I've been trying to figure out if bowden extrusion is a good option. I've read lots of people's opinions online - some say it makes for much better quality prints, but others say it has worse printing. For me, I'm don't care about the potential speed increase - just the quality of the print and the amount of troubleshooting/adjusting needed post-setup.

Is the difference in opinion just because it takes a lot of work to get bowden extrusion to work better than direct drive? Many of the opinions I've read are dated, so I'm wondering if Bowden extrusion is much more reliable nowadays or easier to implement now that there has been more people using it. Maybe there's a good way nowadays to fight hysteresis and ooze.

Lets say I went with bowden extrusion for building my own printer. Once I work out all the kinks and figure out the right slicing settings, will bowden extrusion work well for a long time in the future, or will it occasionally mess up and require me to troubleshoot it in the long run? I want something that will last a long time with no adjustments needed for a long time after optimizing it.


Just as a reference, here is some info I've compiled.

Bowden:
- The Good
○ Removes weight (meaning can get faster prints)
○ Higher quality from less vibration transmittance
- The Bad
○ Hysteresis from filament friction/slapping on tube.
○ String/Blobs
○ Difficult to print flexible filaments (ninjaflex, PVA, etc…)
○ More prone to mechanical failure ("bowden popping off")
- Other info
- Can fight ooze with smaller nozzle size.
- Cura has built-in ooze fighter that cleans/wipes the ooze within infill. Skeinforge too but not slic3r (as of Jan 2014. I don't know if this is true anymore).
- 3mm works better than 1.75 mm filament.
- Mixed opinions on quality of bowden over normal. Many people say not as good quality. Others say the non-moving mass makes better quality.

Edited 1 time(s). Last edit at 06/06/2015 10:56PM by jessicabrenner.

I have only experience with Bowden, so I cannot compare but I can reply to two points.

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jessicabrenner
○ Difficult to print flexible filaments (ninjaflex, PVA, etc…)

This is partially true: there are different issues and some of them can be fixed completely, others cannot. The main problem is that most extruders using a Bowden are not designed for flexible filaments. Any extruder design where the filament is never left free to bend will allow you to use flexible filaments reasonably. On the other hand, retraction is not going to work because of the huge spring effect of the flexible filament, which depends only on the distance between the hobbed bolt and the hotend.

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jessicabrenner
○ More prone to mechanical failure ("bowden popping off")

Never had such a problem, neither with pneumatic fittings nor with nuts.

I use a bowden on my prusa i3 and get great results. i have also used a direct fed Polyprinter and it is blazing fast. it has a unique hot end that is nothing like what we use. it is also a $3000 printer...and mine is roughly $500

Quote
jessicabrenner
...don't care about the potential speed increase - just the quality of the print and the amount of troubleshooting/adjusting needed post-setup. . .

I've only known a bowden set up myself.
It works ok for me but for what you are after I would guess that a direct extruder would be (has to be) better.
If you want print quality you need to print on the slow side and the problem of added extruder/ hotend mass becomes less of an issue then.

For troubleshooting/ adjusting you are taking the long tube and 2 fittings out of the equation and associated friction of the tube and springiness of tube and filament.

The issue of flexible filaments is not just the 'flexibility' but they can be tacky on the surface and stick in a bowden tube. Similarly, rough filaments like 'laywood' aren't too keen to go through there either.

You may gain a little head height from a bowden depending on your arrangement.

-a

Bowden is nice, but I'd have to agree. The stringing is quite annoying.

May I interject the flying bowden. It works very well on my delta and stringing is drastically reduced. Although im not completely sure if the bowden is the cause of the stringing I think its more a temp and retraction issue.

Stringing is a function of the whole system.

A bowden extruder is capable of some good quality prints with little to no stringing. The thing that most users seem to fail to acount for is the acumulated slop in the extruder. I only retract 3.5mm and still get almost no stringing on my printer. The accumulated slack I am talking about stems from the fittings, the actual tube and the different transition zones before hitting the top of the build surface. For example I run a namless hot end and I needed to create a small aluminum slug that sits between the fitting and the heat sink. The reality is that the hot end had a 7mm gap between its entrance hole and the exit orifice of the fitting. Installing the fittings properly and locking them in place is also extremely important. Add to that the fact that most extruders out there have some sort of lash and you have hysteresis in your extruder causing uneven extrusion of plastic leading to pressure built up and stringing. If done properly the stringing should be eliminated or no thicker than a human hair and easily removed by hand with no tools.

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I've used both, and they both print well. There's a bit more tuning with the Bowden, but once it's set it prints consistently good prints.

Does anyone know of any guide or tutorial that lists all the best practices for making a bowden extruder printhead? Or are there any pre-assembled bowden assemblies that anyone can recommend?

This is all very useful information everybody, thanks!

Not being able to do flexible filaments might be an issue for me. But that issue aside, I think it would be fun trying to get bowden extrusion working with very little stringing or other issues.

I´m wondering, if anyone tried a flexible shaft instead of the PTFE tube? Like a dremel flex -shaft?
The remote steppermotor would drive the flex-shaft , hobbed gear and idler are placed as usual ontop of the hotend. You could use any flexible filament a direct drive works with.

Ofcourse the flex shaft would have it´s own issues, but the concept would be "best of both worlds"?!
-Olaf

Yeah there are a few different designs for a remote non-bowden type of extrusion including the use of a flexible shaft that you can buy. [forums.reprap.org]

I really like the flexible shaft idea, but will have to give it a try at some other time.

I have both non-bowden and bowden, and while the stringing aspect of the bowden can be tuned out quite well, one additional downside to the bowden is that it doesn't perform well when there are large changes in back-pressure (e.g. when transitioning from printing with relatively low layer heights directly on top of the previous layer, then bridging, then back to printing on top of the previous layer. What happens is that during the bridging the reduced back pressure results in the bowden expunging extra filament such that when the bridge finishes the pressure is too low causing a material deficit.