Dual Geared Extruder

When it comes to FDM 3D printing, one of the most important pieces of hardware is the extruder. While the older Prusa based cartesian printers with moving build platforms were limited in speed mainly due to larger moving masses, new printer designs are capable of reaching much higher travel speeds without sacrificing precision. On these new FDM printer designs, the limiting factor has become the extruder responsible for positioning the filament for accurate material deposition.

These new 3D printers running H-bot, Core-XY or delta configurations can reach travel speeds of 200mm/s. Most extruder configurations can only manage around 20 mm3/s on a 0.4mm nozzle before experiencing failure due to stripping or hotend clog. For this reason, these extruders will fail when running a 0.4mm nozzle at 200mm/s and 0.3mm layer heights as this will require a maximum of 24 mm3/s. Similarly, a standard extruder can typically manage 28mm3/s on a 0.6mm nozzle before failing. However, if you run a 0.6mm nozzle at 200mm/s and 0.4mm layer heights you will need 48mm3/s. This is why most modern printers have a top print speed of 120-150mm/s while having a maximum travel speed of 200mm/s or more.

Last year we set about finding a solution to this bottleneck by developing our dual geared extruder drive. Initial tests pitting the dual geared extruder up against a standard direct-drive herringbone geared extruder have been very promising. The friction force responsible for driving the filament is increased by 72% on the dual geared extruder compared to the single geared extruder. This means that a direct retrofit with any modern direct drive 3D printer would unlock 200mm/s print speeds and extrusion rates of up to 48mm3/s without sacrificing accuracy.

When printing at higher speeds, the goal is to have the lowest moving mass possible. Many new 3D printer designs now incorporate a bowden design consisting of a remotely mounted extrusion drive connecting to the hotend via flexible tubing. The problem with printing with this system at high speeds is the added quality issues that come with the hysteresis which accumulates along the tubed section between the extruder and the hotend. For this reason we have designed our dual geared extruder with direct drive configurations in mind. When compared to a standard herringbone geared extruder found on many direct drive configurations, our dual geared extruder provides an overall weight reduction of 9%. So not only does the dual geared extruder unlock high flow-rate, it also provides enhanced accuracy by reducing moving mass on direct drive configurations.