In FDM 3D printing, a filament is pushed into the hot end to melt by an extruder. There are two types of extruder set up, Bowden and Direct Drive. Both types follow the same principle of a flat wheel and a toothed wheel that grips the filament to push it to and through the nozzle.
In a Bowden system, the extruder sits on the frame of the printer, typically on one end of the print arm, and feeds the filament to the print head through a PTFE Bowden tube. The extruder sits directly above the hot end on the print head itself; no PTFE tube is required, though some printers use one to guide the filament to the extruder. Generally, the direct drive extruder system is considered superior, but the Bowden approach does offer some benefits.
By mounting the extruder and its motor to the frame, the weight of the print head is minimized. This approach reduces the amount of momentum the print head has, increasing the stability. The increase in stability decreases the likelihood of ringing artifacts caused by wobbling in the X- and Y-axis. It’s also possible to move the print head faster without losing quality. Mounting the extruder separately on the frame means that the size of the print head can be minimized.
In some designs, this can mean a slight increase in vertical build volume. The use of a PTFE tube does add a small amount of friction. This means that a Bowden extruder needs a more powerful motor. Flexible filaments and abrasive composite filaments have a higher chance of bonding to or wearing the PTFE tube. This can potentially cause damage and blockages.
Direct Drive Extruders
The proximity of the extruder to the nozzle in a direct drive arrangement means that the filament can be more easily pushed through the nozzle. The proximity to the nozzle also helps with retractions, especially with flexible filaments. The short distance between the extruder and nozzle also means that the motor doesn’t need to be as powerful, making them cheaper and lighter.
Even with the reduced weight, placing the weight on the print head makes it harder to move and more likely to wobble, leading to print artifacts. This is especially an issue when printing faster. In many direct-drive designs, the extruder is mounted on the print head makes it significantly trickier to access some parts to perform maintenance. Direct drive extruders also can’t be used on Delta printers.
Do you have a preference for direct drive or Bowden extruders? Both extruder systems are perfectly functional in the real world, with only minor differences in performance and issues faced. Let us know why down below.