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A Bowden tube extruder (like the stock one on an Ender 3) is known to have issues with printing the most flexible TPU, and with filaments that (either due to composition or condition) don't take well to too much retraction -- though the latter can be ameliorated somewhat with slicer settings. Direct drive extruders, on the other hand, by reducing the extruder to hot end distance to the practical minimum, greatly reduce the amount of retraction needed as well as the effect of filament compression and stretching.

One potential down side I'm aware of is that putting the extruder stepper and drive on the X carriage adds mass that the X drive motor has to both accelerate and decelerate; this could in theory have an effect on print quality, increasing ringing and overrun on the X axis (though this isn't generally a problem with the steppers used on the Ender 3 and similar printers).

What other reasons might there be to prefer a Bowden tube over direct drive?

Zeiss Ikon
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2 Answers2

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There are really no reasons not to convert to direct drive, provided you use a good one. Many of the direct drive kits, especially the ones that reuse the existing giant NEMA-17 stepper, are not very good and have tradeoffs due to excessive mass on the toolhead, imbalanced mass, interference with frame reducing print volume, etc. The modern way to do direct drive is with a "pancake" stepper far smaller and lighter, and gearing between 3:1 and 6:1 reduction to get the needed torque - look at the Orbiter, Sherpa Mini, etc. - or even a remote direct drive.

Teaching Tech recently posted a video on this very topic, titled Why direct drive is not automatically better than bowden tube but then pretty much concluding that all the old reasons not to go direct drive no longer apply.

R.. GitHub STOP HELPING ICE
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Other than higher carriage mass as you already noted, the only other reason to not go with Direct Drive over Bowden is the higher level of maintenance required. In most cases Direct Drive will provide advantages such as increasing the maximum flow speed, enabling the use of Linear/Pressure Advance, shortening Retraction moves, and better resistance to obstructions in the filament path, and more reliable printing of flexibles as you have already noted. As well, A direct drive system would allow a less-powerful stepper motor to be used, which cuts down on the carriage mass problem.

craftxbox
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