruder
The direct extruder and Bowden extruder are two variants of the extruder that’s used in 3D printers. Both come with their strengths and weaknesses. The following is a quick breakdown of these two types of 3D printer extruders:
Both direct and Bowden extruders have their pros and cons, which is why it is best to consider all of the factors when choosing the type of extruder you want for your 3D printer.
Direct extruders provide better responsiveness because of their short distance from the hot end to the drive mechanism. The shorter distance between the two ensures better retractions. This also means that the direct extruder needs less torque to extrude the filament to the hot end as compared to the Bowden extruder.
In this way, direct extruders translate into better, cleaner prints and do away with many of the issues that operators of 3D printers run into, such as oozing or stringing during the printing process. Another benefit of the direct extruder is that it requires less torque, which means it can work on a smaller motor or a lower current setting on a normal size motor, resulting in better energy saving. This is one of the reasons why direct extruders are normally used for printing with flexible filaments such as PLA or TPU. It should also be noted that direct extruders often use two hot ends, leading to restrictions in print width.
One of the strengths of the Bowden extruder is not having the mass of the body, as in, the gear and motor, etc., that is found in direct extruders riding on the hot-end carriage. This means that the Bowden extruder is able to move more fluidly during the printing process. This translates to better precision and quicker prints. Bowden extruders are easier to adapt to single hot-end multicolor heads.