Glossary · Part

3D printing

Extruder

The drive that grips the plastic strand and pushes it evenly into the print head.

Explained in more detail

Gears, often two counter-rotating ones (dual gear), clamp the filament and feed it at a defined speed. Gearboxes (for example 3:1 or 10:1) increase force and resolution. Key figures are the rotation distance or E-steps and the maximum pushing force. There are two designs: direct drive (extruder directly above the hotend) and Bowden (extruder on the frame, filament runs through a PTFE tube).

Where does the term come from?

From Latin extrudere, "to thrust out". In plastics processing, pressing material through a shaping opening has long been called extrusion, and 3D printing took the term from there.

In practice

• If the extruder clicks or rattles, the drive gear is slipping. Common causes: a partially clogged nozzle, a temperature that is too low or a speed that is too high.
• The contact pressure must be right: too tight crushes soft filament, too loose lets it slip.
• After a conversion, check E-steps or rotation distance: have 100 mm of filament fed and measure how much was actually drawn in.
• Plastic abrasion gradually lodges in the teeth of the drive gears. Clean them with a small brush during maintenance.

Not to be confused

In everyday speech the whole print head is often called the extruder. Strictly speaking, only the drive is meant, while melting is done by the hotend.

Frequently asked questions

Why is my extruder clicking?

The clicking happens when the drive gear slips because the filament is not getting through the nozzle fast enough. Check in turn for a clog, nozzle temperature, print speed and whether the nozzle is too close to the bed on the first layer.

Which is better, direct drive or Bowden?

Direct drive feeds soft filaments such as TPU reliably and manages with short retraction, which is why it is standard on new printers. Bowden keeps the print head light, but needs longer retractions and struggles with TPU.