Why direct drive is not automatically better than bowden tube

More and more direct drive kits are available for 3D printers, so you be forgiven for assuming direct drive is easily superior to bowden tube. In this video we explore the merits for each design, including when and why you might like to convert between the two and why modern direct drive advancements are negating the downsides.

0:00 Introduction
0:44 Direct drive and bowden tube 3d printers explained
4:10 Strengths and weaknesses of each setup
7:17 Reasons to convert to bowden tube
9:00 Reasons to convert to direct drive
10:05 Why do many new 3D printers currently use a bowden tube?
10:45 Why are direct drive conversions becoming so popular?
12:01 The hybrid: cable drive extruders
12:39 Conclusion: Which do you prefer?

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[hockeyguy]

One reason to convert to direct drive that was not mentioned explicitly in the video is the ability to print flexible filaments like TPU. These are very difficult to get working properly in a bowden setup.

[mistaecco]

This is super odd to me... I got into 3d printing back when just about everyone had direct drive, and the hype was all about converting to bowden to make your toolhead lighter. I did the John Lawrence bowden conversion on my printrbot back then, and it made a huge difference. Very interesting to see that these days, the cheap printers and general build conventions seem to make bowden builds so much more standard!

[skaboodlydoodle]

I've owned almost a dozen 3d printers over the years and I've upgraded pretty much every one of them to direct drive with absolutely no perceivable drawbacks. I don't get noticeable ghosting/ringing and at this point in my experience that single downside to direct drive almost sounds like a myth. The weight of the print head seems to have very little effect on the overall quality of my prints even at some of the faster speeds.
There are so many pros to direct drive and the only con can be incredibly relative.

Pros:
-consistent extrusion
-less tweaking of settings
-little to no stringing
-easier to print flexible filament
-easier to load/unload filament (something a lot of people don't talk about)

Cons:
-increased ghosting (maybe?/not always)

In my experience and in a lot of my friend's experience, converting to direct drive has pretty much always been a universal improvement. I'm at the point that I really don't understand why so many printers come with a stock bowden setup at all. On top of that there's a lot of direct drive setups now that are very lightweight so that eliminates the only remaining downside of the arrangement. I think in reality direct drive IS inherently better and it's only downside isn't even entirely inherent to all direct drive setups.

[oleurgast]

Nice video. There is one point that's missing in my opinion: Linear Preasure Advance vs. s-Curve Acceleration. Sadly you can not use both at the same time. Linear Preasure Advance compensates for the delay between changes in feeder movement and reaction of the hotend, improving print quality (sharper edges). The correction you need is much higher on bowden setups, so it is much more needed there, while on direct drive the effect is much less. As you have to calibrate each type of filament anyway, Linear Preasure Advance is not very comfortable to use - so with a direct extruder you can get still good results without spending time for adjusting it.

s-Curve Accelaration smooths out the acceleration, which reduces ringing esp. on heavy y-moving printbeds. So with printers beyond 200by200 mm² size it is a very nice feature to activate.

So on printers with y-moving bed ("bedshakers") it is more interesting to use s-Curve Acceleration than using Linear Preasure Advance, if you use a direct drive. If you also want a very flat bed (thick milled casted aluminium) this also aplys to smaler printers. So on bedshaker-design you should always consider direct drive. A bowden setup is senseless (exept for very smal printers).

With Deltas and z-moving bed (or z-moving x-y-gantry) a bowden setup is much more interesting vs. classic direct extruders, as the low moving mass is much more important (and there is no need for sCurve). Of course, with modern extruders like the Orbiter you can use the advantages of a direct extruder, ( I am quite happy you pointed that out in your video), while increasing weight only a bit. You might use a little less speed there - but for printing time over all, this might be already mostly be compensated by the less retraction you need. Anyway, with the most limiting factor in printspeed on this types of printers for PLA being the part cooling, the little mass added by an orbiter might not be relevant at all...

In my opinion Creality mostly use bowden extruders to use single z, to reduce the cost. Which is O.K. fo make it more affordable, but as you can upgrade to dual-z for about $15 it is the one upgrade I recommend strongly before changeing to a direct extruder.

P.S.: I do not totaly comply with the definitions of the parts. "Extruder" by definition is the complete unit that extrudes the filament, beginning with the feeder, through the bowden tube (on a bowden extruder or inside some of the direct extruders) and the hotend. So it starts at entry of the feeder and ends at the nozzle. I prefer using this definition, as while "extruder" in 3d printing often is used as synonym to the feeder, this is not the case in other technics like injection molding. So it avoids confusion if you use "Extruder" for the whole (like "Bowden Extruder" and "Direct Extruder"), but feeder, bowden and hotend if you refer to the single parts. So in my opinion "Bondtech BMG extruder" is not an extruder, but a "Bondtech BMG feeder", as it is not the whole extruder but only a part of it.
It can become very confusing, if you sometimes the word "extruder" for the whole, but sometimes only for one part. I struggled a lot with this as I got into 3d printing...

[blockhead]

Direct and to the point, like I pefer my extruders.

[CanuckCreator]

Swapped all my printers from bowden to DD and wont be going back
The easier tuning, quicker retracts (they add up over time) and more responsive flow control make up for any minor downsides
As for weight, sure on a single z bedflinger its an issue, but any well built modern machine with properly tuned modern firmware can handle it.
Im slinging around a LGX, hotend, dual fans, dual MGN9 carriages, bed probe etc on machines with klipper and input shaper (which is also comming to RRF) and pushing near 7k accel for some moves at print speeds of 140mm/s (flow rate capped)

[johnkim]

Bowden seems to be a cost-cutting measure of printer manufactures. lower mass means getting away with flimsier frames. Also, the design time of the extruding system can be greatly reduced with a Bowden because one does not need to squeeze numerous parts and mechanisms in a small print head. ^^

[soggynode]

Nice explanation and comparison. I have an Ender 3, an Ender 3 Max and a CR-10 S4 and they all print beautifully with Bowden setups. The filament is easy to load, I have good access to the hotend when it's time to do a bit of maintenance and the cost to replace worn parts is minimal. I certainly wouldn't say a Bowden setup is better than a direct drive but right now, I don't have a problem or need that changing to a direct drive would address.

[wabvr]

I think the main benefit of direct drive is that you can use flexible filaments.

[nonchip]

i think the issue why the "hybrid" option isn't as common is that it's hard to imagine a rotational drive cable to be any more rigid when it comes to e.g. retraction inaccuracies than the tiny bit of flex in a decently sized bowden tube. it's simply another possible source of error

[MattewGames]

Switched from a Bowden to a direct drive a year ago and never thought about changing the retraction distance, Thanks for opening my eyes about this!

[johnkosh]

Your explanation of a direct drive and bowden tube is spot on. Also the fact that you showed what "ringing" was makes it much clearer why we may need to upgrade to a different drive. For now my creality CR-10 printer I use a bowden tube, but I keep it as short as possible. This appears to help with retraction. Thanks for all you do, keep the videos coming!!

[shrimp_bucket]

I always end up finding your videos being the most education and in depth while sticking to the point. Thank you for all you do! You've definitely been my favorite channel when it comes to 3D printing

[kieranclarke]

Great video as always Michael. I have no issues with my current bowden setup after putting over 5 kg of PLA and TPU through it with only having two blockages in all that use.

[cklid]

Direct drive conversion on my Ender 5 Pro was a game changer to remove at least 90% stringing. Huge benefit for my setup.

[oliknow]

converted my Creality to direct drive. Motion system is plenty powerful, accuracy is still good, I had no negatives but positives. Now I have less spare parts around, overall less stringy prints and filament doesn't kink anymore, neither gets brittle in the tube anymore. For me at least, only benefits

[jeffb]

@10:10 Why do some manufacturers prefer bowen? Cost. Many printers have only one stepper motor on the Z-axis. Essentially, a cantilever. When a direct dive is used, the forces are greater due the the increased weight, and a second Z-axis motor is needed. Using a bowden drive with its less weight means a company can do away with the second Z-axis stepper motor.

[dakota.zimmerman]

One thing that isn't mentioned that I feel should be considered is maintenance. Direct drive setups are a pain to replace the short bowden tube piece. I print with PETG 24/7 and figured I would try direct drive on one of my Ender 3 Pros. About once a week I have to replace the PTFE tube as it gets burned through near the nozzle with the higher temps and constantly disassembling the direct drive setup was annoying. I also tried an all metal hotend to get the PTFE tube away from the nozzle entirely but that introduced more problems that I couldn't ever completely sort out. I converted back to the factory bowden setup and now I can simply pull the bowden out of the hotend, snip it off, and shove it back in and have zero printing issues. I just listen for the extruder skipping and know its time to snip the tube. Went from a 10-15 minute tube replacement (also had to redo the Z-offset) with direct drive, to a 10 second bowden tube snip on the factory bowden setup. Anyone running higher temp filaments should consider this before converting to direct drive. For PLA and TPU direct drive is fine because you wont be replacing the tube much.

Even for flexibles I run bowden tube, just drill the extruder housing out and cut a V shape in a small piece of PTFE tube and shove it on the back side of the extruder gears. No binding or spitting the TPU out the side of the extruder. I honestly probably won't mess with direct drive again unless I start buying Prusa printers.

[OldCurmudgeonDP]

Glad you mentioned the Y axis on "i3" designs being the limiting factor for ringing.
Pancake steppers on gear drive extruders and printed mounts (instead of machined AL) go a long way to lightening the X loading as well.

[Jacon]

I'd love to see some crazy developments in flex drive extruders like we're seeing now in DD. The concept is awesome, but it still has a long way to go to become superior.